Trying to start my Honda Superdream using comments and suggestions. - Project - Part 23

Continuing in my project to build a Honda CB250N from boxes of bits, I'm trying to understand why it won't start and hoping it will fire up any moment now.

[@InTheShedUK]

I'm sure it will run eventually! First thing I would do is connect a proper fuel supply, either the tank or a small test container. Also leave the throttle alone! it looked like the only time it did start was when you didn't crank the throttle right round... only open the throttle GRADUALLY once it fires. It should fire with easy start even on low compression assuming timing (both valve & ignition) is not too far out... GOOD LUCK!

[@RyansGarageUK]

Thank you for your advice, I'm looking to order a small temp fuel bottle which will only help. Ryan

[@nickyjenkins5381]

I'll keep watching if you keep trying👊

[@RyansGarageUK]

That's a deal. 👍🏻

[@Paul.Gascoyneuk]

It lived for a second it will again , good control of swear words , you’ll beat it for sure 👍

[@Matt-we7si]

Lets work this out , so it ran with a bit of start spray in the cylinders , this means the camshaft is timed up with the crankshaft okay , it means we've got okay ignition, it is sparking, compression looks low but rings haven't seated yet and its an old engine anyways. So this leaves one thing , the carburettors , strip them down again clean them as best you can , ( I strongly recommend an ultrasonic) and I would strongly advise putting all new jets in as the old ones will certainly be blocked up. You can try clean the old jets by leaving them in vinegar (acid) for a day , but sometimes they just never clean up nice. After all this you should be able to start the bike with no throttle choke fully open and it should run. Fair enough you want to check the valves again , but I'm sure the problem is with the carburettor. Good luck. (also was there fuel getting into the bowls, usually there is a little gauze filter behind the float needle which can block up ) Cant wait to see this run.

[@Matt-we7si]

to check carburettor jets hold them up to the light and see if you can see through them , or better yet use a magnifying glass and bright torch , I have had some success using a small blow torch and burning through the jets to turn any crud in them into carbon and then it has a better chance of breaking off. In my experience sometimes you cannot unblock jets no matter what

[@RyansGarageUK]

Thanks Matt, I'll certainly strip carbs and sit them in vinegar overnight, the fuel it 100% getting into the bowls as each time I remove them I'm draining out fuel via the drain screws. I'm still seeking a local ultrasonic cleaner and if I find one that will be my first choice. Cheers Ryan

[@Matt-we7si]

@@RyansGarageUK becarefull putting carbs in with vinegar, the acidity can eat into the aluminium especially very old porous castings , I only soak my jets in vinegar, and I bought an ultrasonic cleaner off ebay for £70 and I use it to put the whole carburettors in with a specific carb cleaner and at a hot temperature I will ultrasonic them until im satisfied , and the carbs on my CB 500 perform faultlessly.

[@gbjeppm]

Agree with Matt's comments , it runs on easystart,, it is the easystart that made it fire up, not the oil in the cylinders. Get a temporary fuel tank, and make sure both float bowls are full and not leaking, and make sure the carb is clean, pay attention in particular to the pilot jet. Not sure where you are in the country, but i have an ultrasonic tank, and happy to help.

[@RyansGarageUK]

@@gbjeppm thanks for your offer. If by any change you are anywhere near Salisbury in Wiltshire I'd be grateful for any assistance. Ryan

[@RustyWrecks]

Keep going you'll get there, it ran for a few seconds so thats a good sign, check the idle jets under the rubber plugs, they may be the type that unscrew, if they are then give them a good clean as well.

[@RyansGarageUK]

Hi Pete, Thanks. I thought that jet was pressed into the carb and couldn't be removed. But I may very well me wrong, so I will check. Ryan

[@RustyWrecks]

@@RyansGarageUK some are pressed in some are screw in depends on the carbs

[@alanpatterson2759]

Me disappointed too. Thought that would have cracked it with the piston rings. My encouragement cupboards about empty! keep going tho...just love to hate that devil bike.

[@stevesimms6215]

Loving your video’s. Fingers are crossed.good luck

[@RyansGarageUK]

Thanks Steve.

[@frankenbikestien5073]

seeing the problem you have, a single battery is no good for trying to start. use jump leads from the car on tickover to give yourself a good 14v. with the head upside down, pour paraffin into the combustion chamber to check for leaky valves, if leaky, regrind seats using back-foward motion, do not use an electric drill. ps, a broken piston ring is good for cleaning ring grooves but be carefull. a wooden chip fork works well too...

[@RyansGarageUK]

Thank youbforbyour suggestions. I will jump the bike from the car if it still won't start when I've refitted the carbs again this weekend that I've cleaned better than before, and fitted new spark plugs. I tested the valves like you describe the last time I had the head off, so I might not need to if I can get it to run for a while to bed in rings etc. ( I hope) Ryan

[@alanpatterson2759]

It certainly seems to be a compression issue. The only time it started was when you popped the oil down the bores and improved the compression. Great find on the rings, they used to use a broken ring to clean the carbon from the ring grooves. You re did the valves and you checked them with petrol for leakage and they were fine. The pistons are standard( no markings on crown) akin to the rings you bought. You did gap the rings as per haynes manual to correct specs. Did check on ebay and a lot on there have that type of oil control ring. You honed the bores. you've got a good spark. Timing is as per manual ie markings, take it it's the L/hand cylinder so the tappets at the correct gap should be slack both valves closed and possibly poke a screw driver down the spark plug hole to ensure the piston is at the top of the stroke. Compression readings are way short of what that vlog said 180psi, cars usually run about 150ish. Starter motor is lazy as you progress to crank the engine 12.8V on the battery but will quickly draw down as you crank. Best to connect either your bike or car running. May well try recreating the oil/improve compression test again and see what happens? another teardown to check rings again see if they're stuck in the grooves. You may well end up with a re bore! So check the timing as above, ensure car or bike running for battery crank, oil in bores and give it some squirt of the easy start. And if all this fails pity bonfire night is past!

[@RyansGarageUK]

All very good advice thank you (including a damm good bonfire) Ryan

[@jamesallen4050]

I agree with the folks saying look again at the carbs - I can't hear the fuel getting through. You should be able to start this on the choke without throttle. :)

[@RyansGarageUK]

Thanks James, If you've now watched my latest video, give yourself a pat on the back for most likely being right. Cheers Ryan

[@johntray1462]

go on lad well done, till next time

[@RyansGarageUK]

Hi John, Thank you for your support. Ryan

[@MirchiBoy]

It will start with new spark plugs. Get a new battery, connect it to wall charger; disconnect charger when cranking. Run the bike with old spark plugs out to clear the cylinder. Spray a bit starter/starting fluid in the cylinder and tread in the new spark plugs. Try a few times after letting the battery charge back up fully. If the bike runs, then you have good spark and compression and you can focus on possible fueling issues.

[@RyansGarageUK]

Hi Rishi, Thanks for your comment. Sorry, I was busy when you wrote comment I this working through almost exactly as you suggested. I appreciate your input. Ryan

[@alanpatterson2759]

I'll have a think and logic this out, run a paper machine for 27 years and it didn't break me!

[@timparker9235]

I am just as disappointed as you Ryan, I really am. you are right though, you will get it running - you will, and I am sure someone will come along and tell you from this video, what to do next. keep going!

[@RyansGarageUK]

Thanks Tim. Great advice. 👍🏻

[@chrisktm2010]

Don’t give up. Compression is low but I’m sure those rings are fine now with that starter motor being slow it may not crank up fast enough to get a true compression reading. If it was me I would be stripping and overhauling or sourcing another stater motor, you may find they are the same motor on many different models of Hondas around that era. Strip those carbs to bare parts and leave everything including all jets and bodies soaking for 24hrs minimum in white vinegar(cheaper option to ultrasonic cleaning) just make sure no rubber o rings, diaphragm’s or seals get vinegar on them and also make sure all passages in carb bodies are clear and clean using compressed air. I think your chasing a few minor issues that are adding up to a non start. 1 - It fired well on easy start so there is a fuel issue. 2 - speed of starter motor, to slow and it won’t give true compression reading and also won’t suck fuel in on vacuum stroke. 3 - new plugs which you have coming will help a lot. Sparks can be lost under compression. Your on the right path but everything has to be perfect to get that magic moment you will get there.

[@RyansGarageUK]

Thank you Chris for you excellent and comprehensive suggestions. I agree with them and I'll try to source a starter etc. Ryan

[@alanpatterson2759]

emulsion tube, the air and fuel mix with that jet

[@RyansGarageUK]

Thanks Alan, I had no idea what it was called. Ryan

[@DD-yh6rb]

Try Adjusting your values top dead centre on one piston. Rotate 360 degrees then do it the other side🤞🤞 maybe your valves are opening the wrong way hence no compression? Love the videos

[@RyansGarageUK]

Hi, I'm adjusting the Valves when the lobes of the cam are pointing down (away) from the rockers on each side. I'm fairly sure that's the correct thing to do, but I am learning. Ryan

[@MarkJames61]

Methodical failure, you will get there once the elimination process has run its course. You and this series are awesome

[@RyansGarageUK]

Cheers Mark for your support.

[@nuskaha]

Ryan, I know you have spark with the plugs out of the cylinder! I’ve known from personal experience, that once the plugs are fitted, they can fail once under pressure. In my case it was one plug in my km 90 as it’s obviously a single cylinder bike, but two out of three plugs that I bought together failed once fitted into the bike. I was told if in doubt try a plug from a working bike to be 100 % sure . It’s worth a thought mate. Keep it going though, you will get there soon 👏🙏🤞 Dave

[@kihestad]

This is definitely a valid point. I have had the same problem on one cylinder bikes, spark plug seemed to work, but did not. I have never had problems with new spark plugs, go for NGK and you should be good to go 😌

[@RyansGarageUK]

Hi Dave, you might be right. I've ordered new plugs and I'll be sure to fit them immediately once they finally arrive. Ryan

[@andyshondaxlsrestorations4733]

Don't give up now I've just keep going you will win

[@RyansGarageUK]

Thank you Andy. It's appreciated.

[@garymorgan628]

Make sure you have decent quality jump leads and jump it from your car, that engine is not turning over fast enough to fire its just flooding itself.

[@RyansGarageUK]

Hi Gary, I do suspect my Jump Leads are not the best so you may have a point. Although I'd hope a fully charged battery on the bike should be good enough once I finally sort my other issues. Thanks Ryan

[@rigsbyrigsby9493]

Hi can you let know how to replace clutch cable if you could let me know how it's rooted thanks colin.

[@1greenkeeper]

Ryan did you measure the end gap on both barrel and you need exhaust on and carbs for back presure.

[@RyansGarageUK]

Hi, Yes I did measure the end gap on both sides, and I agree exhaust and carbs certainly help. Ryan

[@deandempsey264]

Trickle a lil drop of petrol of petrol down into the cylinders

[@deandempsey264]

Rootin for ya on this one

[@RyansGarageUK]

Thanks Dean, I had tried that in the past without success. But I'll be sure to try again. Ryan

[@deandempsey264]

@@RyansGarageUK I have every faith in ya that you will get this one running its gotta be something small

[@tombartram6842]

Forgive the silly question but is possible to put the l/h/s piston on the "wrong" side and vice-versa?

[@RyansGarageUK]

Hi Tom, I'd think that Yes it's possible, but they are handed so once you tried to turn over the engine I think they would hit the valves. I may be wrong but that is my expectation.

[@lyndonwebber1389]

It’s probably low did you mix rings up? Have you checked valves?

[@RyansGarageUK]

Hi, I dont think the rings are in the wrong order as when they are in the same sequence that was agreed was correct when I first fitted them, but leaking valves are a definite possibility.

[@gbjeppm]

HI Ryan, I just watched this again. Did you inspect the pilot/idle jet under the rubber plug next to the main jet, as you did not show it? Make sure that any fuel passages to the pilot jet are clear. That will stop it starting.

[@RyansGarageUK]

Hi Matthew, Yes and No. I understand this jet can't be removed so I only gave it a good spraying with carb cleaner. Although I'm going to check that again as you are not the only person to mention this. Thanks. Ryan

[@gbjeppm]

@@RyansGarageUK If there is a slot in the top of it, it can be removed, some can, some cannot. Either way you need to make sure it is clear. Also fuel needs to get into the area underneath it for it to be sucked through on the intake stroke, somewhere there must be a fuel inlet passageway that needs to be clear. I cant remember exactly how it does it though. Best of luck.

[@gbjeppm]

More than likely there is a tiny fuel passage from the main jet to the pilot circuit that needs to be cleared.

[@edkorff7563]

Hello Ryan, I do not understand why you do not put the patrol tank on and connect the carbs when starting. Also i wonder if jou mount the pistons whith a lot of oil. You can still put oil in the cilinders and leave it for a night. I am from Amsterdam and have a CB400N from 1981. I have done a complete overhaule with a friend of mine. This winter i am going to change the clutchplates. I follow your efforts with great interest and hope you will succeed soon. Don't give up.

[@RyansGarageUK]

Hi Ed, the tank needs to be carefully cleaned out as it had very old fuel in it before I can use it, so was waiting to strip paint and clean inside tank as one task. I will try adding a little oil to sit for a while and test compression again. Good luck with your own bike. Ryan

[@edkorff7563]

Maybe you can use an old jerrycan for temporary use as a petroltank to hang over the bike or a plastic bottle.

[@edkorff7563]

Hi Ryan, here Ed again. I would not bother much about the startermotor. Because you can start the motor quite easely with the kick starter.

[@edkorff7563]

I can not wait for another try. Good luck.

[@RyansGarageUK]

@@edkorff7563 Hi, unfortunately my bike was the model built without a kick start, otherwise I would have been trying that first 😬

[@matthewharmer1656]

You should put the rings into the cylinder bore without the pistons and check the Gap . Piston rings also loose their elasticity/flexibility to seal to the bore. For how much rings cost why not buy a set? It would be worth to take the cylinders piston s and rings to an engine machine shop for advise, also they could check the cylinder head out or they could cut the valve seats.you really need 100psi per cylinder to get going...

[@RyansGarageUK]

Matthew, these are new rings and I have tested the end gap as you describe in a previous video. I may end up taking it to a shop but only when I've exhausted trying to sort it myself, as I want to learn. Ryan

[@edkorff7563]

I should recommend to taken it to a shop because if the gap is to narrow it can cause much dammage.

[@RyansGarageUK]

@@edkorff7563 thanks Ed, when I did test the ring end gap it was within the tolerance shown in the workshop manual.

[@matthewharmer1656]

Check for bent valves, a tiny amount is hard to see,but can give low compression when turning the engine over , a machine shop can check them!! Good head gasket properly torqued down? Treat yourself to new spark plugs,

[@jimbo9310]

Ryan I really feel for you, I was so hoping that the compression would have been higher. Your methods are great and I am learning so much thank you. Have you checked the head and valves for hair line cracking and valve stem wear ? You could be losing pressure via those areas. Also what is the actual compression reading supposed to be? You seem to have never had over 100 psi Good luck with it and definitely do not give up. Oh yes just remembered after reading other posts, when I start mine it was best just to have a touch of choke and barely any throttle

[@RyansGarageUK]

Hi, thanks. I think the readings of a healthy bike should be 150psi+. If I need to strip the head again, I'll try to find a way to pressure test it. I'm hoping to get back in the garage later today and I've got a few more steps planned which will definitely take me closer towards it running, but I don't know if I'll seceded this week or not. Ryan

[@kihestad]

Uhh, really stubborn beast of an engine u got there 🥴 could it be that you have the wrong set of rings? Did you measure / compare the thickness of them against the original ones? Remember they will expand slightly from heat because of friction. Could it be that they move freely when fitted on a cold piston, but when you start to turn over the engine the friction make them expand just enough for them to get stuck again? I noticed the first reading looked promising at the start, then the compression readings stopped increasing very suddenly. On next cylinder it was lower readings, because the rings where already stuck? Perhaps you need to take off the cylinders again, to check if the rings once again has got seized?

[@RyansGarageUK]

Good points. I didn't measure the thickness of the rings, but they felt very similar to the originals and once I cleaned the piston they felt free. I may check them again when I remove the head to reseat the valves to be sure. Thanks. Ryan.

[@timparker9235]

Hi Ryan, I’ve reviewed your video again from about 18 mins to 20 mins. You got it started with oil and easy start in the cylinder, and then it almost went again, it wanted to but not enough fuel to keep going plus it lost that little bit of compression as the initial oil in the combustion chamber burnt off. I think the key is getting it going and keeping it going to let those rings bed in and improve the compression, then it’ll be easier to start - sorry if that’s obvious, just thinking aloud. You’ve got to get a carb kit, I’m positive - apparently allens performance ltd do the best ones in the UK (cant put a link in - youtube stops me) then with new plugs, bit of oil in the combustion chamber, easy start and you’ll be away. Also, look at this video from 43:10 - the starter sounds waaaay healthier than yours kzbin.info/www/bejne/oZqwfnufpLmDqZo

[@RyansGarageUK]

Cheers Tim, I'm putting plans in place to work on carb, fuel, plugs and if necessary Valves and rings. Hope to have everything in place by next weekend . Fingers crossed. Ryan.

[@lyndonwebber1389]

This was painful to watch .