Hey guys, been searching for some info on this problem and I ended up here at your forum, but I havnt been able to find any thing to help me so far.

atv is a 2002 Rubicon. Stock engine / internals 4k miles

Here is my problem:

Just bought this ATV today for a killer price because it had a noise in the valve cover. Quad would start and run and drive, altho it is extremely under powered, and i dare not drive it much due to the noise.

I came home with it and tore it apart. Got all the plastics and tank off. I Pulled both valve adjustment covers off the engine and found that the exhaust rocker arm has around 1/16th to 1/8th inch play above the valves. nothing is broken or damaged that I can see through the cover. I pulled the chain tensioner out to look at it but after I thought about the engine being a pushrod engine, the tension is pretty much ruled out. I havn't pulled the valve cover off yet to inspect the pushrods or the rocker arms, other then what I can see throught the inspection covers.

I cant find any one else with a similar problem so far. What do you guys think ?


P.S. This rubicon is in pretty good shape. No terrible damage. It needs front wheel bearings, a good alignment and the rear rack straightned.

It has installed a warn 2500, warn push bumper, warn 4-2-4, and 25" 589's. Picked it up for $1,100 so even with the engine noise I feel like I got a pretty good deal.


Lemme know what you guys think.


Allen

 

I would be wondering if you've got a cam that is badly worn, or maybe a slightly warped valve.

Specs for valve clearance are .006 intake, and .009 exhaust. There is an inspection plug on the side of the motor, and you rotate it slowly until you line up a "T" marked on the flywheel. Then, if both rockers have play you are ready to adjust the valves. If both rockers do not have play, it's because the piston is top dead center between exhaust and intake stroke and the valves are in overlap. In that case, turn the engine another 360 until the T is back, and both rockers should then have play (both valves fully closed between compression stroke and power stroke).

If the gap is really 1/8" though, that would indicate to me that something is pretty well tweeked.

At the price you got it at, though, even if you had to put a cam in it, or had to have the head rebuilt with new valves, I think you will come out OK.

 

Thanks for that info. I checked the clearance on the intake sides, and they are a little out, but the exhaust is like I said like a 1/8th out.

I pulled the valve cover off today and inspected the pushrods, cam followers, and the rockers. They all look ok. I don't think its a valve issue either, both heights are the same, so I dont know one is bent and hanging open any.

Here is some thing I did notice today though..... While I had the push rods and the cam followers out of the engine, I was able to look down inside at the cam, through the pushrod holes, and I noticed on the cam, in front of the exhaust lobe, there is some thing that is loose on the cam its self. I tried looking up a picture of the cam, and it looks like it isnt one whole solid peice, so im not sure if what im seeing is normal or not.. I think im looking at some sort of a cam issue though. Is there some sort of auto decompression or like a timing advance setup on the cam ? Judging by the pictures I found it isnt a solid peice of metal...

Im about to go button it all back up together, and steam clean the frame and engine with the plastics off so I can break open the engine with out all the crap falling into it.

 

Yes there is a decompressor on the camshaft .. If you need any shop manual sections just PM ..

 

Aight guys.

Took the head off today, and first thing I noticed was the cam sitting at an angle in the bearing blocks. Looked at the bearing a litle closer and realised the rear, or "B" bearing, had lost all its ball bearings. The cam tray seems to have caught most of the destruction. Got a new cam assembly on the way, hopfully she'll be back up and going with in a few weeks.

 

Yeah, I suppose that would account for the valve clearance being way off...

Sounds like it won't be too bad of a repair.