1982 GS750T Carb Rebuild Problem

[Uruka]

My friend and I rebuilt the carbs on his GS750t, we did it the kosher way. Complete disassembly, dip, cleaned all the ports with the special tool, then we used new carb rebuild kits to put em back together. New pilot, main, and air jets; new airscrews, needle valve and seat. The bike ran before the rebuild, but now I can't get it to start. This is the third set of carbs I have rebuilt and I'm pretty sure that I didn't make a mistake in the reassembly. The one change that was made is the new kits had larger sized main jets. The old ones were 76s, the new ones are 112s (I think). I figured it would be alright to go with the new larger jets since the bike already has K&N pod filters and the plugs indicated that it had been running on the lean side. Any tips??

 

[Steve]

Well, you were doing OK until you said you used rebuild kits.

If you had 76 main jets in there, they were not Mikuni, therefore, not stock. Even if they were the proper jets, the jump all the way to 112 would be WAY too much. Something around 90 would be more appropriate. However, I just looked in my sources and found that 112.5 was the stock main jet for the '82 750T. To compensate for pods, you might try 120. If you also have a pipe, maybe 127.5.

.

 

[Uruka]

I thought those 76s were undersize. The kit came with 112s and thats what I went with. You're right, I ought to put 127s in, it has pods and a 4-1 with a Yoshimura pipe. I got it to start now, but it idles at 3000rpm and stalls out when I hit the throttle. How many turns on them air screws?

 

[Nessism]

I thought those 76s were undersize. The kit came with 112s and thats what I went with. You're right, I ought to put 127s in, it has pods and a 4-1 with a Yoshimura pipe. I got it to start now, but it idles at 3000rpm and stalls out when I hit the throttle. How many turns on them air screws?

Try 3 turns but please, don't even attempt to ride the bike since you will burn up the engine without the proper jetting.

 

[Uruka]

I advised my buddy to get larger jets, so we're going to install those after he picks em up. After I got the bike running the strangest thing was happening. I got it to idle at 1200 rpm smoothly; it's smooth through the low range 1200-5000; but when I open the throttle more, around 6000-8000, the engine will drop to 3000 then rev up to 5000, over and over. If I open the throttle even more, 8000+, the engine speed remains constant. I'm puzzled.

 

[Nessism]

I advised my buddy to get larger jets, so we're going to install those after he picks em up. After I got the bike running the strangest thing was happening. I got it to idle at 1200 rpm smoothly; it's smooth through the low range 1200-5000; but when I open the throttle more, around 6000-8000, the engine will drop to 3000 then rev up to 5000, over and over. If I open the throttle even more, 8000+, the engine speed remains constant. I'm puzzled.

The mixture is too lean. You can damage it by thrashing it like that.

 

[Dave8338]

The mixture is too lean. You can damage it by thrashing it like that.

I didn't see anywhere, where the engine was under load. Tell me you're not doing that, on the center stand... :|

 

[Uruka]

On a dyno. I suppose I'll hold off on it until I get the jets.

 

[Uruka]

Thanks guys. We bought the stage 3 Dynojet kit and the machine goes like a bat out of hell!