Hitchcocks Forum

Bullet Loss of compression

Evening all

500 bullet Kickstart only, 2004, 8K miles

Went for 40 odd mile run yesterday, everything ok, plenty of power up hills & cruising at a true 50 to 55 at less than ¼ throttle.

Started it this afternoon, lots of compression. decompressed to get over TDC .

First kick started as normal. It ran for 30-60 seconds then stopped. Tried to start it again and found absolutely NO compression.

Kicking the engine over seems to be hissing at the carb on more than one stroke…..

Took the pushrod cover off, rods going up & down normally and spinning OK at TDC. Pulled the inlet rocker cover off & all looked OK.

Decompressor valve removed and checked, good seat all fine.

Then it got dark, will delve further tomorrow.

Anybody got any ideas what could cause a catastrophic loss of compression and what I may find on lifting the head???

Regards Fred.

Fred squirt a bit of oil down the bore and kick it over a few times

As Norm says. My Bullet often gets these symptoms, but once it starts it gets compression back to normal. I think the rings might get stuck in their grooves at times but the compression from the crankcase will force them out against the cylinder wall again and all is well------till it happens next time. I just don`t worry about it anymore.

It does seem odd that you had compression to start initially, so that sort of rules out stuck rings..

The decomp was a good shout but that has checked out ok.

Anecdotally there is evidence that a composite head gasket can fail in this way, though i have no personal experience of this...

Perhaps a soapy solution sprayed around the joint area may give an indication..

Failing that a chipped inlet valve? seeing how rods and rockers are all good.. blocks torqued ok??

Let us know Fred, all the best..

Gwilly I have seen them do this before but I didn't want to mention the possibility the piston crow has started to compress and grab the rings but with 8000 miles it is always a possibility

Yes Norm definitely a possible, should be blowing like a whale through the crank breather with every compression stroke..

Lets hope not....

Good Morning Gents



Squirt, Squirt, Kick, Kick, Bang, Bang.
Perfick….running well again.



BUT if the rings are being grabbed by the piston does this mean it is going to disintegrate or can I keep riding it with a plug spanner & a sqirty oil can in the tool kit.

I don’t think I want to know the answer but please let me know the best and the worst that can happen.

I’ve never had my ring grabbed before, is this something that only happens in hot Oz, or is it bad pistons, or is it common throughout the Enfield Empire. Mixture too weak or what?



Regards Fred.

Freddy: Usually faulty pistons. As I`ve said many times before; these engines run with a very low oil temperature, around 50/60c. Which is why they suffer from the dreaded mayonnaise/emulsion problem with the oil.

Fred can't give you an answer on this but out here it has a lot to do with the way we ride them, straight, smooth roads and big distances between places and higher temps all takes its toll. Only way to know if the top is starting to collapse is to pull the barrel and check

I'm in the process of putting a bullet engine back together.. I've skipped ahead a page and tried the fit of both my pistons, (one is a split skirt, other isn't)without rings in my new '53 barrel. both seem quite tight. the non split skirt piston was from a failed rebuild where the top 2 rings had been wiped over by the piston just enough to grab them. The gudgeon pin was blue! A lack of care running in - or is the barrel piston clearance too small?