My B-I-L bought a 400ex about a month ago. I'm the same fellow that you guys have been helping with regarding the jetting and such. It's turned into a small headache because the previous owner had stripped the spark plug threads, which we didn't know until we got it home. Apparently, a small piece of something fell into the cylinder when we removed the spark plug and she's smoking like an old diesel and using lots of oil. I talked to a fellow at the local dealer and he said it's happened to him twice.

Anyway, we're getting ready to tear it apart this evening so he can take it to a machine shop and get the cylinder fixed and the spark plug hole fixed too. Any tricks out there that might make the job easier? We don't have a service manual yet (one on the way) but will when we put it back together.

Thanks in advance.

Kyle

 

It's been so long since I was inside a 400ex that I will avoid giving engine related advise. But, a couple of pointers I have used is get a box of gallon freezer bags and a permanent marker. Bag and label everything upon disassembly.....reassembly will be a piece of cake. It's hard too remember what bolt goes where a month later. Also, start with a clean engine. If you 2 are working on it you will need 2 six packs as well.

 

another tip

if you take the cylinder off be sure to pack clean rags in around the rod. one little oops is all it takes to take it from 2 six packs to a case and a half [img]i/expressions/face-icon-small-confused.gif[/img]

 

One thing I do remember is the oil return passage beside the cam can be wiggled out. With it out you can remove the cam without taking the cam gear off.

 

Before you disengage the cam chain tensor use two zip ties to hold the cam chain to the cam sproket. This will help your chain timing when you go put the motor back together. A service manual will be your best freind when you do any work on your quad!

 

Great Idea, but we already got it apart. Getting a bore job w/new piston. I ordered him a manual this evening and hopefully it will be here before we're ready to reassemble.