I am researching my winter project - 103" conversion for my '07 Dyna. Couple of questions -

1) Is there a rule of thumb for when ACRs are required in terms of compression ratio? I was considering JE 10.0:1 flat top pistons. But maybe 10.5:1 ?????

2) If ACRs are required, where does the machine shop drill the hole in the head for them? On the top of the head, LH side, RH side?

 

10: 1... use them. they are installed next to spark plugs.. They save the starter

 

Usually rule is anything at or above 10 to 1. However it is cheap insurance to have them done when heads are already off. Sort of a no brainer. I know the manual one are usually driller next to where the spark plug enters through the head.

 

Thanks guys. So, if they go next to the spark plugs, does that mean I can no longer use the set of fins I bought from H-D that "fill in" the area where the spark plug is located?

 

I'm not sure if the Automatic version gets located in the same place as the manual version, but assuming they do, and Wheel 752 says so. That being the case, it DOES mean you can't use those fillers.

 

There are 2 holes to be drilled 1 for the ACR and 1 to vent the compression into the exhaust port, the ACR goes in the top of the head and it hidden from view. They work great. And there is no compression ratio # that is the magic number that requires releases, its more of a cranking pressure number, like 190 or there about. I have 103" motor 10.5 cr with a 42 IVC camset and crank at 195 and I have the ACR's and I have NEVER had a starting issue of any kind. The speed you drive your clutch with the starter has an effect on the starter too, like if you have changed your primary gearing for more engine rpm it will put more strain on your starter.

 

+1 and battery life too

 

Bench checking my ACR's. 1 is open circuit so it is dead. Want to make sure the other opens and not full of carbon. Would anyone know what the voltage value is which operates them from the ECM? Asked the Harley service desk and he said 12 volt. I am accustom to 5 and 6 volt signals. He then changed his mind and agreed with the latter. I hate people that guess because it's my wallet they are guessing with. I have a DC adjustable bench tester but want to make sure before seeing that little puff of smoke. Engine is presently torn down to the crank and checking every item on assembly so no break downs.

TIA

2009 Trike / 103