Yamaha TRX850 Enthusiasts Forum

http://www.factorypro.com/tech/tech_tun ... s,Pat.html

Excellent reading and gives you a good understanding and steps to tuning your FCR's.
Explains the purpose of all you jets and the interaction with each other and which jets to set first.

The bottom link gives you and exploded view of the FCR and part numbers for reference
http://www.allensperformance.com/exp-fcrd1.html

Nice find Cobba

Found a cheap set of 145 main jets on e/bay the other week, a keyster brand ....obvious a copy of the Keihin option.
Under 5 usd each....so for 10.50 Usd plus post, sent the order off.
A week later and fitted for my run up Springbrook today, ....much better..power still there and no sooty unburnt fuel smoke under full throttle.
Found cold starts still easy and a lighter exhaust colour.
So the tip is ..the keyster 145 mains fit and do the job well.
Still one turn out on the mixture screw..
And maybe a little less mid range slide flutter, but then I have the projection two into one exhaust..
Cheers to Brian for the size hint.

A common misconception with the FCR's with the main AIR jet being too large to start, so they increase the main fuel jet to try and balance things instead of dropping the main air from 200 to say a 180 and then tuning the main fuel to find a good balance.
I know of a trx 850 with 900 barrels and rods FCR's flowed head and Akra system with good dyno time tuned down to a 142 main fuel jet.
The manual confirms what I had learnt from the fellow who originally sold me the Ross pistons with the 900 barrelled TRX.

cobbadiggabuddyblooo wrote:A common misconception with the FCR's with the main AIR jet being too large to start, so they increase the main fuel jet to try and balance things instead of dropping the main air from 200 to say a 180 and then tuning the main fuel to find a good balance.
I know of a trx 850 with 900 barrels and rods FCR's flowed head and Akra system with good dyno time tuned down to a 142 main fuel jet.
The manual confirms what I had learnt from the fellow who originally sold me the Ross pistons with the 900 barrelled TRX.

I actually increased main air to 220 because i had a dip in power way on top where the bike went rich....not anymore

Atmospheric conditions come into play that's why Killer .
Totally different climate conditions and air density than you have up your way killer than here in Oz.
Perfect example of what may work for 1 may not work for someone else because of that 1 simple fact..
Climate..

cobbadiggabuddyblooo wrote:Atmospheric conditions come into play that's why Killer .
Totally different climate conditions and air density than you have up your way killer than here in Oz.
Perfect example of what may work for 1 may not work for someone else because of that 1 simple fact..
Climate..

Yup, we very rare up past 20 degrees here