Yamaha TRX850 Enthusiasts Forum

Hi all, i need a hand with my TRX, ANY hints or tips would be fantastic.
i have a TRX850 2001, its spotless and has never missed a beat and has only done something around 20thou on the clock.
Lately however every time i let it sit for over a few hours, and not necessarily in the cold or anything, it runs really rough after ive warmed it up...no matter how long i let it warm up. It was being especially troublesome today, i let it warm up for over 10 minutes with the choke out then i put the choke in but it kept under revving and stalling (over 5 times). Once i acctually get the bike going again however it runs totally fine.
Its just had a major service and stuff and they found it was one of "the best trx's theyd seen" at yamaha (but theyre probably just saying that).
Only thing i can think of that i may be doing wrong is:
Too high octance fuel? i put 98 in is that bad?
Not letting it warm down?
Leaving choke out too long?
Not leaving choke out long enough?

thankyou all very much for any help its greatly appreciated i love this site
rhys

I have a question?

Have you always let it warm up with the choke out for that lenght of time?
Has this problem surfaced after the service by your Yamaha Dealer?.
Why did you run 98?

Actually thats 3 questions eh.

My trusty mechanic has always stressed that ordinary unleaded 91 is fine for the TRX. (Althought there are always those who would differ)
In my experience summer or winter (You don't say were you are from) {maybe a colder winter clime} there is not the need to use the choke for starting, if you do certainly not for any lenght of time, and certainly not for 10 mins.

Do a search on here for starting procedures, it has been covered,

As to why it is doing it, Can't know. although I would suggest starting it without using the choke or just using the choke to get it running then warm it up just using the throttle. Get one of those cruise control throttle friction lock thingies to set the throttle to warm it up. Phew.

My bike only needs the choke to get it fired and I then wind the idle screw up a bit and slowly back it off as I ride. Usually it only takes a minute or two. 10 min warm up is excessive and I would suggest doing that with the the choke on may have led to a build up of fuel deposits in the carby. (I'm only guessing here)

It may be worth seeing if the service agent used the correct grade of plug (assuming they were changed at the 20000km service?). TRXs run fairly cold and if the weather is cold they can take a while to get going. However if the plug heat grade is incorrect the things will foul, especially on the choke. I suggest starting using full choke and no throttle, once she fires give her a little bit of throttle and back off the choke slowly maintaining revs using a little more throttle. Then get her up to temp by blipping the throttle up to about 3-4000 rpm for a couople of minutes, with the choke in, then take her for a thrash and I mean thrash (speed limits must of course be adhered to! ). If she starts and runs better next time after leaving overnight, then you know you have a plug fouling problem. If she doesn't then maybe the carbs are slightly out of synch. Dunno, could be a multitude of things. Let us know how you go.

An issue with using the choke for so long is you'll cause excessive bore washing which can't be good. My bike only needs a whiff of choke to start then I warm it using the throttle for a minute or two. After it'll idle without the aid of a safety net I just get on and ride it. The potter out of our estate is enough to warm it up.

And 98 octane, why? You'll get better performance using 95. I suppose if your engine was modified and you had high compression pistons and a bit of ignition advance you'd benefit, other wise 95 is fine.

Thanks everyone you helped out alot!!!
I started the bike without using any choke and it ran sweet. My use of the choke must have been running it too rich or something ...
its still strange though because if it was running rich you wouldnt expect it to stall heaps as soon as i took the throttle off??

I guess i was babying the bike too much trying to ensure it had premium fuel and was warmed up before i rode it that it backfired on me...(no pun intended)
I will start using 91 if you guys reckon thats the way to go i guess its just because ive always had high revving turbo cars and got stuck on it.

will let you know how the next few days go..
Cheers and thankyou all very much for your replies
Rhys

That will be a result then?

As others have pointed out, never never use the choke when warming the engine... In fact, don't even warm the engine when standing still, it takes for ever. Best way is to get going as soon as possible, but without stressing the engine, i.e. not revving too much and not using too much of that nice torque on low revs. I recall seeing a diagram on the German site with water and oil temps, it takes considerably longer for the engine oil to get to the correct working temperature compared with the water, so even when the temp gauge says OK, the engine oil is still luke warm. So if you want to be anal, drive carefully for the first 10 kms or so...