Yamaha TRX850 Enthusiasts Forum

Hi All,

Have to overhaul my carbs and wondered if anyone has played around with rejetting or other mods to the standard carbs. Engine is stock, running Staintunes(no baffles of course).
Have had a look around the site, but if I have missed a thread covering this can someone point me to it. Thanks.

Cheers,
Stu

Hello and welcome Stu.
Most members have found that rejetting stock TRX carbs really isn`t necessary,they tend to richen up at the top end so there`s no real issues there,at least not just with a can swap.
One thing that makes a tremendous difference to how they fuel are the float heights though.
It`s 15 mm measured from the carb to float bowl face (on the carb body) to the top of the larger of the two floats.You`ll notice after you remove a float bowl that the floats are two different sizes but share a common plastic link and both act on the needle valve in unison.
The other things you might want to check are your emulsion tubes and needles for wear (ovality),TRX`s for whatever reason (there`s a whole thread discussing it) seem to be somewhat prone to wearing them.
Surging,backfiring and/or poor pick-up are the general symptoms.

when I first bought my trx it was fitted with staintunes(restricors removed) and Std headers. and after putting it on the dyno I was reading 70.13hp... PROBLEM... someone fitted larger jets...staintunes are designed to run std jetting and after fitting std jets once again replacing neddles, setting air/fuel and float levels was back up to 76.59hp with std airbox and filter.. Purchased a K&N filter for the airbox a few mths later and improved the bottom end esponse even moreso.. I think you will also find someone did some tests results on a dyno with staintunes and found another 2 to 3 h/p with restrictors inplace...In amoungst the library of info stored here i found when I first went searching myself... But now that system and carbs are just gathering dust ...

Thanks guys, that'll save me a bunch of time and mucking around. Much appreciated.

Stu