Hitchcocks Forum

Thought you might appreciate pictures of the work to relieve the crankcases for a performance exhaust cam. My local engineering mate did it. He didn't like the idea of just burring away the casting where the oil seal sits. What he's done is remove the cam spindle then centre the crankcase on his boring bar over the spindle hole. He measured the maximum OD of the cam arc, added the clearance then undercut the seal/bearing seat with the boring bar to that clearance.







Minimum clearance (pointy end):







Maximum clearance (blunt end):







Intact seat for oil seal:







On another note. This bike had killed its big end. He showed me the amount of metal swarf that had lodged itself between the primary side bearings. It was significant and Worth knowing about. If your bike eats a plain big-end, everything out!



My future seems to contain much ado with paraffin, a paintbrush and an airline.

A neat job done there Stinkwheel. I am looking forward to hearing your impressions of the 612 when its done!

Hi Stinkwheel-------Isn't it great having access to proper machine tools ??...........Well done your bloke !!..........Also well done you for not skimping on the job either...That seal holder looks OK, doesn't it ??........What camera are you using ?? Those photos really ARE worth the proverbial 1,000 words...Is it a trick of the light but your Exhaust follower shaft seems scuffed to me ??

It's a pretty basic nikon coolpix s33 compact camera. Also has the advantage of being waterproof and bright yellow.



In fairness, close-up flash photography is one of its weaker points, I normally use it for taking pictures on canoe journeys where it excells because I can use it one-handed. The trick with close up stuff is to hold it very steady and make sure it's focused properly on what you wanted it to, not always straightforwards with auto focus.



I see what you mean about the follower. It could well just be flash flare on the slightly more polished "working" section but I'll have a closer look at them.

Now would be a an opportunity to fit adjustable cam gear spindles, for quieter running, if they are not already fitted.

I fitted my last set of adjustable cam spindles a good few years ago in the 350 racer. One of them turned slightly, opening the exhaust valve enough to make the engine stop while in 2nd place on the last lap at Cadwell. Into the bin they went and solid ones went back in and we haven't looked back ...

Agreed Alan R! Excellent posting – and yes worth a 1000 words. Cheers!

I got some adjustable cam spindles from India when I was originally going to do the whole remove cam spindle and gradually burr down the casing technique for the above (didn't know they were adjustable ones at the time, I just ordered cheap ones with the intent of effectively destroying one). I've been looking at them and it did ocurr to me that I would be introducing more moving parts into an already fairly complex system.



If all goes according to plan, I'll be using a crank-end ignition system so I'll be leaving out the idler gears and distributor shaft. As such ought to be a lot quieter than standard anyway (although I've never really found the valvetrain noise intrusive, maybe I'm used to it, I also ride a VFR750 with gear driven cams so I'm used to a high speed gear whine).

But the Enfield suffers from low speed gear whine - totally different thing to VFR high speed gear whine

Nice job BTW.

ric, I can't hear any whine from my "Oilfield," probably because of all the other mechanical noises the bike makes.