650 firing on 3 cylinders

Kawickrice wrote:

The carb for the #1 cylinder will usually clog from sitting a long time, especially when the bike is stored on the sidestand. If you found trash and varnish in the jets I would clean each carb while they are off the bike. Clean and poke the jets again and then make sure the passages are clear. I would clean the tank and petcock also so you don't get trash in your clean carbs. As mentiond before check your plug cap and wire for that cylinder

I concur with above advice from Kawickrice.

With good quality spark in cylinder #1, and valve clearances to specs, (and presumably adequate compression), leaves suspicion of carb (fuel supply and fuel mixture).

If not already done, would also check service fuel level in float bowl of #1 carb (using the clear tube test).

Which carbs are involved? Missed seeing bike year model and if oem carbs are fitted.

Good Luck!

valve lash was checked once upon a time, i remember doing it and picking up the needed shims from Jeff. I can check again, but I am fairly sure compression is not part of this.


I updated my information, it is a 1977 650 c1 with factory carbs.

After cleaning the idle jet (at least thats what I think it was) when I ran it, there was noticeably less white smoke coming from the pipe but as it ran I noticed the smoke came back, right now she is smoking bad again

Tomorrow I will borrow a compression gauge and pick up some new fuel lines and a new filter (the filter is new but hey for a buck I will give it a try)... and I will try cleaning out that jet again.

anything else I should try? New plugs? Hotter plugs?

I know the spark is making it down the plug wire, if you doubt that I would like you to touch my plug wire... it hurts :S (today i learned to grab running plug wires with insulated pliers...not my hand)

Your carbs are clogged, all of them. You need to take them off and clean them REALLY good. You said the bike sat for a year. All the jets are going to be clogged. You cannot clean them up by pouring carb cleaner in the gas or spraying the carbs. You HAVE to take them apart and clean every little jet and hole in the carbs. Hope I have made myself clear on this, CLEAN THE CARBS, that is your problem.

It's all good now!!!

The float was set to low and it was flooding the cylinder with fuel. I put in a new set of plugs, then noticed #1 was just soaked in fuel...so I checked the level and it was way over the top of the float bowl...I am not sure why it was not coming out of the overflow.

the only bummer is it seems that I toasted one of my new plugs before figuring this all out.

Tomorrow I will dive into electric starter repair (i think I need some new brushes...)

But this problem is solved!!!

PS baldy, I cleaned all the jets out yesterday and re cleaned today before I figured it all out.. so those carbs are squeaky clean now!!

hardr0ck68 wrote:

It's all good now!!!

The float was set to low and it was flooding the cylinder with fuel. I put in a new set of plugs, then noticed #1 was just soaked in fuel...so I checked the level and it was way over the top of the float bowl...I am not sure why it was not coming out of the overflow.

the only bummer is it seems that I toasted one of my new plugs before figuring this all out.

Tomorrow I will dive into electric starter repair (i think I need some new brushes...)

But this problem is solved!!!

PS baldy, I cleaned all the jets out yesterday and re cleaned today before I figured it all out.. so those carbs are squeaky clean now!!

Hoping the overflow circuits are now all functional (part of the carb cleaning process).

Would sniff test crankcase oil and check its condition to assure there's no fuel contamination resulting from the previously suspected non-functional overflow circuit.

Good Luck!