Problem Found On Honda 400ex...Worse Than I thought! 

Well I was hoping for better but it is what it is! Any suggestions on what parts to use for this build would be great! Need Motorcycle, scooter, car and truck parts? Check out www.Laptwo.com Please SUBSCRIBE and LIKE the video if you enjoyed! It really helps me out a lot! Thank you for all the support!

A lot of times crank and bearings get overlooked when doing a rebuild, maybe just because splitting cases seem challenging to alot of people, but once you get past the first one it get easier👍🏼from there on. Your doing good sofar keep it up👍🏼👍🏼

Fun fact a battery at 12.1 volts is a dead battery. Battery’s need to be from 12.4-12.6 to be considered good

its the connecting bottom rod bearing the crank bearings are fine... you can rebuild the crank at the shop or just get a new one. Excited for this build btw!

keep doing what ur doing man, love watching ur channels. It helps me in many ways in learning things about these bikes thanks man foreal🙏🏽💯 keep doing what you're doing

Hey I actually got the kx80 from you last year! That thing rips! It would be cool if we could ride some time

Might as well install a stroker kit.

Laptwo.com is now selling Vortex Cahin and sprocket kits. Our seller Chris works directly with the company and trys to get the best possible deals! Here is the link to the kits if anyone is interested! laptwo.com/atvs/honda-trx400ex-sportrax-four-trax-vortex-cat5-chain-and-sprocket-kit-1999-2000/

Yooo I love the vids! At school waiting to watch your videos!!!

Literally just finishing up a rebuild on a 400ex with a motor that was totaled. (New bottom end, top end, full timing kit, full new head, cam, new valve cover with rocker assemblies, even all new bolts.) I've learned a thing or two. No.1 This motor has a one way sprag on the flywheel. It will only turn over one direction. If yours moves both ways, then that is likely broken. You have to pull a side cover and pull the stator housing/ flywheel with a special tool or a generic 3 hole puller and 3 semi long 8mm bolts. You dont have to pull the motor to look at this but if you are planning a full rebuild anyway it will have to be done. Just a heads up in either that is your problem or you have to order more parts. No.2 Im not saying that your crank is good but, even your new crank will have side to side play. Its the up/down play that counts. No.3 That piston and cylinder looks exactly like the Weisco top end kit. I would do a little more digging and micrometer the rings ( cylinder wall to piston ways) and check there ring gap when installed. Just pop them off and put them in the cylinder. Use the piston upside down to make sure the are square in the bore and use a feeler gauge. I dont recall exact spec but .005 rings a bell. Whatever repair guide you use for torque specs should have it in it. Just a couple things that may save you some time and money. Have fun. Keep the vids coming

I’ve never rebuilt a bottom end. Always stressed about splitting the case. The transmission side and all those moving parts. Looking forward to watching you do this to learn how it’s done.

The previous owner obviously abused this motor by forgetting to spray the crank bearings with wd40..

Well I guess that that means the Ebay parts didnt fail 🤷‍♂️ Maybe well u have the engine apart u replace the ebay parts with oem parts

That means that the eBay kit did just fine

Good find before it let loose or froze permanently... Got the same issue on my 87 XR/XL 600 project bike. Tore the XL engine apart and my rod is almost frozen to the crank.... but i'm doing a complete rebuild :-) Got a great local shop going to rebuild the crank for me.

You got this dude. Bottom end is no big deal. If you want any of that stuff vapor honed, let me know. Send it to me and I'll do it while you wait for your parts to arrive.

If it keeps blowing up check the screen on the bottom of the oil tank, also make sure the oil pickup in the case is clean. If it keeps blowing up it may be an oil pump failure or clogged oil return screen

Great video, im glad you found the problem so you can fix this bad boi.

Piston and cylinder are fine just make sure tolerances are to spec and reuse it . I think the head and valves are fine too. Top end sounded fine when running. Just get a complete engine gasket kit and seals and new crank assembly with new crank bearings for right and left. Even a good used crank would be fine. Or install a new lower rod bearing and race than have the crank balanced with new right and left crank bearings. The cheapest easiest quickest way is find a good used crank assembly ebay and complete engine gasket and seal kit . Then throw it all back together. Had to do the same thing to my crf 450 . My engine was pretty much junk . I used a used crank with new bearings and seals gasket kit new top end. Quick clean up of the valves .put it back together. It's been two years this October and zero problems still runs like a beast ..

Awesome tear down video man

Love the vids man

Hey man, ive been watching for a few years now and you have inspired me to start flipping dirtbikes, i bought a 1994 kx80 for $100 and put a new top end and bored the cylinder so i have only put $250 into it so far and im planning on selling for $800-$1000

man i gave this video a thumbs up as soon as you said you was going to replace the piston with a good name brand . very smart move . never run cheap internal engine parts ever lol

IVE been waiting for this

Keep it up man, I love the older stuff. More ATC's!

Love your videos! And love the 400ex! One of the best things about the 400ex is they are super easy to work on and parts are everywhere for them!

The cheap always turns out expensive

I love your videos 2 vintage

440 kits are pretty popular with these . I'd go with a hotrods crank and rod set up. A good forged piston of ur choosing wiesco , JE , collies, etc . And a mild cam while ur in there bud . Perfect opportunity for u to build a motor for one to keep for urself .

Love 400 ex builds ...keep em coming 🤘👍.try wheelies on the road with some speed it stays up no prob if your smooth on the throttle 🤘cheers from canada

your manual should tell you the lateral tolerance of con rod. i’d say crank case bearings are the problem. but if you feel up and down play on rod that’s no good either. seems odd there was no knocking when it ran

Who thinks the guy that sold it knew it had this issue??? I sure do !!

Rod bearings are bad, regardless you’ll be replacing them all!

Piston, rings and cylinder are scored. Probably from bearing material going through the oil. Make sure you clean all oil galleries before you put it back together or you'll score it again.

Needs new crank or that one rebuilt. The connecting rod looks locked up but might as well throw in new bearings as well

Good job bro

Nagura piston rings are the worst piston works great but recommend use wisco rings better compression and less oil burning from oil rings. I had this problem and funny thing came out to be the stator side crank bearing so must be common

i definitely don’t recommend using an impact on any engine bolts. crack the bolts loose first with a ratchet then you can take them out the rest of the way with an impact

Possibly could be one of a couple other things I had a similar problem with my snowmobile and it turned out I had a bad crank seal and I had replaced a ton of other stuff before I figured that out due to many other suggestions and trying to do the easy stuff first also known to do that as far as electrical goes is a bad pickup coil

My 04 trx 450r crank bearing just shitted out have more or less the same Problem I’ll be tearing mine apart soon!

Check your air filter and intake tube bet there is dirt getting by your filter

Rod bearing!! And you should replace the crank bearing also while it’s apart! And oem parts ftw

I made the suggestion that it was the crank the first video you ever posted with this thing, before it was ever running

Buy the wrench rabbit kit comes with hot rods crank weisco piston and comes with all the trans berings and everything u will need

I have used eBay kits from everything from weed eaters. And quads and bikes. To cars an heavy equipment. Very rarely ever had a problem. THE MAIN THING THAT IS A PROBLEM are the rings. 99% of the time they need gapped. People don’t do this and the thing will seize up.

You should do a big bore on this one if you're gonna replace the piston and also do a bottom end. maybe a 416 or 426

If its ur 1st time splittin cases, good luck! Ive done alotta rebuilds myself but at this point, id rather let a shop do it with a warranty. ..😆👍👍👍👍👍👍👍👍

Perfect timing ;P

Easy tip. Drain the oil first if brass is found in oil then its crank bearings. Very few parts in engine contain brass

Sounds like bad rod bearing you can hear a knock at idle

Where did you get the plastic for that bike

I would replace the oil pump also.I would also use a vertex piston kit

i can tell you for sure aasa is a great company in greece at least. I bought parts for my crf 450 from aasa it was kinda pircy tho...Also made my Honda 125 a good 200cc its perfect it didnt blow up its been like this for 1 year plus 200cc 23hp i dont really know if its good or not the hp but its not only for racing you can take it for a normal ride or do a lot of distance without shuting down engine.Sorry for bad english

I could tell it was the big end of the rod as soon as you pulled the jug,I seen the discoloration on the crank from where it got hot an seized common failure point I always replace every bearing on any kind of rebuild,think about anything inside the engine goes there's always metal deposits so where does that metal go,uh in the bearings

you should replace all the bearings in the case ... crank, transmission, and counter balancer (buy OEM) - $180.00 will get you a HOT RODS Complete Bottom End Kit from MotoSport

What motor is better ? With 2 camshafts or 1 ?

Please do an in depth on rebuilding the bottom end

Do the striker and big bore kit and compare the difference between stock and fully built

the rod bearing is what went not the crank bearings. Id still go ahead and get new crank bearings.

Everytime that rod hit the cases...it hurt my heart a little

When I saw that blue color on the crank I could tell before you tried to move it. It takes a lot of heat to discolor metal.

For piston I have very very good luck with those and I race (250) class and when ever my top end goes I buy vertex and I get another 130 hours out of one (racing)

I would replace timing chain too your that far into it already, hope to see it running again

pro x con rod kit send crank to shop to swap con rods put new main bearings in cases then build back up

Id use a hot rod crank if it's reasonable priced

that is a real nice motor that the guy said it was rebuilt ------ good luck getting the motor out i had a hell of a time getting the swing arm bolt out witch goes threw the motor on my 2002 Honda 400 ex ----- go with a good piston and rings ----stay away from the cheap pistons and rings

That namura piston piston is EXTREMELY worn. The skirts should be solid black.

There should be shims on each side of the lower connecting rod where it connects to the crank.

Is the throttle cable backwards

Any crank has side to side play at the rod bearings. It’s the up and down that’s a no go

Those scratches on the piston skirts are from dirt getting past the air filter

Side to side play is fine. Any up an down is not. And judging by the blueng on the crank and trashed piston, it's running very lean.

The cheap ebay rebuild kits are worth the money had one in my old 400 for about 6 months or so when i sold it.

Id definitely be chucking in a new cam chain and factory adjuster them adjusters are junk the chain stretches and when u adjust them out factory spec with them adjusters the chain has to move further and can cause problems with timing and when u took the chain off it looked really stretched

What battery do u think a 200cc engine need?

What impact do you use

I just had the same issue thought i blew it up but it was the stator, would run if i jumped it

Stroker kit with 434 big bore and bigger carb, monster machine

The old battery shit itself. Things don’t run right on low voltage. Not sure what the other issue if not issues are.

Your gonna need some beer music and time for the bottom end

Splitting the case on my 05 tomorrow :(

You should repaint the frame black and the arms but idk what color

I'm going to be rebuilding my 300ex that I redlined for too long and now has no compression... if anyone has any tips that would be awesome, I've never worked on a motor before and I don't want to mess it up,... I'm planning to get a 300cc big bore for it and hopefully if the valves don't leak I will put it back together and be riding it again, should I replace the cam bearings, cam chain, or anything like that in the top end, etc... please reply and if you do thank you for replying.

My prediction was crank bearing also! Lets see

These Honda's are great, but it would be wonderful if you checked out a Raptor 700r big bore...🛵🏍

If you are going to build the bottom end don't reuse the top end. Go OEM honda at least or buy a hi performance kit with crank and top end cams ext. Just my 2 cents lol

The crank lobes look a little blue also

Side to side play is normal the cylinder hold it up right the up and down play is a problem though

Love this bike

Batteries produce voltage. Voltage don't go to it.. unless it has a charging system..and it needs to be running for that

Damn you can fix just about anything

Hope you get it runing rifht

How fast does a lot 500cc 87 because everyone has there own mph and I’m just curious Cause I have one and I took it to a shop because it needed a motor rebuild but can Somone pls give me a exact mph for the zilla

I think it's the Crank bearing

Ngl it would Mach up well sitting next to the grey quadzilla you had

Since it has to be rebuilt maybe a 440 BBK and stroker crank 🙄

What do you do as a full time job?? I was wondering, or are you going to school if yes then what are you studying?

what are you using to film?

Look for a wrenchrabbit rebuild kit. It will give you everything you need.

Also... Check you OIL PUMP, it may be wore out and not pumping the right amount if any oil to the top end. Maybe why he went Thur so many piston n cylinders, no oil flow.