66cc port angles?

I've not made an adapter yet for my aluminum degree wheel so I can bolt it on to one of these engines but really if you've got a spare CD\DVD you can make your own quite easily and figure the numbers out yourself Marvin.

Here's a link to some images that you could scale, print off and then glue to a CD\DVD. I would think it's best to use the magneto side when it comes time to bolt it on and figure out a spot where you might bolt on your pointer. You can make a pointer out of .020 music wire, copper wire etc. Set the wheel and pointer up as instructed at BDC, you should use an indicator to find BDC but eyeballing it and feeling your way should be ok too. Since you'll have to pull the head off so you can see the ports make sure that when your rolling through the crank rotation that the jug stays fully seated or you'll end up with wonky readings.


Good luck and do post your findings, it'll be interesting to see the numbers :)

PS: One thing I haven't seen any mention of with these little engines is the squish band clearance...squish clearance is important! With engines in our CC range you should have a clearance of 0.5 - 0.8 mm for optimal performance. I measured mine and it's darn near 2mm !! When I check my port timings I'll then decide if I should raise\lower the jug, drop the head down with a thinner gasket, machine the top or bottom of the cylinder etc etc to correct the squish clearance.
 
Your results will make sense...we have faith in you :)

You'll likely be pleasantly surprised how easy it is to figure out once you get a degree wheel and a simple pointer mounted to your engine...
 
OK, here's what I came up with. It's kind of an average, because I kept getting slightly different readings? Exhaust port angle=145 Transfer port angle=117 Now what I need to find out is the exhaust gas temperature of these motors. I assume that it can be slightly controlled by the richness of the carb and the diameter of the stinger, but does anyone know a ballpark figure to input into the program mentioned above?
 
Well tuned 2 smokes can intermittently develop an EGT of 1300 degrees so 600 to 800 is feasible for a low power engine like what we are putting on bicycles. Try 600 to 800...you'll never have an exact number unless you have a EGT sensor and a computer to read it.
 
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