Scooterotica

I think sumone needs to design a direct drip feed system straight to the big end if thats possible, that cud eliminate all lubrication problems

I agree mate, im not knocking AF at all, they replaced my first kit and crank F.O.C. and im happy with the service.

Before the first crank failure i was running 3% fully synth oil, but after i rebuilt it, and reading Rays comments on the RB kits in scootering about not going below 4%, because of the Boysen feeds, the big end is not getting the full charge to lube the big end, i ran 4%. So when it went again, it makes me suspect the AF cranks / bearing or is it some sort of RB design flaw? As now im looking for a new crank which one do i choose
Russ[/quote]


I've also had great service from AF, Ben replaced my flywheel a year after i fitted it and a magnet came loose.

with regards to the Boysen feeds, is the crank case not under constant presure when running so it shouldnt make any diffrence, the motor should be sucking in enough fuel air mixture to fill the void.
an adult will prob prove me wrong in a minute.
And i have 2 RB's both running on 3% mix

Leigh

Are the cranks 'full circle'? if so that would reduce the amount of charge circulating in the crankcase. Probably only a problem with a highly stressed motor?

The cranks are full circle, maybe some chamfering of the piston or directional channels in the piston could aid lubrication? I still think a direct drip feed to the big end is the way forward

Ive done 5,000 plus miles on my RB useing 3% MX5 with no lube issues and no super dooper big end bearing fitted either.

The last one to fail was a SIL crank (rebuilt) so not full circle, i do have an alpha ( full circle) crank in my other RB (240) with 2k miles with no issues. So id imagine its the bearings/pins that are the weak point .

I dont know how youd manage a drip feed, as the crankcase is pressurized and would force the oil back out ! so it would need to be pumped ! plus this would play havoc with the jetting

When my early 225 st5 mugello blew up Camlam sent a replacement kit FOC and let me give the old kit back at my convenience. Excellent service!!!

The problem is the boysen feeds, part of the charge goes direct from the inlet into the transfer port, so there is less fuel/oil mix in the crankcase to lube the big end bearing.
You could have a TS1 revving just as hard but without the same problems because the whole charge goes into the crankcase.

Rs125's have big boysens. Mind you they also have better big end bearings.

Drip feed to big end? You'd have to block up the transfers and run direct injection, bit of work, although if you get it working you could sell it to Honda and make millions.

Either that or buy a 4 stroke.