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[bbsiding]

I just completed a 95" upgrade on a 2006 FLHRI  KB pistons 37g  gear drive fueling billet oil pump, new breathers in head  from HD s&s lifters and Pushrods   After 500 miles took it for dyno tune  Tuner said its smoking  I take it for a ride and its smoking bad   Rear cylinder only  I tear it back down and find oil ring has walked around into piston pin cut out   OK seems obvious   Re assemble with new heads this time and same problem  I checked breathers at air cleaner and rear vent is sucking and front head is blowing.  weird   with air cleaner removed and vent tubes off,  it does not smoke. I reinstall tubes and air cleaner and it starts smoking again  Bad   Any direction would be greatly appreciated

[bbsiding]

piston photo

[Snakebyte]

Get rid of the kaboom pistons and get 98 cu. CP or weisco then bore to 98.

[TorqueInc]

 Those KB pistons are sadly scrap metal....the forged ones seem to do OK

   Find something else........starting to like the S&S 97" pistons

[HILLSIDECYCLE.COM]

I just completed a 95" upgrade on a 2006 FLHRI  KB pistons 37g  gear drive fueling billet oil pump, new breathers in head  from HD s&s lifters and Pushrods   After 500 miles took it for dyno tune  Tuner said its smoking  I take it for a ride and its smoking bad   Rear cylinder only  I tear it back down and find oil ring has walked around into piston pin cut out   OK seems obvious   Re assemble with new heads this time and same problem  I checked breathers at air cleaner and rear vent is sucking and front head is blowing.  weird   with air cleaner removed and vent tubes off,  it does not smoke. I reinstall tubes and air cleaner and it starts smoking again  Bad   Any direction would be greatly appreciated

Re-bore to 98" with a Wiseco piston.....problem ended.
We've had Wiesco manufacturing those for us since 2006.
Scott

[prodrag1320]

X4 on the KB pistons,we wont use them here,agree`d with the 98" build,either wiseco or CP.if the breather hose/air cleaner prob is still there,i would think it would be easy to see what the problem is,theres got to be a obstrucsion somewere in either the hoses or A/C

[HILLSIDECYCLE.COM]

Had a Crane HI-4 in an Evo take a dump once(no surpise there)and the clients KB cast pistons, that he wanted us to use, mind you, did not handle the uncontrolled spark event that occured.
He was upset.
Scott

[Snakebyte]

KaBoom.
I just had the unfortunate insident of dealing with these guys. Friend ordered forged flat tops they send dished. They said they didnt have forged flats and the 2.3 cc wont make a difference.  then he said "why dont just build the engine around the piston. Or you can even shave the top of the piston" I asked him if he wantedto fork up for the added cost of doing that...he didnt like that.
Been three weeks and still no refund on piston. My friends not happy..at all

[GMR-PERFORMANCE]

Well I would check piston to bore clearance first off. Good piston or bad if this spec is off you will have issue. I would think that there is more going on then that brand of piston.  If that oil rail was bent I would think that there is cylinder damage and the rail once bent cannot be re used.

One thing I do see is that the oil ring support rail is not in the picture. If you did not install the rail it will cause ring flutter and the oil rail will pop out. Here is the instructions I pulled of KB site.

https://www.uempistons.com/installation_instructions/motorcycle_installation.pdf

Good luck

[bbsiding]

Regardless it seems that everything points to pistons or rings  I don't believe it to be sumping as I have no heat buildup   It does puzzle me about the rear head breather sucking though  The front pushes air out well I had hoped this would be a sign of what failed      I did look closely at cylinder and saw no appreciable damage,  slight scuffs only  the oil ring showed no distortion   

[rbabos]

Both breathers should blow, regardless of the piston issue. Something wrong with the rear breather. Both share the same common chamber to breathe  from= case.
Ron

[HILLSIDECYCLE.COM]

Ron makes a good point.

[bbsiding]

I think the same on that   but   is in the umbrella? would that make it smoke?  really strange that when I reinstall the breather tubes and air cleaner it starts smoking again 
 

[rbabos]

I think the same on that   but   is in the umbrella? would that make it smoke?  really strange that when I reinstall the breather tubes and air cleaner it starts smoking again

At idle the front breather is enough. Block off the rear and see if it changes, as a short term test. If the crankcase cannot be brought into a near vacuum state via the breathers all kinds of weird chit can happen. Oil control at the rings themselve being one and all this extra huffing and puffing induces extra oil vapor into the intake. That's the only explanation I can come up with for smoking when breather is hooked up.
Ron

[sadunbar]

Any chance one umbrella assembly is installed upside down?  It's easy to do with the latest version of umbrella breather assemblies...