Last min. questions before dropin in 416 and xr400 cam...

[JhallettEX]

OK guys, It is about that time. I am going to start on my JE 416 10.8:1 and the XR400 cam. Is there anything that you would like me to keep in mind while I do this. It is goin to be the first time I ever take apart a engine and put it back together. My dad is going to help me and we have a sop manual. Anything else I should know? I will keep you all informed on the progress. I am sure I will be back to ask some questions. Stay Tuned. Thanks

[MIKE400EX]

There is a very small pin and spring under the "decompressor" assembly on the cam. The pin & spring go into a hole in the head.
Best to take the cam gear/chain off the cam and stuff a clean rag in the cam chain galley, then lift the cam up and out slowly. Be very careful and don't let them fall into the engine!!!!!!

Also put a rag or two under the piston before you pop out the pin clip and when installing your new piston.

Go do it! It's a piece of cake!

[sly400ex]

I'm rebuilding my top end at the moment also. Is hard to get the timing gear, cam, and chain all aligned when putting it back together?

[wyndzer]

Nope it's fairly easy, there are two grooves in the cam sprocket that help you align it properly. Just make sure the lobes are pointed down at top dead center.

[knighttime]

Make sure you have a torque wrench.

[004exkid]

Make sure you put the rings in the correct way. There are small letters on them that sould be facing up. I had to tear mine down and double check :mad:

[JhallettEX]

Thanks alot guys, are you sure there is nothin else I should know about, Come on RICO you have to have something to say.

[Adams44]

It is fairly simple. Go slow and you'll do fine.

- I would put a small dab of removable (blue) loctite on the two cam gear bolts when reassembling.
- with the piston at top dead center, cam lobes down, the cam gear has three marks on it. One mark goes to the top and the two other marks line up horizontaly with the head.
- Make sure the cylinder and head where the head gasket goes is perfectly flat. Lightly stone if you have to but that needs to be perfect. Under high compression that head gasket is proned to blowing, so make that is good.
- Torque the cylinder and head down to 33 ft. pounds, I use a small dab of blue loctite on the head nuts (I head a couple come loose).
-Adjust the valves to .005" intake and .006"exhaust and you are good to go.

When you are done and running the engine, don't rev it until the oil temp is good and warm, it is rare with 4-strokers, but you could cold sieze the piston.

I am assuming you are putting in an 11:1 piston, so run a DPR9Z plug instead of 8Z and I don't care what anybody says, you should run at least 98 octane, which means you have to mix. 11:1 is on the border and running pump gas can cause it to "ping" under heavy load. This detonation will help blow a head gasket as well. Trust me I fought this during last years racing season.

The rag in the cylinder and timing chain hole is a great idea.

I wouldn't be a bad idea after you have taken it through a couple heat cycles and before you run the heck out of it to pull the cam and retorque the head nuts. Just insurance. I do this, but only because I have blown head gaskets and have seen them in need of retorqing.

Good Luck,

Be careful when scraping gasket on bottom of cylinder, not to damage O-ring seal. It doesn’t come with your top end gasket kit. Part # 91302-356-000. Fairly simple job, just take your time. Also put a good coat of Cam lube on your new camshaft. I used a hose clamp to compress the rings to get cylinder down, after they bore it you won’t have much taper left in sleeve.