Shoots out carb, unstable idle - I have tried everything.

[Emilws]

Hi guys.

I am so lost!
PMA installed, New coils, New plugs, new caps, new points and condenser. Cleaned carbs several times, also ilde screw hole. Cleaned the really filty petcocks, new gaskets in them. Also changed fuel filters. No air leaks.

I re-checked point gap, and found out that the advance springs was really sloppy, and did not return. I cut some of them off, so they got more tension and returned again.
Still shoots carb of like in the video.
Also if I pull the spark plug, it is fine on the left side, but sooted on the right and sometimes smoke comes out of the spark plug hole right after killing the engine.

What could it be? It feels like I have tried everything, also running without the pod filters - no change.

Here is a video where it happens. Typically when I pull the throttle.

It cannot idle without dying for more approx one minute.

I have had nothing but trouble since I got this bike, but I really like it and need the engine to run reliably

Best.

Emil

 

[TwoManyXS1Bs]

It's running on the right cylinder.

Left side has problems. Probably not enough fuel, or too much air.

Left ignition may also have problems. Try swapping condenser wires left/right...

 

[Brassneck]

Are the carbs seated fully? Aftermarket boots?

 

[grizld1]

OK, you tightened up the advance unit springs. Now check ignition timing in both retarded and advanced positions. I suspect you'll find that the advance curve has stretched due to worn tips on the advance unit weights; what usually causes the carbies to jump out of the boots is idle timing that's rolled way back to prevent excessive advance when rpm's pick up. Check compression on both cylinders.

 

[Emilws]

@TwoManyXS1Bs
Thanks, I will try swap the wires at the points end, to see if the problem lies there.

@Brassneck
I think it's the original boots, although one of the tightning bands are aftermarket. I don't suspect that it is the issue as they seal fine and has no air leaks?

@grizld1
Just to clarify - the retarded position is when the timing mark on the rotor aligns between the two lines by the "F" mark right? And the advance position is exactly at TDC? On a sidenote, I had to make new timing marks after fitting the PMA system. The new TDC mark I made by looking through the spark plug hole seems accurate, but the F and (retarded?) marks measured from the new TDC mark, as the distance specified from the old alternator housing. I hope this was the right way to do it.
I will try setting the timing again after tightening the springs.
Could this be the solution or should the tightening of springs be good enough?
http://www.heidentuning.com/p/28/1844/mo74-cgp2%7C23=1/%2314-0651-auto-advance-spring-%26-clip-set
Do I need a strobe timing light to measure full advance or is a 12 volt light enought to set the ignition?
(Sorry for all the noobish questions)

I guess the easy and expensive way to overcome these issue would be a pamco ignition? I kinda want to avoid this, as it's supposed to be a budget build.
I will also measure the compression. If it is off, isn't solution new piston rings? I guess that would be a bigger operation at this time, so I really don't hope that the problem is related to compression.
Another question; I have bought a carb sync. gauge, bur unlike my honda cb350f I can't figure out where to attach them or if it is even necessary on this bike. On the four cylinder honda, there are wholes to attach it between the manifold and the engine, but not on the this bike?

Thanks a lot guys.

 

[grizld1]

Book spec. ignition timing: full retard at 15* BTDC, full advance at 38* BTDC. You have a bit of leeway on the retard end, and many of us get good results setting advanced timing at 35 or 36* You can't accurately locate TDC by looking in the plug hole.

I told you what the usual ATU issue is. Clips and springs have nothing to do with it. Inspect before you jump to any conclusions, that may not be the source of your trouble. Read and think before you do.

 

[Heimir Bardason]

I have been dealing with a very similar problem in my XS and I found the solution in my case; I had done everything I (and my friends) could think of; Cleaned out the 38 mm carbs thoroughly and set the float height. I went through the whole stock ignition replacing one item at a time. Set the ignition with a strobe light, checked the gaps. No matter what I did, always backfired and ran erratically at idle.

To cut it short, my problem was a small crack in one of the ignition coils. Could not see it until I took it off the bike as the crack was where the coil is attached to the frame !!

Hope this helps your case....
Best,
Heimir Bardason.