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Discussion Starter #1
i see alot of guys with 836cc and they seem easy to live with. they dont make a crazy amount of power and use the stock cylinders.
i have found a few deals on "big block" hondas, 915 1055 1080...what are these motors like? can they be used on the street? do they brake soo much more?
any info would be great
geeto imput knowlage here...lol

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Back in the 70's it was more common to see those "big bore" 900 +cc bikes as street bikes. Of course it was also common to get leaded fuel, and octain was adjusted by bending a little tab up inside the pump (illegally of course).

836 is the largest you can bore a stock cb750 block out (actually it is now 850cc since cycle ex came out with their 65mm pistons). Some drag racers got away with 900cc bore jobs but the walls were paper thin and the blocks cracked often. Anything above 836cc requires the stock block to be sleved which triples the cost of installing one of those kits. Mot all 836 kits are equal, wiseco's are forged pistons which are hella durable, cycle ex-uses cast pistons and their kit is $100 less expensive (but you get what you pay for).

This all depends on your meaning of "street". If you definition of a street bike is an occasional sunday rider that never gets more than a days ride from home you can afford to be a little more liberal with your definition than a bike that is used to commute into the city everyday.

SOHC motors are notorously overbuilt, but they have pleny of weak areas too that more power will quickly bring to the surface. Head flow restrictions, cam and bearings, valve guides, valve springs and seats, and carbs are all issues that are going to need to be addressed the bigger you go.

My definition of a street bike is whether I can commute into manhattan during rush hour on it - which is about as an extreme a traffic condition as I see. I am also an agressive rider who is not afraid to lane split so I factor that in as well.

It also depends on the components being used. RC engineering stuff is great stuff for making power, but it is drag racing stuff and some of it has not held up so well over the years. Considering the last time that stuff was made Reagan was still in the white house it really isn't a surprise to see some of the stuff showing stress cracks and extreme wear. Absolute power was the name of the game for RC, not longevity.

Yoshimura made a lot of the original road race stuff espically endurance racing. A lot of their designs are durabel as hell and they are often considered the best speed stuff to buy for a cb750. The problem is that usually to get the most out of it you need to do expensive machine work to the head (port, polish, flow job) and you need to run premium valve components. Also some of their stuff was kinda expiremental and usually only works best with their other components (like cam and pipe combinations for example). Also this stuff is rare, mostly because it was the most expensive back in the day.

Henry Abe stuff is all discount stuff imported from japan. Everything from wheels to pistons got sold under this brand name. Some if it is decent, some junk. Usually this stuff is a bargain when you find it because quality runs wide.

Action Fours, I don't have alot of info on but they are regarded as decent stuff, amoung the best of the 80s stuff. More durable than RC and more street oriented than Yosh. They were doing these bikes all the way until the late 80s so there stuff is still around, mostly you find it in the honda chopper set (as it was still fashonable to build a SOHC chopper until the mid 1980s).

there is a lot of generic stuff and hacked stuff too so be careful. Yosh sold 811 kits but people also made their own out of 1st overbore honda cb350 pistons (hint hint good source of rings) by relocating the wrist pin.

If you really want big bore, the best sleves come from LA Sleve. Still around and can hook you up.

My recommendation? Unless you are building a garage queen to take down to the local bike night and impress the oldtimers, go with a wiseco 836 kit new and forget all this other crap. People who are nostalgic, racers, and collectors (like myself) have driven the price up higher than it needs to be for what amounts to a bunch of old battle scarred metal. An 836 motor should cost you close to $800-$1000 if done correctly with the right combination of parts (cam, springs, retainers, head work, bore job, etc), anything bigger and right away you are looking at $3000 and a good solid APE crank job.

If you do go bigger than 811ccs, BTW, run an oil cooler. a small oil cooler makes the 836 hella durable.

good enough for ya?
 

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I saw from your shipping post and I think I know of the engine that made you ask this question in the first place....so let me add this:

Most of the major parts manufacturers also made complete bikes and motors. RC and Yosh are both known to have. The most common of these are RC bikes. But there is a big difference between a motor built by Russ Collins (one of the fastest men on a SOHC) and one built by bubba's moorcikels using RC parts back in the day. Always get paperwork as it is usually one of the only ways to ID a built by RC motor.

The motor is question is probably about as radical as I would go and still call it a street bike intending to be used (I am building my ultimate CB at 1036ccs but I fully expect it to be mostly for show) and I would run a massive, new ducati sized oil cooler. When Honda bored it's own DOHC bikes out to 900ccs it made damn sure to use them.
 

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Discussion Starter #4
The 1055 motor is in the dragbike right now and has a andrews d grind cam valve cover with tiged on hold down screws to keep the cam from flexing at high rpms . flat top 1055cc pistons from MTC I think. A backcut trans for racing or an air shifter. Lightened side covers include the chain gaurd ,shift lever cover and the alt cover is completly custom with no charging system. the head has been worked on but dont have any flow specs
thats what i know about the motor. i will use my dyna 2k on it and put a charging system back on too. said that it runs on pump gas fine and went 11.2 in the quarter total 600lb. so thats not bad.
hasnet been used in a while though. i can get this cheaper then some of the 836 pistons and cam kits.
i do plan on using the bike. will be street riden a few times a week. and would like to be able to take it on longer trips when i want. i know stuff brakes and im willing to deal with that to a point.
the idea of a 10 sec CR sounds soooo cool
i also like the idea of getting a sorted and used motor. time and money can be saved that way. but on the other hand if you want something done right you have to do it your self.
how do you get to under a grand for a 836? from what i see pistons,cam,valves,springs,bore,head work,and general lighting is well over that.
but also is there that much of a difference between a 836 and a 1055? sounds dumb but is there?

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Jag,

In a stock chassis (or near stock) that motor wil be lucky to break 11s.

Of coure you forgot the crucial piece of information as to whether this motor will even run off pump gas - What is the Compression Ratio?

I thought you were looking at a 900cc motor. That 1055cc sounds like a serious race piece. Probably looking at a 100 hp+ motor, but it sounds like it was set up for bracket classes which means it was a little more durable than a prostock or nitro class. Chances are you have only a couple more race seasons on it before you are going to need to tear it down.

I know where you live and how light traffic is out there so occasional street riding is probably ok, but you are not taking that motor far from home at all. Seriously, anywhere you couldn't tow that back from with your van is too far (I probably wouldn't ride it further than I could walk home from). Also you wouldn't be able to muffle that bike so you are talking about one loud mutha-trucker. This also brings up another problem, how you going to stop that bike? even if you were able to 80% of that bike's true potential to the ground you have well overstepped the limits of your brakes - honda brakes suck.

And you have another problem, 1055 parts are starting to become unobtanium. When (there is no if) that motor lunches something you are pretty much out of luck on it.

Is there a difference between an 836 and an 1055? Well that all depends on your chassis. A properly setup 836 will always feel as fast as a 1055 in a stock chassis, hell I'll go as far to say that the cb750 frame is so old technology that they will feel about the same in any chassis that isn't hardtailed with a drag slick out back. I think the stock cb750 motor sometimes over powers its chassis so anything more radical is definatly going to be pushing the envlope. Keep in mind Honda won daytona and managed to make 85hp with a 736cc motor (sure they upped the compression ratio), they also blew up three of the 4 bikes in their quest to do so.

I rode a 1000cc SOHC once in my life and I can tell you freight trains wish they had that kind of pulling power, but that was in a dedicated drag rig, hardtailed and rewelded (about the only thing left from stock was the cradle), with a goodyear 8" car tire slick out back. Even then I could hear the frame groan when I launched - I couldn't imagine what that 120+hp would do to an unbraced stock cb750 frame.

Have you ridden a well tuned stock cb yet? It's got plenty of get up and go, they were mid 12 second bikes from stock. An 836 kit should be more than you need to have fun with that bike.

how do I get an 836 kit to under a grand? I start with a good bottom end and the rods are as far as I go. No crank work, no stator work, none of it. And I assemble it myself. I think the last quote I had for carillo rods was in the neighborhood of $350, which is better than $500 for crank lightening (which doesn't make any more real power, just makes it rev faster). Rods, bore kit, and cam and thats it. I have the grind specs and although I am a little rusty I know a couple of pretty conservative head porting tricks. I happen to own the titanium retainers and yosh valve springs so I would probably put them in but I could get away with stock for a while if it was a low mileage K motor. I could even limp by on a properly jetted stock set of carbs.
 

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Discussion Starter #6
the 1055 has flat tops and C/R in the area of 10 to 1. was running on 93 pump gas all the time. builder wanted to at a turbo down the line. im going on the lines that the bottom end is fairly stock. nothing crazy. has a cam and mild head work. so the main difference i see between me building a 836(im 100% up for that if i need to) and the 1055 is displacement. im very much a newbe with the sohc motor so i might be over simplifying things here.
in a drag frame it went 11.2 at 600lb in my math thats like 85-95hp right?
why would you call a 836 better for street use? that brings the bore out to the limits of the stock cylinders so shouldnt the same be true for a "big block"? limits are limits kind of thing. i do hear you about finding replacement gaskets and pistons though.
are those carillo rods 350 a set?
the bike has progressive front and rear susspenion, twin pot caliper twin disc front brakes, and a stock frame.


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Discussion Starter #7
i cant find the rods for less then 1100 bucks a set!
also the undercut trans is that worth anything? what does it cost to have done or is it usless on a street motor?

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quote:
the 1055 has flat tops and C/R in the area of 10 to 1. was running on 93 pump gas all the time. builder wanted to at a turbo down the line. im going on the lines that the bottom end is fairly stock. nothing crazy. has a cam and mild head work. so the main difference i see between me building a 836(im 100% up for that if i need to) and the 1055 is displacement. im very much a newbe with the sohc motor so i might be over simplifying things here.
in a drag frame it went 11.2 at 600lb in my math thats like 85-95hp right?
why would you call a 836 better for street use? that brings the bore out to the limits of the stock cylinders so shouldnt the same be true for a "big block"? limits are limits kind of thing. i do hear you about finding replacement gaskets and pistons though.
are those carillo rods 350 a set?
the bike has progressive front and rear susspenion, twin pot caliper twin disc front brakes, and a stock frame.


There is the right way, the wrong way and the british way to do anything!
I don't think you can make any assumptions about this engine. IIRC from the ad, it is professionally built and the crank has been worked over (lightened). If someone really spent the money then chances are in addition to the lightened end weight it has probably been knife edged and balanced. Although I have heard of 1000cc SOHC running on stock rods, the majority of them that I know run carrillos or yosh or something similar. We won't know though until it is taken apart. You know he has a back cut trans and from that you know 1) that someone has been into that bottom end, and 2) that the thing shifts really fast through the gears with backcutting and an air shifter (heavy abuse too) and must be making some decent hp.

If it uses flat top forged pistons at 10:1 comp, that is about the limit for pump gas and not a turbo comp ratio at all. Most Turbo motors I have seen run 8.5:1 compression to the stock 9:1 compression. 10:1 would have really made that motor a nitro, alcohol, or race gas only motor and it would have pretty much guaranteed a teardown after every pass. The cam and headwork are probably for the sake of relaibility, the head is where the biggest restriction is in a cb750 and you can pretty much control how stressed a hot motor is through the flow. N/A cams and turbo cams are pretty much at the opposite end of the spectrums, so if he was planning on running a turbo he may have been referring to how the bottom end was built. The combo sounds like a bracket class racer which are built for consistency and reliability and therefor not as stressed, but dragstrip reliability and street reliability are two different things.

Lots of factors lead to ET so you can't just say 11.2 and 600lbs is x hp. If I had to guess my ballpark would be well over 100hp, Probably in the neighborhood of 105-110 rwhp. Stock you are looking at around 53rwhp. Honda managed to get the CR750 to 90hp with 11:1 compression pistons, cam, head (basically the entire 970 kit) but the motor was essentially 736ccs. Sam on the board managed to eek out a solid 85 hp with an 836 kit, all the machining goodies, and CR carbs. In his roadrace chassis this was good for 12 second ets. The biggest advantage the big bore motor has over the other ones is torque - it climbs out of the hole harder than the other bikes.

I think the 836 is better for street use because it doesn't build heat like a 1000cc 10:1 compression aircooled motor does. the 1055 basically sees all of its heat cycles 1/4 mile at a time so it may never reach the point of overheating, although I imagine that by the time it is staged it is pretty damn close. I am just speculating here since I have never had a 1000cc SOHC (not running anyway) but it might be that you would only get a mile or so at highway speeds before the thing overheats. I really don't know.

I will say this though - for what he is asking for that motor it is a complete bargain. You have to figure it would cost $4000 to recreate with the parts he has.
 

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Discussion Starter #9
i got him on the phone and he said he bought the motor and didnt build it. doesnt know what rods are in it. said that he never had it apart. also that the motor saw limited street use.
also that it always used 93 pump gass.
i like to be alittle different and like the idea of saying "nope not an 836....its a 1000+"
for piece of mind i would have to tear the thing down and rebuild it. but im hesatent about building a motor thats only good for a mile a day. i work in the hamptons and would like to ride it out there when ever i get the itch.

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I've said all I could about the latent dangers in using a drag motor in a street bike. Sounds like you have your mind made up and it is a good price for such a worked engine. Even if it cost you $500 to ship it is still a deal.

You have your stocker motor in case it blows up. I personally think drag stuff on the street is cool too, just don't have high expectations of what this motor will be able to do road trip wise.

Commuting out to the hamptons probably won't be that bad as long as you observe the don't let it sit in traffic for more than 5 minutes rule.

If you do swing it in, get a frame kit from gordon on the sohc board, as I imagine you will probably be doing head and valvecover gaskets probably once a year or so.

Oh, and run a big oil cooler with a fan if you can swing it. that will help durability.


Edited by - geeto67 on Sep 25 2007 12:33:07 AM
 

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Discussion Starter #11
dont mean to be pushy. i am taking what you say into acount and really tring to learn as much as i can to make an informed choice.
oil cooler is here already. dont know about a fan though.
frame kit check
hell i think i can get the guy to throw in a 1080 jug/piston set up and carbs! he just wants out....

There is the right way, the wrong way and the british way to do anything!
 
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