Cylinder studs, smooth v. spiral

Rick Pope · Post by **Rick Pope** » Mon Sep 25, 2006 9:00 am

I've read several times that bikes with the smooth cylinder studs are very early, and later bikes had spiral studs. But I've also heard that there was a recall and that many early bikes had the studs changed.

Supporting that notion is the fact that one of my '79s has smooth studs, and the other, with a lower serial #, has spiral studs.

Can anyone clarify this?

EMS · Post by **EMS** » Mon Sep 25, 2006 11:15 am

Rick, I don't know wheter this will clarify anything

: The studs were indeed changed , but I have two different engine serial numbers on record. One is 2003478 and one is 2003946. In any case, it was below 4000 when the change occured. I am not aware of a recall (I have my 79 CBX since new and my engine falls into this bracket), but many motors were changed later, even through minor repairs, like a new headgasket.

The thing that makes this difficult to track in the Honda records is, that most major changes are tied to frame serial numbers.

FalldownPhil · Post by **FalldownPhil** » Mon Sep 25, 2006 12:48 pm

I believe Mike is correct on this one. While there was no factory recall there were many early models that got to have their studs changed. It was common practice. I very recently parted with # 2000221 or something like that. Still had round studs and a 3000 mi. odometer.

Best,

Phil

markdam · Post by **markdam** » Thu Sep 28, 2006 2:46 am

smoooth studs

and low low low serial number and shes ALLLLL MINE!!!!!!

Chris · Post by **Chris** » Thu Sep 28, 2006 8:28 am

markdam wrote:smoooth studs and low low low serial number and shes ALLLLL MINE!!!!!!

Congratulations!!!

cbxtacy · Post by **cbxtacy** » Thu Sep 28, 2006 10:06 pm

Of course the reason they had the factory recall to replace the smooth studs with the curly one's is because the smooth one's had a tendancy to stretch a little and you'd get blown head gaskets.

Chris · Post by **Chris** » Thu Sep 28, 2006 10:24 pm

cbxtacy wrote:Of course the reason they had the factory recall to replace the smooth studs with the curly one's is because the smooth one's had a tendancy to stretch a little and you'd get blown head gaskets.

I also heard that they would crack.

I have an early '79 that had smooth studs. It is being converted to spiral studs.

Terry · Post by **Terry** » Thu Sep 28, 2006 10:36 pm

I've got the curly studs but my motor number is way in the back and as far as I can tell the motor was the 5,079th built for resale. Nearing 50,000 now and she does 'use' some oil but thankfully, no smoke yet.

EMS · Post by **EMS** » Sat Sep 30, 2006 10:07 am

Terry, if your 79 motor has a serial number over 5,000 it would definitely have come with curled studs from the factory. Again, I don't remember that there ever was an official recall on the smooth studs. Maybe a service bulletin to replace them. Maybe Mike Nixon remembers??

Jeff Bennetts · Post by **Jeff Bennetts** » Sat Sep 30, 2006 1:31 pm

Honda replaced the smooth studs with the spirals because the smooth studs had a tendency to break at the case after so many heat cycles.

Its still common today to see brocken studs at the case with smooth and spiral studs, symptoms are an oil leak from the stud cap under the valve cover leaking down the length of the stud because it is no longer sealing the stud cap nut and blow by at the jug and case because of the lost torque from the snapped stud.

jb

markdam · Post by **markdam** » Sat Sep 30, 2006 2:00 pm

hmmmmmmmmmmm

if i had a bike that was 25 years old and only had 3000 miles and had smooth studs.... iwonder if theyve"aged" and or if a "retorque" would be prudent

Rick Pope · Post by **Rick Pope** » Sat Sep 30, 2006 10:17 pm

If it ain't broke.......Or, if it ain't leaking, why try to re-torque? I've heard some of horror stories about folks who thought they'd check the torques while doing a simple valve check, and ended up fixing broken studs.

My yellow C2C bike has the smooth studs and no oil leaks with over 40,000 miles. I think I'll just leave it alone as long as I can.

FalldownPhil · Post by **FalldownPhil** » Sat Sep 30, 2006 10:30 pm

Rick,

I concur. It isn't even broken in yet.

I would however, be going through my carbs.

Best,

Phil

Larry Zimmer · Post by **Larry Zimmer** » Mon Apr 07, 2008 7:45 pm

FYI for anyone doing an engine upgrade. The engineering explanation is that the spiral studs have considerably greater fatigue strength than the smooth studs. This is because the were rolled similar to a thread to put compressive stresses into the surface; AND, to smooth over any microscopic fine lines that occur during the forming of the stud shanks. These fine draw lines form the starting point for cracks. If you're doing any rebuild, try to replace smooth with spiral studs.

Dave Hansen · Post by **Dave Hansen** » Mon Apr 07, 2008 8:29 pm

Can you still get them new?

The International CBX Owners Association

Cylinder studs, smooth v. spiral

Cylinder studs, smooth v. spiral

yep !!!!!!!!!!!!!

Re: yep !!!!!!!!!!!!!

hmmm

Smooth studs vs. Spiral Studs