compression ratio difference between cylinders

[roadking705]

What happens when there is a difference in compression ratios between the cylinders? What would be the max % allowable to not impact performance?  Bike is a 2005 touring model. Don't know the numbers.

[koko3052]

Up to 10% is ok...after that start planning a budget.

[Hossamania]

Since it is a 2005, it probably doesn't have compression releases, but if it does, check them for leaks, swap them between cylinders and check numbers again.
How many miles on the motor?

[Mattbastard]

If your lifters aren't pumped up when you check compression you could be off a few PSI.  One time I did a test and I had a pushrod that shortened (lock nut slipped loose) and I had about 50 psi more on that cylinder because the new intake close was much closer to BDC than the cam intended. 

[Y2KRKNG]

If the rear is lower you should be nice and even after a full warm-up. My rear runs about 50* hotter than front and that should equate to 5-10psi cylinder pressure. Not sure if it works that way, but it's been in the back of my mind for awhile now so throwing it out here.
Would an engine builder ever try to build a engine that is even at full operating temp instead of CCP?

In your case, before you touch a wrench, I'd check and recheck. Always be suspect if the 2nd hole tested reads lower than 1st, could be weak battery.

[nosjunkie]

Do a leak down.. then you know where the issue is.

[1workinman]

If the rear is lower you should be nice and even after a full warm-up. My rear runs about 50* hotter than front and that should equate to 5-10psi cylinder pressure. Not sure if it works that way, but it's been in the back of my mind for awhile now so throwing it out here.
Would an engine builder ever try to build a engine that is even at full operating temp instead of CCP?

In your case, before you touch a wrench, I'd check and recheck. Always be suspect if the 2nd hole tested reads lower than 1st, could be weak battery.

Not sure but I think that since the rear runs hotter that the timing on the rear cylinder is different

[aswracing]

What happens when there is a difference in compression ratios between the cylinders? What would be the max % allowable to not impact performance?  Bike is a 2005 touring model. Don't know the numbers.

Compression ratio is something that's designed into the motor. If both cylinders have the same displacement, the same piston dome & valve pocket volumes, the same chamber sizes, and the same gaskets, the compression ratios will be the same, within the tolerances of the parts involved. Carbon buildup levels can also have a slight effect.

The compression you get, however, will vary with things like ring seal, valve seal, variances in cam timing (particularly IVC), etc.

[Boe Cole]

Up to 10% is ok...after that start planning a budget.