[grateguy]

I've got a kick-only SL350 engine that I rebuilt in the spring and have not gotten it to run yet. Triple checked the valves and static timing and everything is to spec. Compression test read 125 psi on both cylinders. I've got a new set of Mikuni VM30 carbs on it (bench synced to the best of my ability). My foot is sore from trying to get this thing to kick start.

So far the only signs of life it's shown have been the right carb blowing off the manifold once and then flames shooting out of it another time.

Any ideas what is causing this or what I should try? It's also been about 30 degrees outside every time I've tried starting it, so maybe that's not helping.

 

[TOOLS1]

I think you have the ignition out of time. It is firing with an exhaust valve open. Edit: Intake valve.
TOOLS

 

[ancientdad]

^^^agreed - the first thought that comes to mind is your spark advance unit. If you pulled the advancer off the camshaft and the breaker cam lobe came off, it's possible it went back on 180° out. That could cause a backfire through the carbs

 

[grateguy]

I'll check the advance unit in the morning. The static timing looked to be dead on when I re checked it with my test light.

 

[TOOLS1]

Static timing can be dead on at 180* off.
TOOLS

 

[mike in idaho]

When you check the static timing, check for clearance at the rockers(both valves closed).

 

[Crashoverride]

I got this off another link, describes it better than I can but I think when you put the points plate back together it is possible to put it in wrong and be 180 off it will never start then.

When you timed the cam gear to the LT mark was the cam positioned with the pin up. Thats the pin located on the end of the cam shaft behind the cam advancer mechanism. That pin locks the cam advancer in the right position and should be straight up when timing the cam, cam gear and the LT mark all together. :-\

CB350 spark advance/points (not starting up)

 

[zgoldwingman]

If flames or backfire is coming out the carb, I would be pretty sure the Intake valve is open. If it comes out the exhaust, the ex valve is open. Timing off and a valve too tight.

 

[grateguy]

The cam pin is locked into the advance unit correctly. Tried flipping the advance lobe and couldn't get it to time correctly, so I flipped it back. Checked the static timing and on each "fire" the corresponding valve tappets have play so I think the valves are closed when they should be.

I installed the cam according to the HSM so I'm sure I did that right.

I'm using an old condenser that I can't confirm worked, so I just bought a new one to be safe.

Also I installed a cam/rockers/cam gear from the early TYPE 1 model cam, and I may have gotten the advance unit from a later model 350. I assumed they were interchangeable though.

 

[doode]

Post a photo of your advance unit off the bike.

 

[Rob Axel]

...You say you have checked the timing and it is correct...HOW are you checking this?? What "marks" are you using? are THEY accurate?
I say VERIFY the position of your piston location with the marks you are using...AND the valve timing....
I would suggest doing this with a degree wheel (on-line printable-glue it to cardboard and attach it to the rotor), pointer and a piston stop..
But like the guys have said...its probably 180 out...

 

[grateguy]

GOT IT. Charged the battery over night, popped on a new condenser, made sure there were no loose wires, reset timing and valves to spec AGAIN and now it runs first kick or two. Not sure what did it, but I'm just happy it's trying to idle. Now onto tuning the carbs...

 

[Rob Axel]

My wife's 450 DOHC was having ignition issues.. discovered the ground for the condensers were corroded... cleaned..bang! No issues..