The Comp Bike Build thread
Discussion
Not sure how many of you folks are interested in something like this, but when I read about custom bikes and tuned Blades and such in the msagazines, I always shake my head and wonder why those magazines never feature drag bikes. They have a hell of a lot more skill and effort put into them than a blade with carbon wheels and PC V..
So heres a build thread of our Compbike, I own half of it and my mate Jeff owns the rest. Jeff does all the hard work while I drink tea and eat his favourite biccies and help out when I can. Ok, where to start?
How about we build our own engine.. from scratch, in a shed
No CNC machines, just a 40 year old lathe and 30 year old miller..
We start by making the crank cases, out of 500 quids worth of high spec billet.. and a lot of careful machining.. note the homemade cutting disk with just one tooth, made it easier to control the cut.
So heres a build thread of our Compbike, I own half of it and my mate Jeff owns the rest. Jeff does all the hard work while I drink tea and eat his favourite biccies and help out when I can. Ok, where to start?
How about we build our own engine.. from scratch, in a shed
No CNC machines, just a 40 year old lathe and 30 year old miller.. We start by making the crank cases, out of 500 quids worth of high spec billet.. and a lot of careful machining.. note the homemade cutting disk with just one tooth, made it easier to control the cut.
Edited by Merch131 on Monday 6th August 20:39
Edited by Merch131 on Monday 6th August 20:40
Forgot to say that we're building a 'comp bike' this is one step down from the very top of the drag race tree. It'll be run on Nitro, its losely based on a Z1, but apart from the head there isnt any std Kawa parts in the motor. It'll have a supercharger, reversed head, seperate two speed gearbox, lock up clutch, belt primary, External high pressure oil pump, twin magneto ignition, 8 plug head (that way if one mag breaks the other should carry on sparking the plug, otherwise you get hydraulic lock and a big bang with Nitro). We're making our own frame, yokes, wheels, discs, everything we can really as its all being done on a shoestring.
Dummy head used to measure up for the blower inlet manifold..
Jeff made this wheel, using rims from a car wheel, and the disc and the frame too.. and now he's busy making a 'better' wheel lol..
The clutch is very important, it acts a bit like a gearbox, as the motor has enough power (about 800bhp) to spin the rear tyre all the way down the track. It needs to slip and gradually feed in more power as speed increases. It has adjustable arms which apply more pressure as it spins up. We're making our own, using clutch plates from a Mk 1 Ford Escort Mexico rally car (they fit the output shaft of the yank gearbox)..
The conrod on the right is from a GPZ1100, the one on the left is whats needed in a Fuel bike running Nitro..
Dummy head used to measure up for the blower inlet manifold..
Jeff made this wheel, using rims from a car wheel, and the disc and the frame too.. and now he's busy making a 'better' wheel lol..
The clutch is very important, it acts a bit like a gearbox, as the motor has enough power (about 800bhp) to spin the rear tyre all the way down the track. It needs to slip and gradually feed in more power as speed increases. It has adjustable arms which apply more pressure as it spins up. We're making our own, using clutch plates from a Mk 1 Ford Escort Mexico rally car (they fit the output shaft of the yank gearbox)..
The conrod on the right is from a GPZ1100, the one on the left is whats needed in a Fuel bike running Nitro..
One reason the bike is taking so long.. three years and counting.. is that Jeff is never satisfied with something he's made, he's always looking to make a better part even when the first version is just fine. Here's a couple of beadlock wheels he made, one for us and one for another drag racing mate.. got to admit they do look good..
Top work, guys, I wish you all the best for your project !
I like the Drag Bikes best where the racers build their own engines,
guys like you can be proud of yourself.
Imagine the moment when the beast roars for the first time,
even it means lots of long nights & weekends in the workshop.
I like the Drag Bikes best where the racers build their own engines,
guys like you can be proud of yourself.
Imagine the moment when the beast roars for the first time,
even it means lots of long nights & weekends in the workshop.
Its been awhile, as not much progress was being made, while I've been busy with my Ironhead/Norton and other projects. But the last few weeks things have started to pick up again. The gearbox and multistage clutch are now all done and fitted at last. Though it sometimes seems we make one step forwards and two back. My mate Jeff has recently discovered Zephr 1100 motors.. turns out the the Zepher motor has bigger ports compared to the old GPz motors, so we're building another engine to use the Zepher head. Because the inlet and exhaust ports having different spacing than the old GPz heads, we need to make a new blower manifold, new exhaust headers and collets, and a machine new block and cases from billet..phew! To date the blower manifold is done.. took a week of machining on Jeffs old miller, the block is next, then the cases. Luckily we have an unfinished billet case which hasnt been drilled yet, so that'll save a lot of time. Oh, and we're using a bigger supercharger too
Machining out the blower manifold..
New Exhaust collets being machined
New blower, manifold on the Zepher head, the old Gpz based billet block is still in this photo
Machining out the blower manifold..
New Exhaust collets being machined
New blower, manifold on the Zepher head, the old Gpz based billet block is still in this photo
Quick update.. Jeff is well on the way to building a second engine to use the Zephyr head and plain bearing crank. I asked which engine we were going to go with initially at least, and Jeff being Jeff replied, dunno yet..
Going back about three years he made a billet crankcase, which were going to use a modified Z crank, converted to plain bearings (from a Hillman Imp). That plan was put on hold as we had a problem finding someone to line bore the cases accurately for a price we could afford.. But now those cases have been dusted off and with a bit more work will be used in the new motor along with the strong Zephyr crank (which already uses plain bearing as std). The rods were made by a chap called Bert apparently for a fuel bike, and we'll be using them with the new crank.
The new block is also nearly done, by the way in the photo you can we a raw Z1 casting, which is probably the last one of a small batch that Rod Pallent had made in the late 70's. Jeff's had it tucked away for years, I'm not sure what he plans to do with it, I couldnt bare to ask lol.
New Block.. the discs are to clamp it down so as not to damage the block..
Going back about three years he made a billet crankcase, which were going to use a modified Z crank, converted to plain bearings (from a Hillman Imp). That plan was put on hold as we had a problem finding someone to line bore the cases accurately for a price we could afford.. But now those cases have been dusted off and with a bit more work will be used in the new motor along with the strong Zephyr crank (which already uses plain bearing as std). The rods were made by a chap called Bert apparently for a fuel bike, and we'll be using them with the new crank.
The new block is also nearly done, by the way in the photo you can we a raw Z1 casting, which is probably the last one of a small batch that Rod Pallent had made in the late 70's. Jeff's had it tucked away for years, I'm not sure what he plans to do with it, I couldnt bare to ask lol.
New Block.. the discs are to clamp it down so as not to damage the block..
Not too much progress I'm afraid, Jeff's been busy making a new frame jig last couple of weeks. But he has been making a new block to suite the Zephyr head. That should be done this week, then fingers crossed progress may speed up a bit.
One reason for making a new frame jig is so Jeff can put together a new 'simple' bike using all the spares we've got, either to sell or have some runs with. Problem is it takes up time that could be spent on this bike..
One reason for making a new frame jig is so Jeff can put together a new 'simple' bike using all the spares we've got, either to sell or have some runs with. Problem is it takes up time that could be spent on this bike..
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