Shovel rear cyl blowin oil smoke.

bc40ton · #1 03-05-2008, 07:52 AM

OK, last yr had the top end done. Valve job, new seals. One head I pressed new guides in, the other head machine shop told me not to press in so they knurled. Still smoked (rear) when hot. Especially after grabbing a handfull of throttle and when it is comming down in revs, that when she smokes oil. This yr, bored out to .040 new KB pistons rings installed. .0015 clearance in cylinder w/ piston. Got about 100 miles so far. And YES, rear is still blowin oil smoke. I have an idea...craked head from new guide. Any others???

Rodney · #2 03-05-2008, 08:13 AM

did you install the gaskets which fit under the lip on the valve guides?
did you check and replace the valves if wore on the stems?
did you install the correct over sized guides in the heads?
when installing guides did you have the heads nice and hot and the guides in the freezer before installing? We have a parts washer that get parts so hot you can't handle them without gloves and a freeze in the shop for this propose [and handy to keep the beer nice and cold as well!!]
theres a few ideas?

bc40ton · #3 03-05-2008, 08:31 AM

Never heard of guide gaskets.
Valve wear checked out fine.
Installed guides that went in pretty tight, Thats when I called machine shop and they advised to refurb old guides on the other head, which they did. I forgot which head I worked on.
Did not heat head and cool guide.

DeJavu · #4 03-05-2008, 08:37 AM

You said it was bored .040, w/new rings. You don't say new pistons. I had the same problem and it turned out to be a cracked piston skirt. Just a thought.

bc40ton · #5 03-05-2008, 08:55 AM

Matched set of keith Black pistons and rings were installed. 8-1 comp.

Rodney · #6 03-05-2008, 09:44 AM

I ran those same pistons for a few years {worked great} one thing if I recall the ring gap was important and different than conventional pistons, you should have received instructions with the pistons. if I remember the top ring needed a little more clearance to accommodate for heat.
Yes gaskets go under the valve guides. they should be in the gasket set.
another thing to consider is the oil draining the heads correctly threw the passage in the cylinder?

If your machinist doesn't take thermal characteristics in to consideration when working with 2 different alloys [ or one for that matter] find another machinist!!

shrktooth · #7 03-05-2008, 09:59 AM

you didn't state the year of your engine....FWIW...there can be a couple different things going on here....
KB needs to be at exact tolerances on clearances and gaps... they are good pistons IMO....
you alsomight want tocheck the seals and be sure they are not traveling on the stem or loose and pushin oil.....(carefull with the locktite on the seals)
you are following the break in procedure from KB on seating their rings?
just some food for thought here.hahaha

Rodney · #8 03-05-2008, 10:02 AM

I run NO valve seals on my shovelhead never have and have no smoking issues!

bc40ton · #9 03-05-2008, 10:54 AM

Yes I followed the install sheet on the KB pistons, rings to the letter. Very specific. If the guides are pressed in what the heck do they need gaskets under the lip of the guide for. Never ever heard such a thing. Seals are tight on guides. Then again, I am the one with the oil smoke problem! breakin is my own rulz, no lugging or overspeed. Mostly city, with a little hiway thrown in. Anyone have a rear head around with band intake style?

Rodney · #10 03-05-2008, 11:08 AM

T Twin MFG.

V Twin Part # 15-0210 for the valve guide gaskets
They've been in every top end gasket kit I have ever used take a look in your gaskets you have left over they should be there.
sorry don't have a head at this time.