Carb tuning issues

[Cbraun]

So i got the bike running decent (with no filters, Airbox busted) until i got up to around 40-45 mph and then it loses power. Now i put some pod filters on the bike it idles fine but it has no power off idle at all. I have no idea what Main jets are in it i cant find any numbers stamped into the brass. I have no idea where to start with the jets.

Any help will be greatly appreciated.    

[movenon]

Others will chime in shortly. But lets start off with more information. What year of FJ are we talking about ?
George

[Pat Conlon]

Chris, it would be helpful to add in your signature line that you have a '85 FJ600. Help us help you.

Assuming that you now have stock jets in those small Mikuni CV32 carbs, a quick look at the microfiche shows what sizes:
http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1985/FJ600N/CARBURETOR/parts.html

So it looks like you have #35 pilots, suggest bumping those up to #37.5 for low speed/off idle response.
You also have #102.5 main jets, suggest bumping those up to 105's
Add a 1/2 step shim on your needles and you should be on the road to recovery.

Buy new jets. Don't guess. They cost chump change.

[Cbraun]

Sorry about that thought i had that set up :/
Yes it is an 85 Fj600

[Cbraun]

Ill order those and see what happens and let you know how it goes. Thanks for the info

[Cbraun]

OK so finally after my impulse buying of cars is over for a while i ordered the jets . I'm currently waiting for the parts to arrive. Now my question is: does anyone know if they went to the EPA needles in 85 or if these needles have the multiple notches in them, and what would be considered a 1/2 step?

[Pat Conlon]

USA bikes had non adjustable needles.

The shims are quite thin. (The small ss washers I bought at Ace Hardware were too thick)
Others will chime in on the washer thickness for the 1/2 step shims.
....or, you can spend $3.00 and have Randy do all the figuring out for you:

http://www.rpmracingca.com/proddetail.asp?prod=Carb%3AMainNeedleShim&cat=50

[Arnie]

The grooves in the "normal" needles are 1mm apart.  The shim washer is 0.5mm thick aka 1/2 groove.

For those who are metrically challenged, 1mm = 0.040 inch  so 0.5mm = 0.020 inch

[Cbraun]

Alright cool Thanks for the info

[Pat Conlon]

Thanks Arnie

[Cbraun]

So I got the Jets all installed and the needles shimmed and Holy Crap the difference took it out on a back road and hit 70 no problem. Thank you all so much for the info and advice. All that's left is to get new front brake lines and minor reassembly and i can go get my licence this spring, maybe earlier with the way the weather has been here lol.