Topic: RC valve cover

[mycb750k6]

Friend sent me this. Sure is purdy. I thought it belonged here. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=250688367221&ssPageName=ADME:X:RTQ:MOTORS:1123

[MCRider]

Friend sent me this. Sure is purdy. I thought it belonged here. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=250688367221&ssPageName=ADME:X:RTQ:MOTORS:1123

A little misleading to say its an RC. An original RC wold have provenance and worth more. This is a reproduction, which he freely admits in the description. My understanding is the Honda Factory did these for their CR750. I might be wrong and I don't know who was first, RC or Honda.

His hold down screw heads are Phillips which seem an odd choice. Hard to get the torque on them required to be effective. Mine are Allen heads. Now that I know, I would have asked for 8 or 10mm hex heads.

They are readily available from many machinists. I think Rob Voxonda is doing them. Mine was made by Les Barker in Vancouver WA, for $175. Though that was many years ago.

Some say with the more modern HD springs and milder cam grinds (RC ran some really BIG bump cams) they are not needed now. My nit picking aside, I agree they are way cool and whether you need them or not, I say why not?  Belt and suspenders, reduces chance of puck leaks and cam flex.

PS: I just noticed the seller is in Springport IN which I don't know, but it can't be far from here, Indiana's not that big. Lots of machinists here in the racing business.

PPS: I see KOS (Mark) at M3 Racing has them for $350 with the allens like mine.

[Sam Green Racing]

Ron, the heads of the hold down screws don't really matter, It's the overall strength in the cam cover screws that matter. After taking the hold down screws down to the the cam housing retainer bolts, the locking nuts on them will give you all the torque you need when you pinch them tight.
Like you said, unless you are running really wild cams with very heavy springs they are just for show, cool factor.

Sam.

[MCRider]

Ron, the heads of the hold down screws don't really matter, It's the overall strength in the cam cover screws that matter. After taking the hold down screws down to the the cam housing retainer bolts, the locking nuts on them will give you all the torque you need when you pinch them tight.
Like you said, unless you are running really wild cams with very heavy springs they are just for show, cool factor.

Sam.

Thanks. My hold down bolts actually hit the round areas, about the size of a dime or smaller, that are machined flat on the tops of the cam holders. Be that as it may, I've always wondered and get mixed or no direction, on how tight to crank those hold down screws. I'd settled on 5 ftlbs. What you're saying is like the phenomenon that occurs when trying to set the valve clearance.

When one cranks on the tappet adjuster jamb nut, if you don't hold the adjuster still it will turn with the nut and close off the clearance. So if that's your guidance on the valve cover reinforcements I can accept that and use it.

Again thanks!

[Jerry Rxman Griffin aka MuthaF'er]

Torqueing them down is a good question. My thoughts are to tighten them until they hit the aluminum cam tower then maybe another quarter turn and lock them in place.

What is the diameter of your bolts mycb?

[Sam Green Racing]

Hey Ron, don't take that as gospel, that's just my take on it, I'm no pro engine builder, If I was, I wouldn't have taken my motor to Mike to be fettled.
Despite the fact that I put the bike in my avatar together for my mate, I know very little about these SOHC4 motors. I specialise in the old 125 and 150 Benly twins. Allthough I bought a new one recently, I havn't used a torque wrench in ages and I've never had a leak from a head or any other joint.
If I build a motor for a customer, perhaps then I would use the TW.

Sam.

[MCRider]

Hey Ron, don't take that as gospel, that's just my take on it, I'm no pro engine builder, If I was, I wouldn't have taken my motor to Mike to be fettled.
Despite the fact that I put the bike in my avatar together for my mate, I know very little about these SOHC4 motors. I specialise in the old 125 and 150 Benly twins. Allthough I bought a new one recently, I havn't used a torque wrench in ages and I've never had a leak from a head or any other joint.
If I build a motor for a customer, perhaps then I would use the TW.

Sam.

Got it. As you say, the hold down bolt just has to "be there" not necessarily really tight. Which takes mer away from my previously held idea that they needed to be really tight. As long as its "there" and it doesn't give when the cam tower tries to squirm underneath, everythings cool.

I think I'm back to 5 ft lbs, as that's a nominal amount and I can get them all the same. But whent the time comes to actually install it, soon I hope, I'll canvas the forum again for guidance.

[voxonda]

Hey Ron,

When installing a valve cover with these hold down bolts, I make sure that the camcarriers have been milled to. Just about .3 to .4 of a millimetre. So that the surface is smooth. The oem carriers are cast and very often not flat in the area where the bolts contact.
Do not overtighten, just let them touch and secure.

Cheers,
Rob.

[MCRider]

Hey Ron,

When installing a valve cover with these hold down bolts, I make sure that the camcarriers have been milled to. Just about .3 to .4 of a millimetre. So that the surface is smooth. The oem carriers are cast and very often not flat in the area where the bolts contact.
Do not overtighten, just let them touch and secure.

Cheers,
Rob.

Thanks Rob: Just what I need to know. I'll double check, but it seems if i remember, that my cam holders have 4 round smooth spots on each, and the bolts do touch down there. I checked with some marking ink and mocked it up.  When I get there again  I'll post a picture.
regards: Ron

[voxonda]

Correct Ron, four round spots but (very) often not flat.

rob

[MCRider]

Correct Ron, four round spots but (very) often not flat.

rob

I'll check er out.

[lordmoonpie]

Pretty much what I did with mine (from Mark at M3) - finger tight then plus one quarter turn but then lock them off tightly with top nuts - seems solid enough for my lumpy cam and dodgy DOHC hy-vo camchain

[Big Jay]

Back in the day there were no valve springs for the CB750, so RC got some from Isky that were made for Pinto engines or something like that. They promptly lifted the cam towers off the head, so this fix came about.

Once proper springs were designed for this motor, the fix was no longer needed, but it looks kind of cool.

[MRieck]

Back in the day there were no valve springs for the CB750, so RC got some from Isky that were made for Pinto engines or something like that. They promptly lifted the cam towers off the head, so this fix came about.

Once proper springs were designed for this motor, the fix was no longer needed, but it looks kind of cool.

Right.