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Feb 05, 2012, 11:09 PM
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autowrench's Avatar
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Saito .91 Rocker Shaft Thread Repair

Thought I'd share my recent experience with repairing the best running engine I've ever had, a .91 Saito Golden Knight that I bought about 7 years ago.

I noticed a louder than normal "clicking" in the top end & discovered the exhaust rocker arm shaft had loosened and damaged the threads to where it would not tighten up which made it impossible to adjust the tappet clearance . I was bummed and especially in these economic times I was looking for the least expensive way to fix it. My alternative was to purchase a new cylinder & probably at least a new piston ring for $115-120 plus shipping & tax not to mention I'd probably have to do some "break-in" on the new parts.

After talking to a number of folks, creatively brainstorming on different repair options & looking through some forums I had come to the conclusion I was going to have to break down & spend the money but then I realized the threads were 3mm X 0.50, pretty standard stuff so I located a heli-coil kit with no difficulty at all and for about $46 I seem to have satisfactorily fixed it.

The first step of drilling out the damaged threads and making sure it was square was a little nerve-racking but the next step seemed to be more crital and a little easier as I carefully lined up the special thread tap and cut the new threads making sure as I went that everything looked good and straight. I then ran the insert from in between the rocker arm supports outwards so I could more easily remove the excess material, which also allowed me to confirm proper fit and depth on the rocker pin and I actually ground the excess insert material with the pin in place and tight which probably kept the Dremel bit from spinning it right out of place.

In addition the heli-coil kit came with another 19 inserts and the same threads are used in mufflers and a handfull uf other applications so it might save me more in the future.

BTW, in my research I discovered that on the larger, 120 & up Saito's the rocker housing by itself is available.

I hope this will help someone in the future and I might consider selling the heli-coil kit for half price if anyone is interested.
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Feb 05, 2012, 11:28 PM
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autowrench's Avatar
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Forgot to add photos to the previous post.
Feb 06, 2012, 07:54 AM
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earlwb's Avatar
That is a really nice repair job you did there. It is looking really good.
Feb 06, 2012, 11:18 AM
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You might have gotten a cheaper price from B.J.'s or Mr Clarence Lee. However, your fix looks great and now you have spares for future applications.
Feb 06, 2012, 04:12 PM
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CSpaced's Avatar
Nice job on the repair Bob! That Saito runs like a Swiss clock, glad you were able to save it!
Feb 06, 2012, 07:26 PM
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autowrench's Avatar
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Originally Posted by Chip01
You might have gotten a cheaper price from B.J.'s or Mr Clarence Lee. However, your fix looks great and now you have spares for future applications.
Granger wanted almost twice that price so I thought I was doing OK with what I did spend, the one I got came from Zoro Tools in IL whom I found on line and I received it within days of ordering so their service was great. I'll keep the others in mind for any future needs, thanks!
Feb 06, 2012, 07:29 PM
Registered User
Nice repair.

Had the same thing happen. I found next size up SAE bolt/screw. Tapped the hole with the threads messed up to the correct size. Cut the head off the bolt/screw and slotted it with my dremel. Screwed it in with a little blue loctite. Didn't even have to re-size the rocker arm. $6 including the tap I had to buy.

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