Topic: CB900 Rods in a CB750

[mick7504]

That's the way we do it Mick.
Works a treat as long as you don't have to many cleansing ales before you do your math.
WE use masking tape around the pistons to cut down on chatter.
Just check the depth of your cutter our you may run into trouble getting your piston to TDC.

Cheers,
Brian

G'day Brian
I'll be having a couple of cleansing ales if this works out ok. 

This has had a bit of a haircut now and I'll throw an old set of cases with a crank, rods, block and pistons together and assemble a bare head onto it with this jigger and see if the pistons will reach TDC.

There's still a bit of room to to shorten this thing up if need be.
I've cut the spacer to 33mm dia so that it opens the relief up slightly more than dia of the valve head.

It's all trial and error stuff but perseverance will wear it down eventually.

Here are a couple of photos of the thinned down version.

The good thing is, that I've got a ton of old stuff that's been collected over the years which can be used for trialling.

Mick

[mick7504]

So far, so good.
There's .099" lift on the valve with the piston @TDC.

Still have to make up an adjustable sleeve with a grub screw to lock it onto the valve stem and glue the abrasive disc onto the base of the alum spacer.

Time will tell how it goes but I think this should do the job nicely.

[evan77]

mick,

any chance for an update?
much appreciated.

evan

[mick7504]

mick,

any chance for an update?
much appreciated.

evan

G'day Evan

I've set this one aside for the time being to finish off an 836 engine before Xmas.
The camshaft that I was hoping to use may have to be switched out for another.

One of the main areas that needs attention is to be able to get enough clearance between the valves and the pistons.
The pistons that I'm using are from a Honda CB360 which have a reasonably thick crown and the valve pockets can  be relieved quite a bit.

The combustion chamber has also needed some reshaping as well.
You can see in these 2 pictures where the casting has had to be rubbed out for piston clearance.
This has just been roughed out at the moment.

Hopefully I'll be able to get back into it soon when time stops running out which will more than likely be after Xmas.

Mick