anyone work on atv or motorcycle engines?

[jeepthing07]

I picked up a Honda 400ex that needed the bottom end case replaced for cheap. So I'm tearing it down and everything looks pretty good so far except for when i got to the wrist pin. its scored some and so is the inside of the rod. The rod is not easily replaceable because its one of them cranks you have to press apart to install a new rod. anyone know how much shops charge to do this or know of a good cheap one?

[Tracker]

Get a bottom end kit and a Wiesco piston and rings set while you are at it. Mortal man does not take those cranks apart with any hope of the engine running again.

Odd problem- That motor doesn't have that problem often unless the PO ran it dry. I'd look for a lot more problems.

[jeepthing07]

Get a bottom end kit and a Wiesco piston and rings set while you are at it. Mortal man does not take those cranks apart with any hope of the engine running again.

Odd problem- That motor doesn't have that problem often unless the PO ran it dry. I'd look for a lot more problems.

 

I finally found a place that will press a new one on and true it up for $75. I might buy a new crank/rod I'm just trying to do this cheaply but have it be reliable.

 

The PO rode it with a loose chain and it busted the case but other than that it ran good. i thought for $750 it was to good to pass up but by the time its done i will probably have over $1000 in it, still not bad i guess.

[JeepcoMJ]

mixed reviews on WISECO pistons.

 

i will not use them as they've destroyed more than one motor that I've built for my snowmobiles.

 

buy genuine replacement pistons for it if you aren't going to bore it out. also, have the cylinder honed and buy new rings (never ever re-use piston rings)

 

my dad and I build snowmobiles and dabble in motorcycles, atv's, and the occasional hovercraft (man, are those FUN ) as well as dunebuggys, sandrails etc. so we've spent a fair amount of time messing with "smaller" engines and ALOT with two strokes.

 

rule of thumb on the crank;

check the cage bearings. spin them around, if you can HEAR them or wobble them then they are junk. a cage bearing on a crankshaft should be silent or almost silent, and operate smoothly. if it's not good, it's actually cheaper to buy a replacement crank than it is to pay to have one rebuilt. (generally)

 

good luck and keep us updated.

 

p.s. have the carbs gone through while you're at it.

[NewToJeeps]

I have a 400ex. mine is an 04 but its still alot of fun. i hope you get it running soon. you will love it !

 

once its fixed its great fun to throw in the back of the jeep and hit a trail..when ya stick the jeep unload it and keep going ! and hope someone has a winch when ya get back to the jeep....

[Tracker]

The PO rode it with a loose chain and it busted the case but other than that it ran good.

I've never heard of a loose chain breaking the case and scoring a rod or wrist pin. It sure sounds like a lack of oil may have been part of the problem. If so, everything needs a real close look.

When I'm that far inside any engine I like to do things right. It's fun to rebuild an engine but it's rewarding to see it last for years with no major problems. Doing it right is not more expensive than doing it twice. As far as pistons there's only one way to do it right: Never buy a piston for a bore- You make a bore for a piston.

Jeepco- You're not to far from Millenium Plating. Do you use them for your NickaSil / bore work? Their cylinder work has been outstanding for us.

[camanchedriver23]

i had the same problem i rode it with the case broke open and i just kept putting oil in it until one day it ran a little low and it locked up when i took it apart the wrist pin was badly scored and stopped it from rotating si i just bought a new piston had it bored and then i took some paper towel and shoved it in my crankcase hole and i sanded the inside of the rod where the wrist pin goes and i putthe new one in and it ran perfect