Topic: 836 Reliability

[750]

Well we're all lucky that APE still has time for us old SOHC'ers, up until recently, the only kit available was the venerable Wiseco kit, but my preference would be the JE kit.

The jury is still out on the CycleX 850 kit, while CycleX is a great company and I've got no complaints with anything I've bought from them, a couple of folk here have had their pistons break up, so I'd steer clear of them.

Mike's heads are brilliant, I was an early customer and my (RC) 836cc engine with his "Stage 3" head will propel my old K1 to 120 MPH in third gear @ 11000 RPM, something I didn't think a CB750 was capable of, great fun!

As far as "as reliable, if not more than stock" goes, well, that's a pipe dream. Any major mods (and the kind of riding that goes along with them) will only reduce the life of an engine. There are plenty of stock CB750's (like my K0) that have survived for almost 40 years and many thousands of miles without a major failure, and there will be people here who will bullsh1t you about how their old 836 has been drag raced every weekend and commuted on every day for the last 30 years with no problems, (not that they've actually ridden in in the last 20........) but at the end of the day, you can't have your cake and eat it too. As Frank would say, speed costs............. 

Having said that, a mild 836 that is ridden with respect and well maintained should last for many years, without any major problems. If you can't afford Keihin CR carbs, go for a set of F2 carbs with K7 or K8 rubbers, in my opinion, they're a great bolt on mod for an K or early F, and get yourself a Dyna ignition. Don't forget the heavy duty Tsubaki cam chain and an M3 cam chain tensioner. Cheers, Terry.

I stole this quote from another thread that I read yesterday.  I have a 750 K8 and it's bone stock right down to the exhaust minus a Honda Man ignition and a K&N Air Filter (I should probably jet up a step for that but I haven't).  This thing is rock reliable and a joy to ride (finally, it took me all summer to get it that way).  That said, I want just a bit more power.  I have purchased everything I want to make it an 836.  I bought 836 pistons, RC315 cam (used but perfect) and I have had a bunch of head work done (new valves, guides, Honda man heme (May need to deck the cylinders or shave the head somewhere around .008" and buy an oil cooler).  Now all of this stuff including bored cylinders has been done with a spare cylinders and a spare head from another K8 motor.  My big question is if I install these parts am I really sacrificing the daily riding reliability I enjoy so much right now or is it more a matter of how I ride it?  I don't want to wreck a good thing.  I guess the positive is for a 100$ gasket kit I can always put it back to stock.  But, really, I would rather ride it than work on it.  I am patient and enjoy doing beneficial work so if it's just a matter of dialing it in like simple jetting and small adjustments here and there but I don't want to get myself into a huge labor that involves more time working on it than riding it minus any initial set up of course.  Please let me know what you guys think.
Thanks

[Sam Green Racing]

I don't know anything about the cam you have but there is no reason why an 836 motor should give you any problems.
They do get a bit hotter but with an oil cooler and not ridden silly you shouldn't have any problems.
The only addvise I can give is, make sure that cam is dialed in correct, get yourself an adjustable cam wheel.

Sam.

[MCRider]

I'd add a set of HD cylinder studs.

As to "daily riding reliability" I'd say no problem. From experience with an 836 and an 888. Both when retired for rebuilds had 50k+ miles on them.

The problem is that with the extra power comes the urge to use it. If you could maintain a 8k redline, watch for overheating, and change oil regularly and religiously, I don't think you'll notice any difference.

But with a cam and springs, you'll be twisitng to 10k+ once in a while, and the frequency of that behavior is the determining factor.

Still you're looking at mileage numbers most people don't even put on stockers.

[andy750]

This is also very useful info for me as I have an 836 engine ready to get built. Thanks for posting this thread!

cheers
Andy

[750]

No prob Andy, good luck with your build.  and thanks for any replies to this post.  The more we know before we take this big step the better off we are.

[MCRider]

This is also very useful info for me as I have an 836 engine ready to get built. Thanks for posting this thread!

cheers
Andy

With head work, I would use the lowest rated cam, maybe even stock, to keep the revs down, if street reliability is the goal. You'll still get plenty of fun for sure.

I will be using a Web-Cam 41, which many engine builders poo poo. But most engine builders are looking for HP, not reliability. Ask your engine builder or cam shaft seller if they ever rode 6000 miles in 4 weeks with that cam and how many times did they get to use the power vs the steady drone of pushing big unused cam lobes against high pressure vavle springs.

Put the power peak where you live. You'll have to sacrifice the 8500+ rpm power. You'll not regret it.

[Sam Green Racing]

This is also very useful info for me as I have an 836 engine ready to get built. Thanks for posting this thread!

cheers
Andy

With head work, I would use the lowest rated cam, maybe even stock, to keep the revs down, if street reliability is the goal. You'll still get plenty of fun for sure.

I will be using a Web-Cam 41, which many engine builders poo poo. But most engine builders are looking for HP, not reliability. Ask your engine builder or cam shaft seller if they ever rode 6000 miles in 4 weeks with that cam and how many times did they get to use the power vs the steady drone of pushing big unused cam lobes against high pressure vavle springs.

Put the power peak where you live. You'll have to sacrifice the 8500+ rpm power. You'll not regret it.

Further to what MCR said, the Megacycle 125-60 (old 65 cam) will give the same results up to 8,500rpm, gives great low down grunt but nothing above what Mr Honda designed the bike to peak at.

Sam.

[MCRider]

Thanks Sam, I just looked at that on the megacycle site. Good choice.

To the original poster, the 315 is a pretty hot cam. While it will work in a 836cc nicely, it goes against your reliability goal. The 295 is better for street. But something more like the 125-60.

Depends on your definition of daily use. Will you be touring? Does your daily riding give you a place where you can open it up once ina while? If not, don't build it that way.

My riding style and riding environment no longer allows such shenanigans. The city has grown up around me and I have to go 60 miles for some open stretches of road. Then it gets pretty twisty and mid rpm torque is the fun set up.

[750]

HMM, that sounds great, and I know this RC315 isn't super extreme but it's no stock cam either.  I'm no engine builder just using the info here and working with an engine builder buddy of mine (your right he's horse power crazy).  Boy, do you guys think I should ditch the cam and go with a stock cam?  I do know one thing, this cam supposedly optimizes HP and torque from 0 threw the power band.  At least that's what I've read from what little info I could find on it.  What are your thoughts??

[750]

Thanks Sam, I just looked at that on the megacycle site. Good choice.

To the original poster, the 315 is a pretty hot cam. While it will work in a 836cc nicely, it goes against your reliability goal. The 295 is better for street. But something more like the 125-60.

Depends on your definition of daily use. Will you be touring? Does your daily riding give you a place where you can open it up once ina while? If not, don't build it that way.

My riding style and riding environment no longer allows such shenanigans. The city has grown up around me and I have to go 60 miles for some open stretches of road. Then it gets pretty twisty and mid rpm torque is the fun set up.

Well, now I need to be honest.  I'm 28 years old and I don't ride it like I'm scared of it.  But I also don't ride it like I stole it.  If you tell me to stay below 8500 rpm and I will.  It's that simple.  I do tour allot.  I have had more than one thousand-mile day under my belt.  So when I say reliable I need something that can take the ocasional beeting and handle the long miles.

[MCRider]

HMM, that sounds great, and I know this RC315 isn't super extreme but it's no stock cam either.  I'm no engine builder just using the info here and working with an engine builder buddy of mine (your right he's horse power crazy).  Boy, do you guys think I should ditch the cam and go with a stock cam?  I do know one thing, this cam supposedly optimizes HP and torque from 0 threw the power band.  At least that's what I've read from what little info I could find on it.  What are your thoughts??

If you held it up to a stocker, you'd gasp. It will give more power throughout the range. The problem is it pushes the range up, if you want to use it you'll need to rev it and rpms are the death of a motor. And I wouldn't want to tour with it. Got any 500 mile overnight trips planned? (I see by your last post you do).

I'd sell it and buy a milder one. You don't need to drop to a stocker unless you can find one of the early pre-K1 ones. They make good power with an 836, I had one.

See if this link works.  http://www.megacyclecams.com/catalog/pages/page%2034.pdf

Any of thee at 125-60 and below would be great without higher revs. Get the 315 specs and see where you fall.

You can put a removable frame rail kit in and then you can experiment with different cams.

[MCRider]

This cam talk comes from experience. I had a 650 Bonneville I put a "road race" cam in which was a big mistake. The power band was too narrow and too high. I was encouraged by shop mechanics to use the "flat track" cam. But i was a youngster with road race aspirations. Thing is you can't hold it in the high rpms in traffic.

I put a really big bump cam in my 888cc. With HD springs. Then took it on a tour to Tucson (from Indy) and parts beyond. Just droning along at 5000 rpm. Big mistake. Got to Tucson and heard the "BING" that many here have discussed. That was the sound of the camshaft seizing in the cam holder and twisting in half. The flex that the cam had induced into the camholders pulled one loose, lost oil pressure and "bing".  had to put a stocker in it to effect the repair on the road. Best thing I ever did for that motor. Left it in for the rest of its life. Plenty power, excellent gas mileage. With the ported head and HD springs, it would still really rev when i asked for it. Just a fun motor.

[750]

Will a K0 cam work??  I may have access to one.  Then I'll sell the RC315.  Someone mentioned they wanted it on one of my earlier posts.  Thanks for all of your advice thus far.  This will help allot as I only want to build it once.

[MCRider]

Will a K0 cam work??  I may have access to one.  Then I'll sell the RC315.  Someone mentioned they wanted it on one of my earlier posts.  Thanks for all of your advice thus far.  This will help allot as I only want to build it once.

Yes it will. They are all interchangeable. Honda detuned the cams as time went on. THe Pre-K1s are the best. It should have an R3 or earlier on the shaft, stamped in. They got up to at least R10 as I have one of those.

The dif between that and a K8 cam should be significant, even in a stock motor. Honda never sold the discontinued cams. If someone needed to replace a cam in a K0 bike what they would get from Honda is the latest available, doggie cam.

[750]

Awesome!!! now I'll have to see if I can track one down.

[754]

I was the one interested in the 315.
 I doubt that you would not enjoy it, unless you are a really conservative rider.

 It really is hard to explain what an 836 feels like if set up right.

 Yours may run different than mine, as I have carbs  with accellerator pump, make a difference.
 The  cammed motor will usually raise your RPM ceiling, but I consider that a plus. Mainly because you can run even lower gearing to take advantage of it, then simply change the front sprocket for touring..

 Way better passing power, safer IMO.. I am riding a stocker right now and it is pretty sluggish..

 I toured with mine, lke a 950 miles one way and a 1300 miles one way, did I ever wish I did not have the 836 in it during those rides.. Never.!

[750]

O, MAN.  You guys sure are making this decision tough.

[voxonda]

Jusr keep one thing in mind, this bike was never intended for like 90 hp. Buy a modern bike if you look for that kind of reliable power. Think a 836,850 or 900 will do a lot of good, even if you would keep the rest OEM. It will have more power 'down under' and will stay in one peace. Even the use of CR 29's can be very good for allround use, seen some very good mileage with these carbs. Better response, thus safer passing like 754 said.
If you want to keep it rideable and reliable, stay away from the 'hot' cams. You will strain the top-end, which is the weakest link in this engine.
But whatever you do, you will enjoy while it last.

Rob

[MCRider]

O, MAN.  You guys sure are making this decision tough.

I agree with 754, you could be happy with the big bump cam, and it may never give you any trouble. As long as it holds together, great fun.

I also agee with Terry that if you bump the power over the original design, you reduce the reliability. That's just common sense.  If you increase the size of the cam lobes, you increase the stress on the valve train and on the cam holders. Honda knew this right out of the box in 1969 and built reinforced cam covers for their racers to keep the cam from jumping out of the engine.

You can mitigate the chance by under riding it, but what fun is that?

Now whether you will ever bump into that maxim is an issue of probabilities.

So yes, now you get to decide.  

[750]

Yea, I know it is my decision in the end and I really appreciate all of your input.  It's all big help.  Just knowing what I could experience and talking to guys who have gone threw this stuff in the past is great.  Thanks.

[754]

Its the excessive spring pressure some used, and hours at high rpms. that kills the cam towers IMO.

 If you run sane valvesprings(ie normal stuff), you can get pretty good life out of them.

 If you guys talk him out of it, I got dibs on the cam which I really need for a bike I am building... i am just trying to be honest about how it will perform..

[MCRider]

Its the excessive spring pressure some used, and hours at high rpms. that kills the cam towers IMO.

 If you run sane valvesprings(ie normal stuff), you can get pretty good life out of them.

 If you guys talk him out of it, I got dibs on the cam which I really need for a bike I am building... i am just trying to be honest about how it will perform..

Yes spring pressure was/is the issue. But without the big bumps, there'd be no spring pressure issue, chicken or egg?  The bike I twisted the cam in had way too stiff of springs. But they were there because the cam was there.

I unerstand these days, it was ewither MRieck or Big JAy that said modern springs don't have to be so stiff as they were and still get the job done.

The bike in my avatar was an 836, ported head, with a pre K1 cam, that spaghetti pipe, and stock springs that were shimmed up a tad, 30thou IIRC. Ran like, well really great. This is 1971/1972. I could be rolling along at 5mph, roll on the throttle and (with a little clutch tweak) lay a patch as long as I could hold it. Blew people away, back then unheard of. Was only on the road about 6 weeks. Too much showing off and it got stolen.

Ah yes can't wait to get mine going again.

Of course my FJR will annihilate it and most any built CB750 on this forum. Reliably and comfortably. But it just doesn't have the history and the soul.

[wannabridin]

The bike in my avatar was an 836, ported head, with a pre K1 cam, that spaghetti pipe, and stock springs that were shimmed up a tad, 30thou IIRC. Ran like, well really great. This is 1971/1972. I could be rolling along at 5mph, roll on the throttle and (with a little clutch tweak) lay a patch as long as I could hold it. Blew people away, back then unheard of. Was only on the road about 6 weeks. Too much showing off and it got stolen.

Ah yes can't wait to get mine going again.

Of course my FJR will annihilate it and most any built CB750 on this forum. Reliably and comfortably. But it just doesn't have the history and the soul.

preach it!!!  

[andy750]

This is all great info for me as well...couple of questions that I had after searching many past posts on this subject.

1. How to handle increased crankcase pressure? Will this lead to greater chance of head gasket leaks? Will it simply be solved by the HD studs?

2. Read about pinging with 836cc kits. Which fuel to run?

For me (and maybe like the OP) I want an 836cc engine to have good low end and mid-range power - as MCRider mentions this is where most of us live on the bike. Street use only and high speed fun on the twisties etc.

Here is what I was thinking for my build (I already have the wisco pistons and cylinders bored)...

   cam   63a
   Valve springs   
keep   Stock retainers   
keep   stock valves   
keep   stock guides   
keep   rocker arms?   
   heavy duty studs   
   base gasket   
   head gasket   
   engine gasket   
   rings   
   valve seals   
   cam tower pucks   
   adjustable cam sprocket   

Porting on the head - stage 2?
Carbs - stock K2 carbs
Air filter - stock (K&N) air filter box
Pipes - stock HM300s

How big a deal are the retainers and guides? An old article from the early 80`s said the stock ones were fine to use but I see a lot of guys running titanium retainers. Huge benefit?

Any comments on the above?

(I hope you are ok with this 750 but seems we are asking the same thing)

cheers
Andy

[MCRider]

This is all great info for me as well...couple of questions that I had after searching many past posts on this subject.

1. How to handle increased crankcase pressure? Will this lead to greater chance of head gasket leaks? Will it simply be solved by the HD studs?

2. Read about pinging with 836cc kits. Which fuel to run?

For me (and maybe like the OP) I want an 836cc engine to have good low end and mid-range power - as MCRider mentions this is where most of us live on the bike. Street use only and high speed fun on the twisties etc.

Here is what I was thinking for my build (I already have the wisco pistons and cylinders bored)...

   cam   63a
   Valve springs   
keep   Stock retainers   
keep   stock valves   
keep   stock guides   
keep   rocker arms?   
   heavy duty studs   
   base gasket   
   head gasket   
   engine gasket   
   rings   
   valve seals   
   cam tower pucks   
   adjustable cam sprocket   

Porting on the head - stage 2?
Carbs - stock K2 carbs
Air filter - stock (K&N) air filter box
Pipes - stock HM300s

How big a deal are the retainers and guides? An old article from the early 80`s said the stock ones were fine to use but I see a lot of guys running titanium retainers. Huge benefit?

Any comments on the above?

(I hope you are ok with this 750 but seems we are asking the same thing)

cheers
Andy

I noticed a cam chain isn't on your list. With a big bump cam and springs, it likely should be. But that involves more of a tear down. This subjsect hasn't been broached yet so lets. Even if you limit you revving, turning that big cam through those HD springs at regular rpms will still load the chain quite a bit more, and I'm assuming its already used. Its going to get sloppy and noisy. Though I've never seen one break on a street bike no matter how hot. Its the ultra high RPMs shifting up and down, that breaks them.

I don't have any problem cutting one and threading it thru, but the master link may be a problem Not changing out the chain would make me lean towards the Ti retainers as they will reduce some of the load you are putting on the chain., but...
best to do both.

PS: I've never seen crankcase pressure as a problem. Luckily with an inline 4, 2 up and 2 down, not much positive pressure is generated, just some huffing and puffing.

PPS: Pinging, I don't remember mine ever pinging, maybe on a very hot day in slow traffic. I think the head porting helps that a lot. As Click and Clack say, use the lowest octane you can get by with.