Help Static Timing Pamco Ignition

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boxbodybangin

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Hello everybody,

I’m gonna try to keep this brief as I tend to ramble, but I recently picked up this 1980 hack-job of a chopper off FB MP to fix up and it’s proving to be more work than anticipated. I’m able to get the bike to kick over with some starter fluid, but it does not start. It back fires and wants to start but eventually dies after 3-5 seconds.
After consulting with everybody I could possibly think of that works with Japanese bikes, I’ve had multiple people assuming it’s a timing issue. The only problem is, the only help I can find for trying to adjust timing with this PMA system is for DYNAMIC timing. I’m a novice when it comes to bike mechanics, but i’ve been doing all the research I can and been buying all the necessary tools. The bike has a Pamco PMA ignition and Mikuni VM34 dual carb kit from TC. Bros. So far I’ve adjusted the cam chain, but again, there’s no real guides on how to adjust the timing of this ignition system that doesn’t involve a timing light, a running engine and measuring RPMs.
Engine has good compression, carbs absolutely need to be adjusted (though I can’t adjust them without the bike running), and both valves show movement. I just need a ton of help and I don’t even know where to begin to try and get this thing running. I should mention, I haven’t tried hooking up a battery and the owner before me deleted all electronic controls. I’m going to try hooking a battery up and seeing if maybe that gets it to start, but I am not extremely hopeful it’s an issue that small.
 
I’m including some pictures here for reference.
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I see an open vacuum port on the one carb .....

OpenVacPort.jpg


That needs to be capped or the bike may not run. It could be as simple as that. Check the other carb for one of those too, and make sure it's capped as well if you find one. You use those vacuum ports to connect sync gauges to sync the carbs, they should be capped otherwise.

If it still won't run after that, do as Jan suggested - move the timing a little at a time until the bike will run. Looking at the adjustment slots on the Pamco timing plate, it appears the timing is set pretty far retarded. I'd move it towards the center of the adjustment slot a little at a time.

But, as I said, that open vacuum port may be the issue, so "fix" that first and try to start it.
 
5twins said:
I see an open vacuum port on the one carb .....

View attachment 349512

That needs to be capped or the bike may not run. It could be as simple as that. Check the other carb for one of those too, and make sure it's capped as well if you find one. You use those vacuum ports to connect sync gauges to sync the carbs, they should be capped otherwise.

If it still won't run after that, do as Jan suggested - move the timing a little at a time until the bike will run. Looking at the adjustment slots on the Pamco timing plate, it appears the timing is set pretty far retarded. I'd move it towards the center of the adjustment slot a little at a time.

But, as I said, that open vacuum port may be the issue, so "fix" that first and try to start it.
Click to expand...
So after capping both holes on the carbs and advancing the timing, I got it started for around 2 seconds, got a super sluggish throttle response, then it died. That’s promising. It’s running straight pipes and it’s backfiring still when kicking over, but now I don’t need starter fluid to get it to make any amount of sound which is good. Any suggestions on where to go from here?
 
boxbodybangin said:
So after capping both holes on the carbs and advancing the timing, I got it started for around 2 seconds, got a super sluggish throttle response, then it died. That’s promising. It’s running straight pipes and it’s backfiring still when kicking over, but now I don’t need starter fluid to get it to make any amount of sound which is good. Any suggestions on where to go from here?
Click to expand...
are you using choke? use the choke to get it started and dont crack the throttle. let the bike get going.
 
I'd keep fooling around with the timing setting. If the cam chain is old and somewhat stretched out, maybe where the timing was set is where it needs to be? The cam chain tensioner pushes against the rear run of the chain. As the chain wears and stretches, the tensioner effectively rolls the cam backwards and that advances the timing. You compensate for that by retarding the timing plate setting. Eventually you'll run out of adjustment slot when the chain wears excessively, and then it's time to replace it.
 
5twins said:
I'd keep fooling around with the timing setting. If the cam chain is old and somewhat stretched out, maybe where the timing was set is where it needs to be? The cam chain tensioner pushes against the rear run of the chain. As the chain wears and stretches, the tensioner effectively rolls the cam backwards and that advances the timing. You compensate for that by retarding the timing plate setting. Eventually you'll run out of adjustment slot when the chain wears excessively, and then it's time to replace it.
Click to expand...
a very good point
 
5twins said:
I'd keep fooling around with the timing setting. If the cam chain is old and somewhat stretched out, maybe where the timing was set is where it needs to be? The cam chain tensioner pushes against the rear run of the chain. As the chain wears and stretches, the tensioner effectively rolls the cam backwards and that advances the timing. You compensate for that by retarding the timing plate setting. Eventually you'll run out of adjustment slot when the chain wears excessively, and then it's time to replace it.
Click to expand...
So if I can’t get the bike to start by adjusting the timing, what should i look into replacing? The plate, chain or both?
 
boxbodybangin said:
what should i look into replacing? The plate, chain or both?
Click to expand...

If by the plate, you mean the slotted backing plate of the Pamco, that wouldn't make any difference because a replacement would be slotted the same. The Pamco is no longer being made so you probably couldn't get one anyway, lol.

As far as the cam chain goes, replacing it is a major operation, requiring a topend teardown. I wouldn't do it unless I ran out of adjustment range on the plate, or found signs that the front cam chain guide had gone bad (pretty common). But the engine needs to come out of the frame to get the topend off so like I said, it's a major operation. And since it is such a big job, it's best you address and "fix" anything else that needs it in there. Normally, you replace the front guide and the chain, lap the valves back in to seal them, and replace the valve guide seals. You check the bores for wear and if still in spec, you can just replace the rings. If worn out of spec then a re-bore and over-size pistons will be needed.
 
in my experience, given spark, fuel and air, these motors will run with grossly loose valves, broken chain guides, etc. I would look at the carbs now. make sure the fuel and air passages are clean. drain the oil, including the oil strainer and see if there are plastick bits in the strainer or the oil filter (that would be the chain guide). But the engine should still run with the guide lining gone. For the long term, put airfilters of some sort on
 

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