Hi Guys,
I bought a gs500 before christmas as my first big bike and at the time it was a non runner, since buying it I have put in a new engine and got it running however I've ran into a spot of trouble.

When i first got it running it would only get up to 40mph regardless of what you did, eventually a backfire and big smoke cloud seemed to have allowed it to reach 60, since then I have replaced the ht leads, coils, coil caps, spark plugs and carbs which has boosted it further however whenever I get it to 80 it then begins jumping and wont go any higher.

I've read that fuel starvation is a problem so today i checked my spark plugs again and one is them is running rather lean, I have put a sock over the air filter and also used PRI which has made it a lot more responsive and doesnt give the initial idle rev lag but still wont shift past 80, I have also removed the diaphram and made the fuel a direct feed. anyone have any ideas what the cause or fix could be? I've spent 80 man hours trying to fix this problem but cant seem to find the fix.

Thanks for reading

I forgot to mention, I have also blocked the loner vacuum pipe on the carb and left the other one connected to the petcock as ive bypassed it, I have also shortened the fuel pipes to the maximum, ive checked the u tube, checked compression and stripped and cleaned the carbs.

Well it looks like it might be running lean, another 3 rolled up socks in the air filter and its as smooth as its ever been and even hits 95mph... time to change the main jets

It may be as simple as adjusting the mixture screws. Maybe another 1/4 to 1/2 turn out. Try that before playing with the jets.

Thought I'd post a recent experience with my bike and fuel starvation at WOT in high gears (8,000+ RPM in 4th, 5th & 6th). I had put a HUGE fuel filter on the bike (between CRF petcock and carb) in hopes that it would NOT cause starvation issues. I don't have a part number, but it's designed for a car & has 5/16" barbs.  Well, it WAS the cause of my problem. I took the filter off and with no other changes at all (to the bike, temperatures, type of riding) I'm absolutely positive it was the cause.

Hope that helps.