Running great until it quit! No compression now

smkummer

My 72D always ran (had it now for 5 years) and it was running outstanding (18-19 mph on the flat) when I changed points and put a new drive belt on it. So while I was seeing if I could hit 20 on the gps it was loosing power going down hill and then it just quit. I wore the battery down trying to start it but only an occasion pop. Towed it home and finally discovered it has no compression at all on 2 difference compression gauges. So is it broken rings, piston or reed valve? Where should I start? thanks ahead of time.

BGW

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Whitespider

Pull the head... have a look... likely rings.

smkummer

That is what I figured. If needed can I do top-end work with the engine still in the cart?

Lochlin

Yep. New piston and rings are pretty easy. Should take all of an hour or two. If you are ordering stuff, order a couple of extra rings as they are cheap. They can break pretty easily when putting everything back in the cylinder so it's nice to have a couple spares.

smkummer

OK, guys it was rings and more. I check the air cleaner and if wet, it would have been the reed valve but it was dry as a bone. This came apart easy. I used a C-clamp to remove the piston pin. It appears the top ring was gone for awhile and when the second ring cracked (but was still in place) that was it for compression. The worn piston area is close to the exhaust port. Ne metal was seen in the engine base and while the connecting rod has sideways clearance it almost has no up/down movement . The crank/connecting rod rotates smooth with no knocking. I have to go to work for a few days and then my hope is to find a shop to rebore/smooth the cylinder and fit a oversize piston and rings.

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Whitespider

I bought a new cylinder, piston, rings and gaskets in a set for something like $125.oo a couple years ago on EBay. You might wanna' check around... even at around $200.oo it would likely be as cost effective as boring and fitting a piston. Machine shop work ain't cheap these days.

Whitespider

Here ya' go, everything ya' need for $120.oo... and you'll likely have it at your doorstep in less than a week.

http://www.buggiesunlimited.com/golf...n-assy-co/4550

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Jwetovick

This the route i went. 27 bucks to ship but still at roughly 150 it is reasonable. I installed mine and it has worked great! Got a great running cart, for now. I did have to sand down every ring to get within spec so make sure you check end gap or u will have problems.

smkummer

Thanks guys, I just got home. I called a old time Harley mechanic and am waiting for his call back to check on re-boring. As you can see, it has a visual scoring of two notches and my finger nails can feel the notches in the cylinder. I notice the Harley shop manual states one can go .040 over and I think I am within spec. to do that. I'll see what reboring costs and compare. This is my first top-end re-build, if this goes well, I'll be ready to take the heads off my flat head 1940 Indian chief and de carbon the heads and install new head gaskets as they are leaking after 14K miles. Update. Ok, I see buggies gone wild has piston ring kits from standard all the way to .070 over. Has someone here gone more that .040 over (the most Harley recommended) and had any issues? thanks If the price is the same I kind of want to use my original cylinder.

smkummer

OK, took it to a machine shop and he stated he would first try .020 over and if needed go to .040 to see if it works. Then if needed he would go all the way to .070. I somewhat see why Harley never went beyond .040 as it starts getting pretty thin. He measured the cylinder and checked the piston and I am starting from a standard bore. He is charging me $50 for the machining and crosshatching the cylinder bore.