My 95% completed project. 1975 CB750F

[cityslicker]

godamn, thats f in Rad, RAD I SAY!!!

[samir_nayanajaad]

According to Cycle X the normal CR is 10.25 that should run on premium gas.  I have a few gas stations with 94 octane premium hope that is enough to not have pre-detonation problems at 10.25 CR.

As a side note my Cobalt has 10 to 1 CR runs at about 200F-220F (scared the hell out of me because i didn't know this at first but its normal) and can run on 87 just fine. Computer controlled ignition,timing and fuel can do amazing things.

[Ronnio]

  I only tacked the pieces in place, had my good friend do all of the welding. He is an awesome metal finisher/welder.  Thanks for all of the info on that 836 kit.. I'm personally a little nervous about doing it. Just seems like there are always problems that come along with modifying engines. I'm going for it though.

  Thanks cityslicker, I appreciate it..

[TOOLS1]

836 kit's have become, so common that they are bullet proof. Honda should have built the bike as an 836 in the early 70's. If they had not as many Kawasaki 900's would have been sold.
TOOLS

[Ronnio]

You guys recommend any kit in particular over others?  Might as well get to buying the stuff. lol

[TOOLS1]

If, you want the best. Check out lowridersbysummers.com He has the Wisco, for $440.00. Cycle-X also has some nice kits. There is also a guy on ebay selling a kit, for $110.00.
One thing. When, you have your cylinders bored, you will need to take the pistons to the machine shop, so they can measure them. I would also recommend having the 2-3 cylinders honed 0.002 larger then 1-4. These two do not cool as well, and this will allow, for more expansion. I got this tip, from an old guy that used to build Hi-performance engines.
TOOLS

[Ronnio]

That's actually a real good piece of info man. Makes total sense too. The old timers know whats going on dont they!

[Daddyman]

Tool's, you the man!

[MarkPBG]

One thing I learned selling auto parts for 16 years is that detonation at high CR's is just as much dependent on composition chamber design and piston shape as it is on raw CR. That is, a high CR engine with domed pistons will detonate much easier than a high CR engine with flat top pistons with/without ported and polished heads. A flat top piston allows the flame front from the spark plug to propagate across the combustion chamber uninterrupted, while a domed piston provides an obstacle for the flame front, increasing the likelihood of detonation. In the car engines we sold parts for, you could run an aluminum head SBC at 11:1 CR on pump gas with no problem if it had flat tops. Keep it under 10:5:1 with domed pistons though, or use race gas.

Do the 836 kits I see have domed pistons? I saw one on sale on CL for $1000 freshly built.

[MarkPBG]

(note that 11:1 is kind of pushing it…i wouldn't go over 10.5:1 on an older engine that doesn't have an O2 sensor to retard the timing automatically. )

if i remember right….it's been 8 years since I've been in that biz. PLEASE correct me if I'm a bit off on the CR! lol