.png "Powered by vBulletin")
Hi all,
I've recently gone through some pretty extensive work on my 1978 GS750 and it runs great but there's some small issues i'd still like to solve. I have replaced the points, did the valve adjustment, and replaced the carburetor O-rings as well as the boot O-rings. I finished installing the carburetors, set the idle fuel screws and air screws. The fuel screws liked to be just barely over 1 turn out on all 4 and the air screws are right around 2.5 out on all 4.
The bike seems to run great almost all the time. But I am getting a minor carb backfire, it seems like it's the number 2 carburetor but I can't really tell for sure. When I took the carbs off, all 4 boots were a little wet with fuel and I couldn't see any obvious signs of backfire on the intake tubes. If I ride say 80 miles in a day it'll only backfire maybe one or two times which I think is strange. It usually happens if I lightly blip the throttle for a downshift or starting out at a green light just off idle. The throttle response is a little sluggish if I go straight to full throttle off idle but unnoticeable in normal riding. I'm also getting some popping out the exhaust on deceleration although this may be normal with a 4 into 1 i'm not sure. I should probably mention the bike is entirely stock with the exception of the unknown brand 4 into 1 and a UNI filter in the stock box. It has a 15 pilot jet and plastic mains that are stamped 120 but I put in a set of 117.5's and they were way to rich so they must be stamped wrong.
The last thing is that I seem to be getting some fuel out of the bowl vents/overflows. I can't see it dripping when I put the petcock on prime and I never see any drips while riding or at a red light. But when I get back from a long ride the bottom of the vent tubes are a little wet and the bike smells like fresh fuel after parking it in the garage.
Some things I've already checked are the vacuum line to the petcock I checked with carb cleaner and by pinching the line with no change in the idle. I've also checked to make sure the new intake boot O-rings sealed. One thing to note is that when syncing the carbs there seemed to be some slight vacuum leaking past the slide into the top cover area on the #1 carburetor and not on the others. Is this normal?
I've recently gone through some pretty extensive work on my 1978 GS750 and it runs great but there's some small issues i'd still like to solve. I have replaced the points, did the valve adjustment, and replaced the carburetor O-rings as well as the boot O-rings. I finished installing the carburetors, set the idle fuel screws and air screws. The fuel screws liked to be just barely over 1 turn out on all 4 and the air screws are right around 2.5 out on all 4.
The bike seems to run great almost all the time. But I am getting a minor carb backfire, it seems like it's the number 2 carburetor but I can't really tell for sure. When I took the carbs off, all 4 boots were a little wet with fuel and I couldn't see any obvious signs of backfire on the intake tubes. If I ride say 80 miles in a day it'll only backfire maybe one or two times which I think is strange. It usually happens if I lightly blip the throttle for a downshift or starting out at a green light just off idle. The throttle response is a little sluggish if I go straight to full throttle off idle but unnoticeable in normal riding. I'm also getting some popping out the exhaust on deceleration although this may be normal with a 4 into 1 i'm not sure. I should probably mention the bike is entirely stock with the exception of the unknown brand 4 into 1 and a UNI filter in the stock box. It has a 15 pilot jet and plastic mains that are stamped 120 but I put in a set of 117.5's and they were way to rich so they must be stamped wrong.
The last thing is that I seem to be getting some fuel out of the bowl vents/overflows. I can't see it dripping when I put the petcock on prime and I never see any drips while riding or at a red light. But when I get back from a long ride the bottom of the vent tubes are a little wet and the bike smells like fresh fuel after parking it in the garage.
Some things I've already checked are the vacuum line to the petcock I checked with carb cleaner and by pinching the line with no change in the idle. I've also checked to make sure the new intake boot O-rings sealed. One thing to note is that when syncing the carbs there seemed to be some slight vacuum leaking past the slide into the top cover area on the #1 carburetor and not on the others. Is this normal?
Comment