Will I get my 100 ready in time for Taupo?

[speedpro]

Not running a counterbalance shaft Dave?

[Grumph]

i'd reckon that's been cracked for a while...And i reckon the crack's started from the pin bore..

i told you some time back that i've been known to hone and polish pin bores as some of the rod kits aren't very well finished.

Speedpro, is your pin solid or same/smaller bore ?

If the seal runs adjacent to the web, dave, it's possible to put a sleeve on the shaft at that point and run a seal with a bigger ID.

[speedpro]

Mine has a hole about 8-10mm, cannot remember exactly. I have not checked the finish inside. I had to have it hollow for balancing

[F5 Dave]

no balancer, reedblock goes right through it. It is smooth at idle, pretty vibey at 8,000 and smooth thereafter.

A sleeve huh? that could work.

Hmm, would have thought it tear from outside but interesting point.

[husaberg]

Worlds worst pic, but the cr80 from 81-81 has a 41.4mm stroke decent size mains so ends up with has overlapping shaft and pinboss
Can't find a decent pic though...... so this will have to do.
I was surprised when I seen it first time.

[F5 Dave]

Thanks. That looks like virtually same webs as MB

[husaberg]

Thanks. That looks like virtually same webs as MB

From memory the crankpin is 18mm the wristpin 13mm
The mains are mb100 size and the crankwheels are MB50 size. but that only from memory.
The pic is pretty shit but there is about 2mm overlap at least.........

[Grumph]

The biggest overlap on a pressed crank I've seen was a Benelli 650 twin. They must have invested most of the company's capital in forging dies cos all the early 4 strokes used the same crankweb forging. The 250 single was 57mm stroke and a smallish pin. The 650 twin was 58 stroke and as big a pin as they could squeeze in. At least 4mm overlap as i recall...
The cranks don't seem to give problems on those either - nearly everything else does....

[F5 Dave]

Think I will go ahead with the offset 22mm pin & undercut be dammed. it isn't actually as scary as I thought & means once modified no machining required.

[F5 Dave]

Won't be ready this weekend but I took the day off and all afternoon with dentist drill in the transfers. There's still a bunch more to do but dropped the floors to add about 20% area with stagger and new angles. Next stop Taumarunui.

[TALLIS]

Won't be ready this weekend but I took the day off and all afternoon with dentist drill in the transfers. There's still a bunch more to do but dropped the floors to add about 20% area with stagger and new angles. Next stop Taumarunui.

Maybe its time to rename the thread... will it be ready for taumarunui?

[F5 Dave]

After a mornings racing I spent a couple of hours grinding ports. So much to do and no where near what an nsr barrel looks like. You can grind the bore ports bigger but you need to follow through with the feed area and in iron that takes forever.

So I'm up say 20-30℅ on transfer area,well see if that helps.

Crank almost finished.

[F5 Dave]

Trial bore, needs cleaning up and for size etc. Just encroaches almost to seal area but can run with std seal ok. Other side is brg so easy. I saw an RG150 crank & it is waaay into the brg area.

Offset inwards to destroke.

[Grumph]

What's it being done on Dave ? Mill, lathe, horizontal borer, black and decker workmate ?
I'd hope some way is sorted of matching the two webs...

With the Macchi cranks when we used big pins, the guy who bored them did it in a lathe in a jig he'd made up so as to do all crankwebs the same. Finish was internally ground...I think we've done six cranks now and never had one move or break.

[speedpro]

If the new holes don't line up EXACTLY the crank won't be able to be trued up. A precision jig would seem to be the go with possibly a near press fit pin to locate the original pin bore prior to oversizing in the new location. Be interesting to know how it's being done.