Bullet Box input shaft

[MartinD]

Hi,
I have just purchased a genuine close ratio bullit box (helical gears), and just found out that the input shaft is for the early crank ie 17mm spigot, and I have a sprint with the later 6 bolt crank and 15mm spigot bearing. Has anyone any experience on the best route to take in making it fit.
My thinking is:
Swop input shaft with original semi-close box, can this be done ?
Machine the bullit box input shaft down to 15mm, a bit one way if I ever resell to the 26R boys.
Find / make a new "oilite" spigot bush to fit, 17mm ID and 21mm OD, (not a standard size).

Thanks for any sensible suggestions.

Regards
Martin

[Tonyw]

Martin,

I am sure that one of the more knowledgeable members will respond but i think the two input shafts also use a different front cover (where the seal fits) I would not recommend machining it down as you would lose the hardening. It is not hard to make a new spigot bearing out of phosphor bronze.

Tonyw

[toomspj]

Easiest way is to have it machined down to the smaller size. That's what I've had done by BGH a couple of times. I've done two full race seasons with no measurable wear .
Paul

[garyeanderson]

I would call around and see if you can find the bushing, surely Dave Bean can't be the only source for these. Seems like a fairly stock part If you can't find it locally, put in an order and don't mess with the gearbox.

Gary

[MartinD]

Hi all
Thanks for the replies, just to finish the topic off I machined a siutable bush to get the assembly togather. This was always my favorite option as I didn't want to strip the box again as I had just rebuilt it with new gaskets and seals. I also spoke to TTR who said they had done the same thing in the past, but they had nothing on the shelf.
The close ratio gears are excellent and really keep the engine in the sweet spot, even with sprint cams (std engine), and a 4.1 diff. I know thats what they are supposed to do but I have just been up the road testing it an it feels great . Roll on march for the first event of the year.

Martin.

[dunclentdr]

I need to get hold of a spigot bush (21/17mm) as mentioned in this post so I can fit an early close ratio box to an engine with 6 bolt crank - does anyone know how to get hold of one?

Thanks

David

[patrics]

Hi,
I machined my own from oilite - not cheap! and you need to be accurate - I was actually fitting a later style gearbox to a steel crank. Anyway make a lot effort to get this right because to much clearance will wreck the gearbox

Regards
Steve

[englishmaninwales]

I'm pretty sure I have a 17mm ID oilite spigot bush in my spares collection. I'll take a look tomorrow and let you know.
Malcolm

[elancoupe]

We turned down the input shaft on mine.