Honda XR400 Piston Up Top End Rebuild Tutorial

Valve Lapping Tool: amzn.to/3oZJL6c
Valve Lapping Compound: amzn.to/3bIS4Q4
All other parts were purchased from Rocky Mountain ATV/MC
Check out my website for merch and informational articles: www.decentgarage.com
Check out my other videos: / decent1stgen
Follow me on Instagram: decent_garage
Follow me on Facebook: / timstevenson1
0:00 Intro
1:21 Tear Down
15:28 Cylinder/valve inspection
18:15 Valve Lapping
24:14 Valve Train Install
27:07 Valve Seat Testing
29:08 Replacing Cylinder Studs
30:26 Setting Piston Ring Gaps
34:14 Installing Piston and Cylinder
40:36 Cam/gear/chain Install and Timing
52:18 Will it Start?
Valve Lapping Tool: amzn.to/3oZJL6c
Valve Lapping Compound: amzn.to/3bIS4Q4
All other parts were purchased from Rocky Mountain ATV/MC
Check out my website for merch and informational articles: www.decentgarage.com
Check out my other videos: / decent1stgen
Follow me on Instagram: decent_garage
Follow me on Facebook: / timstevenson1
Contact Info
Email: [e-mail]
Address: PO Box 154, Payson UT, 84651
#xr400 #topend #DecentGarage

[@decentgarage]

This was a fun process to learn and I hope this video helps give you the confidence and inspiration to tackle this project!

[@Pedro-oy1be]

Genio ! Gracias por el gran video ....abrazo desde Argentina

[@herlesmontano1945]

Excelente

[@jeremywynne5263]

This is, by far, the best and most comprehensive tutorial I’ve ever encountered. Thanks for the time and effort that you put into creating this video. The camera angles, lighting, and editing made it a joy to watch, and your description of the process made this project accessible to those of us who would otherwise shy away from a project like this. I learned a lot. Well done!

[@decentgarage]

Thanks for that feedback. That really means a lot 👍

[@peteratmore3015]

This video is GOLD!!! confidence gained to tackle my xr400. thank you

[@decentgarage]

Thanks Peter! Glad it could help. It's a long video but I tried to make it comprehensive so that anyone could follow along through the whole process.

[@owensbama1923]

Awesome video man. Perfect explanation. Didn't over explain or under explain. No bs. Straight to the point. Just a really great video. 👍

[@decentgarage]

Thanks for the feedback!

[@mikpalffy9107]

I didn't read back all the comments but I hope someone commented on top dead center is suggested to be reached by only counter clockwise rotation. Anyway I loved the video. Lots of information in one hour. My XR400 has just lost compression. I thought I need to take it to a master. Now I am thinking I am going through this step by step tutorial and do it myself. Big thanks! 🙏

[@Unusual-Assumption69]

Piston rings should be gapped alone (i.e. not on the piston). You must press the rings into the cylinder and level them with the piston head and check the gap. It is done this way so that you can gap them correctly under the compression of the cylinder. When you gap them as you did on the piston, when pressed into the cylinder the gap will close up and therefore they could be too small.

[@paulh.5691]

Remarkably clean this one is underneath the rocker cover. Also pleasant to see, you just using your bare hands, not too squeemish about oil and shit. Seeing so many people wearing gloves when working on bikes or cars I almost began to question myself. Otherwise, whereas I could call myself a trained mechanic, I do think you are doing just fine, cleaning everything properly and none too ham fisted either. And this week I bought my first XR400, a 2001. Here in The Netherlands there weren't many for sale, just a few. Mine doesn't leak or sweat any oil and runs like clockwork. Used by a bloke who would organize and guide relaxed off road tours in France. Bike's been very well taken care of and never been thrashed or hard raced.

[@liamboyd3499]

Great video, doing my 2000 XR400 now also, definitely got some great tips 👍

[@jonnybroomhead]

Didn't have to look at your contact info to know you were from Payson haha. Your accent tipped me off, and the RMATV bag in the shot comfirmed haha. Great video! My bike burns oil on startup. It's got over 1,000 hours on all the original top end. I'll probably ride it through the summer and rebuild the top end this winter. Great video!

[@deanhotton824]

Wow, I am impressed how well you teach ppl. You describe everything perfectly. I am restoring a Honda XL250S that I got given and this video will really help. Thankyou so much. I will become a patron to your Chanel as soon as my wife and I finish with covid 😀😀😀

[@Raddudewithabadtude]

Thanks for the time and effort that went into this tutorial!

[@itzjonah]

That was an excellent video bud. I’m about to do a big bore on my ‘01 and came to this video for reference. I aspire to be this thorough and instructional in my future videos. Liked and subscribed!

[@trevorparker20]

Very detailed video! Great tutorial!!! Thank you

[@decentgarage]

Glad it was helpful!

[@hemidart7]

Great video! That bike is in EXCELLENT shape, near mint!

[@gbg888]

Great video! Thanks for all the great information and tips. My hat is off to you for starting an XR 400 cold in Crocs!!! You deserve a medal... or a foot massage haha.

[@robrambo6968]

Great video. Very well made and explained on the process. Nice and clean also. Great job. You have done your homework!

[@decentgarage]

Thanks Rob!

[@HDsauce32]

Awesome video perfectly filmed and perfect amount of instruction with no BS. Thank you for making this

[@DylanTaylor-rs3qz]

Most informative and clear cut tutorial I've come across on any sort of maintenance/repair. Thanks a ton!

[@artiexr222]

Awesome informative vid paced just right the 50 odd mins flew by thanks for posting.

[@decentgarage]

Thanks for the kind words!

[@samcssolutions]

Well done! Like a pro.

[@decentgarage]

Not quite a pro but it worked!

[@chuckingram5966]

I could never ever in my life go that deep into an engine of one of my toys to repair it and not modify the performance output of it! Oh my God I see all that work done and the only new parts are the piston rings and the pistol. I guess I'm just old-fashioned I like to go fast in the dirt and with the motor torn down that far I'm putting it back together with a higher compression piston, larger valves and valve seats a performance cam with matching valve springs and throw a mikuni carburetor on it then and then top it off with one of my custom made exhaust systems.

[@decentgarage]

With this being my first time ever tearing into an engine like this I didn't want to get in over my head so I went with a stock rebuild.

[@colinrout4139]

Hi from Aus! thank you, gave me heaps of confidence to do the top end rebuild to mine. I am doing a ground up rebuild!

[@olivierbarral7929]

Thank you very much! This video will help me a lot for mine that needs to be rebuild concerning the cylinder... Big thanks from France ;-)

[@decentgarage]

Glad it helped

[@project4stroke876]

so glad u made this video man!

[@decentgarage]

Glad it was helping! Break in video will be out next week

[@AloneInTheCheese]

Nice dude, thanks for the vid. So happy that it started, I saw your frustration there for a moment! :D

[@decentgarage]

Yeah, I was really disheartened and worried at first. But it starts way easier now than it did before the rebuild.

[@AloneInTheCheese]

@@decentgarage Yeah also looked like REALLY cold outside, so even a perfectly tuned carb would take some time and a few kicks. Keep up the good work, cheers from greece!

[@Oddman1980]

I remember having to make a ring compressor for my DR650 out of a dryer hose vent clamp and a plastic fountain drink cup. Thanks for the detailed video, a friend has asked me what would be involved in rebuilding the top end of his XR400, and now I know. This looks even easier than my DR650.

[@lastfanstanding999]

whenever grinding valves remember to rotate your tools in between grinds otherwise your only working 1/3rd + - and not completing the needed full revolution valve grind.

[@decentgarage]

Yeah i guess i should have mentioned that. I did that but figured it was pretty self explanatory. Thanks for pointing that out.

[@lastfanstanding999]

@@decentgarage I'm watching you DG ! 😆😉

[@dannyfubar3099]

An Excellent Post, Thank You for Sharing!

[@decentgarage]

Glad you liked it!

[@alanchan1772]

Thanks for a great top end rebuilt

[@decentgarage]

Glad it was helpful 👍

[@kahidunn7907]

What a great tutorial, thats given me the confidence to give something like this a try

[@decentgarage]

Thanks! You can do it

[@roofaloof]

Thanks for the video! Really informative and explained well. I have a 1996 XR400R I'm restoring. I may have to do a top end rebuild.

[@jasonboyes5913]

Mate I bought a Xr400sm 2008 that had the loudest piston slap ever. This video was by far the best ever I could find. Completed it today and with o e push of the button she fired straight up. THANK YOU wouldn't have had the confidence without this.

[@decentgarage]

I'm glad it was helpful! Thanks for letting me know 👍

[@richardlyons5861]

way to go guy.i have done that same bike twice,feel your pain and glory.nice job

[@decentgarage]

Thanks Richard. It's run flawlessly ever since.

[@andycockersole8739]

That is an excellent video, watched every minute and learned a lot. Thank you very much. Am going to save the video cause I have got an XR400 and might need it one day 👍

[@decentgarage]

Glad it was helpful!

[@mackwalls866]

Just a comment for the numbers.. liked and subbed. You deserve it, thanks bro.

[@decentgarage]

Thanks man! 👍

[@mdemartile]

Great tutorial. I did this job with my dad as a teen on our 79 XR250. I remember making a cardboard template for the valve cover bolt length discrepancies.

[@sebastiencaine9781]

Great vidéo, thanks so much! I'm french and I don't speack english very well but I have very like your works of this Honda 400 XR; I will do the same with mine... Thanks!

[@TommyTucker0]

great video, really well done

[@decentgarage]

Thanks tommy

[@KimKim-oo2up]

Ive actually saved your Video into my phone. Thank you so much fpr this vid. Doing my xr400 myself as well. :-)

[@purpleether5405]

Great video. Very precise which you need to be.

[@decentgarage]

Thanks!

[@dukesilver2019]

Thanks. Really good tutorial. Make more.

[@decentgarage]

Thanks for the comment. I'm almost done with the break-in video

[@ingeebeltoft]

Hi man. Great video. Tips from me after rebuild the head on my old XL 500R. Put the piston into the sylinder before monting to the engine. Much funnyer job with the rings 😎

[@dennismacwilliams196]

Good work and well explained also. Thank's

[@decentgarage]

Thanks!

[@joshj1140]

was waiting for the 2nd circlip to fall into the bottom end, you took the towels out for some reason... great video

[@EstebanEliasAguirreMartinez]

Great video the best

[@leclemsdu83]

Top tuto, le meilleur pour les 400xr, merci beaucoup 👍👏💪

[@decentgarage]

Glad this was helpful!

[@gusocon319]

Wow Good job !

[@decentgarage]

Thanks!

[@14mviews25]

thanks so much for the good tutorial

[@decentgarage]

Glad it was helpful!

[@rideaustralia4479]

Keep those rags stuffed around the rod , until circlips are installed, easy to drop one in!

[@decentgarage]

Good call!

[@chiliboom6140]

This is great my friend! I have been looking at getting an XR400 so this vid popped up. The only stuff I am not confident or don’t feel taught about is the machining of the bore and knowing where to take it or if I’ll need a different piston head or something. That’s the only “scary” part out of this video. Otherwise you made me very confident with the rest!

[@justice6436]

I've got the same bike, great video!

[@decentgarage]

It's a great bike!

[@migliaman]

Hi DG awesome video, am now about to buy a 2003 xr400, and its low mileage at just 6000 so hopefully it will be a blast?! I will love tidying it and putting my stamp on it! wish me luck! 🙂

[@kingaire165]

Right on! Good video

[@decentgarage]

Thanks!

[@NVSRides]

Nice video!

[@decentgarage]

Thanks!

[@mickjones2857]

I figure things out. What a guy.

[@decentgarage]

Glad it was helpful

[@armandogardoni892]

Thanks to this vídeo the mecánicos can't lie to me or doing Bad jobs to me, greetings from Veracruz México 👌👌

[@andrewpeeters1288]

Great video. Thank you.

[@decentgarage]

Glad it was helpful

[@1176hambone]

Thumbs up! Great video!

[@decentgarage]

Thanks 👍

[@alexandregiraud1761]

Hello thank you for your video it helped me understand how to rebuild an engine of my 400 xr.

[@decentgarage]

Glad it was helpful 👍

[@teijespratt5926]

Awesome tutorial! you really covered all the bases, but i do have a question; when you first take the valve cover off, after you set TDC, all of you lobes are upright, but when you re installed your cam, still in TDC, you faced all lobes downward. i must know why?!?! it just seems so wrong! but if you can help me understand, maybe i missed you rotate to BDC or.... and help in understanding would be much appreciated! thanks!

[@aspilotro8959]

What a great video. Wow

[@mattmiller8386]

great video

[@decentgarage]

Thanks Matt!

[@253GQ]

Very good video bud. Super helpful. You just need to learn how to kick these bikes... build up comp, then just a slight push past TDC...kick

[@decentgarage]

Thanks!

[@guitarplayerlp7018]

I did a top end rebuild on mine a few years back. just needed a light hone and new rings as it was using a fair bit of oil and lacked compression. Upon disassembly I noticed the ring gaps on mine were all very close hence the excess oil consumption. I set them the same as you did and the compression difference was night and day. I also just did 3 days riding in the Vic High Country and it its still got heaps of power and used no oil so a happy camper here. Honda's biggest mistake was stopping the manufacture of these 2 wheeled tanks

[@rafaelchoque3080]

excelente trabajo. felicidades

[@eddyb6790]

Great video. Maybe reinstalling the manual decompression mechanism would help with starting. It has both.

[@genavil]

gracias por tu video. me ayudo mucho a ajustar el motor de la xr400. gracias.

[@decentgarage]

De nada chamo! Me allegra que te ayudo.

[@ramper50]

great video man! I will say though, eyepro when working with those valve springs!

[@decentgarage]

Yep, i wear my eyepro now for sure! Thanks!

[@Builditathome-Restoration]

Amazing video iam in the exact same process right now and i also make videos about it. Good luck man ive subbed

[@decentgarage]

I'll look forward to your video too!

[@jeffahearn]

Thanks man- good tutorial. One question; because you didn't have a cylinder stud torque setting, did you use some loctite?

[@scottdilalla]

Amazing video..thank you. Where is the best place to get OEM valve guide seals and piston and rings. I didn't see it on the Rocky Mountain site. Thank you

[@tkmusa5211]

Excellent!!!! Thx!

[@decentgarage]

No problem!

[@ericjohnson9080]

Great job! What was the original issue? Valve lash adjustment?

[@bernardodieta2154]

Muy buen video, sigue asi !!!!

[@decentgarage]

Gracias chamo!

[@Courior1200]

The only thing you forgot was thread lock on the cam bolts. They are known to back out and destroy the top end :(

[@decentgarage]

Shoot, i may pull it apart real quick and add that. Thanks for the heads up 👍

[@derrickcosta2459]

Having trouble finding where the oil lines connect on the back end , let me know if you have some type of diagrams

[@davidwilliamson9162]

Would like to see the decomp system please cool video

[@decentgarage]

The auto decomp is pretty basic. Just a dowel in the head that hits a unique lobe on the cam to decomp

[@benkanobe7500]

Since the Valves and Seats looked good and there wasn't a hole in the Piston, what do you attribute your lack of compression to as it was the reason you did the Top End??

[@benkanobe7500]

Did you send the Piston out with the Cylinder so the Machinest could get the perfect fit? Did you use a Factory Honda Piston? Did the Piston come with the rings?

[@lunaperez7899]

Hey man my Honda Xr400 the kick starter got stacked and don’t move what you recommend me

[@rotorhawg8052]

I have the same bike, what is the "special tool" for removing the spark plug and where did you get it? Thanks

[@obsessedwithcars219]

dont forget to rock and valves back and forth to check the condition of the guides. and make sure the old valves arent concave where it seats. if your this far i wouldve got all new valvetrain

[@lanes58]

Hi. I have this same bike. I cross threaded the spark plug while putting the new one in. Now I’ve lost compression. I tried using a thread chaser but to no avail. Is there an alternative way to completely pulling the head off and putting a heli coil in? Thanks

[@kc135cruechief3]

Very very very well organized and presented!!! I have the occasional blue smoke on mine and am going to do the same in the near future. How much of an overbore did you go with and what brand(s) of parts did you use?

[@decentgarage]

I had it bored at .020 over for an 85.5 mm piston.

[@gti20vtMarcel]

Nice and clear vid!, one thing; no Loctite on the cam bolts?

[@decentgarage]

Yeah a few people have mentioned that. I'm going to pull it apart and Loctite those.

[@HotTubOfSexy]

Beautiful job! Did you ever find out what the ticking noise was at the end?

[@decentgarage]

One of the exhaust valves was way out of adjustment.

[@jeckeymekayten7938]

Looks great mate,good job! say,Can you ride on it comfortably for more than an hour straight on a highway-(given you would have a wind shield,a good seat..) at a speed of 70-75mph\100-110kmph!?too much Vibration!?Can the bike endure it!?thx

[@decentgarage]

I rarely drive mine over 55 mph. It can but i use it more for single track riding so i just don't.

[@Hapfletcher]

Pretty impressive instructional video for a guy thats never done one before. I learned a lot. I have two questions. 1. from your experience are you lead to believe that this same information can be used on all the other XR 250, and 500's? 2. At the time of filming, what was your total cast to do the rebuild?

[@decentgarage]

1. The xr250 should be virtually identical. I cannot say that with much certainty for the 500 though. 2. It's been a few years since I did this but I believe it was under 500

[@henrycole8705]

The RFVC motor only drawback is it runs hot. add an external oil cooler. It solves the problem

[@armandogardoni892]

I can't see the diference between My two top pistón rings please help me

[@pablodelafuente5581]

Excellent tutorial, then I will have to change the piston and rings to my 400, it is 1997 and the engine has never been opened. Greetings from Talca Chile

[@decentgarage]

Hola Po! Que fino que es de Talca. Yo también he vivido en Talca. Me encantó esa ciudad. Gracias por comentar

[@pablodelafuente5581]

Hola, hablas español, que gran sorpresa que conozcas Talca, de donde eres?

[@decentgarage]

@@pablodelafuente5581 ahora vivo en Utah. Si po. Viví un tiempo en Talca, Parral, y Curicó.

[@pablodelafuente5581]

@@decentgarage Nunca pensé que siquiera podías conocer Chile, gran sorpresa. Que hacias acá??

[@TheMrRyanV]

Be careful rotating engine clockwise like that ! I know it all worked out, but you stood a legit chance of skipping a tooth on the timing chain- as well, use loctite on cam / timing chain bolts as well as the cam caps. As well, when installing rings, ensure proper end gap 👍🏻 now you know !

[@thusharachandana8543]

Check the valve comprasser need more

[@jamesc6137]

Crazy how it all the sudden lost compression…Would hate to find out it was only a stuck decomposition lifter on valve…or something involving the decomposition system. Great video

[@decentgarage]

I checked the decomp system during tear down and it was all functioning correctly. I still have no idea why it lost compression out of nowhere. But it's still going strong on the rebuild 👍

[@matthorndl6003]

make a cardboard cut out and mark where bolts go on the cardboard, put bolts into the cutout

[@nikosbiologytsiouplis1895]

how much money in parts and boring did you payed? good job!

[@keithtaber1712]

Why did it lose compression?

[@alleneire2197]

I thought you spin the crank anti clockwise to get TDC. Do is make any difference going clock wise?

[@decentgarage]

It can be done either way but anti clockwise is easier

[@SteezerZimmer]

did you rotate the engine clockwise? at 4:45? im pretty sure your supposed to rotate the engine counter clockwise.

[@decentgarage]

It's a been a few years so I don't recall. But, it has run perfect ever since so whatever I did worked 😁

[@frothyshoes]

Just bought one of these, this video is going straight into my favorites. Thank you! Also, kicking it over in Crocs like an absolute BOSS!!!