Very high compression on 1972 H2 motor

[mraxl]

"Okay, I've bought a decent compression gauge and fittings, and have tried cylinders with one, two and three normal head gaskets which gave around 125 - 130, 110 -115 and 90 to 100 psi. All three cylinders were pretty consistent."

A lot of talk about high compression but if those readings are accurate compression is actually LOW. Stock should be 140-145 psi.

[kawonda750]

So, what ever happened with this?? Very curious.

[speedgeeza]

Just getting back to triples after a hiatus. I have experienced a situation where the cylinder was bored and a Wiseco piston used, the L top ring actually hit the edge of the combustion chamber due to the new, larger diameter. If the cylinder was bored second or third over, this could be quite a mechanical interference, and not excessive compression.

[Grant]

There have been some questions:

I am using BUHX surface gap plugs for my compression kicks just to make sure that nothing protrudes into the combustion chamber. The tops of the pistons show no tell tale marks from spark plugs in their light coating of carbon.

The low pressure reading I attributed to the 18" of pressure gauge hose and it's adapter which has a volume of a 1/4" socket bringing more volume to the compression chamber reading.

In the process of selling 6 bikes so I can have some room to work in during the cold weather this winter. I'll pull the heads and cylinders off and check everything.

Grant

[Grant]

Well. I findally cleared enought room out of the garage to put the H2C up on the bench.

I pulled the heads, cylinders and pistons off. I used the turkey baster method to remove two shot glasses of oil from the right cylinder and the others were pretty clean (using a borescope).
Brought everything inside to warm up ( no heat in garage and better lighting ). While I was pulling the rings of the pistons I found hardened carbon jamming up almost everything especially the locating pin area at the rings end gap. This was really caked in on every and so I'm suspecting that there was no route for the compressed gases to easily escape when the motor was stroked. This is problem #1 that I found, I made up a scraping tool from a 6" flat file and cleaned every bit of junk out that I saw. Each piston had an amount of carbon roughly equal to a cube with 1/4" dimensions.

The next problem (#2) I found was that the RH piston has a spot where it is difficult without some pushing to move the piston through the cylinder even without rings, it was located just below the ports area. It was so bad that it would only move by gravity alone 1/2" in the inverted cylinder before binding (I tried all three pistons in all cylinders). I used some sandpaper to try and find burrs but none seemed present, I measured against the other two cylinders and the RH cylinder was -0.035" narrower at a point 45degrees to the crank shaft. Figured whoever bored out the cylinder for 50 over pistons had a problem that they didn't notice and threw the engine back together.

Spent 6 hours trying to find my hone last used about 15 years ago but finally found it and spent about 5 minutes at low spring pressure with a hand drill trying only to hone the area around and below the ports before the hone disintegrated on the cylinder liner cutouts and ports (old age of hone) but that was enough so the piston will now without rings drop through the cylinder like the other two without jamming up.

Hope this might help someone in the future.

[Curtis]

You can’t use a spring hone
It won’t work
Any irregularities in the cylinder will follow with the spring
You need to use a proper hone like a Sunnen that has consistent pressure all the time and use a 500-600RPM drill with full even strokes as not to cause barrel or hourglassing

I just had to clean up someone else’s disaster of a bore and hone job from a “reputable” shop - the piston to cylinder clearance was acceptable at the top of the bore - but it was so badly out at the bottom of the bore it would have certainly tied a piston up early

[Grant]

Hi guys, continuing my saga of the 1975/2 H2C/H2 (what do you call a 1975 H2C chassis with a 1972 H2 motor?). So the bikes back together with all electrics working, great spark (kicking with no plugs) and ready for the road. Took it off the bench which is getting more difficult with age as I now need Maureen at the winch controls and myself steadying the bike down the 9' ramp only 20" off the floor. So with her (Harley or nothing attitude) snickering I went to kick start again, it is barely any easier than when I started this project a few months ago. My language hasn't improved any with age.

Looks like I'll be searching for a right hand cylinder to be bored out, as I don't trust that cylinder at all. It's a shame as my Harley dresser is roughly 850 pounds and getting more and more difficult to handle with age, forcing me to repair it's side car that an 8' x 6" tree branch dropped on during a wind storm.

Any thoughts on my removing all cylinders and having them rebored to 0.060" over and installing new pistons?

[Curtis]

So you never did anything but put it back together ?

[browney]

Did you check the con-rod for that cylinder...With all this talk of oil in the crankcase...Sounds like hydro-lock bent the rod to me.

browney out 

[dickjny]

Grant,
- Just read this story. It gets confusing at times but I feel your pain (I'm going to be 73 next week and believe me; I feel your pain).
- I bought my 1972 H2 in the spring of 1973 ($1250). I drag raced it from 1973-1985 and also rode it on the street. I was at Paris ON in 2009 with the KTC guys. At one of our gas stops on Sunday I did a big burnout (warming up the tire like I did before drag racing). BTW in 1981 I beat the US Nat'l. record holder for my class (on a 1973 Z1) for the class win in Atco NJ.
- I don't think anyone addressed your last question ...
"Any thoughts on my removing all cylinders and having them
re-bored to 0.060" over and installing new pistons?"
I think you need to have pistons with the right clearance and don't see any other way to get there with these cylinders. I would also take a close look at the crank to make sure all bearings are running free; as well as connrod big end bearing. It doesn't sound like you bent a connrod; but the previous owner might have. I still have the original bore and crank in my engine and worry about it all the time. I've heard that letting them sit can allow pits on roller / ball bearing surfaces and can be hard to notice until they heat up and seize. My bike sat for a few years before my 2009 trip to Paris, but I put stabilizer in the fuel and squirted WD40 into each cylinder before winter each year; and, it has always been stored inside.
- Good luck with your rebuild (if you are still working on it). Shoot me a reply and let me know!

1972 Kaw H2: Drag racer - If you can't win, make your competition set a new record!
1970 Yam R5
1972 Yam R5
1975 Yam RD350
Recently sold:
1972 Ossa MAR Plonker 250 single trials bike
1986 Yam TY350 350 single trials bike
Have lots of parts for 1968-1971 Kaw A7 [no CDI unit(s)]

Dick Jamieson - Horseheads NY