Honda XR400 Piston Up Top End Rebuild Tutorial

[@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.

[@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.

[@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!

[@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 😎

[@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! 🙏

[@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.

[@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 😀😀😀

[@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 👍

[@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!

[@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.

[@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.

[@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!

[@Raddudewithabadtude]

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

[@DylanTaylor-rs3qz]

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

[@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.

[@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

[@HDsauce32]

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

[@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!

[@kahidunn7907]

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

[@decentgarage]

Thanks! You can do it

[@liamboyd3499]

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

[@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!

[@leclemsdu83]

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

[@decentgarage]

Glad this was helpful!

[@joshj1140]

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

[@eddyb6790]

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

[@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!

[@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!

[@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!

[@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 ! 😆😉

[@hemidart7]

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

[@mackwalls866]

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

[@decentgarage]

Thanks man! 👍

[@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! 🙂

[@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.

[@trevorparker20]

Very detailed video! Great tutorial!!! Thank you

[@decentgarage]

Glad it was helpful!

[@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.

[@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.

[@mickjones2857]

I figure things out. What a guy.

[@decentgarage]

Glad it was helpful

[@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 👍

[@matthorndl6003]

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

[@rideaustralia4479]

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

[@decentgarage]

Good call!

[@samcssolutions]

Well done! Like a pro.

[@decentgarage]

Not quite a pro but it worked!

[@KimKim-oo2up]

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

[@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!

[@alanchan1772]

Thanks for a great top end rebuilt

[@decentgarage]

Glad it was helpful 👍

[@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

[@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!

[@dannyfubar3099]

An Excellent Post, Thank You for Sharing!

[@decentgarage]

Glad you liked it!

[@artiexr222]

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

[@decentgarage]

Thanks for the kind words!

[@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.

[@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 👍

[@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!

[@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?

[@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

[@purpleether5405]

Great video. Very precise which you need to be.

[@decentgarage]

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

[@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.

[@armandogardoni892]

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

[@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??

[@Expungement-s]

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.

[@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 👍

[@MethuselahMusic]

Kicking over a newly rebuilt xr400 with crocks on, LOL! Thanks for the great video, brother.

[@decentgarage]

Is there any better way to do it?! 😅

[@gertkristensen6451]

there is a special way for adjusting one exhaust valve if the bike have orginal cam and auto decompressor when you turn the motor on the T mark the autodecomp is active and that valve becomes too loose turn motor 1/4 turn too far and back again to deactivate the auto decomp

[@decentgarage]

Thanks for this comment! I've actually learned this since filming this video. I wish I could go back and edit it in.

[@justice6436]

I've got the same bike, great video!

[@decentgarage]

It's a great bike!

[@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!!!

[@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

[@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

[@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.

[@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 😁

[@ericjohnson9080]

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

[@henrycole8705]

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

[@dukesilver2019]

Thanks. Really good tutorial. Make more.

[@decentgarage]

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

[@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!

[@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 !

[@legenderekonwheels]

So what? It needs timing reset anyway 🤷‍♂️

[@dennismacwilliams196]

Good work and well explained also. Thank's

[@decentgarage]

Thanks!

[@sinnerboxdawg]

thanks so much for the good tutorial

[@decentgarage]

Glad it was helpful!

[@rotorhawg8052]

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

[@TommyTucker0]

great video, really well done

[@decentgarage]

Thanks tommy

[@project4stroke876]

so glad u made this video man!

[@decentgarage]

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

[@jeffahearn]

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

[@RideWithTheWolf]

I noticed that your cam journals were a little worn. Did you run it like that or did you replace the head? I also have an issue where the wrist pin wiggles in the rod a little.

[@decentgarage]

I ran the OE head. It had a little wear but not enough to concern me. If you have wrist pin to rod play that is side to side that is normal to an extent but if you can feel play up and down that is not normal and needs to be replaced.

[@gusocon319]

Wow Good job !

[@decentgarage]

Thanks!

[@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??

[@SkinnySkinch]

When you say cheap what is cheap? These bikes are pretty rare and getting more and more expensive as the years go on. Hold onto that bad boy she looks near perfect.

[@decentgarage]

I lucked out and got it for $650 which is a steal 😁

[@SkinnySkinch]

@@decentgarage are you kiddingggggg me? I just paid $3,500 for mine 😂

[@decentgarage]

@@SkinnySkinch Nope! I saw the ad right when it was posted and jumped on it! I absolutely love the bike. People are always telling me to get a KTM or a beta and I never will.

[@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.

[@ingeebeltoft]

You need some kickstart teknic 😂 Set piston to tec and then kicklever all the way up before firekick. She start easily also by hand 😂

[@kingaire165]

Right on! Good video

[@decentgarage]

Thanks!

[@jkimo1178]

Also, you said it was a lot of work and a lot of money. How many total hours and how much $$$?

[@decentgarage]

It ended up being around 300 for new piston, rings, gaskets and getting the cylinder bored so really no that bad. I think i had about 15 hours in to it and that was with filming. Looking back at it being a year ago it really wasn't that bad. I've done two more top ends since then and they just get easier the more you do them

[@nikosbiologytsiouplis1895]

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

[@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

[@cntryby]

The reason there isn't a torque spec for the studs is because they don't compress anything. Finger tight is good enough. Any more and your damaging threads. The torque is applied when the nut on top is installed.

[@decentgarage]

That makes sense

[@andrewpeeters1288]

Great video. Thank you.

[@decentgarage]

Glad it was helpful

[@mikem1738]

Man, great video! Just picked up a 2001 xr400r, it was bone stock, still had the original dunlop front tire and tube on it. Unfortunately the guy had it started when I showed up. Question, how much resistance do you have on your kickstarter when moving it by hand? I havent even started it since I got it home, tore it apart to clean and do all the maintenance. Thanks for your help!

[@decentgarage]

I would say it has moderate resistance to the point that i don't attempt to start it with my hand.

[@mikem1738]

@@decentgarage sould like mines in the ballpark then. Also do you happen to have that shopanual file still, shot you an email, if so I'd love to have a copy

[@decentgarage]

@@mikem1738 i saw your email. Sorry been slammed with work. I'll reply today!

[@mikem1738]

@@decentgarage no worries man!

[@chaddeibler-hunt3610]

@@decentgarage I would LOVE a copy. 🤞🏼✌🏼

[@lemoinexavier]

Great vid! Thx. You never use loctite?

[@decentgarage]

I do sometimes but didn't really mention it here cause people have differing opinions on when to use it or not

[@arthurconrod9825]

@@decentgarage Great video.i am doing a top end rebuild on a friends xr400 next week,just to be on the safe side ill be using thread lock on the camshaft sprocket bolts.All the best and thanks from Liverpool england uk.

[@derrickcosta2459]

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

[@lunaperez7899]

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

[@frankiovino8462]

Hey just a quick question regarding your exhaust header. I am just finishing up doing a rebuild and cant seat the right side header. The left side slips in to place perfect. Gaskets have been replaced on both sides, so there is no double gaskets on the right side. If you are on FB I could send a picture and compare it? Thanks for the help.

[@decentgarage]

Yeah i think i saw your post in the xr400 group. I'm not sure why that would be happening unless the header was bent which is pretty unlikely

[@frankiovino8462]

@@decentgarage OK Everything is lined up and bolted. Left side goes in perfect> Maybe some heat? Thanks for the reply!

[@1176hambone]

Thumbs up! Great video!

[@decentgarage]

Thanks 👍

[@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