how can I tell if my ex is a 440 or 400?

[spec]

ok, well last summer I bought a 440ex from someone. I didn't know him personally and just got to thinking, what if he just said it was a 440? What could I do to make sure that it is in fact a 440? I was thinking a compression test?

[Wheelie]

A compression test won't tell you anything. Take a cyringe and fill the cylinder up w/oil (?) and pay attention to how much fluid it takes to fill up the cylinder w/the piston at BDC.

[400exstud]

That may or may not work. The only way that it would work is if he filled it up to TDC on the money. If he filled up the head also, he could probably gain an extra 40cc's in that space alone.

I would go to a dealership and ride a stock 400ex and conpare power.

If it really comes down to it, measure the diameter of the piston, but that is pretty extream. 85 mm = 400 (397 exactly). 89 mm = 440 (435 exactly).

[exboomer]

Pull the cylinder head off and measure bore x stroke.

[spec]

what does a 400ex top out at? Last summer I took my quad down a backroad and it topped out at about 70-75, do 400exs come close to that? with a T-4 slip on, and a hot-cams (dont know which stage didnt think to ask him that when I bought it)would a 400 come close to that?

[Wheelie]

A stocker will pull mid 60's............modified, I'm not really sure.

[NCexRider]

Originally posted by spec
what does a 400ex top out at? Last summer I took my quad down a backroad and it topped out at about 70-75, do 400exs come close to that? with a T-4 slip on, and a hot-cams (dont know which stage didnt think to ask him that when I bought it)would a 400 come close to that?

That's all a matter of gearing.

[400exstud]

Originally posted by NCexRider
That's all a matter of gearing.

Yeah. Engine RPM ---> Transmition ---> counter sprocket ---> sprocket ---> rear tire height. This gives you your speed.

Theoretically, a stock 400ex can go somewhere around 80+ mph but will take a mile to get there. Then a 440ex can go as slow as 50 mph topped out. Gearing is the only factor in top speed.

Power only determines how fast you get to top speed.

[nosliw]

measuring is the only way.

i've ridden ****ty built 440's that couldn't beat stock

[GPracer2500]

Originally posted by 400exstud
[snip]...Gearing is the only factor in top speed.

Power only determines how fast you get to top speed.

Only to a point. You could have 100mph gearing but that doesn't mean you have the HP to actually achieve that speed.

[400exstud]

Correct. That's why I said theoretically, because in reality it is unlikely that a stock 400ex could go 80+ like a previously stated.

[coryatver]

The only way to tell for sure is to take the head off

[spec]

ok. Are small engines hard to work with?(iv never worked on a small engine before) Can I screw anything up to bad by just pulling off the head to measure the piston?

[NacsMXer]

Originally posted by spec
ok. Are small engines hard to work with?(iv never worked on a small engine before) Can I screw anything up to bad by just pulling off the head to measure the piston?

They are very easy to work with if you know what you are doing. A service manual is a must if you are a first timer at this. You will only screw something up if you make a mistake, and you will only make a mistake if you do not know what you are doing or do not have a service manual ;) It will give you step by step instructions on how to perform any task in servicing the motor as well as the all-important torque specifications.

[boricua]

what about jetting, is it possible to check the main jet size to see if its big enough to be in a 440 with his mods?

[400exstud]

Yeah. Check the jetting. Unless the person that you bought it from has no idea how to jet that might work. For a 400ex the main should be somewhere around 148 - 160.

440ex should be from a bit over that (170+)

[spec]

well i pulled the jet out today, and its a 158.. Could a 440 be running ok on that? I've allways felt that it ran pretty well, but I don't know.. :ermm:

[GPracer2500]

:ermm: is right.

AFAIK, a 158 in a 440 would be awfully lean. Does it have intake and exhaust work? I could maybe buy a 158 being right if it had bone stock exhaust and air filter/intake.

Unless maybe it's a Dynojet 158 (different scale than Keihin jets) or unless maybe you're at a very high elevation.

[spec]

Im not sure what kind of jet it is. There is like a little 4point star in front of the 158 on the jet, I don't know if that helps at all with determining what kind of jet it is(sorry I've never worked with jets before :( ) Also no, it has a t-4 slip on, and twin-air air filter on it.

[Wheelie]

The star means it's a Keihin, with those mods, and that jetting, chances are it's a stock motor, or stock displacement atleast.

[xtullyx16]

ur ****ed

[xtullyx16]

ur ****ed

[xtullyx16]

ur ****ed

have to post it 3 times?


yeah man sounds like a stock motor to me.

how much did you pay for it? what was all done.

[sickmojave]

all this and you are still guessing.. If you want the facts you will need to pull the head.. ;)

[spec]

Well, everything else he seemed to advertise that it came with it did, t-4,hotcams stage 2,new chin and sprockets,dirt digger cluth,wiseco piston, pretty much brand new ITPs on the back,aftermarket airfilter, and I got it for 2k, so it wasn't really that bad of a deal even if it is only a 400.

This winter I was plannin on tearing it down and powder coating the frame, so when I do that I'll probably pull off the head then, and then I'll know for sure what it is.:ermm:

Originally posted by spec
Well, everything else he seemed to advertise that it came with it did, t-4,hotcams stage 2,new chin and sprockets,dirt digger cluth,wiseco piston, pretty much brand new ITPs on the back,aftermarket airfilter, and I got it for 2k, so it wasn't really that bad of a deal even if it is only a 400.

This winter I was plannin on tearing it down and powder coating the frame, so when I do that I'll probably pull off the head then, and then I'll know for sure what it is.:ermm: title?

[spec]

I got a receipt of sale, but haven't switched the regestration over to my name yet.


When I take the tear the quad down this winter, if it is only a 400 what would you guys suggest for racing/dragging/jumping. A 426 or 440 kit?