Author Topic: RC Engineering 1075 stroker motor value? (Read 4728 times)

mrcheeze · « **on:** February 07, 2016, 08:57:42 am »

Hello Everyone,

About a year ago i bought out a gentleman's collection of CB750 stuff, which included a wrecked amen-framed chopper with damaged Fury 10" front end with an alleged 1075 big bore (as well as an alleged 836 motor on the side and a few more parts motors). I took the engine out and set it aside, not really believing it was what he said it was.

well, I opened it up the other day and I'll be damned it appears to be a fully built RC Engineering 1075 Stroker. The moment I saw the Golden rods I stopped what I was doing. The insides are minty fresh and the piston tops wiped clean with a cloth. There are barely any indentations on the cam chain rollers and absolutely no wear on the cam or rockers. Cross hatching is still visible on the barrels, but I have already taken them to get rehoned and dropped the head off for cleaning and inspection as well. I also still have the previous owner's contact information so chasing down the chain of custody may still be possible as well.

so, given all that, what do you all think a fair price would be for this engine? As much as I want to run an engine made entirely out of unobtanium I am building a chopper and a cafe and have little interest in vintage drag racing, so I would much rather see this engine go to someone that will run the dogsnot out of it.

Opinions?

jaguar · « **Reply #1 on:** February 07, 2016, 09:25:50 am »

Have you confirmed that it is a stroker and not just a big bore?

mrcheeze · « **Reply #2 on:** February 07, 2016, 09:32:35 am »

only anecdotally from my admittedly limited experience and word of mouth from previous owner. The 2-3 piston skirts seem to sit lower in the case with 1-4 at TDC. if there is a way to verify (aside from cracking the cases) I can run out to the garage and check.

also, I can take more pics from any angle if needed.

NalleyRacing · « **Reply #3 on:** February 07, 2016, 09:39:03 am »

Welcome to the forum.. Saw this on Facebook the other day. I too wondered if it was a stroker..

mrcheeze · « **Reply #4 on:** February 07, 2016, 09:43:26 am »

Thanks! I've lurked for years as a guest so I guess it was about time to get an account.

Researching this kit has been challenging... I really don't have enough knowledge to truely specify what is in this thing so I'm really hoping you guys can help me out.

NalleyRacing · « **Reply #5 on:** February 07, 2016, 09:45:54 am »

Oh once Billy and George see this they can tell you exactly what your dealing with..

grcamna2 · « **Reply #6 on:** February 07, 2016, 09:48:48 am »

You could measure the stroke by bringing the piston down to the bottom and measuring the depth & to verify bring it to TDC and see how far up she goes.

mrcheeze · « **Reply #7 on:** February 07, 2016, 09:51:22 am »

being that I've got it indexed for disassembly (1-4 at TDC) can I measure from the top of say piston one to the top of piston 2 (which would be at BDC?)

grcamna2 · « **Reply #8 on:** February 07, 2016, 09:56:18 am »

That sounds right

mrcheeze · « **Reply #9 on:** February 07, 2016, 09:58:30 am »

ok... rough measurement (and I mean ROUGH) is 66.3 MM, which would be around 3mm over stock, correct? does 3mm sound like a reasonable stroke for a RC?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #10 on:** February 07, 2016, 10:18:29 am »

Oughta be worth 300 - 400 bucks but I'd give you maybe $500

754 · « **Reply #11 on:** February 07, 2016, 11:42:24 am »

A buck a cee cee, works for mee..
Run it in the chop, I seen a few Cobra choppers on the road..be fun..

gschuld · « **Reply #12 on:** February 07, 2016, 11:52:46 am »

Looks like a nice find. Welcome. Stock stroke is 63mm, RC welded up stroker cranks are 69mm and change. Your halfway, so you'll need to send which way is closer...

Golden rods come in standard length and 3mm shorter stroker length. Otherwise identical in appearance.

I have far more vintage big bore parts/engines than I need, so does Billy. But that hasn't stopped either of us in the past...

Random questions to help identify it:

What cam was in it? I'd guess a 327 if it's an RC cam. Does the cam gear have 3 different bolting pisitions, say RC ENG on it? What's the diameter of the pistons? 70, 71, 72, 73mm? Piston crown height(compression ratio)? Did the head have red anodized retainers? 33.5 SS intake valves? The engine serial number to determine the vintage of the motor? Any signs of engine case damage? Was RC ENG stamped into the head on the carb side fin on the chamber side? Was the RC stamp on the cylinder fin as well? Does it have RC ENGINEERING stamped just above the engone serial number?

Many big bore motors were built, and a substantial portion of these were NOT actually built by RC, but used some or many RC parts, maybe some MTC parts, etc and was built by other shops, or built by the owner of the bike himself. The quality of the craftsmanship in the guy who actually built the motor makes a BIG difference. Many big bore motors were built wrong, and discovered there was a problem (or more) when starting it or before long afterward. I have examples personally. Crap oil pump, bad tolerances, bent kickstart shaft, etc (right Mike

)
It would be well worth speaking to the seller to find out as much as possible about the motor.

Used big bore race motors are not easy to put a value on. The condition of the parts makes a big difference. I have lots of vintage race parts that look great on the shelf, but wouldn't pass a close examination for suitability for reuse. I have a big bore race motor full of great vintage race parts, with a solid and documented racing history. It hasn't come apart yet since I bought it. It could be in very rebuildable condition, it could be 175lb worth of useless paperweight, or most likely somewhere in between.

I was able to purchase it VERY inexpensively. Far less than the cost of the Carrillo rods that are in it. I have aquired other similar motors for similar prices. Maybe I'm just lucky...

Let us know more about what you have.

And again, welcome

George

mrcheeze · « **Reply #13 on:** February 07, 2016, 01:27:06 pm »

Hey George!!

Thanks for the information... Its not an RC stroker then it appears lol

Here's what Ive got:

Engine# CB750E2362045

63 mm stroke, 72mm pistons with 4mm crown height.

cam markings: K134, CWC C1 D1 J8

The head:

valves appeared to be black coated, clips and retainers appeared to be silver Ti (non-magnetic). Valve guide seals looked like they were green in color.

Also upon further inspection it appears there was some minor contact between the exhaust valves and cyls 2-3 but nothing on 1-4.

754 · « **Reply #14 on:** February 07, 2016, 01:35:32 pm »

That was not an offer that I made btw... Not at this time.. Pull the end washer off. Cam if it not marked on other end. That is usually where they mark them. The listed numbers are likely casting and batch numbers..CWC made the blanks.
On the lower front where it says 736.. They often ground off and stamped size in there.
Does the cam cover have the nuts and bolts added up top?

mrcheeze · « **Reply #15 on:** February 07, 2016, 01:37:54 pm »

Also, on top of the head just below two of the springs there are some strange stampings on cyls 1 and 2:

cbr954 · « **Reply #16 on:** February 07, 2016, 01:40:06 pm »

I sent a message to you mrcheeze

mrcheeze · « **Reply #17 on:** February 07, 2016, 01:41:22 pm »

end of cam is marked 77G by indexing marks.

gschuld · « **Reply #18 on:** February 07, 2016, 02:00:46 pm »

Your cam is likely an RC cam. CWC 134 and either D1 or D2 is on every one of my original RC cams. Kenny Harmon also used those blacks, maybe others too.

RC always stamped the very end face of their cams. The stamping style changed over the years, but it should be there. Yours, if it is an RC cam, should read RC327 or RC315. If you can make out a KH in there, it's a Kenny Harmon grind. Either way, that's a 1970s aftermarket cam blank cam based on the CWC 134 markings.

Those retainers look to be clear anodized aluminum. The other option is them being titanium, but the surface finish looks like aluminum to me, I have a set of each. Once removed, an accurate gram scale will positively identify them either way.

Looks like 10- 10.5:1 compression pistons based on the 4mm dome, so likely built as a street rather than race motor. I assume it has a ported K head? It is very unlikely that those are RC pistons, since as far as I know, RC never sold 72s. Just 70, 71, and 73mm for big bore pistons unless they were custom. MTC pistons were very prevalent back then. Heavy but tough pistons, and plenty were sold in 72mm.

From what I am seeing so far, it's extremely unlikely RC built the motor(they would almost never used pistons other than the Venilias/Arias pistons they supplied. That doesn't mean it's not a good motor or anything. Finding the RC stampings on the head and cylinder would be helpful.

The golden rods are RC though, but jury is still out on where the rest of the parts were sourced.

Keep the info coming....

George

mrcheeze · « **Reply #19 on:** February 07, 2016, 02:09:12 pm »

The cam end seems to be marked "77G."

is there a chance that this could actually be run on the street in a cafe racer?

mrcheeze · « **Reply #20 on:** February 07, 2016, 02:11:06 pm »

also, where would I look on the head and cyls for RC markings? what would I be looking for?

754 · « **Reply #21 on:** February 07, 2016, 02:19:30 pm »

Underneath to the back.. On the head.
I think one cam i had from RC was also etched between lobes. Might have said Engle 315.
If can has a distinct grey color( dont think yours is) then it could be Norris and they marked them on a flat spot between lobes.

gschuld · « **Reply #22 on:** February 07, 2016, 02:25:44 pm »

The 3 cams shown are original RC cams. Stamped differently, and can be stamped on EITHER end(2 rt side, one left side of these 3), so check the other end as well. The other cam is an original Kenny Harmon D grind cam, from the same CWC 134 cam blanks.

On the cylinder head. With the chamber side up, look at the fin area, towards the carbs, adjacent to to either the #2 or #3 chamber. It should have an all caps single stamp, RC ENGINEERING. or R.C ENG. , about 2" across. It's hard to miss. I'd take a picture, but I don't have an RC head off a motor right now.

On the cylinder, like the picture, there should be R.C. ENG. On the fins on the upper side of the cylinder. Sometimes the displacement is stamped where the 736 was ground off on the pad. RC always cut the tops of the cylinders for copper o-rings.

George

cbr954 · « **Reply #23 on:** February 07, 2016, 02:30:45 pm »

RC also stamped on the back of the cylinder head between cyl 2 and 3 just below the valve cover surface. I have an early head with the RC ENG stamp in that location.

gschuld · « **Reply #24 on:** February 07, 2016, 02:32:28 pm »

Frank,

Your cam might have read "ISKY 315". If that is the case, you have one of the early cams. ISKY originally supplied the cams to RC under their own name, until about 1973. The Isky cams became RC cams under licence I believe. Your cam specs will likely be different that the typical later RC 315 cam, since they revised all the cam specs at one point.

George

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Author Topic: RC Engineering 1075 stroker motor value? (Read 4728 times)