3rd Gen 250R Top End Gaskets - Recommendations

[jb2wheels]

I have an 85 250R with a great running virgin engine.

During Rampage 2014, it started weeping coolant out the base gasket on the stator side. All the bolts are tight, the 30 year old gasket is just done. So I have to crack it open.

Any recommendations on gaskets? I should only need a base gasket so it will likely be OEM if available.

Any reason I can't take the head and cylinder off as a set - without removing the head? Is there room in the frame?

If I have to pull the head, is the OEM head gasket the best way to go?

I'm not looking to mod it at all. It runs fantastically now.

Any other thoughts?

[Mosh]

It is unlikely your jug is leaking coolant at the base gasket. There are no coolant ports at the bottom that would need sealed. The coolant leak may be coming from up top and landing there. May want to re evaluate the leak. The 85 stock head gaskets were the thinnest of all the R's which raised compression on that year alone. As far as I know it is only available from Honda, and seals better than any aftermarket head gasket available while retaining stock engine specs. It was a 3 layer multi steel shim gasket.
A 89 CR 250R head gasket is a single layer steel gasket which works fine on the R and brings compression up even higher. Any name brand or OEM base gasket will be fine to use. stay away from those aftermarket fiber head gaskets. I have never had one seal reliably.

You can pull the jug without the head. You will have to cock the motor half out of the frame on the stator side to get clearance to do so. But I advise recheck your leak before you go diving in. Your leak may just be from a loose hose clamp.

[Marty]

I agree check hoses and clamps for anything weeping or sweating coolant!
Use only OEM gaskets you can't go wrong with Honda quality, but if you choose to use cr250 head gasket to raise compression have head and cylinder checked for squareness. But if you are sticking to 250r head gaskets buy the new 1985 head gasket to maintain your compression 12254-ks7-881 is Honda part number.

[250rRoostmaster]

Can't go wrong with OEM. I've also had good luck with ATHENA gaskets sets.

[barnett468]

I have an 85 250R...

it started weeping coolant out the base gasket on the stator side. So I have to crack it open.

Any recommendations on gaskets? I should only need a base gasket so it will likely be OEM if available.hello jb32weels;


Below is a supplier of NOS OEM parts. They have the head and base gasket in stock. Base gasket, possibly not longer avail through Honda - 12191-HA2-010 superseded to 12191-HA2-670.

http://www.cmsnl.com/honda-atc250r-1985-usa_model68/partslist/E++01.html#results


Head gasket - 12254-KS7-881

http://www.ebay.ca/itm/NOS-HONDA-12254-KS7-881-GASKET-CYL-HD-/201029605319

http://www.partzilla.com/parts/detail/honda/HP-12254-KS7-881.html




If I have to pull the head, is the OEM head gasket the best way to go?Yes, imo.




Any other thoughts?If it is the head gasket i would do the following.

put a piece of 400 grit wet/dry sandpaper on a granite counter or tape it to a window next to the frame.

clean the head gasket surface then color it with black felt pen.

spray water or wd40 on the sand paper.

with moderate pressure, spin the head around 4 times then look at it.

if all the felt pen mark is not completely gone it is warped and requires more sanding.

[c_hustle]

At what compression do you have to start running 100 octane?

[jb2wheels]

Great information! Thanks!

I'll dig into the leak checking more. The info about (no) water jackets at the base of the cylinder makes sense. I'd rather tighten a clamp or replace hoses than tear into a good running engine.

I have no idea about the 100octane question. I run mine on 93 octane premium. My 350X pings on 91 octane when lugged. I don't know what piston is in it. I have not ridden it with the 93 but my guest rider reported no pinging.

[Marty]

I always run 50-50 race fuel, super unleaded on all my bikes better safe than sorry! On my non ported 250R's I try and get to 180 lbs of compression no more no less. Anything above 190lbs you are really pushing crank shafts limitations. Your on the right track do your research on 250r and go from there good luck

[JasonB]

OEM. I used all OEM for my bottom end in the cr500 build except for a few minor items that used an Athena kit, the top end we used a Cometic gasket kit for. Like Mosh said, you can pull the top end without taking thehead off but if you pull the head switch to the cr250 gasket it ups the compression i did it on my 86 before i went 310