bad idle after carb cleaning

hexec · Sep 18, 2010

Hoping someone can provide some guidance. I've read almost every post and article on carb adjustments and can't find what I need.

I have taken my carbs apart and cleaned every opening I can find with carb cleaner and blew them out clean. I did a dry float adjustment that has you line up the circle in the jet block with the arch in the float when held upside down.

Idle cannot be held at all and it seems very unstable below 3k. The A/F valves do not seem to make any difference at all regardless of how many turns.

I suspect the float level but I'm not sure if the float level has anything to do with setting idle or low RPM stability. The carbs seems to be very responsive above 3k.

I'm going to do a wet float read. Does this have to be done with the engine running to make sure the fuel level in the bowl is maintained? I'm sure filling a tube with gas will lower the bowl level slightly.

Rhoy Carter · Sep 18, 2010

checkand make sure the carbs are seated all the way into the carb joints

hexec · Sep 18, 2010

They are all seated correctly.

2fear · Sep 18, 2010

Did you do a carb synch after install?

Damon · Sep 18, 2010

1st, while checking the float level, yes have the engine running & bike on center stand.
2nd, I have ran across carb-sets that just won't run/adjust correctly for the low speed jets/air/fuel mixture screws etc. The only solution that has worked in these types of cases for me was to replace the pilot jets with new, even if you think you can see & shoot cleaner through them. I don't know how to explain it but I have run into this very same condition.

hexec · Sep 18, 2010

That makes sense Damon. I was also thinking of doing that but just couldn't bring myself to do it since cleaner would easily pass through. The other thing was the pilot valves. One is missing a washer and oring and the rest look like the oring is very flat.

Other thing to note is that I just took this bike out of storage after about 12 -15 years (stopped counting years exactly). I knew I was going to have a problem with the carbs. That's why I disassembled them and cleaned them good. I installed new slides and changed the main jet to 150.

Rhoy Carter · Sep 18, 2010

You can use one strand of 14 or 16 gauge wire to run through the pilot jets

hexec · Sep 18, 2010

Thanks Rhoy, that's a great suggestion. I've got lots of wire. Electronics is my other hobby.....lol.

hexec · Sep 18, 2010

Can someone please confirm what I'm thinking regarding the pilot screw. I think I'm getting leakage from outside of the carb. If air was allowed to enter from the top of the pilot screw because the o-ring was not making a good seal then the mixture would be much too lean to perform at low rpms.

Damon · Sep 19, 2010

Yes what you have referenced in the diagram is the pilot screw-fuel/air mixture screw assembly. The four components are the needle screw, spring, washer, & “O” ring. If you feel your getting leakage and don’t have the “O” rings installed you might want to find a rubber cap/seal that you can install once you have made your final adjustment. This is always a good practice to keep out the moisture that will eventually cause the screws to seas-up.

maleko89 · Sep 19, 2010

Check your idle thumb screw.

hexec · Sep 19, 2010

maleko89 said:
Check your idle thumb screw.

Hey Mark, I know your trying to help and sometimes the really simple things are the ones that bite but not this time. In fact, its the idle screw that helped me determine that the other circuits in the carb are ok. With the idle screw almost all the way in, as soon as I blimp the throttle past 3k it takes off. I suspect that the carb is using a different circuit at this rev. So, I have to fix the low rev circuit which is why I'm focusing on the pilot screws and float level.

maleko89 · Sep 19, 2010

No problem, I wasn't trying to be a smart ass.

Does the condition bet better or worse if you apply the choke?

hexec · Sep 19, 2010

Thanks for all the help everyone. I checked the float levels and they were right on. I decided to blow out the pilot circuit again and I found an o-ring to put in the pilot screw were it was missing. As soon as it started up it raced to redline. I knew right away that everything was fixed because my idle adjustment was way too high. As soon as I lowered it my idle was restored to normal.

I also noticed something rather interesting. The airbox had a puddle of what looked like dirty water. I have no ideal where this water would be coming from but it looks like it's coming from the crank vent entry into the airbox. The oil is a milky color which tells me there is water in the oil. Where would the water come from? I only put a small amount of water in the rad the rest was coolant.

one2dmax · Sep 20, 2010

The "Snot" is common in the airbox. Clean up what you can and don't worry much about it after that. Milky oil however isn't good. Do an oil change and see if it clears up. It may take 2-3 oil changes to get it clear again. If it persists then you may have a blown head gasket. It could get in there from a few other places (like cylinder head crossover tubes).

Sean

hexec · Sep 20, 2010

This thread is turning into an oil/water discussion in a carb forum.....lol

Thanks Sean. Strange thing about the water in the airbox is that there is no water in the engine to draw from. The puddling in the airbox has zero slickness, seems like pure water that is dirty. The only thing I can think of is when I degreased and hosed the motor down before paint. I'll keep an eye on this for sure. I'll try the few oil changes with standard (cheap) oil.

hexec · Sep 21, 2010

Ok, now that I have my idle under control I wanted to tune the F/A mix for each carb. However, the pilot screws do not seem to have any effect at all. Its very strange. I can turn them in all the way or out all the way (one at a time) and it does not stumble at all. Something is still wrong here. This doesn't make sense to me.

btw, oil cleared up and no more dirty water in the airbox. I must have water logged the block when I was degreasing it before paint.

maleko89 · Sep 21, 2010

There are a few things that can cause this. Loose or bad carb/vboost/air box boots, high tick over speed, bad sync, open or leaking choke, a very high float level (under 15 mm wet), needle too high, rubber plugs in jet block too loose or bad.

hexec · Sep 21, 2010

Thanks Mark.....great suggestions.

Loose or bad carb/vboost/air box boots....checked ok
high tick over speed......? (not sure what this is....is this the idle screw?)
bad sync.....will check again
open or leaking choke....choke seems to operate properly, will call this checked ok.
very high float level....wet check ok at 16 -17 mm.
needle too high .... set to the middle clip
rubber plugs in jet block too loose or bad....seemed very snug when I had the carbs apart.

Can I try moving 1 needle to the next position that drives the tip deeper into the jet and test mix screw or do I need ot do them all?

I'm suspecting the gasket under the jetblock. Looked pretty bad when I had it out but thought I could still get a good seal. Will order new ones.

hexec · Sep 26, 2010

Replaced gaskets and still having issues.

- Loose or bad carb/vboost/air box boots....checked ok
- high tick over speed......? (not sure what this is....is this the idle screw?)
- bad sync.....cannot get a reading at idle on sync tool, see this thread http://www.vmaxforum.net/showthread.php?t=14302
- open or leaking choke....choke seems to operate properly, will call this checked ok.
- very high float level....wet check ok at 16 -17 mm.
- needle too high .... set to the middle clip
- rubber plugs in jet block too loose or bad....looks good and tight.

bad idle after carb cleaning

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