Yamaha RD250 Disaster Strikes

[@mred7030]

this was a regular for me back in the day , thank god for electronic ignition .

[@Banditmanuk]

I remember buying a second hand newly re-built RD250 back in 82. Riding it home from the vendor I opened it up a little along a short straight and exactly the same thing happened to me. The joys of two-stroke ownership! Best of luck sorting it

[@malcolmclenton1663]

I wouldn't bet on all the debris being on the side of the crankcase. I'd be inclined to do a complete strip down, just to be safe.

[@RepairandRideout]

Thanks for your comment. There is more to come on this and I think you could be right

[@BillyWillicker]

That will require a complete teardown and washout, the crankshaft may also need bearings from the molten aluminum being run through them. The cylinder can likely be saved by some acid and a light hone, unless it's out of round or tapered too much. Upon reassembly it will need to pass a proper leakdown test. That failure can also be caused by a restricted exhaust as well. Check and address EVERYTHING on it. Crank phasing and ignition timing issues can cause it as well.

[@RepairandRideout]

Thanks Billy. The next video, although some of it may make you wince, will take us in that direction.

[@soggybawsmoto]

Sorry for your loss 😂. You earned my sub for "burning on the expensive side" Great bit of story telling, super watchable. Nicely produced. Looking forward to having a binge watch ghrough your channel 👍

[@RepairandRideout]

Thanks for your comments, just trying to find some humor in the circumstances

[@br5380]

Welcome to the 70's! Mine had that many rebores it was nearer a RD270 than a RD250. I think my RD350LC ended up at 375 🙂

[@RepairandRideout]

Thanks for your comment, trouble is I still think it’s the 1970s and ride accordingly

[@RichardGreen-xu7xd]

I had this happen to my 1973 RD350 in 1976. Got it to the Yamaha dealer who said he was to busy but I could use a bench and he would oversee the work. First he checked the timing and then the carbs, both perfect. He asked me where this happened and I said that I had closed down the throttle to lose speed for a bend. His diagnosis was rubbish in the fuel leaned the mixture and the hole in the piston was the result. When talking bikes now with mechanics and mention this, the all give the same answer. A routine task in those days was removing the bowl at the bottom of the fuel tap and cleaning out the water and rust particles from the storage tanks.

[@robertdrinkall8947]

As already said, you'll have to strip the engine right down, get the bits out of the crank cases, while you have it down you may as well have the crankshaft rebuilt, the bearings are usually shot after 15,000 miles anyway! Then check that carb over, it's running lean which caused the problem. I had the RD400d model ,same colour as yours, parts will be hard to source now, I wish you luck, great bike. 👍

[@RepairandRideout]

Thanks for your comment. Everything is either at the machine shop or has just arrived back. Luckily parts are not too hard to find….at the moment

[@stuartholding6067]

You and me both with holed pistons. Did mine in the middle of France and the bike had to be recovered to the UK. You're really going to need to strip the engine completely as piston grit goes everywhere and the crankcase will be full of it. Swilling it out with petrol might be fine for a trackside get out in the next race bodge but for a road bike it's only storing up trouble.

[@madmaxsdog8040]

This is the first one of your vids I've seen, beautiful job on the resto. I noticed its a CDI model and I'm guessing it was timed with a strobe, if so thats probably the cause, they need to be done with a dial guage as the timing marks always line up with a stribe no matter where you set the stator. Stock is 2mm btdc but with pipes they usually run better at 1.9mm

[@RepairandRideout]

Thanks, I hope you enjoyed the video. The bike runs a Vape ignition system, I've read variously the timing is 2.0mm or 1.8mm btdc and I've tried to get it as close to 2.0mm as possible. So far I've not had the opportunity to take the bike for a test run, hopefully this weekend

[@madmaxsdog8040]

@@RepairandRideout I have no experience with vape I thought it was the stock CDI. You prolly mentioned it but I didn't notice, anyhow as said with the stock ignition 1.9 worked very well with pipes, I tried 1.8 a few times but it always seemed to make the engine response feel a bit "soft" , especially in the midrange.

[@royster3345]

Was on the back of an RD 350 and same thing happened, bits of piston dropped out when the exhaust down tube was removed. Plus a bent con rod when stripped 😢

[@RepairandRideout]

Hi thanks for commenting. Ouch that sounded nasty, luckily no bent con rod on mine this time, just a mess and crunchy bearings

[@bakeredwards]

I've never seen such a big hole in a piston, I had lots of RDs when they were cheap and only had one holed piston, but quite a few mates had them, always considered to be timing related back then.

[@RepairandRideout]

Thanks for your comment. It is a bit of a whopper. I’ll static & strobe light the timing and check for air leaks on the rebuild

[@dennisyoung4631]

That’s a fair bit worse than what happened on the F7 - which developed an Air Leak. The aluminum stuck the rings, which meant zero compression…

[@RepairandRideout]

Hi Dennis, thanks for your comment. I've some aluminum stuck to the barrel, but to be fair the rings are not in good share either

[@iantheo1424]

Twice this has happened on my Australian RD 250 even after replacing crankcasr seals. It turned out that after market jets and needles are not compatible with the C series here in Oz. Found a Keyster kit with correct jetting and bike has been trouble free ever since. As for Debri in the crank case.... I filled with clean oil with barrels removed and spun by hand and each time residue would surface. I repeated many times untill only clean oil observed. I was lucky my bearings were not damaged but of course had to fit over size pistons each time. I am now on 50+ oversize I think. Good luck

[@iantheo1424]

My bike was given to me after 20 yrs out in the open and all rusty. It has been going now for 12 yrs and 3 sets of tyres and as mentioned 3rd set of pistons. It now has a power Dynamo set up as Australian models used different points and Alternator.. Hitachi versus Nipondenso so when the stator failed wads up s..t creek as none avaiable. Power Dynamo fits all models and can be fitted with no mods to wiring other than a relay to cut power to ignition via original kill switch. Great bike

[@RepairandRideout]

@@iantheo1424 thanks for sharing, I think you’re spot on regarding the jets. I’ve managed to source original oem larger size jets and have gone back to oem emulsion tubes and needles

[@teej710]

Sad news 😞. I've holed several pistons in my LCs, years ago. Always happened under heavy load, caused by either an excessive lean mixture at full throttle or bad ignition timing settings. Hopefully you can identify the cause and sort a repair. Good luck

[@RepairandRideout]

Hi Teej, thanks for your best wishes. It will be repaired, just not sure how long it's going to take at the moment

[@teej710]

@@RepairandRideout I've noticed from a previous video, you've fitted an aftermarket ignition system. I couldn't see how you set the 2mm ignition advance BTDC, but i would recommend you recheck the timing, in case it's changed/slipped. Over-advanced ignition on a 2-stroke, even fractions of a mm, could cause detonation and may hole a piston. I use a dial gauge indicator down the spark plug hole to set precisely. You can always retard the ignition slightly to play it safe i.e 1.8mm BTDC. This may reduce performance slightly. You could also run the bike with larger main jets to richen the full throttle air/fuel ratio. This will help reduce combustion speed and counter potential lean mixtures, which could be caused by poor low octane fuel. Anything that effects the combustion temperature i.e higher compression, wrong spark plug heat, poor squish etc, could cause detonation and hole a piston. I hope these ramblings help. Cheers teej

[@RepairandRideout]

Thanks TeeJ. It was running larger jets but you could be onto something with the ignition. @@teej710

[@stumpy200vetmx]

"look away now..." Spot on! There I was thinking "is this hate vlogging?" I am very triggered by the sight of such destruction in a classic bike! 😳😳😥😂

[@martycech5844]

Beautiful bike! Please get her repaired and running again.

[@RepairandRideout]

Thanks martycech, I'm doing my best to get her back on the road

[@philmuskett265]

Wow, that's as impressive as I've ever seen, mate!!! Good luck.

[@RepairandRideout]

Cheers! I'll keep it as a paper weight

[@miclchaos]

Ouch. Shit happens with our much loved old school strokers!

[@mogendo]

Same happened to mine in 1976, Two barrel rebore with new Pistons and rings for Forty Quid if cost me. Good times.

[@sicks6six]

Bet its a holed piston.the autolube on mine was crap so i ran premix and never holed another one.

[@RepairandRideout]

Thanks for your comment. It is on autolube. I’m going to have to test the output of the pump with the rebuild

[@raymondsteele4142]

Hmmm , welcome to the Club . They always run better just before they let go . Bugger . I remember over taking a row of cars on the local bypass on my 350lc . Then it went quiet , clutch in and coasted to the side . Bugger . When it cooled down it started on one lung and i limped home . When i got the head off to see the damage and formulated a plan it was Beer oclock .

[@RepairandRideout]

Hi Raymond, they always let go in front of an audience. I've not blown the motor I'm coasting to a halt at the side of the road to admire the view. I would like an LC though

[@garfield2279]

Had exactly the same on my RD250E back in the day, on the M20 in Kent, bike felt like it was running out of petrol, coasted to a halt, it restarted after a while, then I managed to ride home on one cylinder, holed piston time.

[@martinhambleton5076]

Strip down, really, I suggest. That debris has been passed around, I would say. Crankshaft seals, and balance, conrod alignment is what a lot of people overlook, reset carburettors. Lovely bike.

[@RepairandRideout]

Hi Martin, thanks for your comments. That's the way I'm heading

[@martinhambleton5076]

@RepairandRideout A friend of mine had a similar experience with an RD 400 years ago, and the conrod alignment was way out. His friends dad was an engineer at Rolls Royce and found this problem after the bike had done this twice before. I can't remember what they did to overcome the problem exactly. It's a very long time ago! But on the final rebuild, she was perfect. Just a thought. Please do an update as it is of great interest.

[@MrBeracah]

What caused your problem is both cylinders running far too lean especially the side that holed the piston and especially for a two stroke. Thks

[@RepairandRideout]

Thanks for your comment. I’m going to have to carefully rebuild the motor and check for air leaks. The jetting is well up on standard, maybe room for more?

[@KoJaksKranium]

Check to be sure your oil injection is working, unless you premix your fuel. Either way that first plug was too light in color for any two stroke, not to mention the melted plug. Too lean (oil mixture) in my opinion, probably fuel too. Good luck. It's a nice little smoker.

[@RepairandRideout]

Thanks for your comments. I'll be testing the output of the pump, probably this week for a follow up video

[@craig380]

Ooof, sorry your ride ended up that way. My old GT380 with J&R chambers put a similar size hole in its left piston after an 'enthusiastic' bit of riding. I knew the left-hand outer crank seal was weeping very slightly but it had been running and riding great for 10+ years. However the slight leak, combined with giving it the beans one time too many, added the extra port to the piston crown. For what it's worth, I'd recommend rebuilding the crank as the molten alloy from the piston usually gets right into the big end bearing and can't be flushed out.

[@RepairandRideout]

Thanks for your comment. I think you're right, the odd thing is all the aluminum seems to be in fragments, as if it exploded

[@jackking5567]

@@RepairandRideout I'm new here and not sure if you've ever welded aluminium before? It turns to a 'globby' state when hot enough - not necessarily at the molten state temperature. The piston travelling up and down creating the pressure variations is enough to then pull the globby metal apart. Those molten fragments likely didn't fully reach the full molten state, instead getting hot enough to shape within the crank chamber as they were bashed around. Here's where it gets interesting. Back in my youth and my 2t days, such events could happen due to us tuning the things. Just takes a slight error and it can happen. What I discovered was that pistons come in a variety of metal types, despite them all being aluminium. As well as alloys of the aluminium, you also get cast pistons or forged pistons. Forged giving a very different quality to cast. From what I've seen, your pistons are of the cast type. We found that they were vulnerable to fuel mixtures being slightly wrong or air leaks weakening the mix. I have no idea about older 2t engine parts availability but if you can, get forged pistons.

[@RepairandRideout]

I think that cast are all that are available. I have heard of folk putting in the pistons from the later LC models @@jackking5567

[@garyspracticalworkshop357]

I feel for you , thats a real shame , hope you can rebuild the motor. Gary

[@RepairandRideout]

Cheers, the rebuild will start this week

[@garyspracticalworkshop357]

​just about to start a Z1 900 engine myself, Gary's practical workshop . Hope build goes well. Cheers Gary

[@RepairandRideout]

Hi Gary, good luck to you too. I did a top end teardown of my Z650B1 to fix an oil seal leak@@garyspracticalworkshop357

[@stressederic64]

Ouch - great looking RD though

[@RepairandRideout]

HI, thanks for your compliment. Yes very painful

[@acooper4482]

Heat sieze and melted holed piston caused by leaning usually an airleak or ignition incorrect. Looked like a black blow mark between head and cylinder? Maybe repeating whats already been said but 2 stroke oil lubricates it the petrol that does the cooling if that makes sense. Just a 1 percent increase in oil can lift the temp 100 deg on the same jet size. Do a leakdown test on rebuild. Look forward to watching more

[@RepairandRideout]

Will be doing a leakdown test for sure on the rebuild

[@brianravenberg6654]

I like your expansion pipes. Where did you get them?

[@kennethm.pricejr.8921]

Big round hole, almost symmetric, it didn't fail because of a manufacturing flaw, it was underdesigned.

[@RepairandRideout]

Thanks for your comment. Interesting idea

[@cagr4249]

Puh. I assume that detonation has caused this overheating. I recommend to check for false air, condition of air filter, ignition timing and jetting.

[@RepairandRideout]

Hi, thanks for your comment. I though I'd just about got there, it was running so sweet......

[@geoffoliver6788]

Hi there, have you ever thought of running a slight 2 stroke mix in the fuel. I would sooner foul a few plugs than seize it.

[@RepairandRideout]

Hi Thanks for your comment. I have read about that one or two racers back in the day added a little oil to the petrol, surprised they were using the oiling system at all. I also read in the workshop manual that it can have the affect of leaning the mixture - sounds counter intuitive. Anyway the output of the oil pump will be measured for sure

[@madeljacky]

@@RepairandRideout correct, adding extra oil to the mixture without adjusting the carb will cause the engine to run leaner, the reason its leaner is if you take the volume of fuel/oil mixture that is drawn into the cylinder and the bike runs fine and you then add extra oil to the mixture you are still drawing the same volume of fuel/oil mixture into the cylinder but now there is more oil and less petrol in the mixture, less petrol causes the engine to run leaner so it overheats and either melts a hole in the piston crown or seizes the piston in the bore. I work at Rotax 503 and 582 microlight engines that run at 50:1 fuel/oil mix perfectly fine, that is until some owners add extra oil to the mix and then wonder why the exhaust gas temperatures were rising on the climb out and then the engine seized, it happens more than you might think.

[@samanthaharrington6549]

If your using crappy standard unleaded fuel switch to v power or any supreme fuel with higher octane rating. Go to your local bike shop pickup a litre can of silkolene proboost fuel enhancer. Its a fuel stabiliser and octane booster. Little eggcup measuring pot comes with it. 1 pot measure add to 5 litres of fuel pour into fuel tank. Give tin a little shake first cos it contains a sort of fine oil in the contents. Double check carb settings as standard set up for standard bike. That stuff will preserve your engine. I know cos my 350lc with skimmed head raised compression did what yours has done. Plug turned into welding electrode burns hole through piston. Unleaded crapshite fuel low octane is same octane as old 2 star fuel use to be causes detonation flame temp too high melts parts you found. I also switched from b8es standard plugs to b9es plugs ngk. 9 plug runs cooler than 8 plug. Cooler plugs use to foul easier with carbon caused by the 1980s 2 stroke oil. Modern 2 stroke oils burn clean now so less chance plugs fouling. When you've rebuilt your motor from crank up and she's running again do a compression check she may have had skimmed heads raising compression so check for that. Then when she goin a treat use E5 fuel v power type stuff and dont forget ya measure of proboost 1 pot full per 5lts fuel. Plugs will colour like when you ran 4 star that lovely digestive biscuit brown on electrodes gives rough indication you have a healthy motor. Ah yes the delights of this crap called petrol verses good ole 2 strokes. My lc went bang when unleaded first came out and 4* disepearing. Didnt think it would hurt a 2 stroke as the only concern was valve seat regerssion in 4 stroke engines at the time. Been running me 350 lc 10 years now v power and proboost and she gets rode like ya stole it. No issues in that time. Biggest laff is when ya mates ride behind you. They either overtake or drop right back cos the hydrocarbons vapours are wonderfull. Car drivers drop way back too when car fills with said vapours ha ha tis a hoot. Your engine will love ya. Now git that motor stripped rebuilt flush exhaust too cos alloy metal will have gone down pipe. All that molten alloy dust will damage cylinder wall so she'll need rebore too snd keep pistons same size so both barrels will need doing. Lastly use a semi or fully synth 2 stroke oil i try to keep fully synth but not castrol R as that wont mix with any 2 stroke oil. It'll turn to jam block up oil pump and oilpipes. Great bike you'll git her sorted. Phil the dood 😊

[@starsailor49]

I suffered repeated seizures on my RD. On further investigation it turned out the crank was twisted, throwing out the ignition timing.

[@RepairandRideout]

wow that's incredible. I'm told that rebuilding them is quite the delicate task in order to get it exactly 180 degrees opposed

[@ianhalliwell8604]

I had a RD250 back in the eighties in fact it was one of the first bikes I'd ever owned. I'm afraid it's screaming nature just didn't do much for me and i soon got rid.

[@RepairandRideout]

Hi Ian, thanks for your comment. Sorry to hear you didn't enjoy your RD experience. I love it's screaming nature and two strokes in general.

[@richardzollinger4750]

Good luck with repairs.

[@RepairandRideout]

Hi Richard, thanks for your comments. I'm making progress already, well parts arrived and engine on the bench. The difficult work is about to begin

[@skts2610]

Good ol two stroke upto its usual tricks!… All the new fuels don’t help I’m afraid🙁

[@RepairandRideout]

I try to avoid ethanol wherever possible on everything I own that runs on petrol. Usually premium 98 octane, where I live, is 0 to 5% ethanol

[@grahamreeve5209]

What pistons are you using. Back in the day I fitted Hepolite. Not to be recommended back then.

[@RepairandRideout]

Thanks for your question. I can’t remember! They’re off at the engineering shop at the moment. What I can say is that they are Japanese and that the technician knew the make and was happy to use them

[@grahamreeve5209]

@RepairandRideout they looked forged which generally means good

[@christosswc]

2-stroke being 2-strokey, the kind of woman that will drive you crazy from pleasure and also the one you shouldn't marry, ever. If the crank survives, there will always be tomorrow.

[@RepairandRideout]

I hope the marriage is strong enough to survive

[@NatMart9394]

Welcome to the pisston and broke club.

[@johntaggart1176]

Same happened to me with my Yamaha two stroke twin, it seems to e an inherent fault with these two stroke machines. Yamaha know about this problem and all the would do was recommend a different spark plug????

[@RepairandRideout]

Hi John, I have been told to run a BS9 plug which is 'cooler' running

[@PhilipHarrington-n1h]

Ok me mate just txt'd me. he sent his 250 LC yam crank to Grampian motors based in Liverpool. They a 2 stroke specialist they rebuilt with all new bearings con rods etc. They the guys to chat cranks with. They prob do piston kits and rebores also. Send barrels and crank to them. They'll have it sorted for you. Mr phil

[@RepairandRideout]

Cheers Phil. I'm on to a local engineering company and waiting a call back to see if that can rebuild the crank and do the re-bore. www.snr81.com (it's all in French) They are swamped at the moment as they're the best in the area (still and hour away from me). I now have everything for the rebuild.

[@JB-yn4cs]

I second that - Grampian motors are spot on. Had my rebore done in no time

[@alanhowatson3462]

Oh dear, what a pain. Did you put bigger jets in to compesate for the expansion chambers?

[@RepairandRideout]

Yes, it's running 140 mains & 27.5 idle (up from 115 & .25) Thanks for your comment

[@davidbrayshaw3529]

A couple of things. We have a saying for this, in Australia: "Fv@k!". Secondly, are you running pre-mix or still working with the oil injection? RD 250's were like bad hair cuts here, back in the 70's and 80's. Everyone had one. The oil injection was noted for being problematic. Mine wouldn't do anything other than over oil, but they were also known to under oil. The solution was to delete the pump circuit and use pre-mix in its place. I can't remember for the life of me where the feed from the oil pump went to. If it's fed into both manifolds, it could be something to investigate. I'm probably telling you something that you already know. And yes, I feel for your bad luck, but I'm happy that you didn't end up in hospital or worse.

[@RepairandRideout]

Thanks for your comment. I grabbed the clutch lever pretty quick! It is running off of the autolube system. Right exhaust has always been drier than the left so there could be a problem to look into

[@sidecarbod1441]

If it was a pump failure the piston would just seize in the bore, it would not cause a huge hole to be punched into the piston crown. I would normally say that a hole in the crown is caused by detonation but in this case something does not look right with regards to it being detonation, it does not look like the hole has been 'sandblasted' through the crown. The edges of the hole are too sharp and ragged, it looks to me more like a foreign object went through that cylinder. Of Course there is no harm in checking things like the fact that the pump is working, the ignition timing and the jetting. The pump can be checked by running the engine on pre mix, with it idling hold the pump fully open and allow each tube to deliver oil into a small container for something like 5 minutes with the engine just ticking over, you could then at least check that both tubes are delivering the same volume of oil. I suspect that you can actually find out off the web or the manual the exact amount of oil that should be delivered per minute. I also think that the engine needs a full strip down, parts of the crown will now be stuck in the mains and big end, it sort of gets pressure welded to the inner and outer races of the mains and the big end journal and conrod, you can never get the stuff out of the bearings and it will cause the rollers (big end) and balls (mains) to skid, the bearings won't last long when this starts to happen. I would through the little end in the bin without even looking at it! Luckily the RD range of engines are easy to strip and rebuild. A blow up is still a pain in the ass though!

[@RepairandRideout]

Thanks for your comment, so much useful information that I will take on. I agree the piston looks as if it has suffered from an explosion! I wonder if I had a brief engine seizure (undetermined reason as yet) and the piston was somewhere in the compression stage. At 6000rpm that's 100 vape powered ignition sparks of energy per second with nowhere to go @@sidecarbod1441

[@sidecarbod1441]

@@RepairandRideout I like the fact that you are thinking about this but I must admit I don't think that is the case here. It would only have one fresh charges worth of air and fuel in the combustion chamber and that would not be enough to blow the piston to pieces. (Unless you are running Nitromethane!!) The fact that you are running an aftermarket ignition system is fine but whatever system you use it can only fire whatever mixture is in the chamber.

[@cleeveofford1720]

Left hand piston got a hole in I bet, all the rap goes into the mains rebuild job Mine did it all the time, they reckon that the timing is set wrong, but mine would do it when yo red lined it Bottom end went wobbly so had new bearings put in at broads motorcycles but that was back in the 70s. You need the ends doing to be safe mate, sorry

[@RepairandRideout]

There's more to come on this......

[@PhilipHarrington-n1h]

Phil the dood here hey thanks for getting back to me I seen first bit your reply. I just txt load a mates now lost ya last reply. Knowing me with these new fangled mobes I've prob delete afore I seen it. I'm ok with a motor but these mobes drive me bananas. Hope info I've sent is useful too you. Do you normally run higher octane fuel. When petrol was petrol in the 70s/80s I seem to rem bikes of your kind were very happy on 2 and 3 star fuel. It was a revelation when the lc's turned up 1980s possibly late 1979. A label on fuel tank from manufacturer said use premium fuel which we called 4 star back then. Un heard of back then putting 4star in a bike specially small 2 strokes. This fuel today hmmm yes entertaining it is. Hey nice lil project in garage keep ya busy mind you it allways comes at a cost. Get all that motor cleaned out. Lube everything as it goes back together. Was the manifold pipe separate to main silencer sealed with a rubber connection tween the 2. Make sure ya exhaust gets a wash out too cos that alloy dust be down there too. Pressure waves move back forth in 2 stroke pipes so you don't want shite goin back to exhaust port. Stan Stephens only rebuilds engines cranks complete now not cranks on own think gramby's took over from Stan's work on crank rebuilds though they don't spot weld crankpins too webs like Stan use to do. Was you blasting when engine let go my LC was up around the 130 when it melted. Crank survived was still straight n true but I had Mr Stan check it over cos of the speed it was goin at when she went pop. I check with me mate where he had his crank done on LC 250 a year ago we stripped rebuilt his motor as had a seal failure and couple noisy bearings sure he said was gramby I double check let you know. Ok disconnect battery and git that engine out n stripped. Nowt that can't be fixed. Enjoy. Phil the dood

[@RepairandRideout]

Cheers Phil. The down pipe are separate from the main exhaust with a slight oily mark. No rubber join, I just thought that was a 400 thing. I hoovered out the exhausts and blew compressed air through it too. I was probably around 80mph when it let go

[@paradiselost9946]

no option. split the crank. dont even attempt to skip. one tiny speck in a bearing and its destroyed again. what was the point? you will never get every bit out of that case without tearing it down. been there, done that. its not worth it! two strokes really hurt when they do this. had my lil nsr150sp sitting in the shed for a few years due to popping the crown at 130kmh... in a corner... that was fun! slowly accumulating junk to make my own pistons and cylinders as theyre damn rare now. fly press, furnace... idea is im gunna do a cast in the mold then slam it with the fly press as its solidifying so its also sort of forged...

[@RepairandRideout]

Thanks for your comment, just awaiting some parts before I go to the next step. Good luck with the workshop, I did sand casting aluminum for O level metal work!

[@paradiselost9946]

@@RepairandRideout the casting is the easy part, getting the fifty thousand other jobs out the way is the challenge!

[@englishpatriot3019]

First thing I would have done is a leakdown test before pulling the cylinder off. If you don't own a leak test kit invest in one before the rebuild.

[@RepairandRideout]

Hi thanks for your comment. How do you do a leakdown test on a two stroke, get the piston up above the ports and pressurize from the sparkplug hole?

[@englishpatriot3019]

The leak test kit I use screws into the sparkplug hole, you have to remove your carb and exhaust then I use rubber bungs to seal the inlet and exhaust port, pump about 5psi into it and see if it holds pressure for a minute or so. If it is losing pressure use soapy water in a spray bottle to find the leak. Never found it makes any difference the position of the piston when doing the test but you could set it at BDC. Hope that helps.@@RepairandRideout

[@RepairandRideout]

Thanks for the explanation, I understand now. Great advice. many thanks@@englishpatriot3019

[@mjshaheed]

I hate the autolube system with vengeance. I have never used it and never will.

[@RepairandRideout]

Thanks for your comment, I'm really hoping to keep mine as it's just so convenient. But I suppose that's a risk if I want to ride the bike enthusiastically. Lets see how I get on

[@PhilipHarrington-n1h]

Ok so pipe manifolds just slip into silencers yea allways bit leak there. Bit clear silicone rubber applied there may help seal oil leak. Leak there will not cause engine fault you have. Ive just txt me mate as to where he sent lc crank too for rebuild. Cranks cant be repaired at home you need a large lathe heavy press and you working with thous of a mm. So unless you a crank specialist it goes to someone who is. Try flush bearings ya self first but if any doubts send it to a 2stroke crankman. I should hear from me mate later where he sent his crank too. We down bottom of cornwall so stuff like that goes up T north. Im rebuilding a matchless 350 g5 single of 1961 vintage that had crank issues when new. I suspected all wasnt well with crank so it went to alpha bearings up dudley. They got 90 years experience of cranks of that age of bike. Special work stuff is crankshafts. Ok buzz ya when matey txts me. Laterz

[@jackking5567]

Don't just replace upper parts. The crank is wrecked and needs a rebuild - the bearings have swallowed aluminium. ALL of the crank bearings on that side are written off.

[@RepairandRideout]

Thanks for your comments, I think you're right. I've made some progress since this initial video and it's pointing in that direction

[@alexandersimpson3638]

Total rebuild, might as well go for the 350 conversion via the DT route.

[@RepairandRideout]

It has crossed my mind but the 350 barrels are quite sought after. DT route is that a pair of 175's? @@alexandersimpson3638

[@PhilipHarrington-n1h]

What exhausts are you running. I use allspeeds on me LC they were designed to run on standard mainjets. If I use me microns I have to jet up quite a bit. Ere check condition of ya air filter too. 350 LC won't start until the air filter element is fitted into airbox. Does your Yamaha have a small rubber pipe like from floatbowl on each carb upto lower part of airbox. Perhaps it was there to alloy filterd air to go into floatbowl or it may have been there to correct mixture I forget now without looking at it. Anyhow check there too. My LC uses bit pipe between carbs at choke circuit. Won't run or will run crap without it big holes sucking air engine would run very weak mix. Ok enuff my babble you got enough to do. Mr phil the dood

[@RepairandRideout]

They are supposedly Allspeeds. I have rejetted to 140 main & ,275 pilot. Running standard airbox & filter (wouldn't run very well without I found) and there are pipes from the float bowls to the airfilter

[@daveversion2.2]

Did a leaned out mixture cause that?

[@RepairandRideout]

Lots of comments suggesting it was running too lean, perhaps timing issue as well

[@fastboy8315]

no oil from the oil pump ?

[@Pokemongold88]

Gutted for you mate where are you ? Southern france

[@RepairandRideout]

Cheers, yes SW France near Carcassonne

[@benpenfold4487]

Sadly, there's nothing you can do,the whole machine is a write-off. Send me your address and I'll take it off your hands 😂

[@malcolmbrady1958]

Those Spark plugs look like they have been running weak to me, that second one was white so great heat was produced in that cylinder, So I am going for weak mixture, or Ignition timing overly advanced The colour of those plugs for a 2 Stroke are wrong, but for a 4 stroke engine they would be fine, also don,t remove oil pump altogether, But the pump needs to be be checked for correct oil injection amounts, even if the oil pump is supplying too much oil, believe it or not that can also weaken the mixture as can obviously not enough oil, The reason why it is a bad Idea to remove the pump is that premixing in fuel tank does not permit the oiling of the Crank Bearings, Those plugs should have had a brownish/Grey colour to them, On a 2 stroke you are better running too rich rather too weak, Tweak your air screws as well for best tick over and even running of cylinders, Also you can tweak those air screws go for a longish ride, whip the plugs out and check the colour of the plugs, just keep repeating this exercise until your happy with the plug colours, Tuned 2 strokes this way for the last 50 years !!

[@RepairandRideout]

Hi malcolm, thanks for your great advice. Will be following it for the rebuild, set up & run-in

[@robertroe1956]

Sorry to see that. Any idea why?

[@RepairandRideout]

Hi Robert, not entirely sure at the moment, could have been oil starvation causing a momentary seizure and the spark plug burning through the piston. Rebuild parts on order

[@topfuelteddy]

​@@RepairandRideoutCould be an airleak causing a heat seizure, sure looks like the piston has got very hot on that side .

[@RepairandRideout]

Will definitely look into that @@topfuelteddy

[@BillyWillicker]

Many possible causes. Air leak, restricted exhaust, ignition timing/crank phasing, fueling, are all possible culprits. The scuffed intake side usually indicates oiling problem, but with the heat-detonation-pre-ignition-failure(in that order) it still could do that damage with proper oiling.

[@drewcecato221]

ceramic coat your entire top end and give it some more fuel. eventually ppl will realize how beneficial it is on 2t. would've never happened with the exact same air/fuel

[@jamesgarrard4361]

stock jets with pipes ????

[@RepairandRideout]

I was running with 140 mains and 27.5 pilots up from 115 & .25 stock

[@jamesgarrard4361]

@@RepairandRideout The piston looked very dry ,not much oil and a very clean piston Crown ,you must check your oil pump settings ,air locks ? Maybe you have an air leak ,cracked carb rubber The motor needs to be stripped You will regret it if you don't As you will have ingested aluminium debris into the mains and big end bearings ,when you got it back together run a larger Main jet and plug chop after running in !! ,looks like you got An air leek or faulty carb ,good luck nice DX

[@RepairandRideout]

Thanks for your help, will have to strip the engine for sure @@jamesgarrard4361

[@BillyWillicker]

At cruise speed you are on the needle/emulsion tube - main has little effect at part throttle - it was likely lean if only mains and pilots were changed. Remember, main only does WOT and pilot only runs idle. The heat will have burned all the oil in the cylinder away once it's gotten to the point it did.

[@RT22-pb2pp]

I am no mechanic but hole in piston is not goid.

[@RepairandRideout]

Very true. No one needs a hole where there wasn't one before

[@jeynes14]

Ouch

[@bananabrooks3836]

Points ign?

[@RepairandRideout]

No it's a new Vape system

[@bananabrooks3836]

@@RepairandRideout Ok, well its got very hot so either it's run lean(carb setting)or lacking in oil.

[@agee8322]

Running weak on both pots imo.

[@RepairandRideout]

Hi agee, could be mixture. I thought I had it about right. Maybe not?

[@agee8322]

​@@RepairandRideoutboth look weak to me - as in air fuel ratio, not oil ratio - l would want to err on side of caution and go 'dark coffee' ........ far better that than 'dark magnolia' ...... also, running any 2t oil in with petrol (in combo with an oil pump) will weaken air fuel ratio. Make sure 2t oil is a good quality one castrol power 1 etc.

[@RepairandRideout]

Thanks for that, will certainly look to run a richer mixture in future@@agee8322

[@dogpaw775]

didn't the guy hear it pinking ?. with that much debris wouldn't you want to split the cases, these 'stink wheel' fans are weird.

[@RepairandRideout]

Thanks for your comment. I think it's more of an addiction than a weirdness but the R1 crossplane crank would be a great fix. No pinking beforehand, it was just great fun right up until is wasn't

[@PhilipHarrington-n1h]

Sell for spares or new engine sorry guys your dreaming everything fixable. The bike is prob matching engine frame numbers and she's a sweetie mint shiny well looked after bike. Mr matey get motor stripped and rebuilt piece o piss. Tis just bits metal that go round and up/down. Nowt there complicated. Ere looked at ya french engineers better take ya phrase book bon apetite bon jour mr engineer X

[@PhilipHarrington-n1h]

Last txt promise. That hole has nothing to do with oilpump its detonation. Flame too hot turns sparkplug into welding gun melts hole blasts through piston. Yamaha spent millions of yen designing an oilpump. Check it pumps by all means. But if it failed pistons would run dry in bores then bores n pistons fuse together it wouldn't cause big hole in piston. I've still got my melted piston and sparkplug with melted away electrode in me shed things like that are a passage of honour and have to be earned ha ha. Wonder if could get pic of them too you I have to figure how to send em. Don't put extra oil in fuel tank I've heard also it can weaken fuel mix from carbs. The oilpump is perfectly adequate for the job it does just check pump plunger setting is correct and cable has correct adjustment too. But it's deffo not a pump issue. Double check ign timing. Phil the dood

[@peterprice5896]

Ceased bearings

[@RepairandRideout]

"No, they're just resting"🦜

[@grahamhider3754]

O shit 🤢😭

[@keithleivers4061]

Sell for spares or replace engine 😢

[@RepairandRideout]

Going for a rebuild

[@keithleivers4061]

@@RepairandRideout good luck i hope it works out we used to ride 250 2 strokes on L plates straight from the garage no training at 17 years old .needless to say plenty thrills spills and fun but lost two many young friends due to exess speed incompetence and " sorry mate didnt see you" 😫

[@RepairandRideout]

Hi Keith, thanks for your comment. Yes very similar experience too, a fair few hospital visits but luckily didn't lose anyone@@keithleivers4061

[@jamesgarrard4361]

weak mixture

[@RepairandRideout]

Thanks for your comment, The mixture seemed fine at the last run out

[@BillyWillicker]

No amount of jetting up will "heal" an air leak. It can mask it and allow an engine to run well enough at idle and WOT, but at part throttle it will become very lean and HOT.

[@jamesgarrard4361]

Yes sure no amount of jetting will cure an air leek nor should it , I was referring to a one or the other situation, Whatever the cylinder looked Very different to the other also A possible air leak or lack of fuel Possibly including incorrect ignition timing, which is a reasonable assumption is it not ?

[@RepairandRideout]

Hi James, I didn't mean to disagree with you and I think that's a very reasonable assumption. There will be another couple of videos on the way as I dig deeper. Hopefully some new parts will arrive today so that I can make a start. @@jamesgarrard4361

[@jamesgarrard4361]

Sorry my comment was a little brash ,my apologies 🙂👍

[@tvexpert_xd2388]

Dont look good Sorry

[@tumblelake63]

Ouch! I hope it's fixable.

[@RepairandRideout]

Thanks for your comment. I think so, I've ordered new parts ahead of a strip down