thinn head gasket or the thick one?

[don250r]

i'm running '89 CR250R head gasket, and it IS runnable at 87 octane.
However, you can hear knocking(pinging/detonation)@ certain RPMs/Load.
the 93 is sufficent in my setup.
no need for race gas.
if it still pings,go to your local airport and see if you can get 100LL.
this goes back to using AV gas thread on here and .org
My dad was running AV gas in NHRA Super Stock cars back in the 70's.
Their are problems and solutions for running AV gas.
If you need more octane than 100LL, then get 115/130(or is it 110/130, i forget),
then ALWAYS mix it half and half with 93 pump gaas.

[PowerTech]

well when you get the compresion to high you will have detonation "precombustion" and that will eat up the top end.so race gas is needed at that point. race gas has high octane. and octane is the fuels abillity to resist auto ignition.

and also when you start geting the head to close to the piston with out recuting the head you will be altering the squish zone or area whatever it's called. that is the area around the outside edges of the head away from the combustion chamber area the spark plug is in. when you get that area to skinny the explosion will sort of blow it's self out and it will be a dog on top,even though the compersion is high it will run like crap . you can remidy this by machining the head.

but i dont want ot get into all of that. i want it to run as good as it can without having to reinvent the wheel.

i have shaved a head doun to far before it did not have preignition. but it did run worse than the stock head. i even after shaving it i smoothed out the lip it created further into the combustion chamber. i brought it back out to teh edge of teh cylinder where it should be, but i did not have the chamber reshaped.

i dont know how far i shaved it but it must of been way to far.i used a piece of glass and fine wet sand paper with WD40 on it and did figure 8's with the head on it.

i went back to a stock head and it runs great now. but i will try the thin gasket and give it a compresion test.

[Unclediezel]

Compression ratio is Far from the only factor in determining fuel requirements. The rich/Lean game comes heavily into play here, as well as the altitude you run at. 300 PSI Compression will run just fine on 87 octane fuel, If your atop the himilaya Mountains. Operating temp is another issue. Just because your buddys bike runs great with 93 octane , DOESNT MEAN YOURS WILL!!!!!!!

[PowerTech]

i'm running '89 CR250R head gasket, and it IS runnable at 87 octane.
However, you can hear knocking(pinging/detonation)@ certain RPMs/Load.
the 93 is sufficent in my setup.
no need for race gas.
if it still pings,go to your local airport and see if you can get 100LL.
this goes back to using AV gas thread on here and .org
My dad was running AV gas in NHRA Super Stock cars back in the 70's.
Their are problems and solutions for running AV gas.
If you need more octane than 100LL, then get 115/130(or is it 110/130, i forget),
then ALWAYS mix it half and half with 93 pump gaas.

i just looked up a 89 CR gasket in ebay to get a look at it. and the gasket kits for a CR come with the exact same extra skinny gasket the TRX/ATC kits come with.

i have heard that using the CR gasket is the hot ticket but i did not know that that was the one in the kit.

i will be using it for sure. if i dont go 300CC .

thanks every one.

[Pete]

you can't go on cranking PSI to determine fuel requirements. Yes, you can make an educated guess knowing certain engines, but to judge octane requirements solely on a cranking compression is a sure way to blow an engine.

For example, 2 different engines with the same heads, but one with an exhaust port 1.5mm higher than the other will read vastly different on a compression gauge, but it doesn't mean their octane requirement is any different!

[Unclediezel]

Thanx Pete----

Everyone overlooks the difference between Cylinder pressure and Compression.

[PowerTech]

i will be running mine on the surface of the earth.

i will also test compresion, check the spark plugs, jet as needed, and listen for strange noises.

[Unclediezel]

i will be running mine on the surface of the earth.

.

It wasnt meant that way----Only a comparison of extremes for atmospheric and Barometric pressures.

[Pete]

if detonation ever is bad enough that you can hear it, you have serious issues. Light detonation can often be seen on the outside edges of the piston crown and head squish area, it almost looks like it was lightly sandblasted.

[hrc85250r]

pete is right, you need to figure out your actual dynamic compression ratio which involves a lot of math. basically you can run a stock motor with a cr head gasket and a shaved head or one or the other on premium without worrying about it. to get cheap cr head gaskets all you need to do is take one of those 3 layered atc head gaskets, not the graphite ones obviuosly and snip the tabs off that have the rivets in them, this will yield 2 cr head gaskets and a piece of galvanized steel. throw the steel away, duh. i have measured them and they are two actual cr head gaskets, same thickness. you can get the actual cr head gasket from nac's just call them up they stock them.

[don250r]

this is the gasket you want for a liquid cooled 250
part # 12254-KZ3-000
price $15.47 @ service honda

[PowerTech]

i know what you ment tri moto. i was making a little joke about it .


seriously thank you all for the input. the colective 3 wheeler knolige of this site is what makes it great. and the fast pace at wich it moves.