Moped racing heathen
Posted: Tue Feb 06, 2018 3:35 pm
Hello,
Butcherous moped racer here, after advice for a long-suffering Cub 90 in need of help...
It's a 12v Cub (no idea what year - we've had three as a team, with engines and chassis mixed and matched). It's a kickstart only type, which we've evolved for the RAF Wittering 6hr/4hr endurance races over the years. Frame/engine are original, but with a brace welded in to the frame, CG125 forks, different shocks and knobbly tyres. Motor has a bigger carb (exact size long since forgotten) and a pit bike CDI. Plus ludicrously short gearing - rear sprocket is somewhere well in to the 40s... We've won two racesa after spending years working through anything that costs laps, and created a very effective bike. It now has a CLR125 fuel tank, which allows it to do a full 4hr race on one tank, as well as being easier to ride with something to brace against and more weight forward.
This engine has been raced since at least 2006, and maybe 2004. It had a rebore a couple of years back, but one of my less than intelligent team mates ran it with a silly pod filter one year, and the ingress of dirt has got it smoking like a good 'un again...
It also has a dicky kickstart which sometimes doesn't engage correctly or sticks down, and the gearbox now almost refuses to get in to third, or back out of it once it goes in. And the crankcase is cracked where somebody fitted an incorrect chain cover bolt. Fair to say it's had a hard life...
A few options on the table: rebuild the motor we have with used original bottom end parts, hopefully just another oversize piston and a hone for the top end. But I'm wary of any C90 lump broken for spares being worn too.
The second is original motor, top end refresh, new 4-speed gearbox from an eBay seller in Vietnam. But worried about it not fitting, or being poor quality. And it still may need other things sorting.
Third is a YX90 engine (the bike needs to remain a semi-auto 90). They seem to have been for sale for years and are the control motor for a kid's racing class, but I can't find any details on the longevity of these (I'd be leaving it standard) or the performance. Roughly equivalent to our original (in better days...) is fine. More speed isn't the issue, the package works over a race.
Had a preliminary search, but will be delving deeper in to the accumulated knowledge for more help.
Chris
Butcherous moped racer here, after advice for a long-suffering Cub 90 in need of help...
It's a 12v Cub (no idea what year - we've had three as a team, with engines and chassis mixed and matched). It's a kickstart only type, which we've evolved for the RAF Wittering 6hr/4hr endurance races over the years. Frame/engine are original, but with a brace welded in to the frame, CG125 forks, different shocks and knobbly tyres. Motor has a bigger carb (exact size long since forgotten) and a pit bike CDI. Plus ludicrously short gearing - rear sprocket is somewhere well in to the 40s... We've won two racesa after spending years working through anything that costs laps, and created a very effective bike. It now has a CLR125 fuel tank, which allows it to do a full 4hr race on one tank, as well as being easier to ride with something to brace against and more weight forward.
This engine has been raced since at least 2006, and maybe 2004. It had a rebore a couple of years back, but one of my less than intelligent team mates ran it with a silly pod filter one year, and the ingress of dirt has got it smoking like a good 'un again...
It also has a dicky kickstart which sometimes doesn't engage correctly or sticks down, and the gearbox now almost refuses to get in to third, or back out of it once it goes in. And the crankcase is cracked where somebody fitted an incorrect chain cover bolt. Fair to say it's had a hard life...
A few options on the table: rebuild the motor we have with used original bottom end parts, hopefully just another oversize piston and a hone for the top end. But I'm wary of any C90 lump broken for spares being worn too.
The second is original motor, top end refresh, new 4-speed gearbox from an eBay seller in Vietnam. But worried about it not fitting, or being poor quality. And it still may need other things sorting.
Third is a YX90 engine (the bike needs to remain a semi-auto 90). They seem to have been for sale for years and are the control motor for a kid's racing class, but I can't find any details on the longevity of these (I'd be leaving it standard) or the performance. Roughly equivalent to our original (in better days...) is fine. More speed isn't the issue, the package works over a race.
Had a preliminary search, but will be delving deeper in to the accumulated knowledge for more help.
Chris
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