Ducati.ms - The Ultimate Ducati Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
My 93' 900ss just passed 39k miles. I had just rebuilt the carburetors and installed a new clutch. In the re installment of the carburetors I switch the coil packs and started getting a really bad knock when trying to start. Once I switched the coil packs back the bike fired right up but quickly climbed to 5k rpm and stayed there. After turning the idle screw all the way out it still idled at 3k. I'm thinking I may have a vacuum leak from the broken head stud on the horizontal cylinder. Which I believe broke from the pre-detonation caused by switching the coil packs. This is my first Ducati and I have next to no knowledge on what I need to purchase to replace my head stud. Should I go ahead and replace them all? Any help is appreciated :)
 

·
Registered
Joined
·
913 Posts
You need a set of hardened head studs. https://ccrma.stanford.edu/~peer/Nichols/headstuds.html
It is simple to verify a broken head stud. just torque on the nut and if it spins, the stud is broken. Replacing them can be simple of very hard depending on where the stud broke and how seized it is in the cases. In the most severe cases people have had to have the studs burned out of the cases. Depending on your capabilities and the knowledge of the service folks available to you and their rates, and the luck of the draw, this is a job that can be good to have someone else do or to do yourself. The horizontal cylinder studs can be done with the engine in place, while the vertical studs require the engine to come out or be partially removed. When the vertical studs break, most people do all the studs since they are all accessible. When the horizontal studs go, most people leave the vertical studs alone since their isn't any significant labor savings from doing them at the same time and there is some significant additional cost.
 

·
Registered
Joined
·
6,561 Posts
I’m not disparaging Nichols studs. I have never heard one bad word about them. I just want to point out there are other alternatives. I went with the ARP studs because they are not tapered like both the stock and Nichols studs are. I have read reports that some of the studs besides the Nichols are not a good fit in the case threads, That did not turn out to be an issue. ARP studs are also cheaper, if price is a consideration. I don’t understand why Nichols made their studs tapered to a smaller diameter, maybe there is a sound engineering reason, but I couldn’t think of one.
 

·
Premium Member
Joined
·
4,008 Posts
Before you do anything else verify you have a bad stud.

Can you turn any of your 8 head nuts with your fingers? if no you probably do not have a stud problem.

I have never seen a broken stud do what you are describing it sounds more likely something is assembled wrong with the carburetors like the enrichener cable is out of the guide at the lever or something similar.

Back track and go slow, if the problem was not there before your repair something was touched that caused the issue you only have to find it. exhaust studs can break and cause issues but nothing you described sounds like the normal stud issue.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #5
I can turn the head stud with my fingers. It feels like the head stud is snapped about half way down the cylinder jug.
 

·
Premium Member
Joined
·
4,008 Posts
Yes if they turn that easily you do have a broken stud. hope that it is half way out and be patient on removal. They are known to break below the case surface and you will not like it if that's the case. Start by removing the engine from the frame if it is the vertical or if you plan to do them all now.

heat the case and soak the stud area with penetrent try hard to not get anything into the lower end. While the cylinders are off be sure to check the crank plug is not out and transmission for oil related wear.
 

·
Registered
Joined
·
920 Posts
OK I have a question, I just purchased a very early 1991 900ss, I am trying to do everything I need to do to get this ready to ride and enjoy--I have checked the head studs and everything is tight just as it should be, Is replacing the head studs something I should just do and be done or not, I doubt it has been done to this bike very very low miles and has been sitting for many years
 

·
Average Weird Guy.
Joined
·
1,224 Posts
Well it's your bike so it's totally up to you how you spend your money Rennsportmotorrad but the general rule of thumb is if it ain't broke don't fix it.

That being said I'm with Duc96cr,I'm not knocking Nichols products here either,but there are cheaper alternatives that will do the job every bit as good.

California Cycleworks sells American Performance Engineering (APE) heavy duty cylinder head studs for the 900SS engine. APE heavy duty cylinder head studs are most commonly used in drag racing bike engines. These studs are $13.00 apiece,so basically $104.00 for the set of 8 that you'll need to replace them all.

Realistically our little 900SS engines only make a modest amount of horsepower in stock form. The APE heavy duty cylinder head studs should be much stronger than you'll ever need.

Click me.>>>Ca Cycleworks Cylinder Studs (each) | ca-cycleworks.com
 

·
Registered
Joined
·
6,561 Posts
Yes , sorry for the mistake. APE are the studs I used . I preferred the full diameter. I replaced only the horizontal cylinder studs, though I had purchased the full Set of 8. The vertical cylinder studs never broke. Now that I have the engine out of the frame to paint it I’ll do the vertical cylinder before reinstalling the engine. The APE studs look much more robust than the spindly stock studs. They fit snugly on the threads as they should.
 

·
Registered
Joined
·
834 Posts
I replaced the studs on my '92 TWICE. Second time a stud was broken below the case interface so required a lot of time and money (about $US 900 in 1995) to repair it. So if you wait until it breaks you may be faced with it breaking in an inopportune spot and have a more expensive repair. However, they don't all break. So if I was going to have to take the motor apart for other reasons, I would replace the studs (and deal with the galley plug). Other than that I would just leave it alone and ride it.
 

·
Registered
Joined
·
1,098 Posts
It's a crapshoot how long they last. I'd probably leave them alone as long as none are broken (assuming you're not depending on it as your sole transportation to work, etc.). If/when a stud breaks, though, I'd suggest replacing them all as long as you're in there.

I bought an M900 new in 1993, and broke the first stud pretty much right away (horizontal cylinder, in 1995 at 19K miles). We didn't know yet this was a wider problem, so just replaced that one. Then a couple months later another one broke (also horizontal cylinder, at 22K), so we replaced them all (I thought). Due to a miscommunication, I thought that we had done all 8 studs then, but he just did them all on that cylinder. 16 years later (in 2011 at 196K miles), I got a base gasket leak in the vertical cylinder, and in repairing that, found that that cylinder still had the original studs, so replaced those then.

PhilB
 

·
Registered
Joined
·
6,561 Posts
If a horizontal stud breaks, no engine removal needed. Maybe I’m lazy ( ok, yes I am lazy) but I’m not dropping the motor for the unbroken vertical studs. I’ll take the gamble.
 

·
Registered
Joined
·
920 Posts
Well it's your bike so it's totally up to you how you spend your money Rennsportmotorrad but the general rule of thumb is if it ain't broke don't fix it.

That being said I'm with Duc96cr,I'm not knocking Nichols products here either,but there are cheaper alternatives that will do the job every bit as good.

California Cycleworks sells American Performance Engineering (APE) heavy duty cylinder head studs for the 900SS engine. APE heavy duty cylinder head studs are most commonly used in drag racing bike engines. These studs are $13.00 apiece,so basically $104.00 for the set of 8 that you'll need to replace them all.

Realistically our little 900SS engines only make a modest amount of horsepower in stock form. The APE heavy duty cylinder head studs should be much stronger than you'll ever need.

Click me.>>>Ca Cycleworks Cylinder Studs (each) | ca-cycleworks.com
Well just so you know I am one of those people that if I am going to fix a problem or just do preventive service I am not going to cry about the cost I do the repair correctly not cheep out and go to the hardware store to find something that may work --I am a BMW Motorcycle Master Certified Tech, so when I do something it is done as it should be or better-cost be damned
 
1 - 14 of 14 Posts
Top