I have a 400ex that the timing chain slipped off cam. Ive been informed that a crf450r timing chain is the upgrade, any specific year then? and is this a direct fit?

Below are pics of the piston, which I believe is okay, correct? the smudging is from my finger to see if carbon would come off, anyone know what kind of piston this is? stock?

Also I attached pics of the valves, the bigger ones are intake right? there’s a small gap where I can see up through them, so theyre toast then? What kind of valves should I order, kibblewhites? and should I do all 4 then just to be sure, or would only 2 be able to bend due to probably jumping time.

Alotta questions here.. any help is appreciated. thanks!

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Ive heard of upgrades for a timing chain for a 400ex, like from a crf450r or something. Anyone know what I should order so that my timing chain doesnt slip off cam again due to so much slack?

Also anyone had luck with the manual tensioners? looking into fixing this so that it doesnt happen again. Thanks!!

Also, I pulled head, and two valves are slightly open, shouldnt they be closed if i pulled rocker arm head off and then the piece that holds the valves and cam etc? because no pressure is down on the springs?

Ive heard of upgrades for a timing chain for a 400ex, like from a crf450r or something. Anyone know what I should order so that my timing chain doesnt slip off cam again due to so much slack?

Also anyone had luck with the manual tensioners? looking into fixing this so that it doesnt happen again. Thanks!!

Also, I pulled head, and two valves are slightly open, shouldnt they be closed if i pulled rocker arm head off and then the piece that holds the valves and cam etc? because no pressure is down on the springs?

First post here, and have good question; I am looking to replace the entire engine in this bike due to a crank failure, it is 2006 trx350fm and have found a trx350fe engine.

What changes do I need to make so it will work and shift correctly?

The more details the better!

First post here, and have good question; I am looking to replace the entire engine in this bike due to a crank failure, it is 2006 trx350fm and have found a trx350fe engine.

What changes do I need to make so it will work and shift correctly?

The more details the better!

I just did the valve adjustment on my 86 350x and before I did it I had lots of compeshion and now after I did the cable adjustment it ridiculous amount of question I have were I’m trying to kick it and its in a compression stroke and it just stops me dead trying to kick it and I’m 190 pounds did I mess up the. I did the adjustment it say in the manual I download clearance ? Attachment 24524

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Hello again everyone! It’s been a few months since i’ve posted on here, but I am back!

I am gearing up to finally do the top end rebuild on my 87 TRX 250 Fourtrax to get it to stop blowin’ smoke. As I was looking up kits on the great and mighty eBay, I noticed that one of the few complete kits with piston, rings, gaskets, etc… said it was for the ATC 250es, 85-87 TRX 250, and, drumroll please, the 88-00 TRX300/fw!

Now my question is, are these kits really compatible? I KNOW the bore is 74 mm on each engine, so will the piston from a 300 work in a 250, like this kit implies? I know there is more that goes into the pistons than just bore diameter. If the pistons are the same, are the gaskets the same as well?
Note: I did do a search and didn’t find what I was looking for.

If so, I would much rather buy a Wiseco piston and Cometic gasket kit for a standard bore 300 rather than the crap I have found for the 250 (there is very little to choose from for the 250 fourtrax)

OK< so a thought I would add this, since we get a lot of treads about getting an atv running thats been down a while, feel free to add to this list if I missed anything
But figured maybe this would help some IF they look before asking LOL

SO< your wanting to get an older atv or what ewer running, ??
that’s been sitting a while, be it a few months or years

here are what I say are basic;s to be done before starting or even trying to start this atv/ or what ever? to save you from having issues down the road or??

First give it a bath, makes life easier to work on
NEXT< GET a service manual, either download a free one, or BUY a hard copy one! used one’s can be found on Ebay and like places too, some times CHEAP! and there priceless to have!

NEXT , drain Motor oil and Diff fluids( , and re fill with CORRECT oils, and CORRECT amounts! MAKE sure you know HOW to check both levels, as there NOT all the same way on every atv or??

NOW Optional maybe to some, BUT< if liquid cooled, , then replace the coolant, OR pending HOW Long its been sitting not run, the longer it sat, the better this option is)

Next, Drain the fuel tank, even better remove the fuel tank and clean and make sure if there is a screen in the tank its clean and not clogged up.

Next, clean and inspect fuel peacock, make sure it flows well,
next can be optional pending HOW long its been sitting again, replace the fuel line(and fuel filter if it has an inline one, and MAKE sure its installed the right way, there directional) Fuel line is cheap so> new line makes sure NO crap is built up on the walls of the old line that will re dirty your carb after you clean it?

Next, remove and clean carb( if its been down long or very dirty, get a carb rebuild kit, and replace all parts you can with new one’s AFTER a GOOD cleaning ( Ethanol fuel leaves a varnish behind, and can be super hard to remove with basic carb cleaners and spraying, so?? learn the boil in lemon juice trick, if you need to, on a filthy carb), just make sure its clean and all holes NOT blocked up!

Next, Clean or replace the air filter, if its a washable one, wash and re oil, BUT if its been sitting a LONG time, many foam filters will start to deteriorate with age, so a new one is NEVER a bad idea! again pending age and condition of your’s!

NEXT replace the Spark plug

MAKE Sure the battery is charged and in good working order, to test a battery, TAKE it to a chain line auto parts store, have it checked UNDER a LOAD, as that is ONLY way to check a battery , if need to RELACE battery, modern atv and likes, need good power to run right today more than ever!

after this its basic’s, make sure air is in tires and there NOT dry rotted, check wheel bearings and steering post bearings and so on, grease as needed, replace as needed, make sure brakes work, have fluid(can replace brake fluid too if its been down long, as that too goes bad)

DO these things before TRYING to start your what ever that’s been sitting, and you will have a LOT less issue’s down the road

I have a complete stock 2005 Recon that has been sitting for about a year. I started tinkering with it the other day and found out the carb was completely gummed up, I cleaned the carb out and it started without any problems and seemed to idle fine, I revved it up and it sounded great. I got on the bike and begin riding through the field as I started progressing from first to second, I noticed the bike was sputtering some, as I got on up into third, fourth, and fifth, the sputtering was really noticeable. I pulled the choke about half closed and everything smoothed out, but as soon as I opened the choke back up the sputtering would start again. I ordered a rebuild kit for the carb and put it on thinking maybe I didn’t get it clean enough the first time, so new jets, and gaskets went on, it made absolutely no difference. I ran it once for just a few minutes with no airbox and it ran fine, with no sputtering, so I cleaned and checked the air filter, put everything back together and it was still sputtering past half throttle. HELP! I am pulling my hair out trying to figure this thing out, the only way it will run correctly is with no airbox or the choke halfway on! Any and all help would be greatly appreciated!

i have finally solved my gear location issue on my son’s 2007 trx90 thanks to this forum, particularly moose wagon and shadetree. i got down to the clutch but then i did not have a castellated nut tool so i took it down to the local mom/pop shop and they loosened the nut for me. while there, i told them my problem, what needed to be done to repair it, and they did just that. the shop took off the shift arm, straightened it, and then re-installed it. cost me $40. it shifts very firm right now, maybe indicating the clutch needs to be adjusted?

next issue is with same 2007 trx90. i thoroughly soaked the carb in yamaha carb cleaner, blew out all holes with compressed air, used a welder’s wire cleaners to pass through all holes, then re-assembled it. it is now idling better than before but loads up/bogs down on full throttle, not fully reaching max rpms. there is no mixture screw adjustment on this carb, only idle. the needle cannot be adjusted up or down, it is fixed as well. the only thing different between before i removed it and then re-installed it is the gasket between the carb and the intake. it fell apart so i cut another one out of a brown gasket material making sure the intake opening was the same diameter. not sure this has anything to do with it. would appreciate your input.

last issue, for now, is with 1987 honda trx 125. it was starting using the electric start button but now i only hear clicking from the solenoid. i substituted a different solenoid(from honda 300 fourtrax) from a known working unit and it did the same thing. put the ‘suspect’ unit on the known working atv and it is functioning properly. don’t know what else might be the issue. starter was working as it should previously.