Sammy Miller Cub Exhaust

[superhondaman]

Is there any reason why this system cannot be shortend so that the silencer sits tucked away where the oil tank was sited. Does it affect running to shorten the manifold pipe? Also how do you get a lighter clutch? apart from the right cable/routing what other mod's are there to get a lighter action?

[alan]

Is there any reason why this system cannot be shortend so that the silencer sits tucked away where the oil tank was sited. Does it affect running to shorten the manifold pipe? Also how do you get a lighter clutch? apart from the right cable/routing what other mod's are there to get a lighter action?

Many competitive cubs have short exhausts as you describe. Conventional wisdom would say a longer system should help power at the bottom end and vice versa. I have R cam, high compression and short exhaust it is a bit flat until the revs build up .. i guess you take your choice to suit your riding style.

You can lengthen the clutch actuating arm. You need to drill a new hole in the casing for the cable to make everything line up again (otherwise you will lose the benefit by having poor angles of pull on the cable).

You will lose a small amount of lift on the clutch pressue plate, but if all your plates are flat and springs evenly adjusted you can get the the clutch to free without dragging.

I beleive Alan Whitton does a four plate conversion that allows you to run lighter springs without fear of slipping.

Edited May 27, 2007 by alan

[superhondaman]

The engine has had a lot spent on it, all with Martin Adams. On the original invoice from July 2002 it shows what i presume is standard clutch plates springs etc & a 2nd hand clutch basket supplied and fitted. I presume you mean welding an extention on the arm, or can this be done some other way. The engine has never been run yet. It has the SM top tube oil tank, how can i tell if this feeds oil to the clutch, as i remember reading somewhere that there is a conversion done within the engine to allow an amount of oil through. Just noticed on the invoice a charge for '3 drain level holes' could this be the level for the clutch oil to rise to? High compresion? Mine is running 9:1 what is that classed as.

[alan]

The standard clutch struggles to cope with increased performance unless carefully set up.

The problems start when a smaller engine sproket is fitted to lower the gearing (a common Serco mod). This means more strain is put on the clutch as the engine turns over faster on the kick start. Heavier springs are usually fitted to overcome this problem. This puts more strain on the cover plate, especially the aluminium ones (another common serco mod). The surflex friction plates are too thick as manufactured but Serco machine them to the correct size, (it is not unheard of for the end plate to fall out when the clutch is operated if unmachined).

The lever can be lengthened by welding an extension on, I made a longer lever with a bigger forked end to accomodate a barrel nipple. I am not really sure it was worth the effort as I rarely use the clutch in sections, but it reduces the strain on the cable.

I am not sure about the "drain level holes". I have heard of holes drilled thro the crankcase to the primary chaincase as you describe, but as i recall Martin was an advocate of running the clutch on a small automatic transmission fluid to prevent slip. He also recommended fully synthetic engine oil which would not aid clutch grip.

Could the holes be part of the breathing system? The crankcase breathes thro the cam bush into the inner case. There is a small hole to return oil back to the sump. Have you got a breather on the distrubutor blanking plug ? if so maybe the drain holes are in the inner case ?I would be suprised as Martin usually recommended blocking this hole up " lets more oil out than it allows back in".

It is easy enough to take the primary chain case off and check for the holes, it there aren't any i would suggest putting in around 150 ml of straight SAE 30.

As for compression, 9:1 is as high as you should go for trails use, some of the more competitive cubs are running 7:1 for more bottom end grunt but usually big bore engines as well.

[superhondaman]

Thanks for the info so far i will investigate the primary side soon. I have e-mailed Venhill re a Featherlite cable, are people running these on their cub's?. Is there a e-mail address for martin adams in Australia?

Edited May 29, 2007 by superhondaman

[alan]

Featherlite eh .... don't they come in a pack of three ? pre lubricated if i remember correctly ... have you tried the ribbed version ? it is supposed to increase the pleasure of riding.

[vinnied]

Featherlite eh .... don't they come in a pack of three ? pre lubricated if i remember correctly ... have you tried the ribbed version ? it is supposed to increase the pleasure of riding.

:D

[superhondaman]

Tried one but it did not make it any easier & not saying where i put it!

[alan]

judging by your avitor you put it in the wrong place