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Bad Day: Triumph 650 Cracked Cylinder Skirts

1722 Views 4 Replies 4 Participants Last post by  Frank D
Yesterday was a bad day for my 67 Triumph Bonneville Build. Brought my cylinder jugs to the machinist to have them bored. After glassbeading the first jug i look and find a hairline crack in the skirt. I say alright good thing I have another jug. Take that one out of my truck and what do I see... another hairline crack.

The pictures are of both cylinders and the cracks in each.

Has anyone has success welding something of the sort. My machinist said he is not comfortable with doing that...

As another alternative has anyone ever sleeved a cylinder in such a case...

Any input is appreciate!

*As a 5 thou an acceptible piston to bore clearance using Emgo pistons and Hastings rings. After looking at the manual I did some searching and found that lots of people seem to have different views on what is 'correct'.


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yes, they can be sleeved, but it costs about 80% of what new cylinders cost to sleeve them, you can get brand new English made jugs for $400.
and the .005 clearance is a bit loose, most times we set them up at .0045 clearance for a street motor, race motors are set up at as tight as .002,
much of that has to do with the piston quality, the Taiwan pistons are fine at .0045 clearance.
I've brazed them a couple times when the crack was tight and well below where the rings travel. Not very good with torch, did an ugly job, both those bikes run fine for some time now. Might not even have needed to do anything.
Thanks for the input guys. It just kills me to drop 400 on a set of jugs while these expensive paper weights stare at me. I have one more set at my parents house that I need to check out. Unfortunately these have a cracked fin but if the cylinder bores look ok I will try to repair the fins. I guess the tech article on fin repair came at the right time.
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