Wildguzzi.com
General Category => General Discussion => Topic started by: arbezc on January 31, 2023, 08:02:04 PM
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Greetings folks,
As part of a rebuild I’m replacing all the crank related bearings on my 1980 LeMans II. The only remaining concern is my wrist pin clearances. At right angles to the connecting rods they are: left 0.0022” & right 0.0027”. In line with the con rod they are 0.001” narrower & within Guzzi’s clearance of 0.0008-0.0018”. I was surprised that most of the discrepancy is at right angles to the stroke. Both the pins & bushings look very smooth, there’s no scoring. The engine has 94,000 Km (about 58K miles) on it.
MG Cycle has bushings but is out of stock on wrist pins. My plan was to assemble the bike as is, ride it a season or two & assess whether to change out the pistons & cylinders. They’re slightly scored but still hold decent compression & don’t burn oil. Could you advise on the following?
• How critical is the wrist pin clearance if speeds are kept below 6,000RPM? (I'm conservative)
• Is there an alternate source for wrist pins? I seem to remember that some VW pins work.
• Does anyone know of a source that could install & ream the bushings in Ontario?
Thanks in advance,
Charles
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Try to find longer pins like my V700 uses, SOL. Lot's of places have yours if you look around. Look to EU.
Any competent auto machine shop can install the bush's and fit to pins. Pull rods & take em in.
Check & see if you have cast liners, can replace them from LA sleeve.
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I needed lighter wrist pins for a customer's Eldo when I put "big bore" kits on it. There are companies that will make anything you'd like. I ended up buying Wiseco wrist pins and had them machined to the proper length. Lost 25 grams each compared to the originals. I could have had this company make some for me that were 50 grams lighter, but I didn't think the customer would understand me spending $200 on wrist pins. :grin:
https://www.pppcenter.com/wrist-pins
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Greetings folks,
As part of a rebuild I’m replacing all the crank related bearings on my 1980 LeMans II. The only remaining concern is my wrist pin clearances. At right angles to the connecting rods they are: left 0.0022” & right 0.0027”. In line with the con rod they are 0.001” narrower & within Guzzi’s clearance of 0.0008-0.0018”. I was surprised that most of the discrepancy is at right angles to the stroke. Both the pins & bushings look very smooth, there’s no scoring. The engine has 94,000 Km (about 58K miles) on it.
MG Cycle has bushings but is out of stock on wrist pins. My plan was to assemble the bike as is, ride it a season or two & assess whether to change out the pistons & cylinders. They’re slightly scored but still hold decent compression & don’t burn oil. Could you advise on the following?
• How critical is the wrist pin clearance if speeds are kept below 6,000RPM? (I'm conservative)
• Is there an alternate source for wrist pins? I seem to remember that some VW pins work.
• Does anyone know of a source that could install & ream the bushings in Ontario?
Thanks in advance,
Charles
I would examine the wrist pins carefully. If they measure good, look good, and have no apparent defect then you really don't need to replace them. Any *competent* auto machine shop can size the bushings, but here in S. Florida I've found that outboard motor machine shops are faster, more accurate, and cheaper than automotive. I can vouch for https://www.pppcenter.com/ , they made the adapter bushings to put Ford Y-block lifters in my '85 LeMans.
You've illuminated something for me, my '89 Mille clangs like a bell when warm and even with the cylinders off I couldn't find reason. Now I'll have to go back and check the side clearance on the rod bushings.
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Thanks for the advice guys,
This is a LeMans II so the cylinders are Nikasil. I fully removed the wrist pins & re-measured to 1.9999mm, they should be usable. The micrometer was calibrated with gauge blocks. I'll double check the bushings but they can be ordered from MG Cycle. Lightened wrist pins is good to keep in mind if I upgrade to larger cylinders. It will be good to hear this bike run again, the LM II is a pretty decent touring machine.
Charles
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The last time I replaced small end bushings, I used steel backed bronze bushings instead of full bronze bushings. They supposedly are better but might be overkill, I don’t know what they use from the factory now, at that time it was all bronze. I think they were an industry standard VW part, 22mm. In my opinion, it takes more care in fitting than full bronze ones.