Big-Sert spark plug repair

Does anyone have the Big-Sert repair kit for the spark plug hole they'd be willing to lend out? Someone used a Helicoil on the Ducati and of course it's failing. Luckily the Norton is fine, maybe they used better alloy? :mrgreen:

Of course I need to check out the other Norton that's on its way. It's pretty rough although I don't think it would have Helicoils, just boogered threads.

swooshdave said:

Does anyone have the Big-Sert repair kit for the spark plug hole they'd be willing to lend out? Someone used a Helicoil on the Ducati and of course it's failing. Luckily the Norton is fine, maybe they used better alloy? :mrgreen:

Of course I need to check out the other Norton that's on its way. It's pretty rough although I don't think it would have Helicoils, just boogered threads.

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Yes

I did a Big Sert on my 72 Commando to repair a failed Helicoil solid insert. Not sure how this translates to a Ducati head but here are a couple of observations. On a Commando the Big Sert ends up almost touching the outer edge of the valve seat. It's worked out okay with good compression but looks a little spooky. Don't know how hard it is to to pull the head on the Ducati but it would make things a lot easier. On a Commando you can't have piston at tdc or the tap will hit the piston, it has to be down in the bore a ways. I did it with the head in place, I thought I was on the compression stroke but I was on the intake and damaged the intake valve which was starting to open. Then I had to pull the head and replace the valve. Be very careful about intersecting the valves because of the oversize tap on the Big Sert. If I was doing it again with the head on, I think I would back the adjusters off to make sure the valves were completely closed. But pulling the head is probably the best idea. It also makes dealing with the swarf easier. I packed the tap with grease and backed it out 4-5 times to remove the swarf as I went along. By the time it cut the final threads it had very little left on it. I also duct taped a small hose inside my shop vac hose and cleaned any remainder out. Be sure and use the red high temp loctite. I've had the plug out numerous times since the repair with no problems.
failed-helicoil-plug-fix-t20622.html

Pulling the head is supposedly simple, compared to a Norton. Plus it's the front head so it's just hanging out there. But I've never pulled a bevel head so it's going to be either really easy or impossibly hard. I need to check the back head to see if it has a Helicoil too.

the heads on a bevel are easy to pull. the vertical has 3 o rings and horizontal has 2 o rings for the oil passages. you will need to watch the timing marks on the gears but the tower shaft will only go together one way as each half is flat sided ( think a half lap joint ) IIRC it takes something like 80 revolutions of the crank for ALL the marks to realign.

swooshdave said:

Pulling the head is supposedly simple, compared to a Norton. Plus it's the front head so it's just hanging out there. But I've never pulled a bevel head so it's going to be either really easy or impossibly hard. I need to check the back head to see if it has a Helicoil too.

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I would not recommend installing a bigsert in a Commando head. It comes very close to the valve seat.
I have seen a few cases where the thin section cracked and the compression leaked under the seat. Jim