A Blast from the Past

Bevelheadmhr

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My mate Jeff won a bid on a few parts on Ebay last week, by one of those flukes, turns out the seller owns the first drag bike Jeff built back in the eighties, the bike that Jeff was slowly acquiring parts to replicate one day. Its been changed a bit over the years, it now has a 250cc engine, a Wade supercharger, an air shifter, hydraulic clutch and a different tank and seat etc. The home made frame and handmade yokes (the first he ever made) are still the same as is the front end. Well, turns out the chap was happy to sell, so we brought it home along with a pile of spares. Including a half completed engine, which Jeff had started to build when he sold the bike more than twenty five years ago. This spare 350cc engine has a much stronger home made three speed box, built by Jeff using CB750 parts, as running it on Nitro used to break the standard box regularly. Its in poor condition so its being rebuilt with a lot of changes, which I'll no doubt be roped in to help out here and there, be interesting to see how it turns out.
 

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Bevelheadmhr

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The old supercharged we took off Jeff's drag bike has a date stamp.. it was made 06/01/1943... what's interesting is that its original use wasn't on an engine, but to pressurise the cockpit of an aircraft, it would've been fitted to either a DeHavilland Mosquito or Supermarine Spitfire photo-reconnaisance aircraft.

By the end of the first day the bike was totally dismantled, with plans to make quite a few changes. The rear Astralite wheel was deemed too narrow and was soon sold on Ebay, as was the Supercharger (pity I would've liked to keep it). A wider Astralite was bought but had to go back as its condition wasnt as advertised. In the meantime a scrap Japanese 3 spoke rear wheel would have to do.

The points / coil ignition will be replaced by a Lucas Magneto, while the rusty fuel tank will be replaced with an alloy one which will live behind the headstock under the top tubes.

We have a new supercharger to fit, along with this empty case which will be used for setting up, along with a manifold and bigger SU carb. The Pistons in the background are from a Yamaha XJ650 Turbo and will give a cc of just under 350cc and a low CR of 5:1 using a plate beneath the block.
 

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Bevelheadmhr

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Jeff had been given a rear wheel with a knackered hub which was dusted down and put to use. The wheel came from a newish Suzuki which had a new tyre fitted (dunno where yet).. a week later on the motorway, the rear wheel bearings collapsed. When the wheel was inspected, the bearings and hub had disintegrated, because the bearing spacer was missing.

I would have thought that wheel was good for nothing but weighing in for scrap, but not to Jeff.. He machined up new plates for the bearings and had them welded to the wheel. There's no need for a cush drive and the sprocket needs spacing out to clear the tyre, so all in all it worked out ok. Then again if another nice Astralite turns up, the Jap wheel wont make the final build.

I did my bit by grinding off the casting marks, the wheel centre will be painted gold and the rims polished when we get time.
 

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Bevelheadmhr

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miffa said:
great story great bike

ive been on the constant lookout for my first build a 76 z750 chop BSH did a feature so it was special to me, sold it to fund the next bike ,35-40 builds later i aint never got the same buzz as the first, bit like your first love i suppose :'(
If you know the reg number you can check online to see if its taxed or sorned. I have all the old BSH mags, if you know roughly when it was featured I could probably find the article.
 

Bevelheadmhr

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miffa said:
cheers for that Bevelheadmhr i dont want to threadjack you
it must have been BSHs all time best selling month only because i brought loads of them LOL ,ive still got a few copies but do you think i can find them ,moved twice since then but wouldn't have thrown them ,i will give you the details when they turn up ,should be good for a laugh, it was when bling was the thing and this frankenbike certainly had enough
would luv to buy it back and redo it properly
i remember the reg what site is it to find out if its still alive

I'm sure everyone buys a few copies of a magazine their bike is featured in, well I do anyway :)

You just need to go to the DVLA site.. This is the link, you need the Reg number and make and it'll tell you if its currently MOT'd and taxed or on a SORN. https://www.vehicleenquiry.service.gov.uk/
 

Bevelheadmhr

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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 :)
 

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Bevelheadmhr

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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..
 

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Bevelheadmhr

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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.
 

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Bevelheadmhr

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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.
 

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Bevelheadmhr

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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.
 

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Bevelheadmhr

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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
 

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Bevelheadmhr

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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.
 

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Bevelheadmhr

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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.
 

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