BIG problems....

[400exrider36]

So after putting a new head gasket in my 400 today i was putting the new head bolt nuts on and realized it wasnt the nuts that were stripping, the head bolts are pulling out of the cylinder.

Not only that but my valves wont stay adjusted for more than 10 seconds. One of the exhaust valves keep getting too tight and stalling the engine. so i have to loosen it up to 1/8 inch or so to keep it running.....

The ride i took a few days ago the cam slid to the right and gouged up the head.....

I feel so helpless.... i have no idea what to do anymore. :(

new stuff is expensive but i dont really know what my options are or what is even causing this.


Any recommendations?

[CJM]

It sounds to me like your head is fubar

[JOHNDOE83]

Maybe it was tapped for bigger studs and the new ones are to small?

Take the head and take the new bolt, put the bolt in the hole and see how much bigger the hole is then the bolt, if its bigger and the threads look good, maybe its tapped bigger?

Try the old bolts? If it works just use them again.

Maybe they were heli coiled?

[400exrider36]

the bolts are still stock, its the nuts on top i replaced

[4reeds]

How did your cam slide to the right?When its bolted to the gear it shouldn't move.Did the bolts come loose?What measurements are you using for your valves?

[400exrider36]

if the bearings on each side of the cam arnt pushed completely in against the cam it can move back and forth. that was my fault for not checking.
i talked to the previous owner and he says its a brand new head and cam....
that leads me to believe it might have something to do with the head bolts stripping out and the head being loose. i also only have 4 bolts holding my valve/rocker cover down because the rest of the bolts stripped. i just got new ones in the mail today.

im going to order a new piston and cylinder and see how that works. apparently the guy blew it up at least once and just changed out rings....
the cylinder walls are scratched and dinged pretty badly. im surprised it ran as good as it did.

but hey, i got myself a good reason to get a big bore kit!

[honda400ex2003]

oh boy :p you got some serious issues son. lol. imo the only fix is a new head and cylinder. I wouldnt fix it any other way. steve

[400exrider36]

ya same, but im gunna try just the cylinder first..... and cross my fingers.

i want a 416 or 426 kit, but cant really find any that come with the cylinders. i dont really wanna deal with getting my studs retapped and sleeve honed out.

however, im finding all sorts of deals on complete 440 kits. im a bit worried....
it would be nice to have the extra power, but i dont need any more problems like a rod destroying my case or somethin..
how reliable are these kits?
(piston and complete cylinder, wiseco 11:1)

[honda400ex2003]

imo if you take care of them and keep fresh oil and such in them along with keeping them cool you wont have any issues. get some good cometic 89mm gaskets and you will be good for a long time. steve

[400exrider36]

ok, in that case, is keeping the stock studs a bad idea?

[440ex. ehhh!!]

i've got stock studs with my 440 and no issues at all.

[sc400ex_rider]

Do you know about the washer under the head nut inside the valve cover? it often gets misplaced and wont let the nut snug up.

[Pt's400ex]

If your cam is walking back and forth then you are missing the bearing set pins on each side. That keeps the bearings snug to the cam and they cost about $10 at honda. My previous owner forgot to install mine and my cam is all beat to hell but it will have to do for now. As far as fixing your cylinder the machine shop can hone it out without removing the studs it will take longer but they can do it. Jim

[400exrider36]

the studs pulled right out of the cylinder so im just gunna get a new one

[hocman123]

i am not 100% sure but i think if u go with a 440 that u will need to run race fuel which is much more money and hard to come by in a pinch
just thought i would mention it just incase u didn't know

[JOHNDOE83]

I got a 440 with no stud issues, still stock, I do have 2 of them heli coiled, only cause of stripping from being tightend to much, the helis are working just fine.

440s needing race fuel is just like any other build, race fuel depends on compression, some 11:1s will need it, some wont, depends on the atv, the kit used, cam...etc.

[TRXRacer1]

A brand new cylinder would be a huge waste of money unless you're getting one of those 440 kits. Nothing you mentioned here so far is all that bad nor has anything to do with a need to replace the head and cylinder. They are simply chunks of metal that need some attention. If you're set on replacing them PM me for my address, I'd love to take the old stuff, cheaply fix it and have spares for my next build.

Cylinder:

Studs pull, get them re-anchored with inserts or get a GT HD stud kit......... done. Your head needs a quick trip to the machine shop so you might as well just have them make the inserts and go that direction. Nothing new here.

Head:

The head can be repaired too and gouging from the cam most likely won't matter, lets see some pics. Chances are you just need to drop it off at a machine shop and get the threads repaired. Someone clearly had no idea what a torque wrench was and over tightened everything!!! Also it's very possible that we aren't doing the most accurate clearance job but more importantly your valves are probably junk and are quickly on the move. Again, a new head will not fix that problem.


There's a reason you replaced the head gasket, was it because it was leaking?

[440ex. ehhh!!]

Originally posted by hocman123
i am not 100% sure but i think if u go with a 440 that u will need to run race fuel which is much more money and hard to come by in a pinch
just thought i would mention it just incase u didn't know

nope. i have 440 11:1 and im just running lowest octane at the pump. aha
once i put the stage 2 in, i will run highest pump octane.

[400exrider36]

Originally posted by TRXRacer1
A brand new cylinder would be a huge waste of money unless you're getting one of those 440 kits. Nothing you mentioned here so far is all that bad nor has anything to do with a need to replace the head and cylinder. They are simply chunks of metal that need some attention. If you're set on replacing them PM me for my address, I'd love to take the old stuff, cheaply fix it and have spares for my next build.

Cylinder:

Studs pull, get them re-anchored with inserts or get a GT HD stud kit......... done. Your head needs a quick trip to the machine shop so you might as well just have them make the inserts and go that direction. Nothing new here.

Head:

The head can be repaired too and gouging from the cam most likely won't matter, lets see some pics. Chances are you just need to drop it off at a machine shop and get the threads repaired. Someone clearly had no idea what a torque wrench was and over tightened everything!!! Also it's very possible that we aren't doing the most accurate clearance job but more importantly your valves are probably junk and are quickly on the move. Again, a new head will not fix that problem.


There's a reason you replaced the head gasket, was it because it was leaking?

Yes, two of the studs pulled through and so it leaked. at the time i just thought it was the nuts that stripped so while i replaced the nuts i did the head gasket just in case since i had a spare.

As for repairing mine, there isnt much for machine shops in my area. My best option would be to send mine out to somewhere which in the end would end up costing me just as much as a new one. Plus with a 440 kit i can get a better deal on the piston.....

Your idea of fixing my existing cylinder is a better idea, i just find it impractical for me. I am going to start asking around though to see if i can find someone who does that work. i just hope the gouges aren't too deep on the cylinder walls.

As for the one valve, i realized it was the decompression valve and the mechanism on the cam wiggles every which way. I thought this could be my problem..... I dont know if this is normal i have never seen one like this, but seems too loose to me. All the other valves stay in check.

As for after market studs, i havent been able to find them on ebay or various sites... regardless i havent looked EVERYWHERE, where can i get them and how much do they cost?

[TRXRacer1]

In this case I would contact GT Thunder and see how much they want to install their HD Stud kit and repair the threads in the head. $60 for the oversized studs, not sure what they charge for labor. Any machine shop could do that locally too if you just wanted to buy them from GT and have local install.

http://www.gtthunder.com/Product/01-001.htm

I don't know what bore you're on now but the EX cylinder has a lot of room to grow. Any idea what it is? You can always measure the across the top to see what the last bore was.

Still would love to see a pick of the head. Any plans on an aftermarket cam? They're pretty cheap and make a big difference. You can always gut the one you have if you think it's giving you issues. Make sure you know where your cam retainers and decomp plunger is.