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[doublerunner]

This past spring I bought a used 2011 RG cvo ultra with the 110 engine and it had about 8500 miles. No upgrades to it other than headers, mufflers and a tune. About 6,000 miles after having owned it, I started to notice a very loud knocking/rapping sound coming from the engine while the bike was idling to warm up and also some light colored exhaust smoke coming from the left side exhaust. This would go on for about 3 minutes and once the bike was warmed up, these issues would stop

So I have my shop look into this and run a  compression test. The compression is real low. They say it should run about 180 - 200 normally. One head is at 120 and the other at 105

They are recommending 2 options;

1. replace the cylinders, pistons, intake guides and valves

or 

2. Bore the cylinders, then put in upgraded pistons, etc for higher performance.

I just want a good performing motor. I don't need to go crazy with a lot of engine work. But since something needs to be done either way, what would you recommend?

If I can get better performance with boring and upgrades, why not? Or am I opening up a can of worms that will lead to more issues down the road?

I am by no means savvy in my knowledge of motorcycle engines. So I am looking here for some insights and knowledge from the experts who do this stuff every day and those who have had work done like this before

Thanks
DR

[T-Roy]

Sounds like the perfect time for a 113 cubic inch build from GMR Performance.

[sadunbar]

This past spring I bought a used 2011 RG cvo ultra with the 110 engine and it had about 8500 miles. No upgrades to it other than headers, mufflers and a tune. About 6,000 miles after having owned it, I started to notice a very loud knocking/rapping sound coming from the engine while the bike was idling to warm up and also some light colored exhaust smoke coming from the left side exhaust. This would go on for about 3 minutes and once the bike was warmed up, these issues would stop

So I have my shop look into this and run a  compression test. The compression is real low.
They are recommending 2 options;

1. replace the cylinders, pistons, intake guides and valves
They say it should run about 180 - 200 normally. One head is at 120 and the other at 105

or 

2. Bore the cylinders, then put in upgraded pistons, etc for higher performance.

I just want a good performing motor. I don't need to go crazy with a lot of engine work. But since something needs to be done either way, what would you recommend?

If I can get better performance with boring and upgrades, why not? Or am I opening up a can of worms that will lead to more issues down the road?

I am by no means savvy in my knowledge of motorcycle engines. So I am looking here for some insights and knowledge from the experts who do this stuff every day and those who have had work done like this before

Thanks
DR

Are you sure your shop disabled your automatic compression releases when they checked your compression?

[*58Vette]

When checking the compression' don't use the start switch.  Leave the ignition off and jump the small wire on the starter to 12 volts.  Make sure your in neutral.

[doublerunner]

When checking the compression' don't use the start switch.  Leave the ignition off and jump the small wire on the starter to 12 volts.  Make sure your in neutral.

Not doing the check myself. I am sure my shop knows how to check compression. I have been using them for a number of years and they have always been straight up honest with me

[Para Bellum]

Are you sure your shop disabled your automatic compression releases when they checked your compression?

I have been using them for a number of years and they have always been straight up honest with me

I don't think sadunbar was necessarily questioning their honesty, but that they could have forgotten to disable the ACRs; easy to do since most Harleys don't have them.  Easier and cheaper to check again than to rebuild an engine.

[HDGearHead]

Sounds like you may have one or more lifters that are bleeding down to quickly and taking there sweet time to pump up when the bike is started.  This will create a loud knocking rapping sound until they are pumped up.

As for the compression, I'm betting that they failed to pull the system relay to disable the ACRs during the test.  The compression numbers that you got are in the ball park of what should get when the ACRs are enabled.  It also would run like crap all the time with those low compression numbers (not be back to normal three or so minutes after you started it).

[tweeter13]

It's easy to forget,  I myself have forgot unit I wrote the numbers down. Then it dawns on you.  Your spark plugs are still out just disable and retest. 

Todd

[T-Roy]

Man I sure am glad all you guys chimed in. I got excited that he may have the perfect excuse to spend his hard earned money on some enhanced performance mods that I forgot completely about the ACR's. It would be terrible though if he had done that without actually having low compression. It is definitely worth a phone call to the shop to verify that they indeed did disable the compression releases.

[grc]

Sounds like you may have one or more lifters that are bleeding down to quickly and taking there sweet time to pump up when the bike is started.  This will create a loud knocking rapping sound until they are pumped up.

As for the compression, I'm betting that they failed to pull the system relay to disable the ACRs during the test.  The compression numbers that you got are in the ball park of what should get when the ACRs are enabled.  It also would run like crap all the time with those low compression numbers (not be back to normal three or so minutes after you started it).

And I believe we have a winner.  A not-so-uncommon problem is lifters, especially on 2011 and 2012 models.  I would change them for a good aftermarket product before doing anything else, since they are not only subject to bleeding down like this but also to major failures of the rollers which can trash the engine. 

As for the compression test, I also believe the shop forgot to disable the ACR's.  Those compression numbers are more in line with what you would get with the compression releases enabled.  And if you do have one lifter bleeding down, that could also account for the difference between the two cylinders.  In other words, unless you just want to spend a bunch of money on a shotgun approach, I think you need to have some proper diagnostics performed to pinpoint the real problem(s) before just writing a blank check.

Btw, the simplest way to avoid the ACR problem when running a compression test is to leave the ignition off and just use a jumper to the starter solenoid connection to activate the starter. On a throttle by wire bike you will need to remember to physically block the throttle plate wide open.

Jerry

[doublerunner]

Sounds like you may have one or more lifters that are bleeding down to quickly and taking there sweet time to pump up when the bike is started.  This will create a loud knocking rapping sound until they are pumped up.

As for the compression, I'm betting that they failed to pull the system relay to disable the ACRs during the test.  The compression numbers that you got are in the ball park of what should get when the ACRs are enabled.  It also would run like crap all the time with those low compression numbers (not be back to normal three or so minutes after you started it).

Correct on the lifters. Replaced with S&S premium lifters. Also put in the quickee pushrods in case they needed any adjustment. The noise is gone.

But the compression problem is still there. Asked my Harley dealer to check this. He laughed and was sure they disabled the acr's. Double checked it and the numbers were still the same. Then did it without dis-abling the acr's and they were at approx 40 lbs. Too bad, I was kind of hoping they messed up and I would not need to tear this apart. So looks like I will go with new cylinders and pistons, intake valves and guides. I decided not to bore out the cylinder wall any more. The 110 with all these new parts and upgrades will be plenty of performance

By the way, saw the piston heads while there and they looked pretty messed. Dark thick buildup on each one. My feeling is the previous owners used cheap gas and/or really lugged it a lot 

[grc]

Correct on the lifters. Replaced with S&S premium lifters. Also put in the quickee pushrods in case they needed any adjustment. The noise is gone.

But the compression problem is still there. Asked my Harley dealer to check this. He laughed and was sure they disabled the acr's. Double checked it and the numbers were still the same. Then did it without dis-abling the acr's and they were at approx 40 lbs. Too bad, I was kind of hoping they messed up and I would not need to tear this apart. So looks like I will go with new cylinders and pistons, intake valves and guides. I decided not to bore out the cylinder wall any more. The 110 with all these new parts and upgrades will be plenty of performance

By the way, saw the piston heads while there and they looked pretty messed. Dark thick buildup on each one. My feeling is the previous owners used cheap gas and/or really lugged it a lot 

Something about this story still seems to be farfetched at best.  If you really only had 40 psi compression with the ACR's enabled, the bike would not start.  Since you didn't mention a starting problem, I don't believe their numbers.  If you trust them, it's fine by me.  But if it was my bike, I'd have someone else run a compression test and leak-down test before throwing a bunch of money at repairs that may not be necessary.

Btw, feel free to ask some of the experts around here, like Steve Cole, if your bike would start with only 40 psi compression.  I do know what I'm talking about, but since you don't know me perhaps you need some input from a few more people who also know a lot about internal combustion engines and H-D's in particular.

Jerry

Oh, btw, why replace only the intake valves and guides?  Exhaust valves and guides have tended to have more problems than intakes.  And without tearing the heads down completely and actually checking all the parts, how would a shop decide to replace certain parts?  Going back to your first post, it appears the shop gave you all these suggestions before doing any teardown.

[SBB]

Something about this story still seems to be farfetched at best.

Btw, feel free to ask some of the experts around here, like Steve Cole, if your bike would start with only 40 psi compression. 

Not to take anything away from Steve Cole but sadunbar is on now and he is the best of the best.
I'm surprised Jerry didn't think of him.

 

SBB

[sadunbar]

Not to take anything away from Steve Cole but sadunbar is on now and he is the best of the best.
I'm surprised Jerry didn't think of him.

 

SBB

Jerry is spot on with his comments.  The motor would not run if there were only 40 lbs.. compression with the ACR's enabled.  Quite frankly, it might not even run with the compression at 120 and 105 with the ACR's disabled.  So before I started making up a parts list, I'd suggest taking your bike elsewhere for a more informed second opinion.  The facts as presented are hardly credible.   

[hrdtail78]

I agree an engine wouldn't start at 40, but we are talking an HD with Delphi fuel injection.  No crank slowing, equals no spark, equals will not start.

How does the bike run?  I would guess you could feel that much loss of compression.  Hopefully they are taking the AC off and opening the plate.  Even the best forget to do simple things.  A low number is usually a reminder.  Gauge might need a calibration also.  Charged up battery as well.  BUT a leak down would also tell the tale.