Rebuilt carbs, new O-rings, now unsteady idle. Ideas?

[chuck hahn]

Inline 4s need some warming up before you get good throttle response..even with well tuned engines. Its the extra cylinder heat that helps vaporize the gas mixture better...least that my theory.

Anyways, what I do is start it and feather back the choke til its at around 2,000 RPMS or so and give it a good minute or two to get some heat in the holes. I try the throttle and if it is weak I just reset the choke and give it a little more time.

I have been told it was the EPA regs that changed the emissions, thus the changes. They just kept track of what engine number they wre at when change 1 took effect and change 2 and so on.

[chuck hahn]

Set the big idle knob till it idles at around 1000 to 1200 RPMS on a well warmed up engine. You can set a fan or two on high speed in front of the engine to do all the adjustments and to get it warmed well without any risks of over heating it.

[G.S.Joe]

I set up the screws per Chuck's recommendation. She runs for a bit, then dies. No matter where the idle screw is. I fiddled with the fuel and air pilots, no change. But I noticed that if I primed it for 30 seconds she would run well for a good minute or so. If I tried to start it (after it died) while just on ON it would fire for about 2 seconds. Repeated this exercise many times with the same results. The hoses are non-original, soft, and snug. Somewhere there much be a vac leak.

No less. I ran it on prime and it kept running as long as I kept the choke up and kept the idle at or above 2K. Let it sit there for about 5 minutes (with fans) and still if I even brought the choke to 3/4 or backed off the idle screw it would sputter out.

Last and maybe worst, once she got hot she was "poofing" white smoke every now and then out of the cyl 1-2 exhaust. Time for a compression test? I need to find a gauge I think. My sense of smell is very poor, I didn't smell oil, but that means little. Before the carb teardown I had it running around my yard for a good half-hour (poorly) with no smoke, so I'm hoping this is a heat issue as apposed to needing a rebuild.



I've never tuned a carb, let alone 4 rebuilds on a 35 y/o bike. I just want her running!

[chuck hahn]

Well if it will run for 5 minutes on PRIme with the choke added. I would say two, things are combining to form a perfect storm.

1...even if they were cleaned, theres still a clog somewhere in the pilot circuit and

2..the petcock isn't operating right. Not open ing with the vacuum like it should be doing. Petcock is probably gone bad.

[chuck hahn]

Puffs of blueish white oil smoke or is it like a water vaporish kind of puffs??

Wonder if you've got an ignition problem as well? Bad plug caps ( bad resistors inside the caps), cracked wires arching to the engine? Does it have points and condensors still or change to electronic ignition? Timing set right?

[elrico]

'Have you replaced the o-rings behind the intake boots which bolt to the head? s the rubber on the intake boots themselves hard and cracked? You may have a vacuum leak there'....as matt110 said. Often overlooked or forgotten .This is a huge vacuum leak area.If those 4 large O rings are bad all the proper measures of cleaning and tuning etc.will not produce results.

[G.S.Joe]

Puffs of blueish white oil smoke or is it like a water vaporish kind of puffs??

Wonder if you've got an ignition problem as well? Bad plug caps ( bad resistors inside the caps), cracked wires arching to the engine? Does it have points and condensors still or change to electronic ignition? Timing set right?

Too thick to be water vapor in my opinion. You could actually hear the puffs. I didn't notice a bluish tint, but given that it looks nothing like vapor and lasted too long I'm guessing it must be oil.


I don't know enough about ignition to say whether it has condensers or electric, but I believe it to be stock. I'd check but I'm at work now. I did not check the timing, that was next on the list after a compression check.

BUT... I fired it up before checking compression and it fired up easily. Said "ok", left it on prime, and let her warm up. Backed off the choke, and for reasons I do not understand idled nicely. I tweaked the idle screw and rode her around for an hour. Stopped and started over a dozen times, ran great, no issues. Didn't even pop with rev/gear changes.


I don't understand this. Clearly there's still a problem somewhere. I'm running her on prime for now as I'm putting every penny towards my car right now, but when funds are freer I'll pony-up and get a new petcock and other things. Those rebuild kits were a waste of time.

[G.S.Joe]

Well if it will run for 5 minutes on PRIme with the choke added. I would say two, things are combining to form a perfect storm.

1...even if they were cleaned, theres still a clog somewhere in the pilot circuit and

2..the petcock isn't operating right. Not open ing with the vacuum like it should be doing. Petcock is probably gone bad.

Likely agreed on #2, but with #1 I ran gauge pins through all holes. Not to say that I couldn't have stirred something up and re-clogged it. I did a thorough job cleaning the tank, but with all the pulling off and putting on parts over and over checking for things I could have easily gotten guck in there.

[G.S.Joe]

'Have you replaced the o-rings behind the intake boots which bolt to the head? s the rubber on the intake boots themselves hard and cracked? You may have a vacuum leak there'....as matt110 said. Often overlooked or forgotten .This is a huge vacuum leak area.If those 4 large O rings are bad all the proper measures of cleaning and tuning etc.will not produce results.

I replaced the intake/head rings and they were in horrible (flat and cracked) condition. Overall bike runs much better after that and a carb rebuild, valvecover gasket, plugs, etc. My boots are very soft surprisingly so I did not replace them. Also has to do with the cost of them and my suspicion of the petcock. Though she runs great now it's only on prime. I can track down a vacuum leak, it'll just take time. I may buy a new petcock when the budget affords just for piece of mind.

[elrico]

Good to hear things are doing better for you and GS.