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2002 Honda 400ex locked up


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Im about to buy a 2002 400ex and my buddy is selling it to me for 300 bucks he told me he was out riding it and it ran out of oil and locked up. when he got home he said the oil drain plug came out and all the oil drained. he hasnt messed with it since last summer. i need your guys input on whether i should buy it and what to look for when i pick it up. oh and what you think could be wrong and what ill have to replace

Thanks guys

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If it ran out of oil, then I would just plan on rebuilding the entire engine from top to bottom because more than likely, if it locked up, everything inside is pretty much cooked but you really wont know till you start tearing it down. If the rest of the quad looks decent... then it doesnt sound like a bad deal .. because even if you have to dump $700 or so into a rebuild... when its all said and done you will only have $1000 into a strong running quad.

I picked my 400 up really cheap.. and rebuilt it.. I put a 416 kit in it with a stage 2 hotcam and it totally rips... If you do the rebuild correctly, you can have a great running quad for a fraction of the cost of a new one.. but it all depends on how much you want to get into this project. It can be super frustrating and time consuming but when its all said and done.. I think its worth it.

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well i bought it the bike is really nice and clean everything else works just need to eplace some a-arm bushings. i tore the top end apart and the piston was seized but i got the jug off but the wrist pin is froxe and i cant get it out. any ideas on how to get thatout so i can replace the piston? the kid o got it from gave me a brand piston and told me it was a 440 any deas n how t =o find out if it is and the compression ratio. the crank spins over real smooth and i noticed a litle oiil in the bottm of the case and theere was a=some oil in the head so i dont think the valves are shot or the main bearings but whaat will i have to do if i put the 440 in it? thanks guys

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alright i just measured the cylinder and its at 85.85mm ao im just goin to do the 416 kit ,

my brother i goin to try and use a press to get the wrist pin out for me

oh if i do the 416 kit will any topend kit work or will i have to get a kit for 86.mm

im thinkin bout just getting either namura or wiseco any suggestions thanks guys

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I would always run premium in any atv. As long as you aren't running over 12.5:1 compression, you will be ok to run pump gas.

We all run 91 in our crf250r's and we are running JE 13.5:1... They guy that builds our heads and sold us the parts builds race motors for a living and he said 91 is suficient...

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We all run 91 in our crf250r's and we are running JE 13.5:1... They guy that builds our heads and sold us the parts builds race motors for a living and he said 91 is suficient...

I know some people run up to 13.5:1 on 93 octane and get away with it, but that is really pushing the limit for most bikes IMO. Your CRF is a high rpm motor and most likely runs a cam with alot of overlap and therefore lowers the dynamic compression of the motor. So you can get away with more static compression than a slower revving air cooled machine like a 400ex. Now that I think more about it, I would not run over 11:1 in an air cooled motor. Keep in mind also, there are also alot of other factors that go into how much compression you can run. Humidity, air temp/density, how hot the engine runs, cam shaft profile.... Static compression is simply the volume of the cylinder when the piston is down vs the volume when the piston is at TDC. This is where you get the compression ratio. Dynamic compression is the actual compression that the engine makes. All of the previously mentioned variables contribute to your motors dynamic compression. If you run bigger cams, there is likely to be more overlap, which allows some compression to bleed off because the intake and exhuast valves are open at the same time for a longer period. This allows you to run a higher compression piston without taking the static compression too high. In short, the actual compression in the cylinder measured with a compression tester is what you really need to keep an eye on.

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  • 4 weeks later...
  • 4 weeks later...
Im about to buy a 2002 400ex and my buddy is selling it to me for 300 bucks he told me he was out riding it and it ran out of oil and locked up. when he got home he said the oil drain plug came out and all the oil drained. he hasnt messed with it since last summer. i need your guys input on whether i should buy it and what to look for when i pick it up. oh and what you think could be wrong and what ill have to replace

Thanks guys

its a good price junk ones here are going for as mush as 1500 and look like junk replace oil pump crank oil filter and piston and maybe the sleve.

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