which head gasket for a 425???????

[TC426EX]

As I have posted recently, I broke my shift shaft and will be splitting my cases sometime early next week. I ordered the shaft and a complete bottom end gasket set, but I need to know about the top end. What size base gasket and head gasket do I need for a TC 425cc motor? I only ask because I have been getting conflicting opinions.... Dave at East Coast ATV told me I can use stock ones, but Nac's and Baldwin's told me that the stock set is only good up to a 416. Does anyone know? I am gonna order them first thing monday so I can get the parts by the end of the week, and I couldnt get ahold of Tom Carlson, so Im trying to get an answer from someone here by the end of the weekend...

[Bill Fuller]

On my 426 I am pretty sure I used a stock gasket.It's been awhile though,so you might want to check around.

[Bill Fuller]

Depending on the year of your machine I would check out the tranny gears closely 2nd gear has been known to get chewed up.Might as well do it right while you got it apart.

[INFANTRY RACING]

call up fdo and get their special head gasket. it's made for a 440 but works on a 425 too. 30 bux but i should never leak

[cals400ex]

i think they only recommend the stock one up to a 406 if i am not mistaken. i believe the other ones will be a bit larger to accomodate the larger piston. whether it matters or not, who knows???

[Bad Habit]

Call up Cometic and order one from them direct. The make the 3-layer steel gaskets in 85mm (stock), 87mm (416), 88mm (426), and 89mm (440). If memory serves, it was like $28 from them.

Cometic
1-800-752-9850

[Bill Fuller]

Now that you mention that I do believe you are right.I ordered my gaskets through Cometic and it was for a 88mm bore.

[TC426EX]

Thanks guys, Ill be going with the 88mm on monday probably from Tudors, I heard they got good gaskets. I'd really rather not run a cometic but was thinking about those as well. I basically will get whichever one has one and can get it to me quickest. I have the heavy duty head stud kit so I shouldnt blow the head gasket as long as it is halfway decent...

[cals400ex]

i have had great luck with the cosmetic flexsteel headgaskets. just don't get paper ones.

[UglyMotha™]

don't forget a new set of rings and get your cylinder honed ;)

[TC426EX]

Originally posted by UglyMotha™
don't forget a new set of rings and get your cylinder honed ;)

See, Ive heard this from some, and not from others... When splitting the cases, is it required to get a hone and new rings?? I got my motor kit put in last fall, so what do you think?? Someone told me as long as the crosshairs are visible its ok so we'll see... If I got the thing apart anyway, which I have to, then I will probably get it done just for the hell of it to be safe... What do you guys think?? New hone + rings???

[UglyMotha™]

you MUST install rings if you want it to perform at it's peak, when you break in rings the hone acts as a file and contours your rings to the cylinder so you get maximum seal once you pull the cylinder off there is no way that you could get the rings back in the exact same posistion as there were when your first installed it so that is why you must redo the whole process if you choose not to then the rings will never seat and your compression will not be up to par might even start burning oil

[deansfastway]

Paul youll want to call cometic and get the trick 4 peice preload center gasket from them 89mm bore #H1416030HP its got a slightly thicker preload ringlet around the bore circumference . It mimics what we do when we ORING the drag bike motors cylinder decks. its probably only like 28 bucks . You dont really want to use a stock bore gasket as it can protrude into the edge of the bore area and actually stary glowing on a big load , could lead to engine damage . If you use that 4 peice youll want to pay attention on assembly to keep that ringlet centered though. I like the .020 base gasket in MLS from cometic also#B0244020RC its got a steel composition and wont blow out or slip. Take a good look at that 3/4 cluster gear on the trans mainshaft , check that the hardfacing isnt wearing down to the softer powder metal beneath. Good Luck

[TC426EX]

Thanks man, that info really helped me. Luckily those part numbers were the exact ones that Cometic sent me and they worked out great. I just got it done yesterday, I had to ball hone my cylinder and wait on the rings before I put it all back together. The bottom end went together well, the tranny looks to still be in good shape, and I didnt see any signs of major wear inside the motor which is always a good thing (especially for being used as a race motor). Got the top end put together mostly, just need to set my lash and break it in (and check it again after of course) and Ill be ready to hit the track again this weekend. The only thing that was wierd to me is that how the EX motor has a gasket between the middle cases. Some other motors I have worked on usually just call for some yamabond in the middle or some type of sealing agent. I always thought that this was because a gasket could throw off the tranny tolerances by a little bit if it isnt tightened exactly the same way every time. I just torqued everything to spec and it seemed to go together good so i ll see this weekend when Im pounding it hard again. All in all, Im glad this job is finally over, and rest assured I will NEVER put a stock shifter on that bike EVER again!!!!!