Topic: What Engine Upgrades Needed for 836 Kit

[Finnigan]

My winter project is to build up my cb750 engine to have a little fun on the street and be a faster than my buddy.  I want to go with 836 kit, mild cam and maybe carbs.  It's hard knowing exactly what I NEED, looking at cycle x's site they offer a git kit for 2k$ and I'm thinking I don't need heavy duty everything just to have a reliable bike for weekend fun.

I hope to use my yoshi cam with a 835 10.XCR piston kit and maybe a valve job.  I've decided to use heavy duty studs with this rebuild, are heavy duty upgrades beyond this needed for a street engine (no race no drag no real plans for future power).

[seanbarney41]

sure...it will probably be fine as long a you check everything to make sure it is healthy...but even the modest parts selection you have chosen will cost a considerable sum to get running and an engine failure could trash it all. 

The rule in high performance engine building...you have a choice of cheap, fast, and dependable, but you can only pick two.

[trigger]

If you want a faster bike then, buy a faster bike. Old famous saying , "Speed is just a question of money, how fast do you want to go and how much do you want to spend ? "

[Jerry Rxman Griffin aka MuthaF'er]

Just use what you have with the 836 pistons. I'd use heavy duty valve springs if you don't already have them with the Yoshi cam. Hold off on carbs. That would cost you more than the 836 kit and boring

[Finnigan]

If you want a faster bike then, buy a faster bike. Old famous saying , "Speed is just a question of money, how fast do you want to go and how much do you want to spend ? "

Does anyone know how to block people on this forum?

My friend and I both have cb750s, i'm not going to buy a faster bike.  Save your Mad Max quotes...

[Finnigan]

sure...it will probably be fine as long a you check everything to make sure it is healthy...but even the modest parts selection you have chosen will cost a considerable sum to get running and an engine failure could trash it all. 

The rule in high performance engine building...you have a choice of cheap, fast, and dependable, but you can only pick two.

Will do, thanks

Just use what you have with the 836 pistons. I'd use heavy duty valve springs if you don't already have them with the Yoshi cam. Hold off on carbs. That would cost you more than the 836 kit and boring

Good advice, cheers!

[Stev-o]

My K4 has an 836 kit with a Kenny Harmon cam.  The bike runs great and is very dependable.
It has pulled on my buddy's stock 750. "There's no replacement for displacement"!!

Just ignore posts that you would rather not read and they will go away.

[Finnigan]

My K4 has an 836 kit with a Kenny Harmon cam.  The bike runs great and is very dependable.
It has pulled on my buddy's stock 750. "There's no replacement for displacement"!!

Just ignore posts that you would rather not read and they will go away.

Great to hear, did you beef up any components like rods or chains or other internals?

[seanbarney41]

Come on Steve-O...you honestly should show him the hole in the engine case pic

[Stev-o]

My K4 has an 836 kit with a Kenny Harmon cam.  The bike runs great and is very dependable.
It has pulled on my buddy's stock 750. "There's no replacement for displacement"!!

Just ignore posts that you would rather not read and they will go away.

Great to hear, did you beef up any components like rods or chains or other internals?

No....not really necessary, Honda over engineered the bottoms end.  Unless your racing, you’re good.

[Stev-o]

Come on Steve-O...you honestly should show him the hole in the engine case pic

Ha...I don’t want to scare him off!   Ironically, I still have that lower end with the hole in it, you’d think I would have tossed it in the bin by now.
#BigBangBike!

[PeWe]

As written earlier, carbs can be a later thing.
Head will cost since it probably will need new guides, maybe ex side only. Valves too. Race springs are relatively cheap.

Porting, a little bit more.
Mike Rieck stage 3 can be something.

(5mm stemmed valve guides (bronze) do not live as long as stock 6.5mm steel guides. I have a head in need of repair)

Engine needs most likely a general overhaul that will cost.
Like primary chains, cam chain with tensioners.
When open cases, crank bearings might be worn.
Another thing is the primary hub cush rubbers that are very old.
Clutch if never replaced. Stock style fibers with Barnett springs.
Cruzinimage clutch work fine and cost not much.

All engine rubber stuff as tensioners and carb boots, use Honda stock, not cheap aftermarket

My K6 got 836cc, ported head with 34mm inlet valves (F2), cam and VM29 smoothbore carbs in the 80's.
The carb boots cracked very quick so stock carbs back in. Same top speed. VM29 gave a little better throttle response, mostly midrange.

Lightened alternator is another detail my bike got. No charging issues. CycleX has similar as mine on the shelf.

[RAFster122s]

Might need to check or just go ahead and replace the rubber cushions in the primary drive gear while you have it apart. Definitely check all bearings in the crankcases if you open the bottom end.
Starter clutch springs and rollers may need replacement, best to remove and measure springs or just replace them if they are inexpensive. Rollers only need replaced if they show wear.

[RAFster122s]

Lightened alternator as Per suggested will allow motor to rev quicker than stock alternator... As you are aware, the alternator in our bikes act like a flywheel on a car's motor. Performance mod for car is to lighten flywheel. Especially if you are drag racing, Some racers will delete the alternator and stator entirely on a drag racing or racing bike and go with a total loss design battery, not possible for a street bike.

[Jerry Rxman Griffin aka MuthaF'er]

There are many things you can do and spend a lot of money on BUT stick to basics on your first rodeo.

[Finnigan]

 

[Don R]

 Hmm, I lost my post. Anyway I like my cruisin image  836 kit. Oddly my motor had a higher than normal piston deck height. I stacked two base gaskets to help clearance and lower the comp a little.  It has a "too big" KH cam and a home brew port job. I had a stock F2cam, missed a shift, over revved it and bent a valve so I did the obvious and got a bigger cam with a set of springs and retainers.  I like the torque increase even though I probably don't get into the rpm range of the cam very often. I did remove the 4-1 header and went to a 4-4  replacement exhaust just because I love the look.  I haven't run it at the drag strip yet but am curious about what it would run. 

[Bodi]

Just opinions, not definitive.
The 836 kit alone will give a worthwhile boost to an otherwise stock engine. With a "hot" street cam you get a bit of low RPM power loss with some midrange and more top end pop. Race cams are not for the street, idling is really poor, midrange gets stock power or less, top end screams... top end is rarely used on a streeter.
Almost every cam upgrade will have higher lift and longer duration with faster ramps: stronger valvesprings control the valve movement to avoid valve crashes and float at higher RPM. And wear the cam and rockers quicker. Rockers must be checked when changing cam, refacing them is recommended. The rocker face and cam lobes wear in together, so a fresh flat face is best on a new cam.
Even with a ported head and hot cam, the carbs only limit flow at high RPM WOT. What carbs are you looking at? Avoid race carbs (ie CR) as they are not too good for street. Using big Mikunis from a Kawi 900/1000 is a better plan for a streeter. Direct controlled slide valve carbs are easier to tune than CVs.
Good idea to replace the primary chain and its wear pad, plus install a heavy duty (or at least new endless stock type) cam chain. The tensioner should be carefully inspected, and there are upgraded mechanisms available for it if it's looking bad.
Undercut gears help hold against higher loads. Check shift fork pins and drum grooves for wear.
Stock clutch plates are best, replacements are not super costly... but either new stock springs (originals will be weaker than they were) or aftermarket springs help the clutch hold if you do notice any slippage. I've experienced and heard of clutch sticking and material shedding (oil filter caked with fibres) trouble with Barnett clutches. Barnett springs are fine but lever effort goes way up.
Stock bottom end is pretty damn strong so for "normal" use keep it as is. Stock rods are good for normal use but extended at/over redline work or a missed shift can break them. Many aftermarket rods are dodgy, avoid aluminum ones... Carillo rods are f'ing sweet but the price is insane. I have had stock rods shotpeened but unsure of its worth.
Check your bearings, plastigauge is a lot cheaper than destroying the crank or sending a rod out of the case. New shells are cheaper than that as well.
Have a look at the oil pump. The scavenge rotors will probably look scary but that doesn't really cause trouble. The pressure rotors can have some damage but not a lot. Clearances are more important than unscarred rotors.
More power = more heat. Consider an oil cooler.
Chassis has to be checked. Swingarm bushings and steering bearings have to be in good shape, typically the swingarm is loose and the steering bearings dry.

[Jerry Rxman Griffin aka MuthaF'er]

Which Yoshi cam do you have? If you are not sure check the end of the shaft for a letter designation and I can tell you. A or B?

[PeWe]

CycleX clutch fiber plates I ordered some years ago were very sticky.
EBC and Cruzinimage in my bikes works fine.
A costly domino effect occure when tuning the engine.

But most of it must be done anyway if restore/repair a stocker.
I had no issues with stock rods frequntly enter 9000+9500 rpm.
836cc
17:48 sprockets make bike to work better too.

My K6 with 1005cc had no issues at low rpm. I changed front sprocket to 17 from 18 to make life easier for the clutch.
Bike felt better after that. My almost stock K2 has same gearing.
Gears feels to match better.
Stock sized wheels/tires. (Rear affect gearing).

836 piston kit with valve pockets supporting hotter cams cost some. JE or Wiseco.

If lucky you might find a cylinder and piston kit if asked for it in the Classifieds, Wanted or check for sale for around $400-500 US.

Not only me that has new bored cylinders with new or almost new pistons on the shelf for future use, RC 836cc, CycleX 849cc and 61.5 mm Cruzinimage K7 pistons in K1 cylinder

It was one seller on eBay that sold a batch of NOS early style cast RC 836 piston kits 2012 for $250US.
Worked fine. I'm sure many here has a kit of those. Chambers needs to be widened a little for these.

I reused my old RC 3-oil rings since the kit had the old single.
From the forged RC pistons sold in the early 80's.

Those pistons have got another cylinder with fresh bore, used cylinder bored to next step, 849cc. I found a set very cheap on ebay a few years ago.

Here when those 836 pistons enter 10.000 rpm