Rebuilt 450cc Dirt Bike Has Major Problem (What Went Wrong?)

[@mattdogg02]

I appreciate the 'Previously on' segment at the beginning to recap where we are

[@gb3450]

Yeah... I basically can't tell tear down from build videos. You figure he would label them.

[@Michael_Koeppel]

3:21, anyone see that nut or something fall on the ground? Lol Good luck Joe!

[@johnekhaos]

The one thing I love about this channel, is the garage slowly filling up with bikes and such. Kidding. I always learn something.

[@calviopus]

Unrelated to the video, mostly. But every time your phone “dings” I check to make sure it’s not mine, as the volume is about the same. Haha Really informative videos by the way. Keep it up.

[@PhunkyChikin]

Nice work. Some years ago I bought an old 84 XR 250R that smoked. Replaced valve stem seals, still smoked. Removed piston and found cylinder walls scratched. Cylinder head guide broke, so needed new guides. Local race shop reamed the new guides with existing valves. Lapped valves. Rehoned, ball honed cylinder, and installed new oversized piston and rings, and it ran good, no more smoke.

[@rinferno1]

My experience is when you let off the throttle and see smoke its valve seals. Also if its sitting awhile and it smokes on startup then goes away, it could be valve seals. BTW when you tested the valve seals the wear is usually on the stem not around the base, since those are umbrella type of seals. Love watching your videos !!!

[@rollafatonedude]

Was going to say tge same about coming off throttle, guides and seals would be the fix here i would say, be worth checking the diameter of the stem of the valve

[@oldgreybeard2507]

I had exactly the same thing many years ago on a highly tuned totally rebuilt mini engine. The valve seals had been replaced but there was smoke when revving. Head off again and one inlet valve seal was leaking. Replaced it and it was fine. Just a dodgy seal.

[@prestcoldandy910]

It looks like he may have a twist in the dongle spring , buy a new one fit it an that bike will be spot on like new

[@clintonpaul3516]

I just went through this on the same bike . 05-06 had 5mm valves and 4.5mm valve seals , 07 had 5.5mm valves and 5mm valve seals . Mine was mis matched , threw in vertex piston and ring set with gap at 14 thousands and swapped and valve seals for correct OEM and repacked muffler , good as gold now .

[@anthonygaroutte809]

I like the quick recap in the beginning of the video!

[@baby-sharkgto4902]

Man I have been following you for years and it’s awesome to see how far you have come! Pro tip; if the valve seals are going to leak they will leak in between the seal and the valve, probably not in between the seal and the head as you tested 37:30

[@AliasTekTV]

It's possible that they can leak between the valve guide and head as well if there was any work done on that. If there isn't oil in the carburetor body or the intake boot then it has to be the seals or the crankcase is blowing it up there.

[@808Sometimes]

You are changing the used bike market. I am more apt to buy a model in which you have done a trouble shooting video. These videos add value whether you are buying or fixing to sell. Thank you!

[@darkiee69]

You could buy almost and model and follow the steps he takes troubleshooting on another, similar, engine. they're all pretty similar.

[@markturner2646]

Hey Joe just to be on the safe side I would go ahead and lap the valves it only takes a few minutes and it may save you from having to tear it all back down again!!!! Keep up the good work

[@grandprixgtpjy]

I was just going to type the same thing 👍🏻

[@jaime7890]

Better check if they are Titanium valves first. You do not want to lap titanium valves as the hardening coat wears off and then they only last a couple of hours

[@FourRingsAuto]

@@jaime7890 came here to say the same.

[@TeunS133N]

​@@jaime7890 perhaps previous owner did not know this

[@highcountryadv9828]

From the manual "CAUTION Do not lap the valve to the valve seat, using the grinding compound. It will come off oxide film treated surface of the valve" Granted the english isnt very good but they clearly do not want the valves lapped.

[@paulcunvin1800]

I really enjoyed that, it was starting to look like a real mystery! nice and thorough work there, looking forward to seeing it running properly in the next video, I bet its a proper ripper with all those fresh components

[@luuk-out-below9804]

I always enjoy the teardowns and your diagnosis! But no Vinny 😥.

[@dopeman420]

Why do people care about other peoples dogs?? Wtf is wrong w you who the hell cares

[@ftsfrosty2]

Protest until Vinny back 🐕‍🦺🙏

[@luuk-out-below9804]

@@ftsfrosty2 Maybe he's just on Xmas break?

[@jchavins]

Most youtubers haven't figured out that on these 4 strokes when your going into the engine its usually only 4 or 5 more bolts to just pull the engine out and work on it on the work bench. I used to do this on 250f and 450f Hondas and Yamahas.....If you aren't looking at the piston and rings (like working on transmission) you can slide to piston down just enough to remove the wrist pin leaving the piston inside the cylinder....

[@mattcollins3572]

I had this happen. Not seals. Oil ring bad and not honing and not breaking in with non synthetic oil. My guess. Love the suspense on this one. Can't wait for next video. Cheers.

[@metrocaptain]

Nice detective work. I'm learning something every video about working on small powersport engines. Love the vids! Keep 'em up, Joe!

[@fifteen8]

Enjoying your vids. My ASE Master Tech uncle (RIP) taught me about cars: smoke all the time = piston rings; smoke on startup/acceleration/deceleration = valve guides (or seals), less often the seats.

[@TheDoozie43]

Pain in the butt, but sweet modern bike for $1500 plus parts! Happy New Year Joe!

[@tomdombrovski432]

Great video Joe! No matter what you are working on you seem to make it interesting and you are so humble about it

[@michaelovitch]

When running ,you have smoke when blipping the throttle,and less at full throttle. When blipping the throttle,you have high and increasing vacuum in the intake,and very low vacuum at full throttle. High vacuum will cause oil to pass through the valve seals if they leak,and way less when full throttle. Worn rings would cause blowby and oil would escape through cranckcase vent,and burn more at higher throttle,since the increasing cylinder pressure would increase leakage.

[@Cajundaddydave]

Very thorough teardown. It seems like 9/10 times if the bike won't start and the timing is right. Check... that... carb... completely. Something is fouled. A simple issue that many overlook.

[@roberttdubel]

Have to check valve guides for play as well

[@paulbarlow8286]

Great content! Your work flows very well.

[@kochykoo]

You know If you start getting yourself in a habit of doing leak down test you save yourself a lot of headaches and money... Despite everyone saying you only do it for the content. Diagnosing problems and knowing how to look and narrow them down without spending useless money is content...

[@douglasr.c.5622]

*useless.... unnecessary ?

[@jimw6991]

Please elaborate how an upside down top ring would show in a leak test? Blow by and valve leaks between head and valve but would you find stem seals? I don't think so. I think his diagnostic skills are fine.

[@kochykoo]

@@jimw6991 funny how you got it all figured out. You say it's pointless and useless but upside down ring would show it's self threw the oil fill and the crank case breather. If he had bad seals and gaskets gaskets it show it self exactly in the areas it should. Pretty simple to find what you need. Don't tell me it's useless and pointless because you don't know how to talk and listen to an engine. If take was a 2stroke engine it be blow the air right buy the piston and out the intake and the exhaust at the same time and anything would show it's ares exactly where it should.

[@undecodable6145]

I was stressed for the problem but now, what a relief

[@abbyson2834]

i watched the first video and i only now Noticed it.. Did you see that it was still Leaking at 1:00 ? There is something Dripping out of the Engine. Nice Video :)

[@pats6381]

You may want to double check the oil ring tension to make sure it has pressure on the bore. Didn’t look like much on the video. With no intermediate ring the oil ring performance will be important. I think you do a great job!

[@DRZWhisperer]

Hopefully you rebuild that blown out shock as well. Its no fun riding on spring alone

[@Johnbruzzi4234]

He doesn’t rebuild shocks,lol

[@78Shovel]

I don't have a lot of experience on dirt bikes, I'm an old Harley guy but an engine is an engine. I didn't notice any cross hatching in the cylinder, maybe just the video and I couldn't see it, but if the seller put new rings in without honing the cylinder those rings won't seat. I'm not ruling out the valve seals and or guides, just pointing something out.

[@johnbernardo4338]

Just another thing you might want to check if there’s a new top end with new rings and piston. Do not run fully synthetic motor oil to break it in. I had this happen on a KTM the fully synthetic oil is too slippery for the rings to actually break in. You need to run regular motor oil for the first hour then drain it and put in full synthetic oil

[@Johnbruzzi4234]

That’s common knowledge for any half good mechanic

[@Deezertillgeezer]

Still a good comment for you tube

[@jayjudd6518]

This is a good one love tear downs. I was surprised on a comment the other day about how many hours are a lot between rebuilds. Just guessing they blow up sooner. Following from the arm chair.

[@rotax636nut5]

I came across a very similar thing once and it turned out that some unknown guy who had been working on the engines top end had mistakenly installed the 2nd piston ring (the scraper ring) the wrong way up, the ring was taper faced and like this did not pull the oil off the cylinder wall when the piston went down the bore like it was supposed to, the engine still ran great but with similar smoke to yours from the muffler. Roland, HT Racing Ltd

[@dennisbagatin4480]

Wondering why the seller would cheap out on valve seals having done all that work but looks like you might have found your problem love the content ✌️

[@ramranch887]

If a shop did it, it would not surprise me... my buddy had a shop rebuild his bike.. took them forever and they used a cheap rebuild kit and the bike was blown up in 3 hours after rebuild..... he ended up having to rebuild top and bottom end on his own... they were willing to fix it but id be damned if I would bring my bike back to them... so short answer is the only person who can guarantee a job done correctly is you....

[@DIYDaveT]

I think the seller had every intent of doing a good job. Bought good parts, etc. The issue is probably knowledge. The seller was probably intimidated by the carbs and thus no desire to tear into them. 2 squirts of ether would have told him it was a fuel issue. But he clearly didn't try that either.

[@666gun100]

I agree.@@DIYDaveT

[@creek_made]

i could watch these all day! TY!

[@JyveKilla]

just a tip for next time, you checked the spark plug and confirmed oil burning in the combustion chamber so oil is getting in before the exhaust. i wouldnt be surprised to see no leaks on the exhaust side. youu need to start investigating on the intake and rings side with that spark plug finding

[@DIYDaveT]

Very methodical. I think these kinds of videos are equivalent to a semester in small engine repair.

[@datograt]

Better, because the students are there on their own volition, learning at their own pace

[@roryk.3568]

Easy way to diagnose smoke is if it smokes on startup and goes awayas it warms upor when decelerating its valve seals. If it starts to smoke as it warms up and continues its rings.

[@voiceofreason9238]

Interesting.

[@bpetnoi1472]

Suggestion for camera work. Most cameras will have focus lock or a manual focus. When you plan to keep the camera in the stand for a time either lock out the autofocus or put it on manual so it can't auto focus. Just a suggestion to help with your video production.

[@862057]

You can get an idea how bad the valve seals are by looking at the lip on the seal and pull the valve out and stick it back in checking if the seal is actually expanding and dragging on the valve stem with some resistance. Also check the oil rings end gap.

[@DenverPolly]

You are one of the best motorcycle mechanics I have ever seen! Always love watching your videos and I have learned a lot from you! Keep the videos coming.

[@Johnbruzzi4234]

Are you serious

[@RDAmidwest]

Back in the Dark Ages of my "YamaHawk" 360 Enduro, we called the Skuzzukis "Inger-Bingers". We adopted nicknames for the brands based on their sound. You can easily guess which bikes we branded "Humda". The only problems I ever had with the Enduro was with defective nuts... the one that twisted the throttle, the one that shifted, the one that never wanted to brake, the one that was supposed to keep 2 cycle oil in the small tank... I thought the nut that held the handlebars failed once but my trail riding partner said that the tree jumped right out in front of me, so... put the nut on crutches for a couple months and then put it back on the Enduro. Good memories seeing those dirt & R/T bikes.

[@markward6076]

Your saving the broken souls of these great stand up bikes. I'm sure they are grateful. Amen.

[@discharge29]

always love watching your vids - grass roots mechanics - great for an amateur like me - keep em coming

[@dwansbo]

I agree with your diagnosis, valve seals are hard and brittle, not sealing to the valve stem. Would have liked to see how they fit the stem. Check the oil is draining from the top of the head properly, too much oil in this area could cause similar smoking problems. Was it an aftermarket barrel fitted by the previous owner? Is there sufficient clearance in the stud holes to allow the oil to drain? Finally the bore looks shiny or glazed. I suspect the previous owner did not posess a honing tool, he didnt have a valve compressor tool either! Some manufacturers recommend a lower viscosity oil during the running in period to allow the rings to bed in properly, again an inexperienced home mechanic would be likely to disregard this advice in the belief that they are being kind to their rebuild engine by using a thicker oil. Dirt bikes are sometimes bored loose, an extra 4 thou is common. This prevents seizures occurring due to the cooling system (radiator) and air filter clogging under racing conditions. A little grey smoke is inevitable, it is the lesser of two evils. Nice bike, makes me want one. Unfortunately I'm too old or so the wife says 😂.

[@AaronMorgan-g9h]

Ring cap on all pistons is diff … ring gap will be on the box. Always go with what’s on the box. I like your work

[@neutonrenda2303]

Wow, such a great engine condition wise, spoiled by valve stem seals. He wouldn't have known though, didn't get past the carb problem.👍

[@mikeolson7188]

Get a set of oem stem seals and make sure the valve guides are not worn out Joe.And measure that piston to cylinder clearance to make sure it is in spec.De-glaze your cylinder with a wiseco honing brush then clean it thoroughly and i woulda used the oem piston,ect...

[@AliasTekTV]

It's not an OEM cylinder. I wouldn't OEM swap it.

[@ek2156]

Wow! To go to all the trouble of rebuilding the top end and not replacing the valve seals?!?! I would think that would just be part of the process, regardless of how good the seals look at that time. Great Video! I bet you will get this 2-stroke.....err.... 4-stroke :D it was smoking like a 2-stroke though lol, back to normal in no time!

[@johndoe3johndoe382]

I have owned a 2005 rmz 450. It was also a major pita to start. The crank went out in mine as well, and not long after buying it. I had to walk it back home like 2 miles, Got it rebuilt and sold it.

[@paulweigle6872]

Very good diagnostics young man. Excellent video.

[@chihuahuaverde425]

I appreciate the follow up videos.

[@markward6076]

I would say I would be stumped. Are you a bike whisperer. It like they talk to you. Kool man.

[@buzzy1011]

It’s a dirt bike. And that thing is a beast…. Just ride it like you stole it… a little smoke isn’t going to hurt anything….

[@christophermilam8028]

Suggestion when taking off valve stem seals. Use a pair of automotive hose removal pliers. The smallest one works best and if the angle isn’t right I have another set I heated up the tips and bent the tips 90 degrees.

[@randalljames1]

as a professional wrench twirler, these videos usually make my skin crawl... you appear to have some master tech skills.... Been long time since I worked on bike engines but I saw that jug after the head came off and though wth... 1" stroke? lol doh..... soggy intakes look pretty suspect.. you should have a leakdown tester

[@davesplace1307]

If the valve seals dont do the trick I think the next culprit would be the piston. Rebuilt a 350 raptor a few years back installed a high compression piston and it smoked. Never knew why until one day I decided to use the stock piston and it quit smoking

[@dirkhuman760]

Cylinder taper and ovality or out of roundness are measured with an inside micrometre or a cylinder bore gauge. When measuring the diameter of a cylinder with a telescopic gauge, the gauge is extended and locked to measure the inside cylinder after which measurements are made using a micrometre. FYI

[@bradley7723]

Central tools made a taper micrometer. All it does is measure taper and not diameter. I've used mine countless times and is is a handy tool.

[@repsollldcain2513]

Mann,i had one bike,it would smoke like crazy,cold or hot ,i was beating my head for over a month and couldn't figure out why,everything i could think of checked out..turns out it was cylinder ovality, the bike was probably overheated and wrapped the cylinder..

[@ryanjohnson1814]

I ran into this once, not seals, but the new piston ring, didn't seal with the cylinder for some odd reason, did a re hone and a new ring. Solved. Top end was new, just never sealed for some off reason.

[@Markomyt1]

Great to watch you work!

[@panueldunuel7449]

Usually if its the valve seals, let the bike idle for a few minuites then rev it out if it plooms smoke its the seals as the negative pressure at idle will suck oil past the bad valve seals. Hence why it was clearing when u were reving it but after idle it would come back

[@rcclassiccrawlers4368]

I’m 99% sure it’s the valve guide seals. Like you said, everything else checks out.

[@navigatorx1013]

The way super hot gas was blowing thru the engine it's a good guess that you nailed it.

[@yaboi6006]

could have bad guides too

[@xx3868]

On a tank restoration channel, the new engine was smoking hugely! and they discovered that a rag had been left in the inlet to protect when all the dust was around. So poor engine was choked off and sometimes you have to check to obvious.

[@186scott]

Before reassembling the head you mentioned that it had been shaved down / skimmed check if the head is actually flat using a known flat service as if it was shaved by hand it may not be flat and even tho it holds it's coolant it may not be able to hold its oil

[@MacRODesign55]

I didn't see you checking if the valves were seating properly. My dad was a mechanic back in the 60's & 70's. He used to test valve seating by putting bearing blue on the valve seating surface and pop the valve closed quickly using his valve "seating" tool on the valve head. (a suction cup on a dowel rod handle) This would show if the valve was seating all the way round and whether or not the angle of the seat matched the angle on the valve.

[@moviezaftermidnight6348]

good thing you got the new head gasket.. that carb looks like one of the sentinel out of Matrix.. good call on the smoking.. I would have left it at oil in the pipe.. good time for a quick hone while you got the cylinder off...

[@calvinbass1839]

Clear & informative. Thank you for sharing. Have a blessed day.

[@ragnarironspear1791]

Hope you and your Mrs had a wonderful Christmas 🎄 🇬🇧

[@pietwagenaar229]

Nice video. How sure are you that the gasoline does not contain (2-stroke) oil (since that could cause smoking as well) ?

[@gregmcclure2640]

Love your videos, and Merry Christmas (late). BTW- I kinda skipped through the routine parts of this video; did you verify that the valve guides are not worn? I might have missed that.......

[@banditshane6706]

The recap at the beginning is a great idea

[@engineeredstrength4102]

While the head is apart you might as well replace the valve guides and lap the valves also. Cheap and easy - do it all once and do it right.

[@marchettejw]

I run a lot of old worn out small block chevys, from what I've seen this do and the seals you took out, they appear to be the cause. I've got one right now that needs a head job because of the same issue, rings are still good (compression is good) but it burns oil at high rpm or free revving.. I say this all the time but sitting damage is way worse than plain old neglect.

[@MrATOMBOMB420]

I'm betting it is the piston you checked the compression ring The compression ring has absolutely nothing to do with oil control you need to check the oil control rings the way to do it is install the oil control rings on the piston take the compression ring off of the piston and then put the piston into the bore and see if it fits snug It's good if the piston slides right down through there's not enough tensile strength in the oil control rings to actually scrape the cylinder valve seals don't leak while the bike is running Val seals only cause blue smoke when you first start the vehicle

[@golden-balls-radio]

Not if the guides are worn.

[@Johnbruzzi4234]

He has none of the knowledge you are talking about

[@golden-balls-radio]

@@Johnbruzzi4234low compression test he did. Either seals or guides or both. Valves were oiled up init 👍🤓

[@bradley7723]

While you have the valves out check for guide wear, no valve side to side movment. Quick and easy while valves are out.🙂

[@ThomasBrock74]

Good job kiddo good job.....Now u just need a new rear tire and you are in business my man!!!

[@DblK-BMorphs]

I’ve been wanting to know what the issue with the smoke on this one is.

[@DblK-BMorphs]

Thinking rings weren’t installed correctly. Let’s see how close I am!

[@jameswick8358]

Valve seals?

[@billhartsfield424]

No mention of valve guides. Perhaps they are worn. Seals won’t fix worn guides

[@chihuahuaverde425]

@@jameswick8358 👍

[@kilatore667]

Carb or oil over fill my bet

[@davegeorge7094]

You can check IN valve seals without disasem. . Make a hose that seals to head intake and blow air at TDC it should be air tight. Suck test too afterwards..

[@YGELLYPIKER]

I hope you have a happy new year chap love your channel 🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿

[@YouriCarma]

Yeah, those valve seals should have been replaced in the rebuild and not doing so was a mistake but a nice lesson for everybody watching this.

[@AShearer76]

Another great video. Can't wait for the next one.

[@jd-it4on]

As a engine builder my self ,I really wish u would stop using those gloves while you are inside the engine. I have seen people destroy engines by using those and something transfers to a part or what not. Just saying . Anyways good work ,keep up the awesome videos ,I always like seeing kids like this ,with more and more people getting in to these type of things.

[@scott729]

Joe at this point there is really not much more it could be. You covered everything else.

[@raptorgamer8878]

A 450 for 1500 what a score no matter the issue used going 6k plus either way you profit from it when your done. also the website is down to buy T-shirts etc. could you check on that thank you again for the videos i watch them all..

[@ProjectsWithPat]

hey, next time with the head still on the machine. Take the carb and exhaust off. Look down the runners of the head both intake and exhaust, looking at the valve stems. you will be able to tell if the valve seals are leaking because the valve stems will be wet. You could have noticed that before you took everything apart.

[@MrJmattr3]

Very good advise!

[@anthonyguerrera4196]

First thing you should do is check the oil! 😂 Keep up the good work!

[@RAKINAUS]

Hey mate , good work on the tear down video, I think you found the smoking gun with the oil on the inlet valves! Just check the guides, lap the valves and new seals you should be right. Good video.

[@christophersherratt7299]

Suggestion for when you have cleared out your oil and water catch trays put some strong Neodymium magnets in them and put on your drain plugs catch all the metal bit lol 😮

[@EmxBrandon]

Check the valves in the valve guides for any play. If the valve is slapping around side to side and the surface of the valve is getting scuffed up where it makes contact with the valve seals, it will destroy new seals immediately. Might need new intake valves and valve guides!

[@kentuckyjohn6149]

Are you able to replace the guides in a bike like this or do you need a new head?

[@bren42069]

Amazing, little oversights really screwed this bike up

[@jakevans8352]

GREAT CHANNEL all the BEST from WALES UK👍👍👍

[@alanparis7256]

Go figure 😮 owner had 1000 bucks into it but didn't think to replace 20 bucks worth of valve stem seals 😮 and did he have head skimmed leaving the valve stem seals in place 😮

[@daveroe6480]

Surprised someone would spend so much on repairing an engine, but left the old valve seals in !

[@DailyDoseOfMotorsport007]

I've been watching you for 2 years and i wonder how are you so good in repairing Did someone show you or?

[@jakeslouw3416]

Those models had an issue with excessive oil going through the crankcase breather I think? This would go back into the inlet and foul the inlet valves as you saw when you did the strip down. The later models had a reed valve in the crank case to stop this happening.

[@Rfrank566]

Hey joe I love the your videos I have learned a lot from you your videos so keep up the good work and videos and I hope you had a great Christmas

[@nickhayes5471]

I can’t help thinking how cold that weld bead looks on the frame, there’s a clear line separating the the toe of the weld and the parent metal 🤔

[@peazweag]

Joe how are the valve guides? I noticed you never mentioned that in your video. Love your videos

[@dubiousf00d]

Gunna be a solid machine soon enough 🔥 one suggestion is to replace the valves along with the seals just to eliminate any surprises down the road.

[@jozsef6453]

The short recap is cool at the start of the video

[@swamprattRich]

Hey just wanted to let you know been watching your videos for a while now have to say as a master automotive technician for over 45 years I’m impressed by your knowledge, but can I make a suggestion since your probably earning a good salary from KZbin it be to your best interest to invest in tools related to your work one of the first things I’ve noticed a good parts washer be cost effective versus using brake cleaner, and may I add relating to this particular video removing the valve seals with a straight needle nose pliers will damage them every time they make needle nose pliers with different size circular tips that works great for removing them as well as hoses etc… I love to help out in any way I guess I can start by clicking the Subscribe button 👍🏻