Author Topic: RC240 cam and K/H D grind info, also how to tell non stock valve springs  (Read 3573 times)

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Offline hellbilly1932

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I've been running the RC240 in my stock motor for several years but I can find no info on it what so ever. From what I can tell the motor is stock but I did notice some slight port work was maybe done at some point in its life and there are some stamped numbers under the valve cover near the valves that looks like a machine shop code of some sort, there is nothing like it on either of my other heads I have. Also is there any way to check a valve spring to see if its stock?

I have a K/H D grind cam that I got years ago and never put in a motor because I don't know what it's specs are and if it would be happy in an otherwise stock motor. Any info on this?

Thanks.
« Last Edit: May 23, 2011, 08:23:14 AM by hellbilly1932 »

Offline 754

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RC 240 is a regrind cam..mild.
 int timing 30deg-65deg
 exh timing 65deg-30 deg
 int and exh lift .330
 running clearance cold .014
 RC 240 Street Torque-- for smaller bore lower compression motors. Good for road riding and touring. The only cam that can be bolted in a stock motor without piston valve pocket machining.

 Some may not like the valve clearance, I run 12 thou on a RC 327, and its not real noisy, got another RC list somewhere will check clearance in that 240.

 I think the KH D is a very hot one, are the lobes huge and big duration?? if so you are gonna need a lot of motor work.
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Offline hellbilly1932

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I'm saving the D grind for a big motor build somewhere down the line.

So with the RC240 i've had the valve/rockers set at stock clearances for years is that a no no? I have the motor apart now putting in new studs and gaskets and there is no evidence of any piston valve contact.

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Here's some specs on the Kenny Harmon D grind.

http://www.satanicmechanic.org/megacyclecam.shtml

Scroll down to part number: 125-D




Offline MRieck

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Those Harmon grinds are based on Ducati patterns. I just got a "SuperF" for a customer. It looks like a Chevy small block roller cam.
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Offline MCRider

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As to the valve springs, stockers look like they should be heavy duty. They are more tightly wound with thicker wire.

(Modern) HD are thinner wire not so tightly wound. The wire is a stronger issue. The less frequent winds reduces chance of coil bind on high lift cams. To me, the looks are counterintuitive.

A spring is a lever all coiled up. If you straightened it out, its harder to bend a short lever than a long one.

A spring gauge would tell you for sure. I have such a gauge and would do some measurements if there was a urgent need. Otherwise it can wait.

I'm not an engineer or such. These are amateur ramblings and observations. I defer to anyone who knows better.
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Offline turboguzzi

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As to the valve springs, stockers look like they should be heavy duty. They are more tightly wound with thicker wire.

(Modern) HD are thinner wire not so tightly wound. The wire is a stronger issue. The less frequent winds reduces chance of coil bind on high lift cams. To me, the looks are counterintuitive.

A spring is a lever all coiled up. If you straightened it out, its harder to bend a short lever than a long one.

A spring gauge would tell you for sure. I have such a gauge and would do some measurements if there was a urgent need. Otherwise it can wait.

I'm not an engineer or such. These are amateur ramblings and observations. I defer to anyone who knows better.

more winds (stock) = lower spring K = lower natural resonance frequency = valve float at lower revs.

less winds = higher nat. freq. = less valve float,



Offline Big Jay

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On stock springs, the inners are not interference fit and will slip right through the outers. 

Offline hellbilly1932

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Any more info on what is best to set the vale to rocker clearance at for this RC 240?

Offline MCRider

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On stock springs, the inners are not interference fit and will slip right through the outers.
That's good to know. Will make sorting my box of springs easier. Don't know where I got so many springs from over the years. Most are probably stockers, but you never know.

I got my APE TDC finder today, quick service, thanks!
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Offline NitroHunter

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Back in the day I had that RC 240 cam in an RC 836 cast piston motor, (the old RC 30/30 kit) it was a really good combination. Very nice for everyday around town riding, and I didn't have to wind the daylights out of it to enjoy the ride. Put many highway miles on that one with 52+mpg.

Frank do you have those valve clearance specs handy?
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Offline 754

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 Yes, but I forget to check in my other catalog.
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Offline 754

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Checked my other catalog, got new info . (think there was a misprint on early catalog)
 RC 240
 296 degrees duration
 Lobe centers 118 degrees
 . 327 intake lift, .330 exhaust
 valve clearance intake and exhaust .004
 That sounds more like it!
Maker of the WELDLESS 750 Frame Kit
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Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline MRieck

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Checked my other catalog, got new info . (think there was a misprint on early catalog)
 RC 240
 296 degrees duration
Lobe centers 118 degrees
 . 327 intake lift, .330 exhaust
 valve clearance intake and exhaust .004
 That sounds more like it!
Really??
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Offline 754

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 That Is what it said, will look at what it listed for the other grinds.
 The 240 cam was used in the 30-30 kit.. they claimed 30 % more power and 30 % increase in gas mileage, they used 10-1 cast 836cc pistons, header, and the 240 cam.
Maker of the WELDLESS 750 Frame Kit
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Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline hellbilly1932

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Thanks for all the info guys! just got my head back from the shop today so its all going back together today.

Offline 754

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That 118 degrees center may have been a typo? in the catalog?
 The other Honda cams were 104 and 105 degrees.
 The Kawi and Suzuki cam were 108 or 110 degrees on the streetable cams, the top fuel cams wwere 115 degree centers..
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My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

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Lost quite a few CB 750's along the way

Offline dhb53

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754 if you ever decide to sell your KH D grind cam let me know

Offline MRieck

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754 if you ever decide to sell your KH D grind cam let me know
You can still get that grind in hardweld from Megacycle. I recently purchased a KH "SuperF" cam for a customer.
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