Hitchcocks Forum

I've pulled the top end off my 612 bullet after 2500 miles to take one of the compression plates out. I put both in initially for the shakedown/run in.

This is how it looks after a prolonged period of sitting at maximum cruising speed.

I'm thinking slightly the lean side of ok? Maybe up one main?

Has that touched the spark plug?
Strange mark the middle.?

That was the dead stop tool marking the carbon on the sufrace of the piston followed by me picking at it with an oily fingernail to see what the funny mark was.

That looks like a pretty clean and even burn to me, but you might want to jet up a little for the increase in compression you will have with that barrel spacer gone.

Like the shithouse door blanking plate!

Also like the oil tank breather, how well does it work, does it keep the oil in?

Allanfox wrote:Like the shithouse door blanking plate!

Also like the oil tank breather, how well does it work, does it keep the oil in?

Yes, because it's just a breather. The hole between the crankcase and oil tank has been blanked off and a normal duckbill fitted to the crankcases so they have their own breather. It occured to me that the oil tank was then pretty much sealed because it has a screw in cap and that's also the only way for the timing side to breathe (I may address this at some point). Thought it best not to risk a vacuum forming in the oil tank.

Thanks makes perfect sense, I have retro fitted the crankcase breather but didn't block the hole between the crankcase/oil tank, to be honest maybe I should have, I am hoping the hole will allow an equalisation of pressure but not sure it is, when you unscrew the oil tank cap with the engine running there is a lot of air blasting out, much more than is escaping via the crankcase breather. I have fitted an Hitchcock oil tank cap conversion to try to deal with the oil tank pressure, can't really tell if it is working but my chain is getting lightly oiled so something is happening!

From blocking off the oil tank spigot and totally relying on the crankcase breather I clearly have excessive pressure in oil tank/engine as it was starting to leak around spigots etc and importantly pressure in the timing chest as the oil tank is trying to breath via the timing chest return hole and causing the timing chest to overfill (wet sumping?).

So 100% can see that if I block the crankcase hole and fit a oil tank breather like yours it should vastly improve. I have re fitted the oil tank breather pipe and run it to they rear mudguard and to be honest the bike runs a lot better with the oil tank pressure fully relived and the wet sumping has stopped. I do have more oil than I like coming out of the rear mudguard mounted breather pipe (oil tank level at bottom of dipstick) so may refit the catch can until next full engine strip and think about blocking the crankcase hole up.

So time to replace that oil ring and modify and refit the catch can!

Never a dull day!!!

But is running amazing well, torquey, responsive and actually quite smooth, defiantly a keeper!

stinkwheel wrote: ↑

Tue Aug 24, 2021 4:34 pm

Allanfox wrote:Like the shithouse door blanking plate!

Also like the oil tank breather, how well does it work, does it keep the oil in?

Yes, because it's just a breather. The hole between the crankcase and oil tank has been blanked off and a normal duckbill fitted to the crankcases so they have their own breather. It occured to me that the oil tank was then pretty much sealed because it has a screw in cap and that's also the only way for the timing side to breathe (I may address this at some point). Thought it best not to risk a vacuum forming in the oil tank.

Bullet Whisperer wrote: ↑

Tue Aug 24, 2021 7:06 am

That looks like a pretty clean and even burn to me, but you might want to jet up a little for the increase in compression you will have with that barrel spacer gone.

Hi Matey----Alan Redgrave in Telford.........Maybe re-fit both plates to help with this E10 that's now on the forecourts ??.......Also a tad up on main as well ??

I'm running it on super anyway, tends to pink a little on 95 octane.

I tried going up to a 240 main (from 220) because I had one. That was rubbish, worse than befoe I took out the plate. Then I went back to the 220 and raised the needle a notch and it turned into a racebike sounding rip-snorter with a proper "Rhuuu-barrrb" engine note and a significant amount of "seat of the pants" power increase. It just sounds right level of obnoxious I'd expect from a big, high-compression single. I was actually surprised how much difference such a small change made.

I think the clattering sound is just how they are. I think the alloy barrel doesn't help and I've red several other reports of this piston sounding very noisy. I tried the old trick of shoving slices of fuel lipe between the cooling vanes and it significantly reduced the clattering noise so I've ordered proper rubber dampers off our hosts.

I'll try it with a 230 jest just to see what it's like.