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

[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!

[Nessism]

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.

[G.S.Joe]

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.

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.

[matt1100]

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.

[chuck hahn]

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?

[chuck hahn]

some basic info

Only thing it doesn't state is that the pilot screws ( bottom ones ) go to 3/4 to 7/8 out. I run my 750 at the upper end so I am sure to not be lean.

http://free-pu.htnet.hr/medo/carbs.jpg

and this chart as well...

http://www.mediafire.com/view/?xzzwz5zzyho#

[btbarb]

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

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.

[chuck hahn]

Checked the manual and it states the float hts at 25 to 27 MM so I would hit the center at 26

[G.S.Joe]

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.

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]

Checked the manual and it states the float hts at 25 to 27 MM so I would hit the center at 26

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.

[G.S.Joe]

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.

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...

[chuck hahn]

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?

[chuck hahn]

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!!!

[chuck hahn]

The petcock vacuum goes on number 3 carb nipple..2 and 4 are vents that DO NOT get capped off.

[G.S.Joe]

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?