Topic: A proper 836cc kit

[nitrofish1]

Hi all, I'd like to do an 836 big bore on my K5, and I've searched high and low looked at just about every kit available, APE, Cycle X, Dynoman, you name it. What is needed to have a reliable and proper 836cc big bore?

Also Cycle X is doing an 849cc kit for 250 bucks vs the Wiseco 450 bucks for the 836cc kit, but the pistons are cast and not forged, would this present a problem?

My budget for modding the engine I set around 14-1500 dollars, so the only thing I wasn't considering upgrading was the rocker arms on the top end, but I was also possibly considering lightening the crank. And I hear these combinations are usually around 75hp at the wheel when its all said and done? Will be running the stock carb size just modding jets.

[Sam Green Racing]

Welcome Nitrofish. If you are only using the bike on the street, there's no problem with the cast pistons (all Honda OEM pistons were cast).
The Cycle X 850 piston kit will take you to the limit with the stock block and will make the bike run hotter.
Fitting an oil cooler will help but if you don't thrash it in hot weather, you should be ok.

Sam.

[PeWe]

You might need more than that when you have the engine apart?

I found a bad scratch in one cylinder many years ago.
I went to our tuner in town that just happened to have a set of Russ Collins 836 forged pistons needed to be machined for wanted compression.
Left the cylinder there.

I heard that CB750 gained a lot when porting the head.
So, I left the head there too...
Larger inlet valves (F2 34mm), HD valve springs...better cam... HD cam chain... replaced all bearings in the entire engine, new clutch...Mikuni Smooth bore carbs that i did not use most of the time. (Will use soon)
Left my crank there as well for balancing with lighter alternator.

I really recommend ported head and cam together with 836. My engine worked very well with 836, and not that hot cam.
Cam: Action Fours SS-1. Similar numbers as Webcam 41.
From http://www.satanicmechanic.org/a4scam.shtml
                                                                                                In o/c
                                                                                                Ex o/c
         Valve   Durat-                                                                   btc/abc
           lift    ion       Description                                                  bbc/atc
---------------------------------------------------------------------------
         .360    270       Ok with stock valve springs, smooth and      28/62
         .360    270       tractable as a stock machine. The cam for     62/28
                                those who are worried about "hot" cams.

My forged pistons did not last that long when i had other problems caused a piston melt down. I replaced them with Action Fours cast pistons with lower compression. These worked even better when the engine was not that sensitive needed highest possible octane. Acceleration and top speed almost the same but without the nice wheelies as the higher CR gave.

-836
-Ported head
-Cam like Webcam 41.
-Lightened alternator. (quicker responce)
I used this setup during 4  5000-6000km touring in Europe with very good result. Very reliable performance.

My project now started 2009 to get the bike on the road again... now with hotter cam..and my Mikunis, no need of long touring.

[nitrofish1]

Cycle X would charge near as much 700 dollars to get my heads ported. I can do the work on prepping the heads I just need them ported 

I wouldn't mind running a higher CR, problem is that I like to ride when it's really hot out and all of the oil coolers I've seen for the CB750 look very unsightly TBH.

So I'd at least need cam chain, valves, springs, retainers?, camshaft, and modded jets?

[Sam Green Racing]

Pistons, a mild head port and a mild cam would keep you well inside your budget.
Contack Mike Rieck http://forums.sohc4.net/index.php?action=profile;u=49 he will port your head and might be able to get you a good price on pistons and cam.
There are probably more sohc bikes running around with Mikes porting than all the others put together.

Sam.

[Jim F]

And some that are not SOHC Hondas
He does magic with all types of heads

[nitrofish1]

Pistons, a mild head port and a mild cam would keep you well inside your budget.
Contack Mike Rieck http://forums.sohc4.net/index.php?action=profile;u=49 he will port your head and might be able to get you a good price on pistons and cam.
There are probably more sohc bikes running around with Mikes porting than all the others put together.

Sam.

I will definitely do this, I wasn't planning on porting but if I can, then I will, looking to crank some hp on this bike.

I've seen, like the guy above me said, lightening the alternator rotor, but this only saves about 1.5 pounds of rotating mass, while lightening the crank saves about 6.5-7 pounds of mass, and is cheaper. But with this would I have to upgrade the connecting rods to handle the revving capability? along with the studs?

So as of now I'm thinking porting, 849cc kit, and a built top end, as I stated the only thing I really wasnt looking at upgrading was the rocker arms, the rest of the valve train will be light and strong enough to sufficiently turn the motor, the rocker arms I consider that last tiny detail but a tiny little expensive detail that is not as effective as the other upgrades like the valve springs and the camshaft.

[nitrofish1]

So do I need to call Cycle X and order some parts from them before they divulge the jet sizes I'd need for a ported 849cc with 4-1 exhaust and cam? It's hard to say for sure, but I know I'd like a baseline to work off of before I go experimenting with 20 different jet sizes at various throttle settings trying to find that perfect jet size.

[Jerry Rxman Griffin aka MuthaF'er]

The rockers are really not an upgrade. Replace only if the pads are worn through or if there are any other irregularities. May not hurt to replace the adjuster screws. I have had one break. 

Don't worry about jet sizes yet. Too much else to do and it also depends on air cleaner type and exhaust. 

[754]

Way cheaper to cut alternator rotor than crank..

[nitrofish1]

Could I possibly get the engine to turn just as fast with top end upgrades rather than cutting the crank or alternator rotor?

And is the 280 dollars to get my carbs gone through by Cycle X worth the money and take out all of the guess work or is this something I could do on my own?

[Big Jay]

You are not going to get 6 - 7 lbs off of the crank.

The Wiseco 836 is a direct copy of the cast 836s that we did forever. ( Wiseco did the copy with our blessing ).  It has been a proven reliable performer for over 35 years.

[Bill/BentON Racing]

Jay, you beat me to it.! 3-4 maybe.Good Luck on build, remember porting ........labor intensive! ! Bill