race crank

[jarno]

Hello guys.

been to a parts fair today and spoke to a wel known dutch tuner.

told him about my intentions to build a complete race crank with replaceable bigend pins.

to make a long story short we are going to make one.

it is going to be a full web crank like a rs 125 or a tz 250.

first we wil make on and if it turnes out good and it has been tested, the possebility is there to make a batch if there is more interest.

wil keep this updated when i have got more news.

[JanBros]

I've been investigating a solution for cracking cylinders arround the studs without having to weld them. So I came up with this :



the idea on the pic is to place a spacer of 9mm under the cylinders, mill brackets that fit onto the head and bolt them together to guide the forces that push the cylinders away from the crankcase back to the studs.

using 9mm longer RD400 rods (straight fit). But as they come with new big-end pins and have parts off worn cranks, investigated if it was possible to machine off the pins and make holes in the webs to press fit the new pins, but seems like no one is willing to or would cost way too much

I could use another crank I have (have about 5-7 ?), but as I don't know which ones are good and which ones are not (not has bearring/rod damage, but don't know about the seals) I'd have to test them all just to find out which one to take apart and I just don't have the time

So I'm very interested Any idea f a price range ? might step in directly

[Luders]

Interesting ideas lads, I'm interested in how you get on

[James P]

...to make a long story short we are going to make one.

Good luck Jarno - I'll be very interested to see how it turns out. Will your new crank use any standard KR-1 parts, or will everything be new?
I investigated ways to modify or repair worn-out original crank pins but, as Jan has just said, nobody was willing or the cost was too high.
I have since bought a set of remade crank webs from Grampian Motors (original on the left, remade on the right):





As far as I can tell (with non-precision measuring instruments!), they are the same size in all respects. The weight of the remade web is only 2g greater.

Regards,
James

[Top-shaggy]

Ooo this has the potential to be a tasty thread

[JanBros]

can't be done with original webs James, because there will only be 1.75mm of metal between the 2 holes, and that will probably crack when pressing in the first of the 2.
my idea was to cut of the pin and make a hole of 19.5mm and turn down one side of the new pin down to the corresponding 19.5mm press fit. that would give the same hole/metal ratio as RD350/Banshee webs who have 2 holes :

[jarno]

the crank we be completely new James.

Jan your right he told me after inspection of the crank i showd him,that this crank can't be modify'd do to the construction of the crank.

as for the remade crankwebs, i know there cheaper than the webs i am having made but in the long run i think it wil pay itself back.
also the only have got the webs with the bigendpin, the outher webs are still not availibe.

we are going to use the same bearings ,seals and centrepin.

have got a rough price but in a couple of weeks i wil know more, and as we al know the first is the most expensive after that the wil be cheaper.

[James P]

...my idea was to cut of the pin and make a hole of 19.5mm and turn down one side of the new pin down to the corresponding 19.5mm press fit.

Great minds think alike Jan . That was one of my ideas for repairing a standard crank web (although I did not get as far as choosing a particular diameter for the new pin). However, it is still a bit of work (and cost if you have to pay someone to do it) and the result would be a little "experimental".

I look forward to seeing Jarno's new crank!

Regards,
James