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Author Topic: A Blast from the Past  (Read 8101 times)

Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #10 on: Apr 06, 2015, 17:36:37 »
The bike is in a million pieces now, but at least the rear wheel has a newly machined axle and nut, while the front wheel is in need of a new tyre.. I hope the previous owner didn't race it in this condition. Suitable tyres in this size (18x2.0) are no longer available, so looks like we're going to have to go up to a phat 18.2.25  :)   

Offline john83

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Re: A Blast from the Past
« Reply #11 on: Apr 06, 2015, 23:31:56 »
Very cool.

Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #12 on: Apr 10, 2015, 20:03:04 »
The rear wheel had a non standard bolt pattern for the sprocket, so I blank Renthal one had to be drilled to fit, along with the obligatory lightening..

Then a spacer was required to ensure the chain cleared the drag slick, that's after the wheel was painted gold and the rims given a quick polish, wheel a new disc carrier had to be made.. Next up is to make some Ti wheel spacers..





Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #13 on: Apr 16, 2015, 21:36:41 »
Last time I went round to Jeff's he'd mentioned that the stretch to the clip ons felt a couple of inches too long, he reckoned the frame had been altered more than he thought. I was sceptical and replied, well maybe your not quite as flexible as you were thirty years ago. But no, Jeff insisted it was the frame not him that had changed. Yesterday I called in while I was passing and was surprised (though not that surprised  ;) ) to see the frame was now in three pieces, the headstock/top and down tubes had been cut off, while the back half of the frame had been split into the left and right sections. The plan it seems is to widen the rear end by and inch to take the wider rear wheel more easily and the front half will be shortened by three inches to make a more comfortable reach to the bars. The front end had already been cut and mocked up onto the engine, and it did look better to me.


Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #14 on: Apr 21, 2015, 18:41:40 »
New yokes have been made which are the same as were made for the bike originally. The original yokes having been modified by the previous owner. The forks look smaller than those on my mountain bike, they're 26mm and are from an early Honda SS50.


Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #15 on: May 03, 2015, 09:49:23 »
The frame is back in one piece now, it doesn't look that different but its now shorter and wider with additional bracing and new engine mounts. I was surprised Jeff was keeping the old rear brake caliper and its old mount that he made thirty years ago with just a drill and a hand file. But he wants to keep as much of the bike original as possible, which means modifying old parts rather than making new and better replacements. At least the wheel spacers are new and made from Titanium.

 

Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #16 on: May 03, 2015, 09:51:56 »
With the frame completed, it'll be painted next week, but first time for a tea.. :)

Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #17 on: Jun 15, 2015, 07:11:19 »
The frame was taken to Triple S in Bingley, Yorkshire to be powder coated, if they could fill a small dent in one of the square section frame tubes with some kind of filler that could survive the heat of the powder coating process. Turns out they couldn't, so the frame was blasted clean for 40 and brought back home where it'll be painted by Jeff.

Turning to the engine, the plan was to build a 350 motor with a Sprintex supercharger running Nitro through a big SU carb. A used set of pistons and sleeves from a Yamaha XJ650 turbo were bought off ebay, which would give a capacity of approx. 330cc and a compression ratio of 5:1. That's very low, but with the blower making up to 30psi its what's needed.

All was going well until it was discovered that the ACU / NSA capacity bands had been changed sometimes over the last twenty years, and now the upper limit for the class was 400cc and not 350cc as it once was. Running a 330cc engine in a 400cc class isn't the best idea, yet the pistons had been bought and the barrels machined out to fit the Yamaha sleeves already.

I thought Jeff was joking when he said sod it, I'll make me own bloody pistons... but he wasn't



Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #18 on: Jun 15, 2015, 07:12:38 »
Another job is to make the engine plates which hold the engine in the frame, and double up as mounts for the magneto and supercharger etc.

In this picture the plates are being test fitted to an empty crankcase. The front plate mount will be for the magneto, the centre hole will take an extended crank to provide drive to the supercharger and magneto via belts and pulleys. While the hole over the drive sprocket will house an external support bearing for the drive shaft.

Offline Bevelheadmhr

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Re: A Blast from the Past
« Reply #19 on: Jul 04, 2015, 12:49:46 »
Lot of work on the supercharger this week.. of the two we had to hand, one Eaton was just the right size but badly worn, while the other was in good condition but a little too wide. Another was bought off Ebay which came from a Merc SLK, it was cheap as it had a long cast inlet snout which made it pretty useless for any other application.

But not for Jeff, he cut off the snout, machined the blower case and made a new end plate which will be welded onto the blower case. This will then receive more machining to make it match the rest of the cast blower case. That's why in this picture the machining looks a bit rough, its supposed to be. Notice that the edges of the plate have been bevelled where it meets the blower case, this is to make it easier to weld.