Yamaha TRX850 Enthusiasts Forum

Hi Guys, I've got a quick question about float levels. Have any members found it necessary to alter their float level to get the engine to run cleanly after exhaust and/or airbox mods? I've got a custom 2 into 1, pod filters, and Factory Pro needles and tubes and am getting the bike Dynoed in a couple of days, and am not sure whether the tuner will want or need to adjust the float levels to get it right.

I have never encounted having to adjust a carb float level to accomodate another mod being done to an engine. If a level is too high it will flood like crazy, to low and you run out of fuel, under normal conditions.

+1
std float level.
you can use the front holes of the bowl to mate up to the rear ones to hold it together when making the level adjustment(see the factorypro website).
needle clips in the middle amd three turns out on the mixtures to start with
std airbox with no extra holes and a K&N filter.
if you get a "hole" between 3 and 4 thousand revs when you grab the throttle, try changing your end cap restrictor(db killer) for more back pressure.
mine seems to work.
cheers
fung

Thanks Fung, Stankflapper, bike is running very poorly below 3500rpm. I raised needle to second groove from bottom (that is needle in second highest position) and its improved a lot but still not right. Idles fine and pulls hard above 3500. Previous owner had altered carb setting hugely to try to compensate for worn tubes. Float level was set to 9mm above gasket surface, and main jet was 75 instead of 140. Currently running 137.5 main jet and 14 mm float level. I don't have an endcap restrictor on my muffler. Might be worth trying the Yamaha needles with the Factory Pro tubes. Someone on here tried that with good results. At least now its rideable so I can get it to the dyno on Thursday.

yes . . . . main jet size ! sorry
mine is OEM size (in the specs in the manual online...ssssshhhh)
cheers
fung

Hi Homer, twas me that used new genuine needles with FP emulsion tubes - was just set up in
the shed (no dyno work) & it runs great!! Pulls nice & clean all the way from idle - no flat spots
or fluffiness at all.

I just fitted a factory pro kit only to have the same issues. What I ended up working out after reading some of the issues others had ie common things specially the main jet being 75. That jet is actually the start jet as per the Yamaha supp for the maintenance manual. The jet looks like a normal main jet as per a set of horizontal carbies. The main jet is actually the jet beside this one held in with the clip fitted under the start jet. It has an oring on it, mine was a 142.5. This is also the fuel path to the emulsion tube. Once I worked this out I refitted the 75 jet as opposed to the 142 one supplied with the jet kit and now it runs fine with the factory pro needles as well. Fuel height set to 14 mm. What I also noticed was that it need absolutely no choke to start and if you did use the choke it would not run. The emulsion tubes and the new needles have fixed my down low rich problems and should last much longer than the standard ones. I am using a k&n filter with a 2 into one exhaust.