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920 engine build waffle

Classic Norton Commando Motorcycles.

Re: 920 engine build waffle

Postby Fast Eddie » Sat Jan 07, 2017 9:42 am

Not much progress lately guys I'm sorry to report. I did get the pistons from Jim though, a slight variation on his normal design with a thicker crown and 0.040" dish in the crown. If my fag packet (for avoidance of doubt with oir colonial cousins, that's a small cardboard box containing cigarettes) calculations are half right, this dish will give me the desired CR and still allow for a tight squish.

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Re: 920 engine build waffle

Postby Fast Eddie » Sat Jan 07, 2017 9:51 am

The 920 motor will be fiddled with over summer and hopefully be ready to nail in the the bike next winter. So I thought I'd fiddle about with the bike in its current form ready for spring.

I decided to go back to Cafe Racer guise. I got a JPN replica gear pedal from RGM which goes well with their T160 style kick start nicely, I've not ridden with the reverse lever on a Commando before though, so we'll see what its like. Along with the 2:1 exhaust, the neater footrest arrangement certainly cleans up the RHS of the bike:

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cNw front brake fitted, usual beautiful quality:

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Mikes 2:1 pipe certainly goes with the Cafe Racer stance:

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Still some more jobs to do, but we're getting there.
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Re: 920 engine build waffle

Postby Fast Eddie » Fri Feb 03, 2017 11:38 am

Well, not much progress of late gents, but I have at least managed to get a little shed time.

As ever, we have a little scope creep here, I decided it would be better to build a separate 'stand alone' bottom end, so have another pair of JS's lovely rods now ready to go in the Maney bottom end.

The cases will receive a little fettling, just to ensure the nicest fit in the chassis etc and also to clean things up cosmetically, then I'll drill the extra oil hole below the pump, then they're ready for 'tumble cleaning'.

The barrels will be double checked for clearance with the new pistons, the bores will go for carbide treatment before the barrels will also be ready for tumble cleaning.

I wouldn't usually have bothered with tumble cleaning, but that's what Comnoz did to the head, so it's kinda raised the bar for the rest of it!

I'm just in the process of looking at cam / follower fit etc.

Hopefully the bottom end will be ready to button up in the not too distant...

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Re: 920 engine build waffle

Postby gripper » Fri Feb 03, 2017 1:43 pm

Jim, can you explain the machining process involved in "waisting" the barrel bolts? I'm guessing it's not just a case of running a lathe tool along them.

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Re: 920 engine build waffle

Postby freefly103 » Mon Feb 06, 2017 5:20 am

Jim's video on how to "waist" an ARP bolt:

https://www.youtube.com/watch?v=zkfLr9MZlCk
70-750, 71-750, Seeley-750 (Titchmarsh frame, Fullauto Head, Maney crank, cases and barrells, FCRs by NYC Norton)

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Re: 920 engine build waffle

Postby Brooking 850 » Sat Feb 18, 2017 1:51 pm

Nigel did you get the email I sent with cam timing pics and data?
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Re: 920 engine build waffle

Postby Fast Eddie » Sat Mar 18, 2017 2:56 am

Another small step for mankind...

I received the barrels back from Laystalls who have silicone carbide coated the bores. I've never had this done before so it's all new to me! Its a nice finish, has a kinda dull, off-grey appearance similar to hard anodising on aluminium.

I have a few weeks away from the workshop coming up now, so hope to get the Pistons sent away for Diamondyze treatment and the cases and alloy barrels sent away for tumble cleaning.

There should then be very few remaining (viable) excuses in the way of beginning bottom end assembly.

Onwards and upwards...
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