Calling all Carb Gurus!

[Anonymous]

Keith, how exactly do I bench synch the carbs. I found a post of yours about the VM carbs, but is the process the same for the CV carbs?

Brian

[lhanscom]

Get a small drill bit, with the carbs off the bike, set the idle so the drill bit just fits under the butterfly in the carb throat. Then set the other butterflys using the sync adjusters until they're all the right spacing, then readjust your idle to where it was. I've also done it with a bright light, and just comparing the light shining thru the carb bodys, but the first method is probably more accurate. A vac sync should be done as soon as the bike is running, it's the only way to get it right, as having the butterflys the same, may not be what you want exactly, but it will get you close.

[KEITH KRAUSE]

Keith, how exactly do I bench synch the carbs. I found a post of yours about the VM carbs, but is the process the same for the CV carbs?

Brian

Those Chilton manuals don't even show basic stuff like a carb synch? :?
I think Luke answered you good enough. The idea of the bench synch is to get the carbs close enough to run decent and then the vacuum tool synch must be done. Be sure to put a couple of fans on the motor.
If you still need more detailed synch info, I'm sure someone will help.

[Anonymous]

For the pod filters, you'll have to re-jet all 3 circuits or you'll run very lean.

what would you suggest for jets for the pilot circuit? Is it the same rule of thumb as with the main jets? 2 sizes up for 4into1, another 2 sizes for pods?

also what are the the 3 circuits? Idle, Pilot, High Speed?

[KEITH KRAUSE]

For the pod filters, you'll have to re-jet all 3 circuits or you'll run very lean.

what would you suggest for jets for the pilot circuit? Is it the same rule of thumb as with the main jets? 2 sizes up for 4into1, another 2 sizes for pods?

also what are the the 3 circuits? Idle, Pilot, High Speed?

Those "rules of thumb" are intended to get you in the ballpark. It depends on how the filters flow in this case. On Brians bike, for the pilot circuit, I would try mixture screw adjustments first. Nothing to lose. If by 4 turns out you don't get it rich enough, then I'd go up on the pilots a step and return the mixture screws to where they were and test. The air jet may have to be changed too. Do what the performance/plug reads tell you. I just cruise around at mimimal throttle position to get pilot plug reads.
Vacuum synch the carbs before getting plug reads.
The 3 circuits I'm talking about are the pilot, jet needle and main.

[Anonymous]

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

[KEITH KRAUSE]

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.

[Anonymous]

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

[KEITH KRAUSE]

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

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.

[Anonymous]

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

[Anonymous]

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

[KEITH KRAUSE]

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.

[Anonymous]

This is a photo of my needle assembly apart.



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

Brian

[Detman101]

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.

[KEITH KRAUSE]

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.