Cylinder studs
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6th Gear
Joined: May 2020
Posts: 12
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From: Illinois
Cylinder studs
I started to tear down my 1999 evo engine and noticed the head bolts were really hard to undo. After I finally got enough leverage on them, they came out. One of them unscrewed the cylinder stud with it. The hole doesn't look like the thread has stripped and apart from the unscrewing they all look in good condition. Anyone else had the same thing happen? Is it worth replacing the studs with some S&S ones or something similar.
The engine has been sitting for the last 11 years but has only done 1300 miles just want to be sure everything is kosher before I put the bike together. Anyone have any thoughts?...replacing bearings, splitting the cases, vapor blasting?
So it's like I'm starting with a fresh engine.
I have a Mikuni HSR42 carb, adjustable push rods and an Andrews EV 27 cam to go it.
The engine has been sitting for the last 11 years but has only done 1300 miles just want to be sure everything is kosher before I put the bike together. Anyone have any thoughts?...replacing bearings, splitting the cases, vapor blasting?
So it's like I'm starting with a fresh engine.
I have a Mikuni HSR42 carb, adjustable push rods and an Andrews EV 27 cam to go it.
Stellar HDF Member
Joined: Aug 2020
Posts: 3,182
Likes: 2,225
From: College Station, TX
Yeah, that's fairly common. It happened to me last time I removed the top end on an EVO engine, and as long as the case threads are good then you should have no problem replacing them. Be sure everything is clean, including the case thread holes so the studs can bottom properly and provide the correct stud length.
S&S cylinder studs are a good option, but replace the head bolts too. But pay careful attention to make sure the threaded holes in the cases are clean and oil free. But be careful to not remove any thread material that would weaken it, meaning I wouldn't run a tap in the threads unless absolutely necessary to start the studs. And, make sure the cylinder bases are clean and true. I had about .001-.0015 removed last time, and then assembled without gaskets to verify piston deck height to calculate which thickness base and head gaskets to use. Ideally, having .030-.035 squish is beneficial. Based on that, I used a Cometic MLS .030 head gasket.
While you are in there, I'd still have the cylinders check for true and then hone and replace the piston rings. As well as have the heads reworked. If the engine only has 1300 miles on it total, it may not need a valve job, but I think I'd still replace the valve stem seals.
Paul
S&S cylinder studs are a good option, but replace the head bolts too. But pay careful attention to make sure the threaded holes in the cases are clean and oil free. But be careful to not remove any thread material that would weaken it, meaning I wouldn't run a tap in the threads unless absolutely necessary to start the studs. And, make sure the cylinder bases are clean and true. I had about .001-.0015 removed last time, and then assembled without gaskets to verify piston deck height to calculate which thickness base and head gaskets to use. Ideally, having .030-.035 squish is beneficial. Based on that, I used a Cometic MLS .030 head gasket.
While you are in there, I'd still have the cylinders check for true and then hone and replace the piston rings. As well as have the heads reworked. If the engine only has 1300 miles on it total, it may not need a valve job, but I think I'd still replace the valve stem seals.
Paul
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
Likes: 7,638
From: Poolville
Just get one OEM stud and replace it. Don't do the rest.. Earlier Evo's had a tendency to pull a stud not the later models. And If I recall the the thread design on the stud and case are not standard SAE thread pitch. The thread is more square than pitched and this is why you don't want to run a standard tap to chase the case.. Use red loctite and torque to I believe 10 foot pounds and let sit for 24 hours before assembling. Trueing the base is a good idea but don't worry about the rings or even honing. Just make sure all is very clean upon reassembly...
Cruiser
Joined: Jan 2019
Posts: 162
Likes: 50
From: NY
I just had the same thing happen. One stud came out with the head bolt. I replaced the stud with an S&S that I had and used new head bolts. I had to run a thread chaser into the case because the new stud has regular threads vs the interference fit threads of the oem stud. So far so good with 25 miles on the odo....
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