Hi, I just bought a 93 1200 from a guy that says he just had new pistons and cams put in. He says it doesnt have as much power as it did before.
I got it for my wife for 2300 bucks. Looks great, seems to run well but I never had a Harley so I dont know what to expect.
I checked the compression and get 120 in the back cyl and 110 in the front.
These numbers seem a bit low to me. If they are, does someone have a suggestion what might be the problem?
Thanks....B

 

You have any specs on the pistons and cams? Both of those can affect the compression ratio dramatically.

 

No, i think he put in stock pistons but not sure. I dont have a clue what cams he used. I scoured the paperwork he gave me but only saw mention of r/r the cams because the bike wouldnt run at all after the rebuild

 

Well according to the HD manual for the newer rubber mounts:

883 125-140psi
1200 200-225psi

Unfortunately I don't have the manual for the older models like yours. It's prob close but yours definitely has different heads and cams, maybe other parts as well.

Even with the differences I'm guessing that the 110 is a little low. If you have a air fitting that connects to your sparkplug hole you can fill the cylinder with air from a compressor. With the engine on the compression stroke you should hear the air bleeding down if it is leaking.

Most popular culprits would be the rings or valves. Remember that a leaking valve can be caused by other things too, like the cams, rockers, pushrods, etc.

 

Thanks, I really appreciate the input. I think Ill make an air fitting and see if I can hear anything leaking in the cylinder. Probably save me from taking something apart that I dont have to.
Thanks again
B
PS.. I have the 92 93 Harley manual but dont seem to see the figures in it. I'll look again

 

Most likely the compression test fitting can be treaded onto an air compressor quick connect. At least worth a try.

If it helps, I found it in the "Troubleshooting" chapter of the newer manual.