The 1956 Harley ST165 "Hummer" rebuild begins today!

[Squiddley]

Or start with getting the compression right with a new head gasket and going from there,never had one run right with low compression.

 

[Risk Man]

Pulled the head last night. Looks like seepage under gasket at cylinder surface… plenty of residue left after gasket off. Can not flatten head easy enough but scraping crap off top of cylinder and not being able to flatten it in place sucks… dont want to remove cylinder, though it is possible without removing engine, but must take at least one stud out, then worry about lower gasket tearing and re sealing etc, All better done with engine off But that my friends requires manny other parts and wires off first, Going to try to get it sealed after cleaning and using RTV HIGH temp on both sides of gasket.. i have two new gaskets if i gave to start over… PITA… should have been more careful on head bolts on first rounds of heat treatment which i did not do until 3d 5 minute interval…..

 

[Risk Man]

Pulled the head last night. Looks like seepage under gasket at cylinder surface… plenty of residue left after gasket off. Can not flatten head easy enough but scraping crap off top of cylinder and not being able to flatten it in place sucks… dont want to remove cylinder, though it is possible without removing engine, but must take at least one stud out, then worry about lower gasket tearing and re sealing etc, All better done with engine off But that my friends requires manny other parts and wires off first, Going to try to get it sealed after cleaning and using RTV HIGH temp on both sides of gasket.. i have two new gaskets if i gave to start over… PITA… should have been more careful on head bolts on first rounds of heat treatment which i did not do until 3d 5 minute interval…..

I am finding out that these "expert" engine rebuilders don't flatten the head and jug "unless it looks messed up".....I cleaned up the goop on the cylinder head, but won't be able to hone it in place. Did the Head and it looks great.

 

[Risk Man]

Finally had a chance to get back to the Harley engine improvements. I put the new gasket on using Permatex High Temp gasket maker in a thin layer on both sides of the gasket. After tightening the head bolts to 135 Foot Pounds, I let it dry for 48 hours just to be sure.

Ran it in the driveway with the fan on it for 5 minutes. Cooled down and was surprised at how much the head bolts had loosened. Almost half a turn. Got a new compression gauge and easily got it up to 100 lbs. They say 90 on these engines is good. So compression is not a problem.

Next 7 rides were 8 minutes at under 30mph. Cool and re torque bolts. Gradually they took less and less turning to tighten with after the 7th trial they remained to torque.

Not sure yet if this leak solved my top end problem. Going to do a 15 minute ride today and one more torque check before taking it out of the Hood on the highway this weekend. Also noticed that the recommended plug does not go all the way into the chamber. Got an NGK plug that is just slightly longer but one more heat range hotter. Will try that this weekend as well, mindful of overheating. STay tuned!

 

[Chainlube]

Finally had a chance to get back to the Harley engine improvements. I put the new gasket on using Permatex High Temp gasket maker in a thin layer on both sides of the gasket. After tightening the head bolts to 135 Foot Pounds, I let it dry for 48 hours just to be sure.

Ran it in the driveway with the fan on it for 5 minutes. Cooled down and was surprised at how much the head bolts had loosened. Almost half a turn. Got a new compression gauge and easily got it up to 100 lbs. They say 90 on these engines is good. So compression is not a problem.

Next 7 rides were 8 minutes at under 30mph. Cool and re torque bolts. Gradually they took less and less turning to tighten with after the 7th trial they remained to torque.

Not sure yet if this leak solved my top end problem. Going to do a 15 minute ride today and one more torque check before taking it out of the Hood on the highway this weekend. Also noticed that the recommended plug does not go all the way into the chamber. Got an NGK plug that is just slightly longer but one more heat range hotter. Will try that this weekend as well, mindful of overheating. STay tuned!

Check the threads in the head if the plug doesn't seat.

 

[Risk Man]

UPDATE: Have about 50 miles on the new gasket and head reseat, with at least 8 re torqueing of the head bolts to where they are finally stable. Found that the sputtering and no high end power (besides the engine not really broken in yet at less than 225 miles) was way too rich. Moved the needle back to center and it was better. Still too rich. Moved it all the way tot he top and much better, with top speed now at 45, but still not there. Put in hotter NGC plug with little difference but still runs cool at 280 degrees after 10 mile ride.

My mechanic in TX says might need the smaller jet (no 5) of the early 1948 125cc which he said is unusual. But, he has sent me one to try and it arrives on saturday. He said i might need to "drill" it out to no 6. While I know I can buy these micro jet drills, what do you use to drill with Small hobby hand drill?

 

[Johnny_]

UPDATE: Have about 50 miles on the new gasket and head reseat, with at least 8 re torqueing of the head bolts to where they are finally stable. Found that the sputtering and no high end power (besides the engine not really broken in yet at less than 225 miles) was way too rich. Moved the needle back to center and it was better. Still too rich. Moved it all the way tot he top and much better, with top speed now at 45, but still not there. Put in hotter NGC plug with little difference but still runs cool at 280 degrees after 10 mile ride.

My mechanic in TX says might need the smaller jet (no 5) of the early 1948 125cc which he said is unusual. But, he has sent me one to try and it arrives on saturday. He said i might need to "drill" it out to no 6. While I know I can buy these micro jet drills, what do you use to drill with Small hobby hand drill?

This is the one I got for jet drilling and it works great....

Amazon.com

You can also get the kits that have the sizes marked.

Amazon.com

 

[Wrench]

To use micro drill bits with a normal chuck
Use a piece of stranded copper wire, Pull out a strand or two and insert the micro drill bit in the center
Now the chuck will grip the micro drill bit