Guys need help with carbs. long story but had to change  carbs. Since this i have had a prob.
Bike pulls well through all gears except top gear. At 70 mph the bike starts to splutter and has
no lift. (not that i would ride in excess of the speed limit   ).  It's as if the bike is
running out of fuel. Back fires quite a bit as well. Is really annoying.
The carbs have 120 jets. Is this standard size?
Can anyone give me some advice on solving this one.


d33k3s

(Keep 'er between the hedges)

df3

Welcome!

Why did you have to change carburetors?

In the stock carbs, the main jet sizes are 122.5, but should be 125.

If you have completely different carbs in your bike, we need to know, what kind, model and size carbs you have.

Hi,

Thanks for your advice. Its a long story, but I damaged my carbs taking a restrictor kit out of it. So I bought a standard set of carbs from a GS which was being broken.
They were the exact same carbs as the ones I damaged. The main jets in the restricted carbs were 117. I put the standard mains back in (125). So it should be pretty much
standard. I Checked the plugs and found the tips were white, so its been running lean. I dropped the clip on the needle to the bottom notch. It has been running a bit better. If you 'wind the bag out of it' and push it past 6000rpm it will pull ok up to about 80mph before dying a bit. But if I am cruising about 5000rpm and try to accelerate there's just nothing. Its driving me mad at the moment. I use the bike everyday traveling to work so I need it sorted before the winter really sets in.

Cheers for any advice you can give me

D33k3s

What year model?  We need to know some more.  You're in Ireland, which is okay; if you have an '89 to '00 model, you should have size 40 pilot jets.  The needle should be set to the second from the bottom, with 125 main jets.

See if your in-tank fuel filter is clogged.

Also, did you set your float levels?  Having them even is important, but also the fuel level should be up to the float bowl gasket surface.  Check it using the clear tube method (search).

Next is carb synchronization - synchronizing the vacuum between the two carbs, or just making sure that the butterflies open at the same time, the same amount.

Another thing that may be causing problems is the frame mounted vacuum petcock.

Lastly, I would inspect the fuel lines for detrioration.  There will be little black things floating in the gas from the floatbowls.

Valve adjustment might be something else.  When was the last valve adjustment?

Scratch has some good advice, you should do all of those things, but if you're still experiencing that problem, there is a modifacation on the racing section of this site to replace the petcock with a simple higher flow one. If that dosen't work you may want to go up to a 130 main jet, but if everything is stock, 125 should be fine.

Also make sure that you put a fuel filter inline just before the carb, the paper wones work best in my oppinion, the sintered metal lets the fine stuff through. All it takes is one little piece of junk in there to make your bike nun like crap.
good luck 

Cheers Guys,

Some excellent advice. I'll work my way through all the tips. My bike is 1998. Had been running fine
on the resticted kit. Hopefully will get it running again.

Noticed another problem. Was wondering if it might effect things. The main 30amp fuse has been
damaging the fuse holder. Have repalced fuse three times now. Would this effect the spark at high revs?

If I get this sorted I owe a pint or to if anyone is over in Ireland



D33k3s