cb915 (you poor stupid crazy son of a bitch engine build)

[rockcitycafe]

oh yeah, gonna do it now! finally got my bridgeport boring setup working and bored a few practice holes .020 over with honing, not as exciting as it sounds, but now I KNOW I can take the kz440 pistons and rings I have, resleeve my cb750 block with cb360 sleeves, and bore them the .020 over required to turn that bitch into a 915!!

posts and pics will follow of course

 

[crazypj]

Re: cb915

Cool stuff, easy when you know how (and have the equipment )

 

[ApriliaBill]

Re: cb915

I was going to ask why you didn't just buy 900 cylinders, then I saw your "I make things" and decided to keep my pie whole shut. I once owned a KZ 400 that ran better than any small bore bike I ever owned (and I've had dozens). Is there something special about the KZ pistons???

 

[rockcitycafe]

Re: cb915

I was going to ask why you didn't just buy 900 cylinders, then I saw your "I make things" and decided to keep my pie whole shut. I once owned a KZ 400 that ran better than any small bore bike I ever owned (and I've had dozens). Is there something special about the KZ pistons???

yep, 15mm wristpin and similar dome height to the cb750F pistons, that and 67.5mm brings the 750 displacement to 915

 

[rockcitycafe]

Re: cb915

Cool stuff, easy when you know how (and have the equipment )

yep, not sure I know how, but how else do you learn anyhow... the bridgeport needed some fixin before I could do this though, the spindle feed was broke so I had to go in and repair that before even attempting this

 

[rockcitycafe]

cb915

Yous is goin in yous, imma make yous fit... Propane fumes gone to head, apologize for bad humor

 

[crazypj]

Re: cb915

What are you doing with the bare 360 blocks?

 

[rockcitycafe]

Re: cb915

want em?

 

[crazypj]

Re: cb915

Of course ;D
I have GS850 liners which are a bit rusty but will bore to 70mm (if I can find some pistons with 16mm pin )
PM me with a price and shipping to Florida

 

[rockcitycafe]

cb915

Advice? Do I need to weld and rebore? Will it weep oil? (It's 4 under right now, so there's still material to hone, but I wasn't planning on boring it again)

 

[crazypj]

Re: cb915

Nah, that's normal when you go big
Knock off the rough edges, hone about 0.003" smaller than outside of 'new' liners, heat block, slide liners in
They may need pressing about 0.010" when everything cools down, don't machine top until your 110% sure liners are all the way down
Honda support base of block all the way round so you (probably) won't get any oil leaks from capillary action wicking oil between block and liner (I put a bead of sealer around base of liner. XS 650 doesn't support base of cylinder so it's real difficult to get 100% seal)
Main reason they 'leak' is fit between block and liner is too loose, Honda used around
0.001"~ 0.003" interference, at 0.001" the liners can spin when honing if you leave too much in (and block heats up)
I aim for 0.0027" ~ 0.003" smaller than liner OD, LA Sleeve recommended 0.004 interference but it was too tight so liner cracked when I bored/honed to size (although I did go 2mm bigger than originally planned on my XS'650' - 840cc : )

 

[VonYinzer]

Re: cb915

Whoa... This is rad. Tuning in.

 

[Maritime]

Re: cb915

Sign me up

 

[Sonreir]

Re: cb915

Following along for this one.

 

[MR915]

Re: cb915

What are you going to use for rods?

 

[rockcitycafe]

cb915

Think I could spray copper gasket on the block before tossing it in the oven? Would that prevent any possible oil seepage or just make it hard to get the liners in?

 

[rockcitycafe]

cb915

Think I could spray copper gasket on the block before tossing it in the oven? Would that prevent any possible oil seepage or just make it hard to get the liners in?

 

[rockcitycafe]

cb915

What are you going to use for rods?

Stock for now, I saw somewhere the cb900 rods are stronger, might try to find some, object of this project is cheap scrounged Frankenstein, so no carillos for now

 

[crazypj]

Re: cb915

I wouldn't worry about it, just fit liners.
I think copper gasket may cook and prevent liners dropping in but I've never tried it.
Maybe do the bottom 1/2" or so?
You can always re-heat to get liners out if it doesn't work

 

[rockcitycafe]

cb915

Got a couple holes done