News 2005

1st September

OF course we had to start the bike up again and yes it worked, and if anything seemed even louder. Unfortunately when I came to spin the engine over with the plugs out, the starter made an ominous clunk-clunk sound. Stripping the starter gearbox down revealed utter carnage - barely a tooth left and the casing badly damaged! In desperation I started looking for those CB500T starters I know I threw away 6 months ago, and yes I did throw them out, but I saved a pair of sprockets and a chain. A call to my mate Toad in sunny Poole produced a Goldwing starter; a quick redesign was in order!
SO what little spare time I had in August was spent making a new starter from what I could salvage of the old one. Another test proved this one worked fine; only snag was the starter rotated the wrong way.
A quick message to those great guys at Electrex (specialist bike electrical spares) gave me a hint as to what to do. Just reverse the polarity of the armature; Er! OK then.
This proved to be pretty fiddly and I sussed out involved rotating the brush plate 180° followed by reversing the insulation status of the brushes and connecting the supply wire to the other brush. To my amazement it worked, so on to the bodywork.

MY enthusiasm for preparing and spraying bodywork expired many years ago, but I couldn't afford to pay anyone to do it so I'll apologise in advance for the less than perfect paint job, think I'll stick to engineering in future! If the weather behaves itself you can have a look for yourself at the Jap Racer Day at Shakespeare County on 2nd October, see you there.

26th July

It wasn't until I removed the head gasket that I realised that we had another problem. When I made the cylinder block I couldn't find any flanged liners to suit, however the manufacturers assured me their plain ones would not shift. As soon as Steve at P.B. Engineering in Bristol saw them he assured me they would. In the circumstances I had no option but to carry on and I added some grub screws as insurance. Well of course Steve was right; they have both moved by a around a mm! There is no time or spare cash to get them re-linered now so we are back to 500cc and 8.5:1 compression - bugger. Or not, I feel a drop of nitro coming on, yes if things go OK at the next test we will be "tipping the can" a little soon.

At right you can see the problem, and a standard barrel with the fins hastily milled away for quick warm up on methanol.

Sunday 18th July

THE Sun hadn't long risen before I was back in the workshop, finishing the bike off whilst pondering the hassle of loading it into our little van for the first time and heading off to SCR. My frayed nerves weren't helped when I discovered the A429 was closed and we had to make a 20 minute detour to rejoin the road about 5 miles further on!
However once we reached the track, things began to move smoothly aided by the professional staff at SCR and we were soon signed on, just in time for action to start. What followed was an object lesson in how not to go racing; Team Laurel and Hardy would have been a better description of our attempts!

THE relentless blazing heat didn't help, my brain just seemed to shut down after a while; not what you need with so much new stuff to think about:
YOU just can't switch the engine off anymore; fuel must be shut off first allowing the engine to use up the fuel in the carb - then switch off the ignition. Take out the plugs and spin the engine over to clear the cylinders. The potential for a nasty backfire is ever present if there is any fuel in the cylinders, as we found out when switching the ignition off!
Add to this, far more boost than I ever hoped for (30psi at 8000rpm) and even a tiny pin hole in the inlet manifold becomes a jet of fuel with methanol. The burst panels have bowed out too! The general consensus was that our fuel tank would be big enough at 2.5 litres, though the contents don't half disappear rapidly.

MEANWHILE Dom (who at 20 hasn't ridden a bike for 3 years), is getting a bit nervy and incredibly hot in black leathers and helmet. His enormous size 13 boots can't find the gear lever and the linkage is a bit springy which makes gear selection near impossible, oops!
Frantic nods from the start line, which I interpret as problems, end up with me rushing over and switching off the ignition after seeing spots of fluid on the track (dummy - see above). In fact all he wanted was his visor put down...aggh!
Add to this a couple of screws vibrating off and Dom was half jokingly muttering "you guys are nuts" ('On Any Sunday' fans will know what he meant). Did I say a couple of weeks ago it didn't vibrate like a Triumph? Err... well actually the carb disappears at 8000rpm!

EVENTUALLY we managed to get our act half together and Dom launched, but at too low revs and the engine just sulked at such tentative behaviour. At about half track he managed to find 3rd gear and the revs got to a point where things began to work; in response Dom gave it a handful and the roar was impressive back behind the start line, but the sudden burst of fierce acceleration together with steamed up specs and sweat dripping in his eyes meant he got out of it pretty rapidly. I don't suppose me wiping my greasy hand across his visor as I pushed it down helped, can it get worse:
Of course! As we didn't have a tow bike Dom was almost ready to pass out when I got to him on the return road.

'The Fang' is dwarfed by 'Bear's' Top Fuel Harley. Paintwork is now a priority.

7th July

HAVING spent the last couple of weeks struggling with fibre glass and seemingly tons of body filler the bodywork is beginning to look somewhere how I imagined it.
Plan 'A' was to have a session on Tim Blakemore's dyno this week but unfortunately due to pressure of work I didn't have the time. However I did get around to making a selection of jets and fitted a much larger one to err on the side of caution. Click on the animation to listen, or right click and 'save target as' (200Kb).
It is much 'fatter' now with raw fuel coming from the exhausts at lower revs, but revs cleanly.

WE are really hoping to test at the Mini Nationals at SCR next weekend, but there is still quite a lot to do, so no promises.

Click on the animation to hear a CB500T like you've never heard before!

12th. June

20 months after it's last disastrous outing with the old Shorrocks supercharger, The Fang finally burst into life again yesterday.

FRIDAY saw a dash into Bristol to the impressive Tim Blakemore Racing shop to pick up a gallon of methanol, and at 5 o'clock on Saturday all the final little jobs were complete. With daughter Bryony in charge of ignition, fuel and throttle I plugged in the starter and, not sure what would happen pressed the button. To our delight the engine roared into life and settled down into a fast tickover. Good job we were wearing ear protection as it is pretty loud now plus we have that lovely smell of burning methanol.
DESPITE a 3.3mm main jet it sounded really sharp when I blipped the throttle so I think a bigger jet may be in order, good job I went for 8mm bore fuel pipes! Mindful that the neighbours might not appreciate supercharged methanol burning dragbikes, I pulled the fuel cut off pin and this was followed by the final icing on the cake as the fuel leaned out and the revs rose before the engine died. The silence, as they say, was deafening!

AS to the new crank, yes it does sound like a blown Triumph, but it doesn't vibrate like one, so it looks as though all my theorising was right, quite a relief!

ALL (!) that remains now is to finish the bodywork and fabricate the wheelie bars, a track outing beckons.

www.timblakemoreracing.co.uk

2nd May

DESPITE the lack of updates this year I've been very busy working on the bike, with the result that we are only 3-4 weeks from our first test.

TO recap, I had decided to change the crank so that the throws were 60° apart. Due to a slight communication problem the right crank ended up leading the left one, the opposite to what I'd requested. Fortunately I hadn't modified the cams so it wasn't a problem. Anyhow we now have firing intervals of 300°/420° which should give more even cylinder filling without too much vibration - I hope.
I had to cut the cams on the right side of the centre line in order to continue using the Honda timing marks, though this introduced a slight problem: there is a quill inside each cam on this side to get the oil feed near to the centre. As I had to sleeve the cams under the weld these quills had to be remade to a new design.

MODIFYING the ignition pickups was tricky too, though I did manage to utilise one existing threaded hole! However I had to make up a new cover as the newly configured wiring wouldn't fit into the Honda cover.

THE 75mm Wiseco Z1 forged pistons donated by a Scottish enthusiast (whose name I have temporarily lost - sorry mate), needed extensive modification to clear the flywheels and valves which was handy as they are now close to the weight of standard Honda ones. The increase in bore takes us up to 588cc, if only it were twice that! Compression ended up at around 11:1 so if we get near 20psi boost it should make the right noises! I made the new head gasket from solid copper.

THE oil feed plumbing has been replaced with some special hose and and anodised fittings (Christmas present from my lovely daughter). Twin output coils donated by my mate 'Toad' fire the new twin plug setup, and at vast expense the new fuel system is plumbed in with spring loaded shut off valve ready to take nitro. The fuel line is in -8 hose and minimum bore throughout is 8mm so no fuel starvation this time. Main fuel tap is a stainless steel one from the RS Components catalogue, from which I carved off 80 grams as it was a bit overweight. The other spring loaded valve is from Goodridge, but extensively modified and feeding into the custom float chamber cover.

LARGE diameter blue hose behind the carb is a crankcase breather, and feeds into a custom aluminum catch tank squeezed between the blower and battery.

THE offboard starter is currently under construction. This utilises a Honda VTR1000 starter motor driving through a gear train in an aluminium casing. The whole lot locates on extensions to the engine mounting bolts visible in the photo above right. The starter drives a short shaft behind the clutch near where the kick starter shaft used to reside. On the end of this a spare crank primary drive gear drives the clutch and thus the crank.

JOBS to do include wheelie bars and finishing off the carb: This needs new main jet to suit methanol/nitro, blocking off all the other passages and fitting an 'O' ring to the bottom of the piston. This should just allow sufficient fuel to seep through for the engine to idle.

DURING his Easter break 'Dr' Dom takes time out from his Eigen Physics and Hamiltonian Mechanics to try the bike for size. Unfortunately at 6' 3" he has outgrown it a bit! Anyone need a fanatical drag racing physicist to ride their bigger drag bike?