Yamaha TRX850 Enthusiasts Forum

As you can probably tell I am not a mechanic so dont know much about engines but if my TRX is running too rich could I damage the valves and pistons/

Steelback wrote:As you can probably tell I am not a mechanic so dont know much about engines but if my TRX is running too rich could I damage the valves and pistons/

Other way around, lean condition and your valves wont like it!
....rich and you will see a lot of black crap (as i have) in head outlets.....god knows i need a headjob! Jak??? (sorry, could´t help it....)

Simple answer is yes - the lubrication of piston, piston ring and cylinder bearing surfaces becomes increasingly ineffective.

However, you would have to be running way rich too cause any serious problems.

What makes you think the bike is running rich?

Using a lot of fuel - running rough under 3000 rpms

Steelback wrote:Using a lot of fuel - running rough under 3000 rpms

Have you tried running it without the "snorkel" in airbox?

Killerwhale wrote

Have you tried running it without the "snorkel" in airbox?

Doesn't the snorkel hold the airfilter in?

Steelback wrote:Using a lot of fuel - running rough under 3000 rpms

And this is after replacing the emulsion tubes? What main jets are you running? What is a lot of fuel - how many miles to a tank full?

Can you whip the plugs out easily and post a pic on here?

check all them rubber hoses around the carbs
same symptoms as mine pull the throttle back under 3000rpm and it farts pops and no pull just 1 hose had a restritive kink in it re routed it and it was a instant fix hope this helps

Cant see any kinks in hoses - went out at weekend with full tank and did 60 miles and she went on reserve. Think the last owner has dynojetted it, I havnt done anything to the carbs - would it be easy to get carbs back to factory spec if so how and what would I need ??

running rich increases the risk of burning out your exhaust valves (rare) but most likely burning out you exhaust headers.. To the point of making them glow red hot..

If they dont glow, your fine.. Too rich means excess fuel, which also burns in your exhaust, and thus, burning on the WRONG side of the valve.. which is bad.

but as others stated, bad lube, wrong temp conditions (its actually a colder burn, lean is WAY hot) etc...

simple tuneup via your local mechanic should be fine.. like a 10min job to get it properly ratio'd...

Thanks guys

Steelback wrote:Cant see any kinks in hoses - went out at weekend with full tank and did 60 miles and she went on reserve. Think the last owner has dynojetted it,

I havnt done anything to the carbs - would it be easy to get carbs back to factory spec if so how and what would I need ??

The dynojet kit would have contained special needles and needle clips, and a selection of main jets. The needles are DJ specific, but the main jets are simply stock Mikuni items.

To return your bike to stock would therefore mean going back to the original main jets (140 jets, I believe) and original needles. Haynes manual will tell you what to do. I would also pull the plugs and check that they aren't fouled.

Note that if your bike has race exhausts on it, going back to stock jetting will have it running very lean. Probably not a good idea, although TRXs are supposed to run rich at high revs in stock form.

However, if you are sure it is not the hose problem previously discussed (as the symptoms are v. similar), then I would suggest that emulsion tube wear is by far the most likely culprit for an overfuelling problem like this. Just replacing the DJ kit parts with stock won't cure that, since DJ kits don't change the emulsion tubes in the first place.

A clued-up Yamaha mechanic who knows his or her TRXs will probably include the emulsion tube issue in the list of possible causes, but I worry that if you get someone who doesn't, they will put the problem down to a bad carb setup by the last owner, rejet the bike, and the problem will then recur in short order. If you don't want to do the work yourself, suggest you at least check that the mechanic who does it understands that emulsion tube (a/k/a "needle jet") wear is a potential cause that should be looked into.

Great thanks for the info will get it properly checked out

Sorted - carbs out and back in and out again - mechanic was about to throw them at the wall when he noticed a small hairline crack in one of the floats - put in new one - bike running perfect now

Killerwhale wrote:god knows i need a headjob! Jak??? (sorry, could´t help it....)

Maybe I can help????