Topic: Cylinder studs for a cb650?

[Soos]

Stock cb650 uses bolts, not studs to hold down the head and cylinders.
I want to change that with my next cb650 motor.
Probably not needed on a 59.8mm(stock) bore, but i'm going out to a 65mm bore.



Has anyone came across a set of studs usable on a 650 to replace the stocker bolts?


l8r

[Soos]

BUMP, seriously, anyone know of anywhere?


l8r

[ct_racer]

Since I couldn't find a decent set of studs for my cb500 I went to a welding shop and had a set made up.  It was only like 80 bucks if I remember right...  They're much beefier than stock ones as well.

[paulages]

soos- why do you want to switch? the 650 bolts have comparable dimensions and torque values to the HD studs sold for the other SOHC4's (APE cb750 HD studs for example). i'd guess you'll end up looking for HD 550 studs if that's the route you want to take. you might try some random stud supplier and just provide sizes... i found some a tacoma screw (fastener supplier in the NW) here in portland that seemed like they would be good. i ended up going with OEM 650 bolts because they seem strong enough.

be glad you have one of the advanced SOHCs. 

[ghost]

advance sohc? built at the end of the stone age?

[Soos]

be glad you have one of the advanced SOHCs. 

Well, I want to source some out for my 65mm pistons I plan on running.
They were High comp. pistons for the 750, so they will be crazy high in my 650.

HAHAHA..... Advanced....
I think mine is more advanced than your norm 650!
BIG carbs, 2.2 coils, dyna2000(with custom advance curves), headwork, bored out, and a ton of other stuff...


I think i'll stick with 650's if the 750 is less advanced.... and I thought the 650 needed help.
 


I'll post if I find a source.


l8r

[paulages]

Well, I want to source some out for my 65mm pistons I plan on running.
They were High comp. pistons for the 750, so they will be crazy high in my 650.



l8r

you'll have to work the pistons anyway, so you'll decide the CR. anything over 10.5/1 and you'll be needing higher than pump octane fuel anyway. unless i'm mistaken, then APE studs which torque to the same as the stock 650 studs (22 ft#) are about as good as you can get. unless you can find something that torques even higher, i'm not sure what the advantage would be unless the honda metal is lower-grade.

maybe cross reference studs/bolts from some modern bike? CBR or something?

[MRieck]

Well, I want to source some out for my 65mm pistons I plan on running.
They were High comp. pistons for the 750, so they will be crazy high in my 650.



l8r

you'll have to work the pistons anyway, so you'll decide the CR. anything over 10.5/1 and you'll be needing higher than pump octane fuel anyway. unless i'm mistaken, then APE studs which torque to the same as the stock 650 studs (22 ft#) are about as good as you can get. unless you can find something that torques even higher, i'm not sure what the advantage would be unless the honda metal is lower-grade.

maybe cross reference studs/bolts from some modern bike? CBR or something?

I'm quite sure the stock bolts will be fine. If you were going to be disassembling the engine often I'd opt for studs but if that is not the case....Quite often the head and cylinders can be removed with the engine in the frame with the bolts. Studs often require removing the engine especially with newer bikes. Believe it or not some OEM bolts are stronger than studs.

[Big Jay]

Are they 8 mm or 10?

Jay

[scunny]

bolts are 8mm with 12mm head

[Terry in Australia]

I can't help but doubt that the OEM 8mm bolts are as strong, or stronger than APE 10mm studs. I torqued mine in my 836cc engine down to 25 ft/lbs, but I've no doubt they could handle considerably more, the OEM GS Suzuki 10mm stud torque value is 30+, depending on the model. Cheers, Terry.

[paulages]

I can't help but doubt that the OEM 8mm bolts are as strong, or stronger than APE 10mm studs. I torqued mine in my 836cc engine down to 25 ft/lbs, but I've no doubt they could handle considerably more, the OEM GS Suzuki 10mm stud torque value is 30+, depending on the model. Cheers, Terry.

you 750 only guys wouldn't know, because honda changed quite a bit by '79, much for the better. they may have slipped a little on style and weren't necessarily breaking new ground, but let's not forget that the little 650 was only a scant 5HP under the 750. i could be remembering wrong, but i thought i had measured them to be the same. here's a picture i took of a cb650 bolt next to a cb750 stud.

i thought i had a picture comparing to the APE studs, but this one appears to be OEM. i'm not sure they're 8mm. i thought that was the 550. i'll measure when i'm at the shop.

[MRieck]

I can't help but doubt that the OEM 8mm bolts are as strong, or stronger than APE 10mm studs. I torqued mine in my 836cc engine down to 25 ft/lbs, but I've no doubt they could handle considerably more, the OEM GS Suzuki 10mm stud torque value is 30+, depending on the model. Cheers, Terry.

you 750 only guys wouldn't know, because honda changed quite a bit by '79, much for the better. they may have slipped a little on style and weren't necessarily breaking new ground, but let's not forget that the little 650 was only a scant 5HP under the 750. i could be remembering wrong, but i thought i had measured them to be the same. here's a picture i took of a cb650 bolt next to a cb750 stud.

i thought i had a picture comparing to the APE studs, but this one appears to be OEM. i'm not sure they're 8mm. i thought that was the 550. i'll measure when i'm at the shop.

Whoa, whoa, whoa......us "750" guys aren't all dumd (on purpose). I get it....I think but I just forgot....what were we talking about??

[Soos]

Wow, I blink and the thread explodes....



Thnx all!
The threads are 8X1.25
I have the bag of bolts(labeled) from my completely torn down cb650 motor.
The washers used average 0.095 thick.
12 bolts in whole set.
12mm hex head flange bolts, flange:17mm dia., 0.080 thick.
When I mention step length it is a larger diameter section just below the head of the bolt, up to the shoulder of the angle going to the smaller .281 stem diameter.

2 longer bolts :
Overall length    - 6.005 / 152.52mm
head thickness  - 0.295 /     7.54
thread length    - 1.187 /   30.15
stem diameter   - 0.281 /     7.13
step diameter   - 0.312 /      7.92
step length      - 0.590 /     14.98

10 shorter bolts
Overall length    - 5.012 /  127.30mm
head thickness  - 0.295 /     7.54 
thread length    - 1.145 /    29.08
stem diameter   - 0.281 /     7.13
step diameter   - 0.312 /      7.92
step length      - 0.590 /     14.98

The block can fit 10mm bolts....but barely, the holes are only 0.403 to 0.405.
the hole pattern for the bolts both in the upper motor case and the cylinder block are close enough they would work IMO.(or at least it wouldn't be a nightmare amount of work to get them to fit with a little clearance.)
Hey Jay, do you guys roll your threads, or cut them?



NO I don't intend to have to tear down the engine often(hopefully)....

Another thought that came to me lately about this, But I have thought of just putting heli-coils in all the holes for the block.
Mainly, the material in the block I worry about stripping out, not the bolt snapping so much.
But any added insurance sounds good to me on this motor build.



l8r

[paulages]

I can't help but doubt that the OEM 8mm bolts are as strong, or stronger than APE 10mm studs. I torqued mine in my 836cc engine down to 25 ft/lbs, but I've no doubt they could handle considerably more, the OEM GS Suzuki 10mm stud torque value is 30+, depending on the model. Cheers, Terry.

you 750 only guys wouldn't know, because honda changed quite a bit by '79, much for the better. they may have slipped a little on style and weren't necessarily breaking new ground, but let's not forget that the little 650 was only a scant 5HP under the 750. i could be remembering wrong, but i thought i had measured them to be the same. here's a picture i took of a cb650 bolt next to a cb750 stud.

i thought i had a picture comparing to the APE studs, but this one appears to be OEM. i'm not sure they're 8mm. i thought that was the 550. i'll measure when i'm at the shop.

Whoa, whoa, whoa......us "750" guys aren't all dumd (on purpose). I get it....I think but I just forgot....what were we talking about??

ha! i think you've had your hands on enough other engines to not call yourself a 750 "only" guy. 

[Terry in Australia]

So, all "750 vs the rest" arguments aside, was I right to conclude that APE 10mm heavy duty studs are possibly just a tad stronger than OEM 8mm? 

[scunny]

what ya trying to say Terry..... we 650 bolt people are slightly narrower at the waist than you heavy duty Ape stud 750 guys ? 
well, it's possible I suppose 

[Terry in Australia]

Ha ha, you "non-750" blokes are a sensitive lot!

[scunny]

on with the show......I've cut one of the 650 bolts with my junior engineers hacksaw and it seemed to be normal steel.
my money is on the Ape heavy duty. Which brings up a question, at what stage does the ability to increase the torque applied compromise the aluminuim threads ability to hold it

[Terry in Australia]

Well that's right Scunny, as the "advanced" 650 (or any of it's junior siblings) wasn't intended for competition work, the cylinder bolts were probably a good idea, but if you were intending on "hot-rodding" one with mega compression etc, I suppose an APE 10mm H/D Stud conversion would be in order, (if physically possible, of course) because I imagine it'd be pretty easy to strip the threads in the upper crankcase by over-torqueing the bolts? Cheers, Terry.    

[Big Jay]

All of our threads are rolled, after the material has been heat treated.

Let me check and see if we have any 8 mms the lengths you need.

Jay

[Soos]

Ha ha, you "non-750" blokes are a sensitive lot!

No like short mans syndrome(thinks everyone over his height is out to get one over on him)

I think we 650 riders just have short block syndrome...
Always trying to prove we have something(we don't have)over the rest of you "750" guys.
 

J/K....



Or am i?


Hey Jay, I would be more interested in a set of 10mm ones if you have some the right length!


thnx,


l8r

[paulages]

for the record, i wasn't trying to say that the OEM 650 bolts are as strong as the APE ones, only that they torque to the same relative values. "strength" here isn't as important as the elasticity of the metal and the ability to hold to the correct torque (which i'd suspect is a product of the metal used- jay would probably know) . it's not as if high compression is going to shear a stud or bolt off with vertical force, but those few pounds extra torque might help stave off leaks when they inevitably relax on run in. OEM 550 and 750 studs torque to about 16-18 FT# if i remember right, and the 650 bolts and APE studs torque to 22-25 FT#.

Soos- you do have an advantage a 750 wouldn't have (without a frame kit like gordon's), and that's the ability to retorque after run-in. i'd wager that's more critical that the studs being HD. FWIW, i'm running OEM 650 bolts (reused even) on the 718 with 10.6/1 CR, and have no leaks at the head.

[Terry in Australia]

Yeah, you're right Paul, I should have chosen my words more carefully, "strong" is too generic a term when comparing the relative elasticity of cylinder studs, but obviously my point was that OEM cylinder bolts are far more "elastic" than APE 10mm studs.

I'd normally add "if they weren't, Jay wouldn't make them", but as I previously mentioned, the smaller SOHC4's weren't designed with competition in mind, and as so few were (or are now) raced in comparison to the 750, it probably wouldn't be viable to start production now.

The 750, being a much older design than the 650, had a few weak spots, and the cylinder studs was one of them. Just adequate for a stocker, and rubbish for anyone contemplating a big bore kit with higher compression pistons, and lots of revs. The technique I learned back in 1981 when I rebuilt my first stock CB750 engine was to enure all the old head gasket material was completely removed from both mating surfaces, (I use a 3m nylon "Strip Disc" on my Makita sander/polisher, it'll remove the crap without hurting the surfaces) paint the head gasket with "silver frost" enamel paint (engine enamel seems to work fine too, but no other gasket adhesive at all) clean and oil the threads on the studs, then torque it down to 19 ft/lbs in small increments. (5+5+5+2+2)

I leave it overnight, then loosen all the stud nuts, and torque it down again, before re-installing the engine. It really is amazing after the second torqueing, how much more you can then tighten the 6mm screws under the cam tower rubber "pucks", and the 6mm screws fore and aft of the cam chain tunnel. I've done this probably a dozen times over the last 27 years, and have never had a head gasket leak. Of course, on my 836cc engine and the 1060cc engine I'm building shortly, I wouldn't consider anything less than APE 10mm H/D studs. The 1060cc engine is going into my long-neglected "Endurance Racer" project bike, and I've got to install Gordons frame rail removal kit, to allow for any cam shaft changes etc. Cheers, Terry.    

[MRieck]

Yeah, you're right Paul, I should have chosen my words more carefully, "strong" is too generic a term when comparing the relative elasticity of cylinder studs, but obviously my point was that OEM cylinder bolts are far more "elastic" than APE 10mm studs.

I'd normally add "if they weren't, Jay wouldn't make them", but as I previously mentioned, the smaller SOHC4's weren't designed with competition in mind, and as so few were (or are now) raced in comparison to the 750, it probably wouldn't be viable to start production now.

The 750, being a much older design than the 650, had a few weak spots, and the cylinder studs was one of them. Just adequate for a stocker, and rubbish for anyone contemplating a big bore kit with higher compression pistons, and lots of revs. The technique I learned back in 1981 when I rebuilt my first stock CB750 engine was to enure all the old head gasket material was completely removed from both mating surfaces, (I use a 3m nylon "Strip Disc" on my Makita sander/polisher, it'll remove the crap without hurting the surfaces) paint the head gasket with "silver frost" enamel paint (engine enamel seems to work fine too, but no other gasket adhesive at all) clean and oil the threads on the studs, then torque it down to 19 ft/lbs in small increments. (5+5+5+2+2)

I leave it overnight, then loosen all the stud nuts, and torque it down again, before re-installing the engine. It really is amazing after the second torqueing, how much more you can then tighten the 6mm screws under the cam tower rubber "pucks", and the 6mm screws fore and aft of the cam chain tunnel. I've done this probably a dozen times over the last 27 years, and have never had a head gasket leak. Of course, on my 836cc engine and the 1060cc engine I'm building shortly, I wouldn't consider anything less than APE 10mm H/D studs. The 1060cc engine is going into my long-neglected "Endurance Racer" project bike, and I've got to install Gordons frame rail removal kit, to allow for any cam shaft changes etc. Cheers, Terry.    

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