86-89 TRX350 cam chain replacement

[Goober 1,555]

I’ve got two 87 TRX350A they both start fine but foul plugs very quickly and then stumble afterward. I had a tech acid-wash both fuel tanks, install rebuilt petcock, new pumps, filters, fuel hoses, rebuild both carbs, and change intake manifold gaskets. No cam chain noise but i did check one cam chain yesterday and found it’s down to 3/16”.

 

I’m gonna review @TrxPipUK thread where the heck he been lately? Hey @kevin_c also needs a TRX350 cam chain thread, so others can follow. I may not be able to start right away, because it’s a shop quad.

 

what’s best way to start?
remove the engine or in the frame?

i know how to remove the valve cover.

Remove the right side cover never done that before.

Edited April 21, 2021 by Goober

[Goober 1,555]

Great info From @shadetree:

“Here's how to tell if the cam chain is bad ?. remove the two bolts from the tensioner, pull it out from the cylinder, if the cam chain is too far stretched ?, you wont fill much resistance on the tensioner when you go to pull it out, now try to push it back into the cylinder, it should bottom out before the tensioner comes close to the cylinder, your looking for anywhere between 5/8-3/4 inch gap before it reaches cylinder. if the tensioner goes all the way to the cylinder bolt holes with ease ?, then your cam chain is too far stretched, and needs to be replaced.”

Edited April 21, 2021 by Goober

[Goober 1,555]

Will need a clutch cover gasket, Hondabond or Yamabond and a D.I.D cam chain.

Question: Will the master link also be needed?

 

here’s the link and part number

DID SCA-0412A-SV

https://www.ebay.com/itm/303268349355

 

Edited April 21, 2021 by Goober

[Fishfiles 20,147]

Just throwing this out there for hard times  , like when it is the Mad Max days and there are not more part stores , "  The last Honda ATV on the planet "  which might not be too far off , if your chain is worn past specs , you can stick a 10mm socket over the end of the adjuster and stick it back in and it gives it a little more stroke and make it run a little longer , bet Shade will freak out on that repair recommendation , not saying do that until the time is right  , LOL 

[Goober 1,555]

I reinstalled the tensioner—the service manual makes it seem needlessly difficult.

I used a small screwdriver to back off the tensioner a bit each time i got the tensioner further in. First to get the bolts started. Then i ran the bolts down finger tight with an 1/4” x 8mm socket and extension. Then I tightened the bolts and made one last reset of the tensioner before reinstalling the cap bolt.

 

i found there to be 3 full turns of slack in the tensioner; i think this could help me screen my other 3 shop quads.

[toodeep 1,760]

There looks to be plenty of adjustment left on the adjuster to not need to replace the cam chain. If you do replace it just remember the nut on the centrifugal clutch is left hand threads. When the plug fouls is it wet or just very black?

[Goober 1,555]

Plug is very black. It starts great and runs good until it warms up then it stumbles constantly and blows a little black smoke like it’s too rich. I rebuilt the carb and installed new enrichment valve that didn’t help; tried my spare carb no change.
i have not started it since I replaced the manifold gasket; and i have a new plug i can try.
no chain noise or tapping

 

[Goober 1,555]

Ok i tried it again with a new plug; same story. Carb pilot is set 1.5 turns out like the last one. Starts great, likes the settings but stumbling and a little black smoke typical of rich FAM. Time for a compression check.

Edited April 23, 2021 by Goober

[Fishfiles 20,147]

1 minute ago, Goober said:

Ok i tried it again with a new plug; same story. Carb pilot is set 1.5 turns out like the last one. Starts great, likes the settings but stumbling and black smoke. Time for a compression check.

Does it "stumble " from idle ( I would guess enrichment valve )  , or if just from 1/2 throttle on ( I would guess diaphragm )  ---

 

I have had the valves bend and stick before on the 300s , a 350 is double trouble with multiple valves 

[Goober 1,555]

It idles smoothly until the plug gets fouled; afterwards stumbles badly with throttle 

Edited April 23, 2021 by Goober

[Fishfiles 20,147]

I just looked at a 350 carb print and it doesn't have the diaphragm like a 300 , so that ain't it 

[Goober 1,555]

Everything is OEM on it; the fan has never come on before—i know it’s got hot. I need to check it.
it use to run great. can tell you I’ve ridden this thing to check property and it’s never quit on me. But last year it’s started this; I’ve another does the same thing. New CDI on the other.

I haven’t set the valves since 2013 but I haven’t ridden it much maybe 50 miles. Onliest things i think are compression, cam chain, valves.

Edited April 24, 2021 by Goober

[toodeep 1,760]

Where do you have the clip on the needle for the throttle and have you tried adjusting it? Are the throttle linkages timed correctly?

[shadetree 5,977]

have you checked to see if the choke is sticking in the carb ??.

[Goober 1,555]

Thanks @toodeep and @shadetreefor replying i rebuilt two carbs and tried both. OEM choke and throttle cables. Needles at midway setting as per manual. New OEM choke valves seem to be working. it really does seem like a carb synchronization problem but i thot i had it nailed. 

[shadetree 5,977]

30 minutes ago, Goober said:

Thanks @toodeep and @shadetreefor replying i rebuilt two carbs and tried both. OEM choke and throttle cables. Needles at midway setting as per manual. New OEM choke valves seem to be working. it really does seem like a carb synchronization problem but i thot i had it nailed. 

deff have a look at the carb linkage !.

[TrxPipUK 169]

I'm back! Lol.. seen that I was mentioned in this.

I'm really interested to see if you @Goober found out why your quad is fouling plugs? My 350 still seems like it runs a little rich but haven't bothered sorting it much.