Topic: 836 kits and stock cams

[Trav-i]

As my subject line states I was wondering about the compatibility of 836 kits and the use of a stock cam.  I have finally gotten to stripping the top end off my 75 super sport engine, which up until now was just to replace the valve stem seals and leaky head gasket and cam tower pucks.  But now after looking into the bores they too are going to need to be cleaned up with either honing or boring as there is some pitting in the cylinders I don't like.  Since I'll be paying my local machine shop to do the work for me, the thought crossed my mind to just up the bore size.  I'm really not looking to crazy with money on this engine, I just want to make sure I have a clean reliable ride.  If I can use the stock cam I would like to.  I'm not looking for crazy performance, just maybe a little added umph.  I've got a GL1500 for going faster. 

So any info from the great high performance group here would be greatly appreciated.

Thanks,

Travis

[Jerry Rxman Griffin aka MuthaF'er]

No problem doing that. Your F has a little better cam anyway. Put it back together and compare your before and after plug readings AFTERWARDS and adjust the carbs but ONLY IF YOU NEED TO. May not need.

[PeWe]

Cruzinimage sells K7 pistons ( 392). +0.50 for worn stock bores.
$120USD
https://www.cruzinimage.net/2017/08/17/77-78-honda-cb750k-k7-k8-0-5mm-over-size-pistons-set/

I have a set of those waiting for a cylinder to be bored for them.
Probably to my K2 also using the F/K7/K8 cam

That's the cheapest refresh of pistons.
Bore a stock 61mm to 65mm will cost some since they must bore several times.
First step is max 1 mm.

I found a cylinder on eBay that have had 64 mm pistons, perfect to rebore for my fresh used 836cc (65mm).

Cruzinimage sells cheap 836 pistons for stock or almost stock cams.

[Trav-i]

Thanks Jerry, if anyone knew the answer to my question I figured you would!  Considering how damaged the cylinders are I suspect they will need to be bored anyway.  Seems a good time to me to up size a little.  Time to see just what the local machine shop is gonna charge.

[Trav-i]

After talking to my machine shop, it looks like my 750 is going to be an 836. I'll be calling cruzinimage for some new slugs.

[HondaMan]

Make SURE the machine shop sets the clearance for those CI pistons at 0.0008"-0.0012", NO MORE. Then they will be great.
You won't need to rejet, either.

[Trav-i]

Hondaman, thank you as always for the keen insight.  I have been digging for those numbers for a couple of days now.  I'll be ordering the kit in a few days and taking the jugs soon.  I'm still in the process of removing all the awful cheap, poorly prepared, and applied black engine paint.  One question I will ask while I am here... the intake valves look nice just typical light carbon build up on them, the exhaust valves show to be tan/white across the board.  Was the engine a little lean or is everything ok as it was?

Thanks,

Travis

[PeWe]

Check if valve guides are OK. Usually ex guides that goes first.
Valve in without springs, lift around 8-10mm into chamber and wiggle it sideways. It should not move much sideways. Compare all and you'll see if any of the ex guides are worn in need to be replaced. I'm not surprised if all 4 ex guides are bad.

[Sam Green Racing]

Travis, going to 836 will waken any CB750 but for a great cam, Dynoman sells a great Russ Collins profile cam made by Webb Cam in their DP295. It will make any CB750 pull like a steam train, It has tons of torque and a good top end and is quite happy on the street.

[PeWe]

Agree on DP295.
My K6 has a cam with RC295 engraved under the washer.
Best cam I have used in that engine.
DP295 is a new cam with RC295 profile.
In has almost 10mm lift so Cruzinimage 836 pistons have not deep enough pockets. Use Dynoman JE pistons when order the cam. Racing springs needed too.

[Trav-i]

Thanks for all the camshaft information guys.  I think at the moment I'm going to work with the stock cam.  Was never intending to go this far with this engine.  It was supposed to be just a head gasket and some seals, kind of a budget top end job.  I do eventually want to build even a better engine but, at the moment other projects are calling my name.

Also I need some replacement wheels for the cam chain tensioner, any idea where I might be able to find some that are better than the hard rubber stock ones?

[PeWe]

That is how it starts....
My K6 got a scratched bore early 80's, noticed at a tear down early winter.
My shop here just happened to have a set of forged RC836 pistons on the shelf. Next step was ported head, larger in valves, cam with springs, lightened alternator.... A few months later followed by new carbs Mikuni VM29 ...

I brought more and more parts to the shop.

I guess each step happened at several occations, weeks between.
It was very fun next spring, huge difference!