Cylinder studs, smooth v. spiral

[EMS]

The interesting issue then is, that the change happened so early and that many motors were not done. I would think that none of the very first bike was out of warranty before bike with engine no 3478 was delivered and the new studs were in production. If there really was an official program by Honda to have the studs changed, I would think that all bikes under warranty would have been done

[Mike Nixon]

As you'll recall, there were only four (very few) factory service bulletins that addressed the CBX specifically. There were a number that touched on it tangentally (for example, the Wrench technician newsletter that explains the hash mark codes on the valve lifters), but only four official "CBX" only bulletins.

http://www.cbxclub.com/protect/hsbcbx1.pdf

#1 announced the special oil filter part number that later became the default number for the current models.

http://www.cbxclub.com/protect/hsbcbx2.pdf

#2 recommended the fitting of spacers at the swingarm on selected units.

http://www.cbxclub.com/protect/hsbcbx3.pdf

#3 was the gooping the stud bulletin.

http://www.cbxclub.com/protect/hsbcbx4.pdf

#4 was the infamous updated ignition advancer bulletin.

None of these are recalls by the way, just limited service bulletins, and the stud seal one does not recommend the replacement of the studs.

If a dealer said a bulletin called for replacement of the studs, he was speaking unilaterally, not on behalf of Honda. Furthermore, while there may be a memo or bulletin that in the middle of addressing general service issues on the Honda product (various models) briefly mentioned the spiral studs introducecd on said models (there could be, but I don't recall it) that is not the same as calling for the replacement of the other stud types. This may be, if it exists, what the dealer was referring to, though if so, it is a misinterpretation.

Bulletin #1 is information only, no warranty, no response required.
Bulletin #2 is also information only, no warranty, no response other than a special procedure during the normal course of maintenance.
Bulletin #3, while it does not mention warranty, was in fact covered under warranty. I was there, on both sides of the issue. While at American Honda, I paid dealers to do the repair, and while a tech at a dealership, I did some of the repairs. The coverage of the bike was only 6 months remember, so most bikes covered, when they were in fact covered, were out of warranty and were done for customer goodwill, not as true warranty. But notice, again, the studs were sealed, not replaced. It was crankcase porosity at the bottoms of the threaded holes, and only those at the rear of the cases, near the oil galley. Note also the problem did not include any other model but the 79 (although Honda did pay to fix some 80 models also).
Bulletin #4 both specifies warranty coverage and payment and recommend the work on certain models.

I am still on the road, so I have yet to check my files. However, I don't think you're going to find a CBX bulletin that recommended cylinder stud replacement. :)

[Ringnalda]

Chiming in a little late, but the reason that Honda replaced the smooth studs, was indeed because they would crack (usually flush with the crankcase) after some time. When Honda tested the CBX engine to destruction (10,000 RPM for 20 minutes) the engine failed due to a broken smooth head stud. At Marlington some years ago we actually replaced the studs in a CBX club member's bike in two days, but this was after one of the studs had broken flush with the crankcase. If the studs are OK, the job can be done from the top without breaking any gasket seals in about 2 hours. Question is, How lucky do you feel? If you have smooth studs, and you feel your pant leg getting warm and notice a lack of traction from your rear tire, that'll be a strong indication that you may have just sheared a stud... Cheers, Jan

[msnitker]

Well, this is good information. A few ?s--I found some NOS studs, spiral type. According the microfilm, there are 2 lengths of the 8 MM studs-

1. Does the 221 MM and 222 MM difference matter?

2. Do you think I can mix and match spiral and smooth studs, as some are NLA, and the smooth studs I have appear fine.

Thanks

[CBX-tras]

1. Used spiral studs are available from private sellers, just ask.

2. It's unlikely that 1mm can make a difference. I've learned that you only need 3 full threads of engagement anyway.

3. I've never seen (not that it hasn't happened) a broken smooth stud in all of the motors I've built/serviced. And, that's a lot.

[msnitker]

1. Used spiral studs are available from private sellers, just ask.

2. It's unlikely that 1mm can make a difference. I've learned that you only need 3 full threads of engagement anyway.

3. I've never seen (not that it hasn't happened) a broken smooth stud in all of the motors I've built/serviced. And, that's a lot.

Thanks for this--all makes sense, and appreciate it.