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DJinCA, gavin eisler, johnu
Total Likes: 6
Original Post (Thread Starter)
by johnu
So I got my b50mx project done but it is running really hot and I've been told that it is a timing issue. The bike starts fairly easily once you give the carb a good tickle. I have an Electrex ignition which I set exactly as the instuctions that come with it indicate. And to my knowledge the valve timing is set correctly. This is my first time working on a fourstroke engine so I don't know for sure if I have everything right! I am looking for a shop or an individual in Southern California who go through and check to make sure all is correct and rectify if not. If anyone has suggestions as to where I could go in Socal I would appreciate it!
Here is the bike running.
Liked Replies
by Stuart Kirk
Stuart Kirk
There's a saying among ICE (internal combustion engine) repairmen. "90% of carburetor trouble is ignition.) The basic idea is to be sure the ignition system is working proper before going on to solve carb problems.

I just had a look at the Electrex install instructions and note there is a basic problem. Their timing marks "move" when you rotate the stator to adjust the timing. A fixed, non moving timing mark is needed to accurately verify timing. (Like the original timing pointer in the primary case.)

Also, the rotor is not keyed to the shaft but secured by the grip of a tapered collet. Tapers and collets usually hold just fine if torqued properly but the possibility of slippage is real. It would most likely slip towards being retarded.

So, first check the rotor position relative to TDC as per Electrex instructions and correct if needed. Once properly located, consider pinning it.

Next, arrange a fixed timing pointer and mark the rotor for 34 deg BTDC.

Then, check timing with a timing light between 3000- 4000 rpm and adjust as needed.

Finally, ride it to see what jetting work it needs. (Popping on decel is usually an air leak at the head or a lean idle setting or plugged idle jet.)

Hope this helps.
2 members like this
by Stuart Kirk
Stuart Kirk
Definitely check your timing with a strobe light.

Retarded timing will make your pipe glow red pretty quickly and performance will be flat. Advanced timing clue is kick back when starting.

And don't run it like that for any length of time.

Avoid much idling, verify oil flow, get your timing set, and then go out and ride it to load the rings to begin seating them.

These engines are pretty simple. Get yourself a timing light and check that first.
1 member likes this
by BSA_WM20
And before you start, verify the timing line on the stator with a piston stop & timing disc.
Lucas Stators all had the same mountings but there was different positions for the timing line.
Even brand new ones have been known to be wrong.
1 member likes this
by C.B.S

Sounds lean (backfiring & popping)

How did you set the ignition timing?

How thick is the pipe tubing?
1 member likes this
by DMadigan
Rotating the pickup in the same direction as the crank rotates will retard the ignition. To go from 34 degrees to 35.5 degrees, rotate the pickup 1.5 degrees clockwise.
1 member likes this
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