LCGB Forums

Well for a variety of reasons I’ve not put the miles in on this engine but with the dyno deadline approaching I need to knuckle down.

The test ride/maiden voyage highlighted a major problem with the clutch. Massive drag. I didn’t build the engine, if I had built it I might have checked the clutch a bit more thoroughly.

So pulled it apart and the first thing to check is the thickness of the friction plates, which should be no more than 14mm.




Oh dear. That’s almost certainly the problem

What make plates?

Unfortunately I don't know, sourced by my mate who built the motor.

Camlam say the thickness of clutch friction plates is so random now that they always recommend 1.2mm steels. However even if I substitute the steels for 1.2mm that only gains me 3 x .3mm = .9mm so that is not enough to solve this problem with these plates.

Putting the clutch under the microscope reveals a certain amount of wear and tear. I have decided to bite the bullet and upgrade this clutch.

My S1 uses an AF six plate cassette, first consideration was buying another of these but on reflection I'm going for the Andy Francis five plate which uses standard shaped plates (but obviously thinner) and its the same sort of price.

Four reasons for this choice... my mate Andy recommends it - he has one in his red GP200. Second reason is that if I'm broken down on a rally I've got a better chance of getting standard clutch plates that I have of getting replacement AF cassette parts. Third, I've heard of people cracking their AF clutches using the AF holding tool. Fourth, Andy Francis uses standard shape springs and I may be able to experiment with lighter springs - balancing off clutch slip against a lighter pull.

So clutch ordered, waiting on Andy Francis now.

Just measured a set of 4x plates Readspeed Supergrip, bang on the 14mm.

Will be using these in next 4 plate rebuild

Dyno day



With Andy - we are visiting Al at Diablo Moto Dyno.



New BGM flywheel doesn’t like BGM stator. Added two shims under pick-up but that’s made it worse. Substitute flywheel and problem solved. Need to remove two laminates. to see if that improves things with the BGM flywheel. Without inspection holes it’s trial and error. Not particularly scientific.

Al's built me engines before and I've had bikes dynoed before. Up and down road like a ferret Knows his stuff

He knows his onions does Mr Terry and likes a biscuit or two

Here’s the graph



So 25mm carb through the SR big throated airbox with BGM filter and V4 BGM exhaust. Result was 14.4 hp, and that’s pretty much as expected.

To my surprise the torque is over 12 ft/pounds, which means it’s only dropped 1 ft/pounds against the one in Sticky’s book and that was running 30mm open carb.

I’m happy with these numbers, should be a very rideable scooter, good for long distance rallying.

Next stage is to finish the build, and then put some pre-France miles on it.

So the flywheel doesn't like the stator, there is a misfire regardless of how many laminates there are under the pickup. The BGM instructions say that nine out of ten flywheel problems can be sorted by altering the pickup height. I guess this is the one in ten which can't.

MB will change it. Meanwhile I will fit another flywheel and hopefully the pickup is back in it's original position.

alex_hughes wrote:So the flywheel doesn't like the stator, there is a misfire regardless of how many laminates there are under the pickup. The BGM instructions say that nine out of ten flywheel problems can be sorted by altering the pickup height. I guess this is the one in ten which can't.

MB will change it. Meanwhile I will fit another flywheel and hopefully the pickup is back in it's original position.

The last few builds I've done have used external pick ups. Saves all this malarkey and I've found keeps a much more steady firing angle. Sometimes you just don't want to though. My current build relies on internal too, hopefully less hassle than yours.

The dyno graph looks really nice, almost like a 4 stroke (can I say that on here?).

Dickie - the external pickup does seem a good idea - but are they still available? I think the idea came from Anthony Tambs/Scootronics but there are none for sale that I can see... Scootronics website just says sold out...