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

  • Thread starter Thread starter G.S.Joe
  • Start date Start date
G

G.S.Joe

Guest
Finally finished rebuilding the carbs, new O-rings, checked tappet clearance and put a new valve cover gasket on and changed the plugs and plug boots. She starts first kick now, which she didn't before, but I can't get her to idle. I start half to full choke, and ease it off as RPMs jump. RPMs dive down to ~500 and tries to die. I bump up the choke to 1/4th...still almost dying. Half choke, almost dying. 3/4 choke, RPMs rise up to 3K and settle to about 2K. Give her a few seconds, drop down to 1/2 choke and we start the whole "500 RPM and almost dying" thing again.

If I give her throttle I get a metal-rubbing-metal sound. New to me. Any ideas?


I've done this routine about 5 times today. Also, how long in front of a 2' box fan at full blast on a 80 degree day before I should begin to worry? This is my first bike, I'm not sure how long I get until overheating comes in to play.


As always, thanks for your input!
 
Is the bike stock? Did you vacuum sync the carbs? Were are the pilot screws?

Good on you for recognizing not to run the engine without airflow. If you keep the fan blowing high speed, you should be fine to run it long enough to tune the carbs and such.
 
Nessism said:
Is the bike stock? Did you vacuum sync the carbs? Were are the pilot screws?

Good on you for recognizing not to run the engine without airflow. If you keep the fan blowing high speed, you should be fine to run it long enough to tune the carbs and such.
Click to expand...

She's got pods and 117.5 pilots, bumped the needle up 1 slot. But do the pilots come into play without throttle?

I did not vacuum sync the carbs. My plan was to get her running and take her to the shop. Is there no way to get it running decently without a sync?



May have found the culprit(s). Fuel was dripping out of one of the pods when the bike was off.. I've been having problems with the petcock, rebuilt it, the rebuilt kit's plug in the center of the diaphragm was too short so I made a Frankenstein petcock with some new and some old parts. It held water when I actuated it with my mouth, but I suppose this is a different ball game. Apparently I need to gap the floats better too.


Are there any known GOOD petcock rebuild kits out there? I'd hate to go to an on/off petcock as I'm forgetful.
 
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. I've read here that tuning with pods is difficult.

Did you at least bench sync the carbs?

The forum consensus is that petcock rebuild kits do not work. Z1 sells a good aftermarket unit.
 
Got the vent nipples open and not capped off? They need atmospheric pressure down the vents to equalize the pressure in the bowls..sort of a vapor lock condition.

Bottom pilot screws are at?

Side mixture screws???

What float ht did you set them at and did you set them without a bowl gasket in place?

If your not using the vacuum to the petcock off number 3, be sure that IS capped off or youll have a massive vacuum leak.

Once it starts have you turned the idle knob in a bit to see if it remains running?
 
G.S.Joe said:
She's got pods and 117.5 pilots, bumped the needle up 1 slot. But do the pilots come into play without throttle?
Click to expand...

Yes, pilots come into play from zero to about 1/4 throttle. From memory, I don't think the pilot jet of 117.5 is right, I think the stock pilot jet is 15 and the next size up is 17. 117.5 sounds like a main jet size.

When you say "bumping the needle up", if that means you put the clip on say the #2 slot from the top instead of #3, that would force the needle lower which would lean the mixture out, I think that's the opposite of what you want to do with pods. The pods give you more air. To get the air/fuel ratio right, you need more fuel, not less.
 
Checked the manual and it states the float hts at 25 to 27 MM so I would hit the center at 26
 
Bottom pilots are at 1.5 out

Sides (air?) are at 1.5 out

Floats were at 25mm, I just bent them up to 26mm with the the gaskets out.


Hmmm... the petcock... I put it on #2 and did not cap any off. Are all the unused ones supposed to be capped?

I diddled with the idle while it was running and it liked higher idle a lot more. Once it hits around 1500 or lower it would drop itself to about 500 and sputter out.

chuck hahn said:
Got the vent nipples open and not capped off? They need atmospheric pressure down the vents to equalize the pressure in the bowls..sort of a vapor lock condition.

Bottom pilot screws are at?

Side mixture screws???

What float ht did you set them at and did you set them without a bowl gasket in place?

If your not using the vacuum to the petcock off number 3, be sure that IS capped off or youll have a massive vacuum leak.

Once it starts have you turned the idle knob in a bit to see if it remains running?
Click to expand...
 
chuck hahn said:
Checked the manual and it states the float hts at 25 to 27 MM so I would hit the center at 26
Click to expand...


They were at 25 and I brought them to 26, but would 1mm cause fuel to pore out the carbs into the pods? Even 25mm is still in tolerance. I'm confused.
 
btbarb said:
Yes, pilots come into play from zero to about 1/4 throttle. From memory, I don't think the pilot jet of 117.5 is right, I think the stock pilot jet is 15 and the next size up is 17. 117.5 sounds like a main jet size.

When you say "bumping the needle up", if that means you put the clip on say the #2 slot from the top instead of #3, that would force the needle lower which would lean the mixture out, I think that's the opposite of what you want to do with pods. The pods give you more air. To get the air/fuel ratio right, you need more fuel, not less.
Click to expand...


You are correct about my poor use of jet terminology. Pilots are stock and mains are 117.5. I'll have to check which way I moved the clips. I thought I did it in a way described on this site, but it's been a few weeks so my memory is blurry...
 
Yes theres a tolerance of 25 to 27...not all carbs are spot on the same though. At 25, the fuel would need to rise HIGHER in the bowls to apply enough pressure to the float needles to shut off the fuel flow FULLY.

At 26, theres gonna be now enough pressure to shut off the fuel BEFORE it gets to an over flow level...follow the way it works now?
 
Set the bottom pilot screws at 7/8 out...that's way way too rich for stock jets. Side mixture screws per that chart AND go by the engine number stamped on the flat above the edge of the clutch cover!!!
 
The petcock vacuum goes on number 3 carb nipple..2 and 4 are vents that DO NOT get capped off.
 
Well Chuck, you've managed to find the problem when I didn't even talk about petcock hoses. I changed the petcock over to carb 3 (and tweaked the float tabs) and the bike went from sputtering to smooth. She cuts out the second I back off on choke, but that sounds like a air/fuel mixing screws issue to me. Or maybe I was pussyfooting around too much about overheating and didn't let her sit on choke long enough. I'll change the settings you recommended tomorrow for the screws. Anyway, I need to be up in 5 hours, I'm calling it since I don't have a flathead that can get the mixture screw under the bowl without pulling the carb rack.

Out of curiosity, if the VM26SS carbs are the same, what did Suzuki change in the engines to accommodate for the different mixture in different serial numbered engines?
 
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.
 
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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.
 
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!
 
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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.
 
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?
 
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