thinn head gasket or the thick one?

[PowerTech]

250r rebuild over the next few weeks

i have used the thick head gasket in the gasket kits in the past.

the kits i get come with 2 i think the thin one is for a CR 250.but i am not sure?

it is thin and steel ,like two layers of thin steel , it is coated in black stuff but it is all steel.can i use this thin one to make it run stronger? does it seal good enough?

wich one do yall use?

is there a problem with the squish area using this thin gasket?

i know about carb jetting......well enough to get it done and a hand fulls of jets.


i have allways used boysen power reeds .the ones that are 2 stage. and the stock cage.what about going with that Vforce reed cage? is this thing worth the money? and were do you feel the power it makes if any? i dont need it to start any easyer she has allways been a first kicker

and has anyone made a air box ring for the ATC 250R?

thanks for taking the time.

i want to get this baby rite better than ever. i allways maintained it well. i am a mechanic. but this time around it want it to be even better than last build.

[deathman53]

I have a airbox ring on the atc airbox on my quad, the tube it fits right in and stays tight, the air filter you need to wrap it in some tape the take up the extra space for a tight fit. Don't use the thin gasket unless you want to use ONLY race gas.

[PowerTech]

the part of my airbowx that is colapsing is on the outside of it were the boot hose clamps to it. any remidy for this?

[Pete]

I take a stock Honda gasket, and lightly drill the 2 ends where it is held together. I then take the thick middle part, and one of the metals, and set them aside.

I then spray copper gasket coat on the remaining metal part, both sides, and put the head on using that. It hasn't leaked yet.

[MathGSR98]

I would use the thin gasket to get higher compression. I don't think you will have to use race gas. Best thing is to do a compression test and see how many psi you got. Run it with 93 octane and you will be alright. I am rebuilding my top end and I plan to separate the stock head gasket and then use just 1 thin layer.

[Fox250R]

Some say use race gas only, some say using 93 would be just fine.. WITCH IS IT??? LOL......I mean comeon..Does anybody out here really know?

[MRPoopie]

my friend has a high compression piston in his 400ex and hes runs 93 just fine
but im sure you would get better performance from ras gas

Clayton

[MathGSR98]

Some say use race gas only, some say using 93 would be just fine.. WITCH IS IT??? LOL......I mean comeon..Does anybody out here really know?

It just depend of your final compression ratio. It's not all the engine that use a thin gasket that will have the same compression ratio. It depends of you ring wear, piston type and other things. If you are above 195 psi you should be good with 93 octane.

[Billy Golightly]

You can, IMO, get by with 93 until about 190-195psi. Anything higher then that and your gonna need some higher octane.

[PowerTech]

thanks . i will test it.

[leetwanker]

I have a airbox ring on the atc airbox on my quad, the tube it fits right in and stays tight, the air filter you need to wrap it in some tape the take up the extra space for a tight fit. Don't use the thin gasket unless you want to use ONLY race gas.

I just rebuilt my top end and the Vesrah gasket kit came with a thin copper head gasket and I'm running 87 octane without issue.

[hrc85250r]

umm, i run a race ported R, with a cut head and the cr head gasket(thin)..it has 220-ish compression and i have ran race gas in it, 50/50 and 87, i have more power with no detonating with 87. i also have my ignition advanved 3 degrees with a 38mm carb and a big reed cage plus a crazy custom pipe that hits hard....still no detonating, top end looks like new had it apart a week ago. one thing i will note, if you dont glue it down good with some gasket shellac or something similar and let it dry you WILL blow the head gasket a couple times a year.

[deathman53]

your nuts, I'm not very familar with a air cooled 250r, but liquid cooled ones are really close to the race gas line with a thin gasket. Do a compression test to tell what octane you need to use. Detonation can cause alot of problems. I was told by several knowledge people that anything above 190 needs race gas. If your head is cut, rechambered dome, extreme porting or other mods may require race gas even if compression is below 190.

[PowerTech]

I just rebuilt my top end and the Vesrah gasket kit came with a thin copper head gasket and I'm running 87 octane without issue.



i put together one of those air cooled R's a long time ago. the kit only came with one gasket and it was the coper one you are talking about. but my bike is a 86

[gravelord]

well, im not argueing any ones knowledge, or saying i know alot - but as long as its mixed and jetted properly - i dont understand why there would be any problem running 93 octane on just about any 250R engine thats not alky..... im sure it may not perform as good, but why would it cause a problem? does any one know the real reason why ? explanation please? im just curious, because i was thinking about going with a thinner gasket my self...

[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.