Rear cylinder low compression

[Blackhawks]

Hi all,

I have a 96 road king F.I. with low compression on the rear cylinder. Just had both cylinders honed out to .005 & new pistons with rings installed. When I measure the front cylinder & turn the engine over I get an immediate 90 lbs of pressure. When I measure the rear I only get 30 lbs of pressure. However when I put a spark plug in the front cylinder and fire the bike up on 1 cylinder i get 90 lbs on the rear.


I have a trouble code of 56 which is a crankshaft or camshaft position sensor. The bike starts really rough, like it is only firing on the front cylinder then once I give it gas for a couple of minutes it will maintain an idle on its own, otherwise it backfires and dies until warmed up.


I had the cylinders honed out because of the same readings above. Did'nt help matters as I thought it was a compression issue.

I would appreciate any input.

[frankysfree]

possibly a bent valve. you can do a leakdown test prior to teardown. that should give you a good idea of what the problem is. once you tear it down a good way to check is to put water into the head and see if there is any seepage around the valve