E: Engine Comet Mongrel

[Bill Thomas]

Whatever the standard advance curve was for my single plugged bike ( Lucas RITA), think the customer bike was on twin points and atd so both likely fully advanced before 2500. Not really an issue in the limited rpm range to which we are restricted assuming even a highly tuned Vin runs past the power peak by 6400 rpm at most. As I have said our race bikes ran OK without an atd on fixed ignition but could be a pain to start from cold but seldom came under 4000 rpm when warmed up and in action. Does depend on the intended purpose of the machine.

I rode Ian's Bike round the paddock at Cadwell ! = Nightmare !. Cheers Bill.

 

[BigEd]

Yes it is stomach churning here is an early vid of the first time we used one....

http://www.oldracer.co.uk/video-gallery.html#prettyPhoto[group1]/6/

My two most vivid memories of the first time using a dyno:

1. The wonderment of standing next to a flat out machine as it roars away.
2. The eery silence that suddenly descends when the head comes off the exhaust valve.

 

[Cyborg]

I could deal with the eery silence.... the preceding expensive sounding death rattle not so much.

 

[eglijim]

I haven't made a final decision on a chassis. I have a few different options but leaning towards one that currently has all of the necessary paperwork. Unfortunately it would likely cause the club to issue a fatwa. If it doesn't work out or I come to my senses, there is a nice Monster trellis frame that came attached to that swing arm. At first glance, it does seem wide and would probably look odd.

I have a 600 Monster but find the handling overrated, gets very front light over 90 mph, much preferred the SZR 660 Yamaha, nicest handling big single I have ridden, possibly worth buying one to just do the engine transplant. On the assumption that you are building a non standard "special" then all bets are off and I would not compromise your vision to try to "conform" to please he rivet counting fraternity.

 

[eglijim]

My two most vivid memories of the first time using a dyno:

1. The wonderment of standing next to a flat out machine as it roars away.
2. The eery silence that suddenly descends when the head comes off the exhaust valve.

Amazing how quickly you can slam the throttle shut when the chain snaps at over 6K.

 

[Cyborg]

I have a 600 Monster but find the handling overrated, gets very front light over 90 mph, much preferred the SZR 660 Yamaha, nicest handling big single I have ridden, possibly worth buying one to just do the engine transplant. On the assumption that you are building a non standard "special" then all bets are off and I would not compromise your vision to try to "conform" to please he rivet counting fraternity.

Don't think there are any SZR 660's to be had on this side of the pond. This is defiantly a non standard special. While I was searching for a swingarm, I found one similar to the one in your photo (Honda 600RR), but if I used it, I'd have to get some better forks and brakes to go with it. I'm determined to use up some of the shed contents that I have been schlepping around for eons.

 

[eglijim]

Don't think there are any SZR 660's to be had on this side of the pond. This is defiantly a non standard special. While I was searching for a swingarm, I found one similar to the one in your photo (Honda 600RR), but if I used it, I'd have to get some better forks and brakes to go with it. I'm determined to use up some of the shed contents that I have been schlepping around for eons.

The SZR was developed for the european supermono series to take on Ducati and Bimota. Could be the same platform as a TZR Yamaha. The Comet special is the one developed by the late Glenn Cuthbertson as he wanted a modern road Comet based on Ian Hs BOTT bike(as my avatar). His plan was that ALL of the cycle parts would come from a single donor bike, in this case a 400 Honda. Ash Bennett in the UK is trying to do something similar with a Spondon rolling chassis he has but may have a problem with the engine height and the large frame spars.

 

[Cyborg]

A complete donor bike makes sense on so many levels, the main one being time. I did explore that avenue and searched around for something. I also contacted the local motorcycle breaker, but he didn't have a rolling chassis that suited a Comet. I want to end up (in relatively short order) with something that behaves reasonably well and looks like something I want to ride. The short order part seems to be out the window and just in case my frame ends up in here, what 400 Honda are you referring to?

 

[Cyborg]

BTW, this gives you an idea of where I'm going with the brakes.

 

[eglijim]

A complete donor bike makes sense on so many levels, the main one being time. I did explore that avenue and searched around for something. I also contacted the local motorcycle breaker, but he didn't have a rolling chassis that suited a Comet. I want to end up (in relatively short order) with something that behaves reasonably well and looks like something I want to ride. The short order part seems to be out the window and just in case my frame ends up in here, what 400 Honda are you referring to?
View attachment 20048

Glenn chose the NC23 or later 400cc "Baby Blade" as a donor but you still need the bespoke main chassis to bolt the running gear to. Before his premature death, he was also looking at putting a short stroke Velo engine into a complete SZR, I sold my good running SZR and he also bought a frame frame a badly crashed SZR to use for a bench mock up and engine plate design. Whilst I understand your wish to use components currently in your hands I do like the idea of buying a suitable complete donor( maybe with a bad engine), may also ease any registration troubles if that is an issue in Canada ?.