Topic: 836 Kit or .25 Overbore"?

[Terry in Australia]

Yep, I've just got some old RC "improved" stock rods in mine, and when I had the RC 12.5:1  pistons/Megacycle 125/75 cam/CR29mm carbs I'd rev it to 11000 RPM in the first 3 gears often, without any issues. (apart from scaring myself silly........)

[PeWe]

+1....go 836, you won't regret it.  Try these and let us know how they work....


http://www.ebay.com/itm/Honda-CB750-750K-69-78-836cc-65mm-Big-Bore-Pistons-Kit-10-25-1-compression-ratio-/112021588836?hash=item1a1501cb64:g:2UsAAOSwu1VW4I0-&vxp=mtr

I have a couple of questions for us inexperienced engine rebuilders:

Do you think these kits would work with the stock valves? just get an overbore of the cylinders and "plug and play"?
What is considered a mild street cam? Is there a plug and play upgrade option for that as well?

Really CR10.25:1? I doubt that those flat ones give that high CR.
They look like cruzinimage $130US pistons. I do not remember but Hondaman has mentioned a CR a little bit above CB750 OEM. NOT 10.25:1 for sure!
Higher lift cam is not an option either. These pistons can be used as cheap repair without any high HP dreams. Perfect for a "cheap" (not so very expensive) restore where seats might be cut and valves lapped. New bearings, chains tensioners. Use std cam or a very moderate cam possisible for OEM engines.  Cheaper alternative than stock 736 over size 0.25/0.5 or how much that need to be bored to fix the sleeves

Add a few hundred bucks and get 10+ CR and deep valve relievs making it possible to use a hotter cam not causing valve and piston gangbang. CyxleX sell their 65.5mm (849cc) pistons for $249US. I should add about 200 more and go for 65mm and get a little bit thicker sleeves. 849cc when a 836 sleeves are damaged and avoid new sleeves.

Here a comparison of pistons that are sold as 10.25-10.5:1 CR pistons for CB750. These have domes and deeper valve relieves.
Oldest model called "New" since this was the last one I bought. Pistons from the 70's, early 80.

[754]

I could see a bit of domes on that kit , but no close up ..if they were only cut for stock lift, cutouts would be small.

 Two things should be mentioned , i ran stock head , cept triple cut and springs.
And Andrews coils, and a Maxi-Dwell.
At one point sold the chopper frame it was in less engine, then later put it in a 73 frame with stretched arm.. The coils had gone with the frame, so I decided to use stockers I had on hand, thinking it would never pull as hard on topend... Till I got hotter coils..
 To my surprise i couldnt tell any difference, at least not noticeable.... Strange..

[Imago]

Got a "Cruzinimage" set on it's way, (from a nice fellow here) but I'll need an 836 head gasket.

Any recommendations or does someone have an extra?

[Terry in Australia]

Got a "Cruzinimage" set on it's way, (from a nice fellow here) but I'll need an 836 head gasket.

Any recommendations or does someone have an extra?

The kit comes with a head gasket mate, or has the "nice fellow" kept it?

[Imago]

Got a "Cruzinimage" set on it's way, (from a nice fellow here) but I'll need an 836 head gasket.

Any recommendations or does someone have an extra?

The kit comes with a head gasket mate, or has the "nice fellow" kept it?

He used it, but I knew that when I bought it, so he's sill a "nice fellow".

Terry, have you got a gasket for a fellow Comonwealther? (Is that a word?)

[Terry in Australia]

Ha ha, I dunno mate, probably is a word, what about "Royal Subjects"? That sounds both fancy and degrading, all in one phrase?

Now, I ordered two 836 gaskets for my mate Fred from Cruzinimage a couple of months ago, but I've since passed them on. I do have a huge inventory of CB750 parts in my garage though, so if you get stuck, remind me later in the week and I'll check it out when I get home on the weekend. (I work 400 miles from home) Cheers, Terry.

[PeWe]

MLS head gasket is really good. Use that and no need of re-torque the head nuts. This can be used again if head is lifted within low miles.

The rivets need to be hammered flat. I drilled indents on head and block so the rivets will not cause problem tightening head. 8-10mm drill for a nice wide indents that for the thicker rivets.

[Terry in Australia]

That just put me off MLS head gaskets Pewe, there's no way I'm ever gonna take a drill to the mating surfaces of my head or cylinder block.............

[PeWe]

That just put me off MLS head gaskets Pewe, there's no way I'm ever gonna take a drill to the mating surfaces of my head or cylinder block.............

No problem since the riveted ears are further out, not the mating surface.
Below 2 blocks 836/900 and 1 head. Same hole pattern.

I'll see this winter if a 72mm MLS head gasket have same pattern for rivets. Probaly.... 3:rd block I'll drill 4 small dimples in
I like MLS headgasket after successful use.

I have heard that its possible to remove the rivets too. The MLS layers will be separated then which might be a problem if removed and need to be re-used.