No 4 cyl not working

[colin9623]

Just finishing a resto project on my GS1000EN, It is running on 3 cyls . When I pull no. 4 lead off the rpm doesn’t change. It has had a complete topend rebuild with new piston’s, head reconditioned, new timing chain etc. carbies cleaned with new O-rings including intake O-rings (thanks Robert Barr) float level set. Fuel pilot screws set at 2 turns out, air pilot screws 1 ¼ turns out. New petcock, I have good compression, good spark, when I cranked it over before doing a compression test quit a bit of fuel shot out of that cyl, but of cause the fuel iwas not being burnt I guess. When I had it running with the top covers of the carbies off there was a noise of perhaps a leak getting past the slide on no. 4. Not sure if this is a wore slide, or something else is causing it, but didn’t notice it on any of the others. The bike is looking good and I would just like to ride it, it been a year since I started this project. Any idea’s are welcome. And thank the those that have got GS Resoures happening!!!! I would send a photo if I knew how. I do I set up a URL?
Colin9623[-o<

[psyguy]

dunno much about vm carbs
but this should enable you to show us your toy :-D

Use your Photobucket (or whatever) picture listing. Depending on the settings you have in your account options, you might see up to four lines under each photo. I have found only two of them useful for posting pictures on this forum.
These are the options that are possible:
Display Share URL Display Direct Link Display Tag Display IMG
I only have the Direct Link and the IMG options listed for my albums.

To show up to 4 pictures in your post, open Photobucket in a separate window from the GS forum. Find the picture you want to show, click on the line that has IMG. You will get a message that says "Copied". Now go back to the message you are typing, make sure you are starting on a new line, and paste the link (Ctrl + V). You will only see the link until you preview your message, then the picture will appear. To make the picture sit better in the post, be sure it is on its own line, with no typing in front of or behind it.

[Nessism]

Fuel screws should be about 1 turn out, not two - at least for starters.

Not sure about the carb noise difference but if a cylinder is not firing it makes sense that there would be some difference in the way the air is being pulled through that one carb.

Only other thing to suggest is check the plug again to make sure it's firing. The plug caps sometimes go bad and/or the plug wire develops resistance. It sometimes helps to snip off one cm of plug wire and screw on the cap back on.

Good luck.

[KEITH KRAUSE]

So right now, if you placed a good plug in the 4 cap, you'd get a good bluish spark just like the other three?
If so, then it's obvious you have too much fuel in the mixture to allow combustion.
Considering what you said is already done...
Did you do a bench synch? Are you positive the slides are uniform? Don't synch these carbs with a drill bit either (if you have). Use your eyes and adjust all slides to their lowest/uniform position.
Next thoughts would be float level adjustment and float assembly operation. .94/.95" is right in the middle of the factory .90 to .98" float level range. Verify fuel level with a float bowl level gauge if you make one up out of a spare bowl drain bolt and tubing. Anything incorrect, such as a leaking/weak/
worn float needle valve, sticking float operation, missing/damaged float needle valve seat fiber gasket, will allow too much fuel.
If all that is verified OK, inspect the choke plunger to be sure it's seating fully when the cable is released and that it is in synch with the others.
As for the pilot fuel (underneath) and side air screw adjustments, it's sometimes necessary to adjust the pilot fuel screws a little differently from each other to allow for any differences in each cylinder. If this bike is stock, 2 full turns out from lightly seated is way too rich. The other three cylinders may be operating OK at the moment with the same adjustment but there could be other factors combined with this excessive screw adjustment to foul the #4 cylinder more easily. Even a modded 1000E like mine (pipe/pods/piston kit) generally doesn't want the pilot fuel screws that far out. Try 1 turn out across if stock, 1 1/2 turns out if pipe/pods, and initially adjust #4 pilot fuel screw 1/4 turn less than the others.
The side air screws are to be adjusted using the highest rpm method, with 1,000/1,100 rpm as the base rpm. They generally end up 1 1/2 to 1 3/4 turns out. Too little air flow and poor fuel atomization can be the result if adjusted incorrectly.
Also be sure the air jet and passage (filter side) are 100% clear.
I'll assume you know all parts are in factory order, including jet needle assembly and e-clip position, and all other jets and parts are correct/identical.
Something above should be the cause of your problem. If it re-starts and fires on all 4, warm it up fully and adjust air screws for best idle (highest rpm method). Then you'll need to final synch with a vacuum gauge.

[earlfor]

Remove the #4 spark plug, stick it back into the plug boot and ground the tip against the engine. Crank it over a few times with the starter button. If you have spark on the plug gap, it is not an ignition problem. Considering everything else you have done, and if there is spark on the plug, then it is a synch problem. #4 is too far out of synch (either rich or lean) for the mixture to ignite.

Earl

Just finishing a resto project on my GS1000EN, It is running on 3 cyls . When I pull no. 4 lead off the rpm doesn’t change. It has had a complete topend rebuild with new piston’s, head reconditioned, new timing chain etc. carbies cleaned with new O-rings including intake O-rings (thanks Robert Barr) float level set. Fuel pilot screws set at 2 turns out, air pilot screws 1 ¼ turns out. New petcock, I have good compression, good spark, when I cranked it over before doing a compression test quit a bit of fuel shot out of that cyl, but of cause the fuel iwas not being burnt I guess. When I had it running with the top covers of the carbies off there was a noise of perhaps a leak getting past the slide on no. 4. Not sure if this is a wore slide, or something else is causing it, but didn’t notice it on any of the others. The bike is looking good and I would just like to ride it, it been a year since I started this project. Any idea’s are welcome. And thank the those that have got GS Resoures happening!!!! I would send a photo if I knew how. I do I set up a URL?
Colin9623[-o<

[colin9623]

No 4 cyl not working

Thanks for all the advice, let you know how I go! Tried to upload photo, have fitted brake lines since and will send more soon. Colin, Aust.

[KEITH KRAUSE]

The bike looks good!
Now that I see you have a stock intake, that's even more reason to lean the pilot fuel screws. 2 turns out is just too much as I said. Try 1 turn from LIGHTLY seated. Don't want to damage/break off the sharp tipped screws.
The factory often sends them out at as little as 1/2 turn though that's rare. 3/4 to 1 turn seems to be the most common straight from the factory. Should work fine at 1 turn, then maybe a little fine tuning later.