250 N/C cyl head refurb

[Mike]

Progress! (I think). The cam bearings are in place, along with a fresh bearing on the upper bevel shaft. I've spent a fair amount of time trying to get the gears shimmed correctly with no backlash, aligning surfaces, and avoiding the gears from hanging each other up when the bevel tube is tightend - I was surprised at just how much adjustment was necessary.

This looks about right to me, but interested in views from more experienced eyes - is it possible to assess from a photo? (click to make it bigger). The cam nut isn't yet fully torqued up, just nipped up to try and get the clearances right first.



Also piston assembled, rings gapped and installed..




Mike

[blethermaskite]

Mike, setting the bevels is always a bit of a pain, in my experience I have seldom found a pair of bevels (top or bottom) that will have precisely the same backlash through 360 degrees of rotation, rightly or wrongly I have always set the bevels with about 1 thou" backlash (dry) at their tightest point......the common grind mark on both gears (should) set them in perfect mesh alignment.....but I would get the old engineers blue out and check the tooth contact pattern to be sure. The bottom bevels are pretty hard to set without a little backlash unless the crankshaft has absolutely zero run out....again as above for me 1 thou" (dry) at the tightest spot. This how I have always done it...others may disagree.
By the way I hope you are going to clean those bits up to get rid of the metal filings before your final build .
Cheers,
George

[themoudie]

Aye Mike,

Good to see progress being made.

As George says and get that swarf cleaned out, with brake/clutch cleaner, afore final assembly. I know it's a faff, but nothing worse than running a bearing, scoring the bore, afore the engine is run-in.

Good health, Bill

[Mike]

There's no swarf in there from the machining work - all parts were spotlessly clean, but point taken - I realise that I hadn't fully cleaned the gears as well as I could have - will fix that in due course. Engineers' blue on order, and will take a look at that when I get back from India.

[themoudie]

Aye Mike, safe travels and steady away, with the gears.

I have yet to start on the '75 350 MKIII.

Good health, Bill

[Mike]

Hi Folks -

I've been somewhat distracted by other things over recent weeks, but keen to get going on this. I'm ready to do final assembly, and whilst torquing the cam nut, I've learned exactly what others have already said - that 3d-printed tool was not strong enough: there was more movement there whilst putting torque on the nut. It was good enough to remove the nut, but not put it back on unfortunately.

Although I would happily order the £40 tool from Nigel, it does seem a bit of a wasteful indulgence for something that I'll likely only use once - does anyone have a proper tool that I may borrow please? - happy to cover any expenses with postage.

Thanks,
Mike

[George]

Hi Mike, happy to lend you my cam locking tool. Send me private message with address and contact phone number and I will pop in post.
Regards George

[Mike]

Very kind, thank you George - Private Message incoming!

[Mike]

Very kind, thank you George - Private Message incoming!

[themoudie]

Aye Mike,

Hope that your arrangement with George worked out OK?

I was away on the Moray coast for a wee break, hence my silence to your request, I could have loaned you mine, nae bother.

Good health to you both, Bill