Cylinder studs, smooth v. spiral

[alimey4u2]

Can you still get them new?

I think you can still get heavy duty aftermarket ones, can't remember the vendor... APE ?

[EMS]

Just try to ask for the part-number. The 10mm stud is 90031-422-003 and the 8mm stud is 90034-422-003. The two longer ones on the left engine side are 90039-422-003.

[alimey4u2]

I thought the failures were due to thermal stress caused by the temperature differential at the cylinder head. By spiraling ( effectively forming fins....Juha take note... ) That point of stress was alleviated ?? Maybe utter b*llox but it made me think...

[Juha]

I thought the failures were due to thermal stress caused by the temperature differential at the cylinder head. By spiraling ( effectively forming fins....Juha take note... ) That point of stress was alleviated ?? Maybe utter b*llox but it made me think...

Wow, do you think I could go somewhere to be effectively formed? For my head to be able to handle more stress and temperature differential? Cool, I need to learn more about this.

[alimey4u2]

Wow, do you think I could go somewhere to be effectively formed? For my head to be able to handle more stress and temperature differential? Cool, I need to learn more about this.

[EMS]

Wow, do you think I could go somewhere to be effectively formed? For my head to be able to handle more stress and temperature differential? Cool, I need to learn more about this.

Well, Juha, you are there already..not much that can be done. I think Larry referred more to the forming of new fins. Which will take a lot of fun out of those long winter nights up there....

[Juha]

Well, Juha, you are there already..not much that can be done. I think Larry referred more to the forming of new fins. Which will take a lot of fun out of those long winter nights up there....

Ahhhaaa now I think I understand... now that's something I need to put some effective effort on

[Larry Zimmer]

Honestly, I don't know. Dave, Jeff, anyone have any info on this availability?

[Mike Nixon]

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??

No service bulletin to replace the studs. Was a bulletin to seal the rear couple stud threaded holes however. Not a recall, just a service bulletin. And not for the studs, just the leak. The leak occured on the fours also, official word from Honda porosity of cases in area of drilled stud holes, nothing to do with the studs. Although Honda used the spiral studs on all their car engines before putting them on the CBX and later model bike engines, I am not convinced it's as big a deal as people make it to be.

[daves79x]

Mike:
I always assumed there was at least a dealer bulletin on the studs, because my dealer called me to replace mine in late '79. I had them do it, and I assumed then that many others did also, but I have never heard of anyone else's dealer doing it. How could my little dealer out here in the middle of nowhere have found out about it?

Dave

[Mike Nixon]

Mike:
I always assumed there was at least a dealer bulletin on the studs, because my dealer called me to replace mine in late '79. I had them do it, and I assumed then that many others did also, but I have never heard of anyone else's dealer doing it. How could my little dealer out here in the middle of nowhere have found out about it?

Dave

Dave -- I suspect, as I say, he was referring to the stud reseal bulletin. Again, I could be wrong, I will check when I get home from being on the road, but I don't believe there was a stud bulletin, just a stud reseal bulletin. What the bulletin had us do was remove some of the rear studs, smear red silicone on their threads, and reinstall them. I'll check.

[daves79x]

Mike:
It would not surprise me if you found a bulletin to replace the studs. I'm remembering that the dealer showed me something from Honda about it. It was a total warranty job. I also remember about the leaking issue. Anyway, I think you are right, it's probably no big deal and not worth doing unless you have an upgraded set and the engine is apart.

According to the parts book, '79 engines up through number 3478 had the smooth studs. So there are a lot of them runnung around alive and well with the smooth studs.

Dave

[EMS]

Mike:
So there are a lot of them runnung around alive and well with the smooth studs.

Dave

I checked my records and of 70 1979 CBXes that I could record over the last 3 years, only 18 had numbers that low. Only roughly 15% of all 79 CBXes produced were made before the change. My guess would be, that not more than maybe 2,000 bikes are still there that have engine numbers below ...3478, and how many of those have still smooth studs? And how many are being ridden in a way that a problem would occur?

[CBXter]

My 79 has the smooth studs, my engine number is 940 very early number I believe, I do have a very minor issue with gasket seepage around my heads but it's not enough to justify engine rebuild and stud replacement.

[daves79x]

Mike:
Well, relatively a lot. I have taken note over the years of '79s I've seen and every one except mine with an engine # below the 3400 or so still had the smooth studs. I have 3 engines here that have them as well. The East coast got many '79s in the serial # range (frame) of 750-2500 in the first shipments to Baltimore. You used to be able to predict that any '79 CBX you found in the Mid-Atlantic that was sold there the first year would be in that range. Now, they have gotton so mixed up around the country(world), it's hard to follow the lineage of any particular one.

A couple of notable very low 3-digit serial numbers have show up here in the region that were supposedly sold here new as well, but it's hard to prove. Kind of interesting to follow if you are into serial numbers - probably a real yawner if you're not.

Dave