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Issues with Cylinder 3, Vaccum leak?

  • Thread starter Thread starter mortation
  • Start date Start date
I have CV carbs and everything is connected right. I am gonna ride it for a while and see how it makes out. Right now it only sputters a little at high RPMS other than that everything is fine. All pipes are equally hot, everthing is connected right, synced as best I know how.
 
OK then, I think doing a precise vacuum synch will solve the problem. Manual synch's are really not meant for anything more than getting the engine to a point it will run so you can do the actual synch. The problem you are having could be caused by the #3 slide being out of position by as little as fraction of a mm in position. you would not even be able to see that small amount when doing a bench/setup synch.

Earl

mortation said:
I have CV carbs and everything is connected right. I am gonna ride it for a while and see how it makes out. Right now it only sputters a little at high RPMS other than that everything is fine. All pipes are equally hot, everthing is connected right, synced as best I know how.
Click to expand...
 
earlfor said:
OK then, I think doing a precise vacuum synch will solve the problem. Manual synch's are really not meant for anything more than getting the engine to a point it will run so you can do the actual synch. The problem you are having could be caused by the #3 slide being out of position by as little as fraction of a mm in position. you would not even be able to see that small amount when doing a bench/setup synch.

Earl
Click to expand...

Well after swapping the engine side boots on 2 & 3 cause I had them wrong it is popping out of both exhaust pipes at high RPMS off the throttle. If I stay on the throttle there is no popping. So I must still have a small leak some place right?

Grr this is frustrating :(
 
I've had the same problem. It used to be #3 and has now moved to #1 so it's not a leak in the boot because nothing has changed.
 
N56629 said:
I've had the same problem. It used to be #3 and has now moved to #1 so it's not a leak in the boot because nothing has changed.
Click to expand...

1 & 3 use the same coil. Your issue may be coil related.

Mine was a leak. It now runs the same temp as the other pipes now that I fixed the bunched up boot. But I think I screwed up my sink ports by tightening the screw to much and shewing up the rubber around the hole. I am gonna do one more sweeping replacement of boots, Orings, sync screws and gaskets. If it still pops after that I will be replacing the exhaust gaskets and chain tensioner cause it sthere :P If it still pops I am gonna go get my hammer....
 
I would think that if it were a coil the problem would be at all speeds. Besides, I replaced the factory coils with accel. I would say boots but I haven't made any changes there. I am thinking about replacing the boot orings just so that they get removed and inspected. Even though I've just cleaned the carbs I'm thinking the pilot circuit might be the culprit because I've never removed the sealed screws. I think that might explain the low speed fuel starvation on #1. I know I have spark because I can see it and the plug is not wet.
 
I am REALLY about to loose my $h1t. This bike is driving me NUTS. I put an old boot on #2 with a new O ring and new sync screw and it is still popping. Maybe #1 is making it pop? I don't know but I am starting to get a little frustrated here.

#3 has started to be cooler again while idling.

I am about ready to smash this thing with a 50 lb sledge hammer!

I can buy all new engine side boots (Again), O rings (Again), exhaust gaskets, Coils, Wires, Plugs (AGAIN!) I am sure somewhere around $500 total and then I may still end up in the same boat.

ARGH!
 
I'm still thinking pilot circuit. One thing I noticed is that I couldn't possibly do a carb sync when the engine is cold. The vacuum on my #1 cylinder is way high. Once it warms up and is getting gas like the other three the vacuum is very close to the same.

Anyone know when the main jet takes over and the pilot no longer delivers any fuel? I'm thinking between 1500 and 1800 rpm.
 
Well I will see where I stand next week. I ordered 4 new boots with gaskets, 4 new O rings, 4 new exhaust gaskets, and a new tensioner gasket (Hey its in the same area and it was only $3!). If it still pops after that I am gonna track down a color tune and do my mixture exact. Then re-sync. And if it still pops I guess I will have no choice but to replace the exhaust. Than still popping I will rejet. Then still popping its for sale :P
 
Popping = Lean

Popping = Lean

no other reason....unplug one plug at a time and replace back while the bike is running. Check if the popping stops when the plug is removed ...if it does you know the problem is in that cylinder area. then you can go deeper...may have to increase the idle so the bike does not go off.


make sure you have rubber gloves or something when you do it.
 
N56629 said:
I'm still thinking pilot circuit. One thing I noticed is that I couldn't possibly do a carb sync when the engine is cold. The vacuum on my #1 cylinder is way high. Once it warms up and is getting gas like the other three the vacuum is very close to the same.

Anyone know when the main jet takes over and the pilot no longer delivers any fuel? I'm thinking between 1500 and 1800 rpm.
Click to expand...

According to the instructions you are not supposed to do a carb sync till it is warmed up. Dunno if it matters though...
 
anikmankar said:
no other reason....unplug one plug at a time and replace back while the bike is running. Check if the popping stops when the plug is removed ...if it does you know the problem is in that cylinder area. then you can go deeper...may have to increase the idle so the bike does not go off.


make sure you have rubber gloves or something when you do it.
Click to expand...

It only pops when riding. Dunno if I should ride it with one plug disconnected...
 
I had same problem with '79 GS1000S. Check vacuum hose from #3carb to back of fuel tap (petcock ?). Previous owner had removed it. I blanked both connections using short pieces of fuel line and zip ties although now run position is now OFF,no reserve and bike runs on PRI. I refuel using trip meter as guide. Good luck
 
This is a funny situation. I have had something similar, though. Do you have the vacuum-controlled fuel cock? I do. Mine had a vacuum leak, and was only letting enough fuel trickle in to feed #3 adequately. I actually vacuum-sycnhed the carbs and it ran really hot on 1, 2, and 4. Couldn't figure it out for the longest time, but I had the tank off and the carbs, doing the dyno stage 3 kit 'cause of new V&H kit thinking I was just out of whack from the new pipes, but I got to looking at the petcock and tested it, and got no fuel on the PRI position, and a bare trickle on the run position with a large sucking sound around the screw. Theoretically, you're giong to get enough fuel for the #3, and depending on the severity of the problem, you starve everything else. Rich #3 and lean 1, 2, and 4. I've heard the Pingel gravity feed with adapter plate touted highly, but I got original on ebay for $50, so decided not to reinvent the wheel. I'll find out tomorrow if my theory is correct. I'll let you know.
 
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