Problems with #1 Cylinder

[Anonymous]

Here's my problem; My number one cylinder isn't firing at idle. The pipe stays cold. (colder than the others) The bike feels like it has all four working at higher RPMs, but I'm not going to reach down and pull the plug at 75+ mph I have a good spark there and I have fuel to the carb. Empty the bowl, hit prime, the bowl fills again. I dropped the Bowl and cleaned the needle and jets on that carb. All seemed to be in working order, but I cleaned them anyway. I also don't smell gas when its running at idle. The plug is not wet when I pull it out. Where is the blockage? Is it a sticky intake valve? is it the set screw at the top of the needle? Does that need adjusted. And the biggest question follows, are there any springs inside the carb? As I was putting the bowl back on the carb I discovered a small approx 3/8" by 1/4" brass colored spring on my garage floor. I know I lost one during an unrelated project a while back. I'm hoping it belongs to that and not my carb!!!

It also runs a little rough at the lower RPMs.

Any help will be appreciated,

Dave W.
Mount Joy, Pa.

[redliner1973]

Sounds like a clogged pilot jet. remove carbs, float bowl, take out jets and clean everything. may have happened to gotten rust inside it. install a filter inline if you haven't already. :twisted:

[Anonymous]

Thanks for the response Prop, but I already did that. I have had an in line filter installed for a while now. Is the main jet the one that the needle seats into? If so, then I cleaned that one already. This has me stumped. :?

Dave W.

[Anonymous]

On top of the jets themselves, there are drillings in the carb body which get clogged. Ensure all the drillings are clear, best way is with compressed air, and lots of it.

[Anonymous]

The only spring that I can recall is on the air pilot jet screw. And they are silver colour, not brass, on two sets of carbs I have.

Kim

[Anonymous]

I appreciate the help so far guys. I know I'm going to sound like an idiot, but do the jets have smaller holes on their sides? I have never taken the carbs apart before. If thats right, then they are as clean as they can be. All smaller holes are clear.

Will it harm my bike if I run it on three cylinders until I can figure this out?

Thanks Dave W.

[frosty5011]

Dave,

Have you had a chance to look at the "Carb cleanup" series?

http://www.thegsresources.com/gs_carbrebuild.htm

If you want to rebuild/clean the carbs correctly - then this area is an invaluable tool. It also tells you the names of each part.

As far as running the bike on only 3 cylinders, I don't know what to tell you. Personally, I do not think it's a good idea - I've done it in emergencys, that's it. Others may say it's OK. It all depends, I guess, on why the 4th cylinder isn't running. I just don't like the idea of cylinder possibly slowly filling with fluid (gas), and not combusting. Now you're suddenly trying to compress a liquid......and so forth.

[Anonymous]

I did look at that link, but the carbs are newer than mine. I don't know if it is a carb problem. Would a sticking intake valve, no vacuum to the fuel, cause something like I indicated? I will probably dismantle everything this weekend, I'm wishing myself luck.

Thanks

Dave W.

[frosty5011]

Sorry Dave,

Didn't know you had the older VM style carbs. I really have no experience with them, but they should be similar. If things don't work well with you having cleaned pilot / main / needle jets, then good possibility is either one of the passages in carb body is clogged....or perhaps something is wrong with the float (either defective, or height is set wrong).

If all the above is OK, then it may be the mixture adjustments. I think your style carb (VM) has 2 different adjustment screws on each carb. Someone with experience on those carbs will have to help you out there.

But, from what you say....(cylinder not firing at low rpms/idle, but seems to work at higher rpms), my first impression would have been clogged pilot jet - or perhaps float height set wrong, fuel level too low.

Really hope you get this worked out - Good Luck !!!