TRX main-jets

burty · Post by **burty** » Mon Aug 21, 2006 10:09 am

Does anyone know what's the official standard main-jet for the TRX?

I still couldn't get my TRX to run right and finally decided that the 142.5 main-jet I was running was probably was too large. My factory pro kit came with 142.5 and 137.5, and implies that the stock jet is 140. But I have two sets of 142.5 so I guess that's what was in my bike originally. Consequently I've dropped to 137.5 as it's the only other jet I have available, it's better (might be best), although I might have to play with needle pos and pilot screw to see if I can get it better. But I wonder if a 140 might be the best main-jet.

I have a K&N filter in the standard airbox, Renegade cans and the factory pro needles and emulsion tubes, everything else is standard so would be curious to know what jets other people found work for them.

jpe · Post by **jpe** » Mon Aug 21, 2006 8:40 pm

Main probably differs between countries, we've got the 142.5 as standard in Sweden.

Post by **phuk72** » Thu Aug 24, 2006 9:30 am

Yep, 142.5 is standard and tends to run rich as standard

free flowing cans and filter tend to level this out though. sorry can't help anymore as my motor is anything but standard!

burty · Post by **burty** » Thu Aug 24, 2006 11:00 am

Thanks Phuk.

Actually I'm beginning to get a little f*&ked off with trying to get the TRX to run right.

I've been running 142.5 main jets for a while, I had the needle at the centre clip, and the bike would surge at speed at around 6K. On the dyno we found that moving the clip up the needle gave around another 4bhp at the top, but now it's got flat spots at 3K and 6K, so much so that it's easy to get bogged down pulling away from stationary and it still surges at speed, only worse.

I was thinking that the 142.5 jet is too large seeing as shifting the needle clip up one improved the top end bhp.

I've tried various other settings, and ran with the 137.5 main jets for most of this week, to be perfectly honest it's difficult to tell the difference. According to Factory Pro's tuning procedure you should select the main jet that gives you the best top end, but that's hard to tell on the road. Other than that it seems to behave pretty much the same as running with the larger mainjet, for the different needle heights.

I think I'm going to start completely from scratch again.

I would be interested in what settings others people are running, particularly if they have a similar set up to mine.

tz250w · Post by **tz250w** » Thu Aug 24, 2006 3:08 pm

You're not going to want to hear this but...

Mine ran way better than the stock setup the second I bolted on the FCRs... Response, smoothness, power and 'mean factor'.

In town, up in the hills and of course, tons better on the track.

I'd never think about throwing the stockers back on.

I know that doesn't help, but I have a bad habit of beating that drum (among other things...)

BTW, Nice to see you with us Phuk!

burty · Post by **burty** » Fri Aug 25, 2006 10:04 am

Well if I could get a set of FCRs, cheap enough. Best keep an eye out...

Current new prices would almost set me back the cost of a decent second hand TRX.

earywig · Post by **earywig** » Sat Aug 26, 2006 10:38 am

Hi Burty

According to my official Yamaha service information the following applies:

Main Jet = #142.5
Main Air Jet = #60
Jet Needle = 5EI85-2/5
Needle Jet = Y-2
Pilot Air Jet 1 = #70
Pilot Air Jet 2 = 1.4
Pilot Outlet = 0.9
Pilot Jet = #45
Bypass 1 = 0.8
Bypass 2 = 0.9
Bypass 3 = 0.8
Pilot Screw = 2-1/2 turns from fully closed.

I presume that the diaphragms aren't leaking/split?

Cheers, Vic