Topic: Cylinder studs for a cb650?

[paulages]

i measured both tonight, and (in between the threads) they are:

OEM CB650 bolts-      8.07mm
APE HD CB750 studs- 8.75mm

[Terry in Australia]

 Get rid of the 6mm screws and put in studs.....with flange nuts and high heat medium strength locking compound.

What's the benefit there Mike? Are you talking about the screws under the pucks? I don't think you'd get flange nuts in there, and it'd be a bugger to try to get a socket in there to torque them, or are you just talking about the screws fore and aft of the cam chain tunnel? Cheers, Terry.

i measured both tonight, and (in between the threads) they are:

OEM CB650 bolts-      8.07mm
APE HD CB750 studs- 8.75mm

That's interesting, the 10mm stud's thread of 10 x 1.25mm makes sense, take 1.25 away from 10 and you've got 8.75mm, but what's the deal with the OEM 650 bolt's thread? Were the threads perfectly clean Paul? If they are 8 x 1.25mm bolts, the measurement between the threads should be 6.75? Are you talking about "in between the threads" or the actual shaft diameter? 

Also, any idea what the relative "hardness" is Paul? Scunny said he had no problems chopping thru an OEM 650 bolt with his "Junior Engineer" hacksaw, and it would make sense to me that they are more "elastic", as they are designed to be torqued into relatively soft alloy top cases, not steel nuts. Cheers, Terry.

[MRieck]

 Get rid of the 6mm screws and put in studs.....with flange nuts and high heat medium strength locking compound.

What's the benefit there Mike? Are you talking about the screws under the pucks? I don't think you'd get flange nuts in there, and it'd be a bugger to try to get a socket in there to torque them, or are you just talking about the screws fore and aft of the cam chain tunnel? Cheers, Terry.

i measured both tonight, and (in between the threads) they are:

OEM CB650 bolts-      8.07mm
APE HD CB750 studs- 8.75mm

That's interesting, the 10mm stud's thread of 10 x 1.25mm makes sense, take 1.25 away from 10 and you've got 8.75mm, but what's the deal with the OEM 650 bolt's thread? Were the threads perfectly clean Paul? If they are 8 x 1.25mm bolts, the measurement between the threads should be 6.75? Are you talking about "in between the threads" or the actual shaft diameter? 

Also, any idea what the relative "hardness" is Paul? Scunny said he had no problems chopping thru an OEM 650 bolt with his "Junior Engineer" hacksaw, and it would make sense to me that they are more "elastic", as they are designed to be torqued into relatively soft alloy top cases, not steel nuts. Cheers, Terry.

The ones under the pucks Terry. The benefit is you can acheive much more torque on the nut as opposed to those 4 bolts. The bolts strip out very easily. Think about it...those 4 bolts go right across the center of the cylinder/head assembly. You can use all the clamping power you can get especially considering how little torque you can get on the cylinder studs (even aftermarket ones). I've done this on engines and recommended it to others with absolutely no fitment problems. RC did it on there Cobra engines too. I use a T handle 10mm tool to get to the nuts. 1/4" drive deep sockets usually fit in there too. You can grind (or cut on the lathe) the OD if it is too tight

[paulages]

i measured both tonight, and (in between the threads) they are:

OEM CB650 bolts-      8.07mm
APE HD CB750 studs- 8.75mm

That's interesting, the 10mm stud's thread of 10 x 1.25mm makes sense, take 1.25 away from 10 and you've got 8.75mm, but what's the deal with the OEM 650 bolt's thread? Were the threads perfectly clean Paul? If they are 8 x 1.25mm bolts, the measurement between the threads should be 6.75? Are you talking about "in between the threads" or the actual shaft diameter? 

Also, any idea what the relative "hardness" is Paul? Scunny said he had no problems chopping thru an OEM 650 bolt with his "Junior Engineer" hacksaw, and it would make sense to me that they are more "elastic", as they are designed to be torqued into relatively soft alloy top cases, not steel nuts. Cheers, Terry.

i was measuring the area between the threads on both, not the thread pitch itself. i'll do a better measurement when i'm at my shop again. as i understand it, cylinder studs or bolts are meant to be elastic, and this is why it is not recommended to retorque them many times. this is all from memory from engine classes years ago, mind you, so i'm not claiming definitive knowledge here. it would stand to reason though that you would want to studs to stretch a bit, as this would provide more tension and allow for expansion/contraction during heat cycles and still stay tight.

i'm all about studs... just trying to point out that the OEM bolts don't seem to be so bad. maybe a cheap alternative for a 550 builder. gotta wonder though: why did honda switch?

[Terry in Australia]

So could you convert a hi-po 650 engine to studs if you wanted to Paul? I've no doubt those 650 bolts are better than the previous OEM studs, but I'm just wondering what the advantage of bolts is over studs?

I'd just prefer to torque nuts down onto studs, then torque bolts down into the cases, if I was building a hot-rod?

The ones under the pucks Terry. The benefit is you can acheive much more torque on the nut as opposed to those 4 bolts. The bolts strip out very easily. Think about it...those 4 bolts go right across the center of the cylinder/head assembly.

You can use all the clamping power you can get especially considering how little torque you can get on the cylinder studs (even aftermarket ones). I've done this on engines and recommended it to others with absolutely no fitment problems.

RC did it on there Cobra engines too. I use a T handle 10mm tool to get to the nuts. 1/4" drive deep sockets usually fit in there too. You can grind (or cut on the lathe) the OD if it is too tight

OK Mike, I reckon I might have to attack the head with the mill to enlarge the holes a tad to make it easier to get the nuts on and torque 'em down, sooooooo.......... why don't I modify the cylinder block and head to accept 8 or 10mm studs while I'm at it?

Only speculation at this stage as I haven't measured anything yet, but if there's room, why not? When I build the 1060cc engine, I only want to do it once, ha ha! Cheers, Terry.

[paulages]

So could you convert a hi-po 650 engine to studs if you wanted to Paul? I've no doubt those 650 bolts are better than the previous OEM studs, but I'm just wondering what the advantage of bolts is over studs?

I'd just prefer to torque nuts down onto studs, then torque bolts down into the cases, if I was building a hot-rod?

I can't see why you couldn't convert to studs. What i was wondering out loud is why they switched in the first place... must've been some advantage.  the 550 head is removable in-frame with the studs, so i can't see that being why.

about the studs for the little 6X1mm bolts on the 750... they have flanged heads already. in my experience, the hard part is getting a socket into the hole. i bet you could get flange nuts that would fit without milling.

[MRieck]

So could you convert a hi-po 650 engine to studs if you wanted to Paul? I've no doubt those 650 bolts are better than the previous OEM studs, but I'm just wondering what the advantage of bolts is over studs?

I'd just prefer to torque nuts down onto studs, then torque bolts down into the cases, if I was building a hot-rod?

The ones under the pucks Terry. The benefit is you can acheive much more torque on the nut as opposed to those 4 bolts. The bolts strip out very easily. Think about it...those 4 bolts go right across the center of the cylinder/head assembly.

You can use all the clamping power you can get especially considering how little torque you can get on the cylinder studs (even aftermarket ones). I've done this on engines and recommended it to others with absolutely no fitment problems.

RC did it on there Cobra engines too. I use a T handle 10mm tool to get to the nuts. 1/4" drive deep sockets usually fit in there too. You can grind (or cut on the lathe) the OD if it is too tight

OK Mike, I reckon I might have to attack the head with the mill to enlarge the holes a tad to make it easier to get the nuts on and torque 'em down, sooooooo.......... why don't I modify the cylinder block and head to accept 8 or 10mm studs while I'm at it?

Only speculation at this stage as I haven't measured anything yet, but if there's room, why not? When I build the 1060cc engine, I only want to do it once, ha ha! Cheers, Terry.

Sure Terry....8's would be better! Not hard on the mill....blow through that with an end mill. The tighter the better. Offhand I'd say there is plenty of room. Do it as I'd love to see the results.

[MRieck]

 Terry
  The 8's will not fit. Stick to the 6's.

[Terry in Australia]

Bugger! OK Mike, I'll stick with the 6's.