[Ironside]

renault-megane-dci wrote:-

Ironside, I understand your bike redlines downhill somewhere around 75mph and probably around 9K and that you were usually around 65 which sounds very much like 8K so the engine might have been used in waste mode.

Have you been looking over my shoulder ?, spookily accurate. I'm not sure what you mean by 'waste mode'.

My point is that streamlining works better if at all with a big gear reduction to cruise a little below peak torque with the throttle at 75% and basically no potential for extra acceleration unless dropping a gear.

I'm currently using the highest gearing I can find off the shelf, 14 x 36. I can't go smaller on the rear sprocket without going larger on the front because the chain has no clearance over the swing arm. The gearbox sprocket has un unusual design and without cutting and welding, is only available in 14t from the USA at $40 + shipping + import duty +VAT (ask me how I know). So I'm kinda stuck with it for the moment.

Peak tourqe for an unmodified engine is 5,500 rpm. which equates to 45 mph. and a quarter throttle. I should try a run at this speed to see what happens.

Although the fuel economy is important, the bike has to remain useable, having only 4 gears means that I dont have a spare gear to use as overdrive.
I've read somewhere that there is a vehicle called the TRX 125, which shares a similar motor but has 5 gears, if I could get one of those engines things might be different. Unfortunately it was never imported into the UK.

Different displacement and cam tunings ect. will throw the mixture off of the map.

Thanks sendler, I don't think I'll bother with that then, time and money would be better spent on an AFR meter to set up the carb properly. Even at today's fuel prices, the payback time won't be too long.

Thanks for the feedback
Ironside.