E: Engine Comet Mongrel

[Cyborg]

Why not just put another lever on with a smaller pivot to cable distance and see how much difference the better lever ratio makes? At least that would identify one possible cause of your heavy clutch. The change in lever doesn't have to be permanent. You can then make a decision as to whether you prefer form over function or vice versa.

Went to try that last night, but the cable end wouldn’t fit in the Doherty lever. I found a Honda one that has a shorter pivot distance that will fit the cable, but is a pinch bolt type, so I need remove the grip to extract it from the bars it’s attached to and then remove the grip from the Comet in order to slide it on. It is clamped in the vise downstairs waiting for me to finish my morning coffee.

I’m thinking the shorter pivot distance will also give me more control over engagement. Can’t really tell from just using the kickstart to turn it over, but it seems to lean towards all or nothing the way its currently set up. Lower lever pressure will help me to be able to control it a lot better. Pressure is so high now, it is difficult to release slowly and smoothly.

 

[Cyborg]

I have a Newby clutch on my Albion Flash and another on the racing Comet with a burman box and a norton mainshaft and one on my Egli Comet with a AMC Norton box we also had one on the egli twin all belt drive they are all light and easy to use. I have a Conways Honda clutch on the road comet and thats a swine to pull apart from the Flash none of them has the standard lever all alloy ones with adjusters

Thanks for the feedback, that’s good to know..... Although I’m not sure you are suggesting I don’t have it set up properly or you are calling me a pussy.

 

[davidd]

As Tim says, the Newby can be very light. I would tighten the springs for land speed runs and loosen them for road racing.

Using the brakes as an example, the amount of force you can generate is a result of the leverage on the lever, which is about 400 lbs (based upon where it is grabbed and the 100 lbs you apply.) That 400 lbs is divided by the distance of the pivot to the cable end in the lever (center to center.) Because that pivot distance in in the denominator, it really changes the cable force dramatically. For example, if the pivot distance is 1" it is easy to see that all 400 lbs is transmitted. If it more like the Vincent, you have 7/8" in the denominator (making it smaller), it would make the force much higher than 400 lbs. If you used a pivot distance of 1-1/8", the denominator is much bigger and the resulting force is much lower.

The reason Vincent could get away with such short brake arms on the brake plates is that they used a small pivot distance in the lever, which created more force. The larger pivot distances tend to use much longer brake arms, which technically could have provided similar forces.

The Vincent brake system, it uses a short pivot distance to create a high force, short travel brake. The other systems use a longer pivot distance to create a low force, long throw brake. The systems should achieve similar results, all other things being equal. However, mixing the two necessitates a lot of experimentation to get to a useful compromise.

David

 

[Cyborg]

Thanks David. I looked at the GSXR lever to see if I could change the ratio, but a quick glance explained why I can’t do that. The lever in the photo solves that with the pivoting adjuster. Who sells those ( just in case)?
No doubt the Honda lever will make a difference. It’s brutal the way it is now. A little frustrating in that the M/C and clutch lever are a matching set that I bought for this project. I do have a Honda M/C that matches the Honda clutch lever assembly. It has the correct diameter piston, but the reservoir fouls the casting of the clipon, so can’t use it unless I flip the bars from side to side. That might make them look odd and it moves the bars back a bit.
Just so anyone looking at the photos doesn't think I've lost my mind completely and arbitrarily slid the tubes up so I can install clipons above the top bridge and knackered the geometry ... they are the original CBX 550 tubes and were designed that way.

 

[vibrac]

I did look at a MX (why did they loose the name Scambles?) clutch multiplier to use the Conways Honda Clutch
see here

 

[Cyborg]

Well I'm building a momentum exchange tether for my decompressor, so why not make one of those...
Interesting... thanks.

 

[Bill Thomas]

Well I'm building a momentum exchange tether for my decompressor, so why not make one of those...
Interesting... thanks.

I went down to Brother Ron's the other day, He fitted a USA decompressor that I got 2 of, One for him and one for my next Comet build, Goes in the second plug hole.
No cable, Just push the button down and kick, Like used on H.D.s.
He has not been able to start it with this, Anyway, He has been having a bit of Mag' trouble, So we converted it to "D" type Coil, And now it starts !!, I wondered if it needed electric starter, To spin it faster, But now Ron can start it, Also found that if you want to stop the engine, With out using the valve lifter, You can just push the button. Cheers Bill.

 

[Cyborg]

Given the hoops I jumped through to get the second plug hole in there, along with the fancy twin lead coil and programable ignition, nothing on this planet will make me stuff a decompressor in that hole. After exchanging pleasantries with Magnetoman, I'm starting to wonder how much fun it would be to have a second programable ignition, so the two plugs can have independent curves.

When slowly (thank goodness) kicking it over yesterday to check out the clutch, it didn't show any signs that I couldn't live without a decompressor. As usual, in the middle of the night I'm pondering something motorcycle related and realize.... oh shit the intake port is still plugged with a paper towel because my apprentice has a habit of filling any void he can find with his plastic toy nuts and bolts. Popped the manifold and carb off from its temporary moorings this morning and was happy to see the wadded up paper towel hadn't disappeared down the port. So now with intake unplugged, throttle W/O it is still quite manageable to get past compression, so unless it decides to croak at a red light, not an issue.

 

[Cyborg]

I switched levers which turned out to be a longer task than planned because the cable end was too large. The force required is now at a manageable level although not sure how much riding in traffic I could handle. No doubt will get used to it without having to follow Robert's physiotherapy regime. I think something like that multiplier may still be a good idea. Time will tell, I could see it making the clutch easier for the limp wristed to engage smoothly. Obviously haven't ridden it yet, but there doesn't seem to be much travel between disengaged and fully engaged.

 

[vibrac]

I went down to Brother Ron's the other day, He fitted a USA decompressor that I got 2 of, One for him and one for my next Comet build, Goes in the second plug hole.
No cable, Just push the button down and kick, Like used on H.D.s.
He has not been able to start it with this, Anyway, He has been having a bit of Mag' trouble, So we converted it to "D" type Coil, And now it starts !!, I wondered if it needed electric starter, To spin it faster, But now Ron can start it, Also found that if you want to stop the engine, With out using the valve lifter, You can just push the button. Cheers Bill.

I did speak to the Venhill rep at Stafford they will supply the long reach 14mm decompressor without the lever they still want too much for it though. I may try and make a long bodyone myself like the RE one for the next build. As for the US (be honest hardly ableson) push button system I tried it but found it harder than a lever. Its still on the shelf