Recumbent Honda 90

[P-hack]

Originally Posted by renault_megane_dci

The calculator is not really bike friendly because we have a pretty lame drive train with higher than standard (read car) transmission loss.
Yes a brand new chain is good but is only brand new for 1/20 of its life.

There are a couple mitigating factors however, so I'm not sure what this is based on. Namely bike transmissions are usually straight cut, and chains (when tensioned properly) are more efficient than gears, especially helical.

Also if you use an even number of teeth on the front and rear sprockets, and index the chain to the sprockets, then you should see minimal stretch over the service life of the chain and sprockets (props to sheldon brown!).

Originally Posted by PeterS

IIRC there is a real difference between O ring and non O ring chain but the main difference is a clean , preferably unworn chain . The old Honda chain guards made a BIG difference to chain condition and life.

Yes, yes they did, without the friction of o-rings, this would be a fine retrofit for any modder.

[renault_megane_dci]

It is my personal experience that a chain can be much less performing than it is given credit for.

Same slight downhill to my garage : my barely worn chain XF 650 Freewind required some help when my R65 beemer of pretty much the same weight required some braking.

Chain performance is only a myth or an engineer's wet dream in my book.

[P-hack]

This seems like strong language for such a limited experiment, and you were originally comparing bikes to cars to make the statement. Tire inflation and size, clutch design and adjustment, chain tension, loading, brake adjustment, bearing condition all come to mind. I mean Matsuzawa got 470mpg with a chain drive, it is no wet dream, no handicap.

As I attempted to point out, chains often don't get optimal consideration at installation, but minimizing "stretch" and contamination are trivial to do. My v65 doesn't coast so great, but there are a lot of variables so I don't leap to "it must be the driveshaft"...

[renault_megane_dci]

Strong language ?
Maybe the wet dream mention ...
Excuse my french ...

Bike engines are tuned towards big specific power, the Surface is not too easy to determine and the drag is definitely empirical so I like to double check the results of the calculator to alter the coefficients according to actual measured performance (like top speed).

As for the limited measurement, the difference was that big that there is no contest.

And bikes usually have a 1/3rd reduction in the sprocket so 1/1 would be interesting to say the least ...

[Ironside]

Thanks for the feedback guys, I will attempt to clarify.

Thanks Peter S, I am aware of the Chinese 'copy' engines, many of my fellow c90 club members have fitted these motors, some have given many thousands of miles of trouble free use, others have expired rather quickly. Gearboxes invariably fail at around 6000 miles, I suspect the five speed gearbox may be even weaker.
These motors will fit a later model frame, but modifications are required for my frame and I believe the 'postie bikes' also.
I am keen to stay with genuine Honda motors, given good maintainance they are virtually indestructable.

I have just taken delivery of an identical spare motor, ATC 125m circa 1984. This will be dismantled and rebuilt with as many new parts as is neccessary, this will save any down time.

According to Honda, the standard motor produces 8.6 BHP at 7,500 rpm., (but will rev quite easily to 8,500 and more in top gear) and maximum tourqe 6.45 ft.lbs at 5,500 rpm.

I've been using an internet program called 'gearing commander' to calculate my gearing changes. I can confirm that the bike pulls away easily in first gear, and now that I have a spare motor I can experiment with larger front sprockets. There is enough room for a 16 tooth front sprocket, I will then have options from 36 - 42 at the rear. Should I be aiming for peak torque at my normal cruising speed?.

I feel that using that using the highest gearing possible may be counter productive, as with such a low power output, I'd be spending more time in third gear ( I live in a very hilly area ).

Regards,
Ironside.

[PeterS]

Thanks for your thoughts on the Chinese replacement motors Pete, you probably just saved me some money !

I keep going back to the calculator and fitting in all the variables. Personally, 50 to 55 is my preferred cruising speed so I'd probably go for maximum torque right there. That would work out at about 100 rpm per mph in top.

What sprocket ratio would that be ?

[cRiPpLe_rOoStEr]

Originally Posted by PeterS

Google finds a 125 cc Honda style tilted engine called a Loncin with a 5 speed box.

Loncin is the only Chinese manufacturer that entered in the 125cc Moto GP class, but I still don't feel confident enought to buy a Loncin engine

[jkv357]

Originally Posted by cRiPpLe_rOoStEr

Loncin is the only Chinese manufacturer that entered in the 125cc Moto GP class, but I still don't feel confident enought to buy a Loncin engine

I agree with the second part, but there is no 125cc MotoGP Class.

The lowest "Moto" class is Moto3, which are 250cc 4-stroke singles.

[cRiPpLe_rOoStEr]

Originally Posted by jkv357

I agree with the second part, but there is no 125cc MotoGP Class.

The lowest "Moto" class is Moto3, which are 250cc 4-stroke singles.

I'm not so up-to-date to MotoGP, Moto2 and Moto3. I didn't get the same enthusiasm about it after Daijiro Katoh's death.

[PeterS]

Originally Posted by jkv357

I agree with the second part, but there is no 125cc MotoGP Class.

The lowest "Moto" class is Moto3, which are 250cc 4-stroke singles.

There was up until 2012, fairly recent.