'85 250R top end gasket (pics)

[pismorat]

So I've got all my bottom end issues resolved. I'm about to button up the top end with the new 67mm piston and the top gasket doesn't seem to line up that great with the water jackets (about 1:30 & 10:30). Does this look normal?

[ONEBAD350X]

Yep, the unrestricted hole goes over the exhaust port.

[pismorat]

So should those little holes have that much overlap with the ports? It seems that they would at least line up with the top part of the port (no overlap).

[Marty]

Just want you to know if you can avoid using that fiber gasket please do yourself a favor and not use it!
Stick with OEM Honda head gasket!!
That aftermarket fiber head gasket has been prone to leak

[bkvette3]

Just want you to know if you can avoid using that fiber gasket please do yourself a favor and not use it!
Stick with OEM Honda head gasket!!
That aftermarket fiber head gasket has been prone to leak

I agree with Marty. Here's what you need.

[pismorat]

Cool, I'll try and pick one up today. Will it line up better with the water jackets, or is what mine is showing acceptable if its the same?

[3wheelrider]

That gasket lines up correct, smaller holes are partially blocked that way. However-those gaskets dont seal for crap & may even weep coolant as soon as you pour it in.-lol. Also, they are extra thick which lowers compression more/& affects squish. The 3-layer metal gasket works the best & lasts longest -IMO-....
Thats what I run- except I use just the 2 thin outer layers of the gasket.

[rdonald1979]

You can go aftermarket on the bottom but the top you should always use OEM. Cause of the metal gaskets. Goes for 2 and 4 stroke.

[poohbee1]

I was under the impression 12254-ha2-000 were also the ones that you wanted to stay away from. There thinner and will give you a little more compression but they are leakers also. I think these guys are trying to get you to buy these 3 part gaskets.the one in the pic is taken apart and used . 12254-ks7-881 is the one you want 3 part metal

[Red Rider]

The 85-86 ATC 250R came from the factory with a fiber head gasket, and I never had any issues with leakage, but I always used an OEM replacement when doing top ends. Later on I switched to a thin metal CR250 head gasket for better compression, and I never had any leakage issues there either. Sometime during the TRX250R years, Honda switched to the multi-layer, metal head gasket, which is what you'll get now from Honda if you order a head gasket for the ATC 250R. I used those as well, but would cut off the rivets, to get 2 thin metal head gaskets for slightly more than the price of 1 CR head gasket. The multi-layer head gasket has 3 layers. Basically, it's 2 CR head gaskets sandwiched around a single, flat, metal disk. If you cut these apart, save the 2 head gaskets and toss the flat disk in the recycle bin. Metal head gaskets make removing the head a breeze, as the head won't stick to the cylinder like it will with a fiber gasket.

Once I got an o-ringed cool head, I quit using head gaskets altogether, and once again, no head stuck to cylinder issues.

[poohbee1]

The 85-86 ATC 250R came from the factory with a fiber head gasket, and I never had any issues with leakage, but I always used an OEM replacement when doing top ends. Later on I switched to a thin metal CR250 head gasket for better compression, and I never had any leakage issues there either. Sometime during the TRX250R years, Honda switched to the multi-layer, metal head gasket, which is what you'll get now from Honda if you order a head gasket for the ATC 250R. I used those as well, but would cut off the rivets, to get 2 thin metal head gaskets for slightly more than the price of 1 CR head gasket. The multi-layer head gasket has 3 layers. Basically, it's 2 CR head gaskets sandwiched around a single, flat, metal disk. If you cut these apart, save the 2 head gaskets and toss the flat disk in the recycle bin. Metal head gaskets make removing the head a breeze, as the head won't stick to the cylinder like it will with a fiber gasket.

Once I got an o-ringed cool head, I quit using head gaskets altogether, and once again, no head stuck to cylinder issues.

I use 1 layer of the headgasket also but I cant run pump gas . If you try it do a compression check or you will be rebuilding it again very soon.

[RIDE-RED 250r]

Also it should be noted that the coolant ports in the gasket are restricted intentionally and for good reason. The 250r does not run a t-stat like a Tri-Z. You need to slow the flow of coolant down so it stays in the head and radiators long enough for heat exchange to occur. No t-stat or regulation on coolant flow will cause poor cooling.

With aftermarket O-ring type heads for OEM and big bore cylinders you will notice the coolant ports themselves on one side of the head will be significantly smaller than the other side. (I dont recall which side is what, intake and exhaust). ESR had some issues awhile back dialing in the coolant port size differential from one side of the head to the other and some big bore owners had some overheating issues..more so than usual..big bores tend to run a bit hotter to begin with. These restrictions are on the head only..cylinder ports are all the same just like OEM.

So in short, yes... There is a reason for the smaller coolant passages on one side of your head gasket. Should tell you in the manual which way they should be oriented. It's been awhile since I had a top end off... I can't recall with 100 certainty which way it should go. Consult the manual.