Head Gasket Problems 2
Q. Head gasket , help ken. Do you use a standard head gasket on your engines or an uprated one. mine has just started blowing the coolant out of the system into the expansion tank, seems to be ok until I am riding through town and then up goes the gauge and fills up the expansion tank. it has only done 1000 miles since rebuild.
A. Uh OH! Do you have an overbore? What year what model? On the 91-92, I use the stock 71MM gasket even with a 72 (1MM) overbore as the head gasket is slightly large enough OKAY. On the 91-92 with a 2mm overbore you have to “CUT” and enlargen the head gasket, The same applies for the 93-95 also. On the 96-01 model the same applies. A 1mm overbore and the stock gasket works. Now, Cometic makes 2mm overbore gaskets (73mm) for the 91-95 models which is far better than what anyone can “CUT” by hand.
The only time I have ever had a head gasket pressurize the coolant system was when I had the top of the block milled .005 by a machine shop with a new 40,000 dollar SERDI head mill, and I committed the ultimate sin of not checking it. As it turns out they did not chuck the head in the mill right and as the cutters went from the aluminium block to the steel liners it fluttered slightly and the end results was not a flat surface. It looked beautiful when I picked it up, but it was F#@CKED! I took it to an old man with a 0 year old surface grinder who had to mill 10 thousand more off to fix it and then had to place a thicker base gasket underneath it to get the deck height back right or the pistons would hit the head.
I use stock head gaskets with stock bores and with 1mm over bore, and I use Cometic if the overbore is 2mm. I’m currently running a stock Kawasaki gasket on both my turbo and nitrous bikes with nary ever a failure, no, not even 1 ever in my whole life of ZX7s, except for the 1 described above. Even my homemade CUT enlarged gaskets always worked fine.
Next post is By Chris Law
Ken I live in the uk, the only mods are a 95 crank and race cams into a 98 engine. one thing i will say is that i dropped her a couple of weeks ago on the left side (hit a patch of diesel on the road at about 30 mph)anyway i limped home and just as I got home I noticed the temp going right up, the coolant pipe on the left side had been crushed and was leaking.
I replaced the pipe a few days later an all was fine for about 500 miles until she started overheating i must also say that when she got hot i was flogging the tits off her until I saw the temp gauge going up. when i pulled over the lad from behind me said every time I nailed her the coolant was coming out of the overflow. and the fan is cutting in ok.
just one more thing what are the benefits of having a crank lightened and balanced does it give any more power or do you lose all the bottom end grunt
Next post is By Ken
I use a leak down tester to check for this stuff. I remove the radiator cap, and pump air into each sparkplug hole. Bubbles? you have a leaking head gasket. A very slightly leaking head gasket will pressurize your cooling system with engine compression and the water pump can’t fight that kind of pressure, so it overheats.
I did this test on a bike a few years back. First I tried #1 cylinder, then 2, then 3, then as soon as I connected the air supply to #4, antifreeze shot all the way up to the ceiling.
Cranks are lightened primarily for quicker acceleration as the bike will tach up much faster. Does not usually give any Horsepower increases, and can loose torque in some cases. I have had good luck with APE.
There was a case were I was doing a motor for a friend and he wanted to have his crank done by some company I have never heard of. Balance Tech in Michigan. Supposedly they did a lot of Dale Earnardts cranks in Nascar. This crank came back looking like the worst job I had ever scene, but boy was it perfect, and did it ever perform.
That sucker would rev up like there was no tomorrow!