#3 cylinder seems to not be getting fuel. ( I think??)

[LandscapeMan]

Hi,
1981 GS 850L. Has been in my basement workshop for the past 9 months.
I recently adjusted the valves. Installed some new gaskets and a new clutch cable. New plugs. The bike did not fire when I tried with the old gas. I drained the bowls. And put fresh gas in the tank. And it fired up.

But.... It would only run with the choke on and only at higher RPM. It runs as if the engine is cold. I took it for about a 20 mile ride. It did run better when completely warmed up. But no low end. Had to wind it way up to get started from a stop. Would not idle without me keeping the throttle slightly open.

I pulled the plugs which were all just installed new. 1,2 & 4 had a light tan crusting of deposits. # 3 was completely clean. And the # 3 header was cool compared to the other 3. 1 & 2 were the hottest then 4 a bit cooler and 3 cool. That is after I let the headers cool enogh for me to touch them.

All the plug wires have spark.
I can run the bike with # 3 plug wire off. And it runs about the same with it on or off.

Any ideas on how I should proceed to get this problem repaired? And where the problem might be?

Thank you for your help!
Charlie

[SqDancerLynn1]

Sounds like it needs A good carb cleaning, another check is to swap the 2&3 plug wires

[LandscapeMan]

Sounds like it needs A good carb cleaning, another check is to swap the 2&3 plug wires

Thank you for the reply!

Is there some section of this site that refers to how to do a correct carb cleaning on a GS.

And, what should I look for when switching the #2 and 3 plug wire. I tried switching 3 and 4 but it did not seem to make a change.

Thanks,
Charlie

[Nightmare]

You can't (well shouldn't) switch the #3 and #4 wires because the firing order. Both the #1 and #4 fire together and the #2 and #3 fire together.

Check "In The Garage" VM Carb rebuild, its not EXACTLY like yours (which is a CV carb) but it'll give you enough of an idea as how to do the job... If you are buying carb kits I would avoice the Keystar carb kits as 1/2 of the parts from mine weren't the right size/style.

[LandscapeMan]

You can't (well shouldn't) switch the #3 and #4 wires because the firing order. Both the #1 and #4 fire together and the #2 and #3 fire together.

Check "In The Garage" VM Carb rebuild, its not EXACTLY like yours (which is a CV carb) but it'll give you enough of an idea as how to do the job... If you are buying carb kits I would avoice the Keystar carb kits as 1/2 of the parts from mine weren't the right size/style.

Thanks for the reply. I will try the 2&3 switch and see what happens.
I looked around and found this link.

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

Which looks like it refers to my carbs.
I dread getting that far into my carbs.

Are there any likely possible things to check/clean without doing a total carb disasembly.

If The problem can be isolated to be possibly in one carb. Is it possible to just work on one carb?

I saw a reference to a fuel pickup tube being blocked in another post. Can that be checked /cleaned with out a total carb disasembly?

Thanks,
Charlie

[chef1366]

Just do it. It's not as hard as you think it is. You're just afraid of the unknown.

[tfb]

Double-check that spark plug before you go through all the hard yakka of dismantling carbies.

Last year I had a brand new spark plug give me trouble. Threw it in the bin, popped one of the old ones in, fixed.

Sometimes it can be the darndest things that give you problems. :shock:

[Nightmare]

You could run some carb cleaner designed to clean the carbs with-out disassembly (when I first got my bike I used some of Motomaster's Carb & Combustion cleaner, it did a really good job (which I saw when i rebuilt the carbs later).

"Rebuilding" the carbs is a LOT easier then you think it is, I agree with chef1366, its just fear of the unkown. If you decide to go this route, my advice is: KEEP THE OLD PARTS (at least 3 MONTHS after you are done, as I discovered that POS Keyster carb kit had the wrong fuel valve, but I had my old valve so no biggie), and get proper fitting screw drivers. Also, it wouldn't hurt to buy a replacement screw "kit" off of ebay for the Mikuni CV (constant veloicty) carbs as they replace the horrible phillips screws with hex screws which will help if you need to get back into the carbs later or strip any of the screw heads.

Don't hang me if i'm wrong, but if the problem is a blocked fuel passage its most likely blocked at the fuel valve filter inside of the carbs because I believe the #4 carb is fed through a "T" from the #3 carb.

The previous owner of my bike had a simillar problem with his #3 cyl. he replace the ignition coil, so make sure you swap thoes wires.

[chef1366]

I never use the POS carb kits jets. Just the float needle and seat, gasket and idle mixture screw. Just dip your mikuni jets and reinstall them. The only jet in your carb that can wear out is your needle jet.

[LandscapeMan]

Thanks for all the great responces. Those are the kind of details and discussion that I am looking for. As far as the coils go. I have installed Dana coils. I will try the switching plugs and wires on 2&3. I do have spark on # 3 cyl. And I will look for a blocked passage as suggested.

As far as fear of the unknown. Your right, I have never had to pull the GS carbs down. But I have pulled other carbs down. I have fear of the known and the unknown.

Thanks,
Charlie