webbie
XS650 Member
Hey all, first time posting to the forum - though I've been around on the 650garage and a few others.
I'm not new to the xs, however. Mine (1982 Heritage Special) has been in a perpetual status as project / PITA for a few years now. Bought it straight out of a muddy ditch next to some guy's house in Queens, and I've been slowly nursing it back to roadworthiness since.
I've not had the time or money to do a full rebuild prior to now. Finally, I decided to make a proper attempt, and I've stripped the bike to the frame for cleanup, painting, wiring, etc. I've got a PMA + CDI kit from Hugh's ready to install upon reassembly, and I'm looking forward to a running bike. I also decided to freshen up the top-end with gaskets, valve-lapping, etc. I was under the impression that the mileage was low, but I'm not so sure now, based on the number of wear-items.
I should mention - this is my first engine rebuild. I haven't gone deeper than replacing the head prior to this, so I'm trying to learn quickly.
Took the jugs+pistons to a machine shop today and the verdict (on the worse of the two cylinders) is:
Min diameter 0.002" (0.0508mm) over spec and 0.0015" (0.0381mm) out-of-round. Stock 75.01mm.
Associated piston is 2.950" (74.93 mm). Stock 74.959 mm.
Giving me an estimated PTW clearance of approx 0.0051" (0.13 mm), compared to a stock number of 0.002" (0.051 mm) - if I'm not mistaken.
In summary, I think I need to go with a bore and oversize pistons. The machinist recommended the same. I want to do everything *right* while I have the engine out and in pieces, I also want to keep this on a short-ish budget (most of which went into the PMA+CDI conversion). Would I be committing some grave error if I sought out some used oversize pistons and bought them at a discount? I'll need new rings, of course, but the machinist suggested bringing him a set of pistons and a desired clearance so he could give me well-matched bores. Any reason I couldn't bring him a set of minimally-worn pistons?
I'm not new to the xs, however. Mine (1982 Heritage Special) has been in a perpetual status as project / PITA for a few years now. Bought it straight out of a muddy ditch next to some guy's house in Queens, and I've been slowly nursing it back to roadworthiness since.
I've not had the time or money to do a full rebuild prior to now. Finally, I decided to make a proper attempt, and I've stripped the bike to the frame for cleanup, painting, wiring, etc. I've got a PMA + CDI kit from Hugh's ready to install upon reassembly, and I'm looking forward to a running bike. I also decided to freshen up the top-end with gaskets, valve-lapping, etc. I was under the impression that the mileage was low, but I'm not so sure now, based on the number of wear-items.
I should mention - this is my first engine rebuild. I haven't gone deeper than replacing the head prior to this, so I'm trying to learn quickly.
Took the jugs+pistons to a machine shop today and the verdict (on the worse of the two cylinders) is:
Min diameter 0.002" (0.0508mm) over spec and 0.0015" (0.0381mm) out-of-round. Stock 75.01mm.
Associated piston is 2.950" (74.93 mm). Stock 74.959 mm.
Giving me an estimated PTW clearance of approx 0.0051" (0.13 mm), compared to a stock number of 0.002" (0.051 mm) - if I'm not mistaken.
In summary, I think I need to go with a bore and oversize pistons. The machinist recommended the same. I want to do everything *right* while I have the engine out and in pieces, I also want to keep this on a short-ish budget (most of which went into the PMA+CDI conversion). Would I be committing some grave error if I sought out some used oversize pistons and bought them at a discount? I'll need new rings, of course, but the machinist suggested bringing him a set of pistons and a desired clearance so he could give me well-matched bores. Any reason I couldn't bring him a set of minimally-worn pistons?
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