Pilot jet size & carb ID

I'll check out the colortune plugs you mentioned.

You were right, I was able to get the bike running today by cranking the idle screw up, then let it warm up and eventually got it all settled back down to a decent idle around 1200. Then I adjusted the pilot screws as you've suggested before. Opened them up then slowly worked them in until the engine stumbled, backed out then tried to find the point where they ceased to increase idle speed. They ended up almost all the way in, maybe half a turn out from set. Then I set the idle set screw again.

The good news was, no popping and a decent idle at just under 1500.

I then took a ride. After a few miles I stopped and the idle had crept up to 2000. Is that normal?

I adjusted the idle set screw and kept riding into town. Sometimes when I'd come to a stop the idle would be high again and I'd fiddle with the set screw to keep the idle at around 1500.

At some point (not entirely sure when) the popping came back.

Am I messing myself up by fiddling with the idle set screw? Is it normal to idle high (2000 rpm) after riding a few miles when you come to a stop?

You asked earlier about whether I checked all the passages with carb spray and the answer is yes. The pilot passages (and all the others) are clear.

Topper wrote: ...idle had crept up to 2000...come to a stop the idle would be high again...popping came back....

Could result from an air leak at carb holder, clamp, vacuum cap, vac hose, etc.

Good Fortune!

I'll check out the colortune plugs you mentioned.

You would only need one plug actually.

You were right, I was able to get the bike running today by cranking the idle screw up, then let it warm up and eventually got it all settled back down to a decent idle around 1200. Then I adjusted the pilot screws as you've suggested before. Opened them up then slowly worked them in until the engine stumbled, backed out then tried to find the point where they ceased to increase idle speed. They ended up almost all the way in, maybe half a turn out from set. Then I set the idle set screw again.

Of course I was... ehem, I mean good, very good. :lol:

The good news was, no popping and a decent idle at just under 1500.

I then took a ride. After a few miles I stopped and the idle had crept up to 2000. Is that normal?

Yes, as the engine heats up the idle can creep up - the bike is not 100% tuned yet, this is why so much.

I adjusted the idle set screw and kept riding into town. Sometimes when I'd come to a stop the idle would be high again and I'd fiddle with the set screw to keep the idle at around 1500.

At some point (not entirely sure when) the popping came back.

Am I messing myself up by fiddling with the idle set screw? Is it normal to idle high (2000 rpm) after riding a few miles when you come to a stop?

Your not messing yourself up really, its all part of the adjusting process. Its not considered normal for the bike to have a hanging/high idle. It should stay where you set it, but there is more to be done.

You asked earlier about whether I checked all the passages with carb spray and the answer is yes. The pilot passages (and all the others) are clear.

Good stuff.

OK, so your carbs have what are called mixture adjustment screws (not air screws), so turning them out increases the mixture (richer) at idle, and in is leaner.

Turn the screws out another half turn and go for a nice ride, just as you had before.
Then once the bike is good and hot, and the idle has stopped creeping up - go back home and now tune your mix screws.

Drop the idle down to 1000-1200.

You need to have a BIG FAN pointed at the headers if you plan on taking a while (5min - more).

Different method on the screws: Turn them out slowly till the engine stumbles/notice a sharp drop in rpm, them turn them in 1/4 turn at a time - listening for an increase in idle. Not far in from the stumble spot will be the point of highest idle on the richer side of things.

This should help considerably. If the idle is still creeping up like crazy, but no popping - could be out of sync. Both mixture screws should end up near the same position. If bike cannot idle without stalling at around 800rpm, then a vacuum sync is necessary.

If the popping is only on hard decell, proper mixture adjustment will likely fix it. If the adjustment is considerably different than eachother (one carb requiring a much larger amount of fuel input) than air leak is present/or pilot system blockage. Popping all the time and constant idle hanging high - deffinately air leak.

Also make sure advancer unit is clean and operating properly.

Good luck!

:evil:

Patton wrote: Could result from an air leak at carb holder, clamp, vacuum cap, vac hose, etc.

Thanks Patton. I've looked for leaks, triple checked my boots and clamps, tried the WD-40 test and can't find any leaks.

TeK9iNe wrote: If you have the carbs off the bike again, reseal the carb to engine holders to the engine with some good Permatex Motoseal, or another gas resistant gasket or epoxy

I've got some gasket sealant, so I can give this a try this weekend. Would I put the sealant between the carbs and boots/holders or just between the holders and the engine? What about between the intake boots and airbox? All of the above?

I'd be a little afraid sealing the boots to the carbs might make carb removal kind of difficult.

What sort of idle should I be shooting for when I pull up to a stop light? I can get the idle fairly low and stable when the bike has just warmed up, but then while riding it seems to want to be around 2000rpm. Is that too high?

I've got some gasket sealant, so I can give this a try this weekend. Would I put the sealant between the carbs and boots/holders or just between the holders and the engine? What about between the intake boots and airbox? All of the above?

The gasket sealant must say resistant to gasoline.

Between holders and engine is usually fine. Not too many people do the boots to airbox, but I have seen it done. No carb contact with the gasket stuff

I'd be a little afraid sealing the boots to the carbs might make carb removal kind of difficult.

Right, I would tend to agree.

You should have good clamps on the carb holders, and good springs or clamps on the sirbox side as well.

What sort of idle should I be shooting for when I pull up to a stop light? I can get the idle fairly low and stable when the bike has just warmed up, but then while riding it seems to want to be around 2000rpm. Is that too high?

1000rpm. When you let off the throttle it should drop right to 1000. Sometimes with heavy oil you can get a little clutch drag that will make the idle drop just a hair lower then come back up after a second or two, but thats fine.

2000 is too high. Tune the mix screws as I suggested and then re-assert the situation.

Cheers.

:evil:

make sure the throttle cables are free and lubed. the rise of idle rpm can sometimes be due to the cables.
also keep in mind that as the engine warms it will naturaly richen. thats why we need the choke to start a cold eng. (nateraly lean when cold.) so make sure it is warmed up before tuning carbs.

Topper wrote: ...looked for leaks, triple checked my boots and clamps, tried the WD-40 test and can't find any leaks....

Might try propane for better coverage.
If vacuum petcock, assure vac hose is in good condition and well attached at both ends.

Also assure throttle cables aren't binding, and have a little slack where connected to carb bell crank.
With engine off, closing throttle should produce a definite "click" as the bell crank makes contact with end of the idle thumb screw.

Good Fortune!

No popping for now...

Well I was only able to go for a short ride (20 minutes) before shooting this clip, but things seem a lot better. The popping seems to be gone and I've got the idle down around 1100. There's still a little gallop to the engine though. I'm not sure what that is, but may require a new thread.

I tried to follow all of your advice on the air mix screws but I realized I was thinking too much and that was getting in the way of really listening to the engine. When I stopped and really listened, I was able to find that point of highest idle. Knowing I needed to do it with the bike really warm helped too. I had been trying to do it after the bike had just been running 5 minutes or so.

I'm going to reserve judgement until I've made a full trip into town (about 45 minutes away) on the bike. There are big thunderstorms in the forecast for the next several days so it may be a while. But for now anyway the popping finally seems to be gone.

olliver.trey-mitchell.com/wp-content/upl...1-03-21-18-50-38.mp4

Right on man. Sounds pretty good. You should be able to set the idle down very low - if not, you probly need a good vacum sync performed.

These bikes even when tuned perfectly, can have a small lope to the idle, when set down low. At 1000 it should purr fairly consistantly though.

Good luck.

Had a chance to go for another long ride today. No popping, no coughing. Decent stable idle around 1100. I think I will do a vacumm sync sometime in the near future. I don't have the right tools right now, but I'll either buy them or find someone who can loan them to me for a quick adjustment. Thanks for all the help.