[killer454]

hello everybody im new to the 400ex and picked one up last week to fix up.

it has a bad piston and cylinder in it i have taken it apart and the piston did not messup that bad at all.the piston skirt just melted to the cylinder a little bit.its like melted alluminum on the cylinder wall.cant find no real bad scratches even in the cylinder,checked the rod and no up and down play at all.

i mainly do trail rideing and some hill climbing when rideing.

here is my question-im going to order a 440 kit for this 2000 400ex and need to know some info on it.

1.it has an aftermarket sylincer on it but they took the baffle out for some reason!!should i replace this and can i run just a stock sylincer with the 440 kit for a while till i get the money for a good one?

2.what jets should i put in the carb?the compression ratio is going to be 11.5 to 1 acording to the 440 piston kit on ebay.

3.is their anything else i will have to change to run this kit? this 400 has all stock cam and everything else.the timeing chain was tight to no play)

im going to buy a filter box and cover for it to off ebay,because i do get stuck in mudholes once in awhile.

thanks for the help everybody i have tryed a search on here but cant find the info im looking for on the 440 kit.i tryed bigbore kit,big bore,cylinder,440 cant find nothing.SORRY IF THIS QUESTION HAS BEEN ANSWERED 100 TIMES.

thanks for the help everybody:icon_ goofy:

 

[njrextreme]

hello everybody im new to the 400ex and picked one up last week to fix up.

it has a bad piston and cylinder in it i have taken it apart and the piston did not messup that bad at all.the piston skirt just melted to the cylinder a little bit.its like melted alluminum on the cylinder wall.cant find no real bad scratches even in the cylinder,checked the rod and no up and down play at all.

i mainly do trail rideing and some hill climbing when rideing.

here is my question-im going to order a 440 kit for this 2000 400ex and need to know some info on it.

1.it has an aftermarket sylincer on it but they took the baffle out for some reason!!should i replace this and can i run just a stock sylincer with the 440 kit for a while till i get the money for a good one?

2.what jets should i put in the carb?the compression ratio is going to be 11.5 to 1 acording to the 440 piston kit on ebay.

3.is their anything else i will have to change to run this kit? this 400 has all stock cam and everything else.the timeing chain was tight to no play)

im going to buy a filter box and cover for it to off ebay,because i do get stuck in mudholes once in awhile.

thanks for the help everybody i have tryed a search on here but cant find the info im looking for on the 440 kit.i tryed bigbore kit,big bore,cylinder,440 cant find nothing.SORRY IF THIS QUESTION HAS BEEN ANSWERED 100 TIMES.

thanks for the help everybody:icon_ goofy:

Yes, you will need work done to make the kit worth it. It needs to be full piped-jet to spec from manf.. Trail port the head. Bore the carb. Stage two or 3 hot cam. New cdi w/ higher rpm. New hi perf clutch. The list can go on and on. What is your budget on your build?
Nick

 

[jgar]

With the money you will have to put into the ex to do it right. It will be cheaper just to fix it, sell it and get a 450r imho. Then you will have the power you want and it wont be broken all the time.

 

[400exrider15]

The 416 and 426 pull harder than the 440. It takes longer for the 440 to get the power than the 416 or 426. plus, it will last longer with the 416/426 set up. You will probably end up re-ringing it every year with the 440. just my opinion.

 

[TRX2fiveO]

Agree^^^ the 440 kit isn't a good trail engine being thinner after boring it will run a little hotter than the 416 or 426 set-up

 

[killer454]

ok thinks everybody,i have read everything you guys have told me and im going to listen to all of you guys.
i have decided to just bore the cylinder to the next oversize just to get it running.i do mostly trail rideing and dont want no overheating problems.

i have another question if i just go up in the bore size will i have to rejet the carb?and since reading your post been looking at pistons on ebay will a 11.0-1 piston work for a stock moter,or should i stay around 10-1?

if you guys have time to help me and know the 400 ex very well could you guys find the piston i should buy on ebay and post the link to it here?i was thinking wisco would be the best but want to see what you guys suggest.


thanks for the help

 

[trailrider894]

Yes you will have to re-jet.... for sure!!!!

 

[TRX2fiveO]

Wiseco, CP, Namura, and powroll all make a nice piston kit. I have wiseco but I just rebuilt a 250EX with the Namura kit seems to work really well. It all depens on what you want to spend? be cautious or what you buy from Ebay.

 

[trailrider894]

You also will want to only go to a 416 or 426. It allows for more rebuilds and more futures bores. I would get a '04 CRF Timing Chain. It fits right on the 400ex and is way stronger... its visible... the CRF chain is wider and is obviously better built. Its always a good idea to go ahead and get better valves too.

 

[trailrider894]

F.Y.I

I use Vertex Pistons in all of my builds...

 

[killer454]

took my cylinder down to the local kawasaki dealership here in town and they miced my cylinder for me for free today.
he told me i need to have it bored to a 85.50 overbore which is .020 oversize i do beleave.

after talking to all of you guys im going to go with a namura piston rated at 10-1 on compression.

i have never used namura but im going to try them on this build and see how they are.

i just want this thing to be reliable for 4-5 hours of trail rideing at a time with no issues at all.

by the way im going to buy a complete gasket kit so i can clean and check the oil pump and bottom end for metal fragments.

what do you guys think on this