Stroker backfiring w/pic

I have a B1 with msd TL #4270. I just put in a new post here for some new suggestions.. It is backfiring in pto side when reving out of water, yesterday I had it in the water and it would barely run. I bought this machine and it has never run well yet. It has 5mm stroker, ported cylinders and cases, B-pipe, dual 44's. I just replaced pistons because of a case leak, so now that was tested and ok. Any other suggestions would be appreciated. It has 130psi of compression, I know it is low, I have another head I just have to machine the squish a bit. The head on it someone has machined it to have about 0.100" of squish and I think thats why the comp is low but I don't think thats why its backfiring?? The pic is the difference between the 2 pistons, one on left backfiring??
 

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Kennay

Squarenose for the _____
Location
Myrtle Beach, SC
Damn. That's an assload of squish. I'd definately say that is why your compression is so low. I would check, double check, and then triple check your timing. The coil is going to fire both plugs at once, and at completely opposite times for each cylinder. How are you setting your timing? Have you tried switch your plug wires or making up a new set?

What bore size?
What dome size?
 
I tried swapping wires, new plugs. As for timing I know I am not doing it right.. I just put it about where it was originally ( it is about 1/4" away from all the way retarded in the slot) is there any way to set it without a light. It is the old msd with no led.
 
Ok timing was way off adv 50deg.. now 30 deg. I noticed my mototr alignment is off as well (coupler heating up). It still back fires a bit and seems rich out of the water anyway. I don't want to drive to the lake again until everything sounds good out of the water. If the timing was that far off, I don't know how far off the jetting could be as well. I just assumed it once ran well the way things were?? any other idea's. heres a couple pics of the pistons after I ran it for a while while setting timing.
 

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waterfreak

I had a vision!
Site Supporter
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Location
s florida
Do a leak down test. Backfiring can often be caused by a lean condition .You also want your squish to be at least .050 or lower depending on your riding style.
 
what happened with this ski did ya get it right? did you ever get the msd manual for the tl setup,I need a copy as well for this model.
 
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