Date: Wed, 10 Jun 1998 09:34:48 -0500
From: Ben English
-Steve "Don't diss the Combat" Bacon wrote:
>In regards to Combat motors, treat the rep like you'd treat the "unreliable,
>leaky British bike" comments you always hear. After going from a 500CC
twin
>to 750, and then upping the comp. ration to 10:1, the bearings finally
>gave up the ghost. [snip] Fast forward to 1998, if you've got a Combat
motor
>with the original bearings, then I'd get them replaced - which is
something
>anyone with any old bike would do during a rebuild. Combats don't
just blow
>up, there's a reason, and this can be fixed.
>I've had my Combat for 5 years now, and occasionally (ok, many times)
have
>gotten a little excessive on the throttle. During that time I've never
heard
>any strange sounds, etc. from the motor. I'm assuming a previous owner
>upgraded the bearings - but I don't know for sure.
The main bearings weren't the half of it. The Combat's principal problems were related to the valve train and pistons. The high lift cam and milled head (for high compression), combined with sloppy production tolerances and ridiculous gearing that encouraged over-revving meant that valves were known to kiss pistons, and valve spring retainers would give the valve guides little love taps. These affections were destructive in the end.
I got my own Combat with only 8700 miles on it, and the DPO had already blown it up and rebuilt it. God only knows what happened. Evidence included: Atlas intake valve guide (no seal) on left cylinder but Commando sealed guide on right, .030" pistons, mystery aftermarket regrind camshaft, and oil passages in the crankcases containing pieces of gasket, piston shrapnel, silicone sealer, etc.
I discovered all that after riding it 7,000 miles. It ran fine- I only took it apart because it smoked on the left cylinder and I was going through everything after crashing and burning it. At the time I looked at the main bearings, shrugged, said to myself those are main bearings alright, and put 'em right back in.
Nearly 20,000 happy miles later, I hallucinated a main bearing noise (which in retrospect I believe was normal primary chain noise) and had it all apart again. The original mains were still just fine, but I did spurge on Superblends at the time.
Ben English
1972 Norton Commando Combat Roadster #201695
1982 Honda FT500 Ascot / 1972 Olmo 10 speed
Amtrak National Timetable / Pocket full of bus tokens / Good shoes
Albany, New York, USA