Hi guys. I hav'nt posted here yet so be gentle. I might be buying a guys 99' 400ex. It is supposed to have a 416 kit and a ported head by snitz racing, thats all I know so far about engine. The guy told me that since the 416 kit it has been blowing head gaskits "several" and it has a bad gasket now. I hav'nt seen the quad yet but will be looking at it soon. He also said that he is pretty sure that it is a 10.5-1 piston. What in the world could be causing this. I know of a couple reasons but that would be operator error. Could the cylinder be resleeved wrong, because he said he had the head resurfaced and that did'nt help. I don't have any other info yet but will try to get more. I may get this real cheap, so if I do I might just put it back to stock if I buy it and can't figure it out. Any help would be appreciated. RUSS

 

A 99 with problems, I would walk away from it. Even if it was $500 it would end up costing you $$.

 

Ya I am aware of the cost, I've rebuilt engines before. I will make that decision when I look at it. I am just curious if this is common or not I guess. I would'nt think it should be blowing gaskits. Thanks for your imput. RUSS

 

hey there - I'd see what brand of gasket he's been useing - my 99' 440 is all kinds of pumped up and I've never had a leak w/ my powroll gasket -it's the only kind my guy will put in a built bike -

 

The reason that it is blowning gasket is that the head studs are coming out. When you put the larger studs in it will stop this problem. You can put any gasket that you want in there any it will blow. The stock studs are to small for the 400 and they only go into the cyclinder, not the case like they do in all of the other engines. Get a set of studs from GTThunder for $60 and you will be good to go. You can use any head gasket that you want and it will last.
Just because it's a 99 don't mean that it is bad. My 99 is just as good or better than some of the 03 and 04's if they are taken care of and parts replaced on time.

 

I also have a 99 440ex I would buy it if it was cheap enough and put bigger head studs in it like tprender said this WILL cure the problem as I have had 3 years on mine not a problem at all I bought my bigger studs from East Coast ATV but paid 95.00 for them took the head to the local machine shop they drilled and tapped the head for 50.00 and run a cometic head gasket .

 

Do you think its the studs, though? 87mm, with 10.5:1 compression, the stock studs should hold it down. I have a stroked 440, with the 87mm JE, from powroll. It has been running for about 3 years, with stock studs, and been trouble free.

 

I looked at it today and have to say that it looks kinda rough. So I don't know if I want it yet. A little money and some hours with elbow grease and it would look decent. I want it but don't know if the engine is gonna be a problem. After talking to him today he said it has been through 4 head gaskets and he has only put 2 of them on and shops did the other 2. Is a 416 a big bore kit or just bored over that far because I can't imagine it being bored that big???? He also said that there is a heli coil in the jug for 1 of the head bolts. He says it runs strong when the gaskit is good and says it still runs good when it's blown. I did notice that the front of the engine was oily, I assume from the blown gasket. Well thanks for your thoughts and chime in with anymore. RUSS

 

I tried a heli coil the 1st time that I pulled a stud. Maybe it was just me, but it didn't last. The large studs are the fix for the 400. If the stock studs have been taken out a few times when the engine was taken apart or if the compression has been up'd the stock studs will come out. The reason for this is that the studs are only 8 or 10mm. Honda used a softer alumuin on the cylinder. I was told this by 2 major engine builders. You hear stories about people saying that you have to go inside after breakin and retork the head bolts. The reason for this is that the studs are pulls out of the alunuim in the cylinder. If you put in the larger studs this does not need to be done.
The reason that I know all of this is that my 440 ran good of 2 years and it had to be resleeved because of wear. After the 2nd sleeve job the blown head gaskets started. I went though 4 head gaskets, 2 helicoils, and different head bolts. I then went and got the larger stud kid from TC Racing and It has been running ever since on the same head gasket that had blown on the last 2 tries before the larger studs. Put some 3Bond on the used gasket the last time and it has been running like a champ everysicne.

 

I had the same problem in my 440. I went through 3 head gaskets and finally realized that the sleeve had slipped down and wasn't compressing the steel ring on the gasket. The third time it burned the ring off the gasket and sent it through the head and out the pipe. With his only being a 416 which didn't need a resleeve, I don't see why it is eating gaskets unless the head wasn't retorqued after a ride or two.