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Calling all Carb Gurus!

  • Thread starter Thread starter Anonymous
  • Start date Start date
Another update. I cleaned the petcock and bench synced the carbs. I put everything back together, and it wouldn't start. I double checked the petcock, One of those crummy 1980 petcocks with only prime and run and no vacuum line, and that was flowing fine. As a shot in the dark I blew into each of the vent lines and it fired right up. It runs for about a minute, and then dies. I can repeat, and repeat, but it will never stay running. Anyone have any ideas. I set the float level, so I think that is correct, but I can double check if anyone thinks that might be the issue.

Thanks,

Brian
 
The only thing I can think of that blowing into the floatbowl vents would do, is the air coming in would displace the fuel a little and that could allow the float valve to drop and let a little more fuel in. This higher fuel level would be used up very quickly, a minute as you say. I can't think of anything else blowing into those vents would do.
So I'd have to say your float level is still too low. How are you measuring? Are your floats round or are they odd shaped and your measuring at the wrong point? Sure sounds like lack of fuel, even if not the float levels.
 
Keith, I thought that may be I did the float levels wrong, I believe I read one of your posts in another thread that you measure from the curved point on the floats and not the high point that goes back to the pivot point. In the morning I will try to adjust the floats using the rounded top of the float and not the flat part to the arm. Thanks again for the help, I thought it might have been wrong.

Brian
 
bjmorel said:
Keith, I thought that may be I did the float levels wrong, I believe I read one of your posts in another thread that you measure from the curved point on the floats and not the high point that goes back to the pivot point. In the morning I will try to adjust the floats using the rounded top of the float and not the flat part to the arm. Thanks again for the help, I thought it might have been wrong.

Brian
Click to expand...
Right. At least you know where to measure now, and without the bowl gasket in place.
If you did measure and adjust at the high point as you said, then you actually set the fuel level too high. This would be a rich condition that seems to contradict you thinking the bike is running lean. You did say covering the carb openings helped the bike run longer. The covering would cut down air flow, so running longer would make you think it was lean. But covering the carbs would also cut down the vacuum and the jets would draw less fuel too. You also say the plugs are black, suggesting a rich condition, but this could be due to over-choking.
I would adjust the floats correctly and at least that will be one possible problem eliminated if you still have a problem. Hopefully, the carbs are clean inside as you say and are synched correctly. If they aren't, the bike won't run well. Also, your spark should be bluish and strong. Fouled/stained plugs will hinder good spark. The spark may be trailing the carbon deposits to ground instead of jumping the gap. Check your spark too.
 
Up here in Canada the Suzuki float gauge costs about 25 bucks. The factory manual gives you the spec for float height with the engine idling so you know for sure if you've got it right. :) I think you could build the gauge for about 2 bucks and an hour of labour. It is just a tube hooked up to the float drain.

Steve
 
OK, new update. I put brand new mikuni float valves and seats in and set the float height. I put in mikuni pilot jet one size larger, and main jets two sizes larger. It now idles really nice, but boggs down when you hit the throttle. I assume that the stock needles need to be raised, but there stock. I'm going to look into spacers and see what I can come up with, but I need to find someone that has a sync tool first. I'll update when anything changes.

Brian
 
Yes, the bike still needs a vacuum synch before any plug reads or performance can be taken seriously. You also need to raise the jet needles. Also, make sure your two float bowl vent lines are removed and the ports left open. This is a requirement with pods and many jet kits include this info to avoid fuel starvation. Pods effect some models differently, but removing the lines helps. I don't know how I forgot to mention this earlier, since you mentioned pods and blowing into the vent lines.
Raise the jet needles first and then the synch. Good luck.
 
This is a photo of my needle assembly apart.

P1010050.jpg


I am going to radio shack to get some spacers, but I need to know where to put them and how many.

Brian
 
Be careful with the diaphragm on that slide!

Either flop it all the way down or all the way up.
If it dries all bent and buckled like how you have it I can guarantee you you're gonna hafta replace it soon after the rubber splits.
:evil:
 
To raise the jet needle, put the new spacer(s) directly under the needles e-clip. Be sure to re-install all parts the same way you removed them.
I don't have a lot of experience with "shimming" the needles, but raising the needle one full position should be about .045". I can't say if this will be the correct amount for your bike. You have to test. But allowing for just Emgo pods (stock exhaust), I would guess one position richer will get you close. I would doubt that you would need more than about .07" (1 1/2 positions) lift or less than the .045 I said. So get spacer(s) that will work within that range and you should be good. Now bench/vacuum synch.
Road test. If it feels good, get plug reads by chopping off at solid 1/3 throttle to be sure mixture color is acceptable. Mark your throttle to be sure.
 
It's Alive!!!!!!!!!!!!!!!

Anyway, I put a size higher pilot jet, and two sizes higher main jet, and shimmed the needles .6 and it now runs fairly well, and I just took it for its first cruise around the yard. In case your wondering, I've never road a bike before, and it doesn't have a plate, so it might not be on the road till I go take one of those weekend bike classes. I just received my colortune in the mail, so I will be going through and adjusting with that until I get comfortable enough on the bike to take it out for some real road testing. Thanks again everyone for the excellent help.
 
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