Ok I need advise from some of the engine guru’s. I know diagnosing engine problems over the internet is pretty hard but well see how we go.
Yesterday I headed up to Sunny Corner for the rally. I took the RMX out for a run and about 40k into a trail I was on the gas on an uphill fire trail and all of a sudden had a grinding noise coming from the bike. Almost sounded like a rock stuck in a break disc. I stopped and the noise was coming from the engine, specifically if you got down close it sounded as it was coming from the left side under the stator cover. The motor still felt strong and revved fine.
I limped the bike back to camp and pulled the stator cover off. Not the cleanest stator I’ve ever seen but nothing looked out of the ordinary. I don’t have a puller so haven’t looked on the inside of the flywheel.
At this stage I was concerned the noise is either a crank bearing or big end. I put the cover back on and fire the bike up and noise was gone. I went for a ride out along the road for a few km’s and no noise. Well being paranoid I packed up and brought the bike home.
I have been planning to pull the top end down for a freshen up and power valve inspection so this morning I ripped her apart. This was after I again fired her up and did some laps of the block and still no noise or signs of any problems.
Just a little history on the bike. It is a 99 model with just over 2500km on it. Before I got it earlier this year it sat in a shed with little use for quite a number of years. I pulled the topend off this morning and from what I can tell this is the first time its been apart since it left the factory.
The piston and bore look ok but defiantly time for a freshen up. Power valve working fine but gummed up as expected. Looking at the crank and bigend, the rod has 0.45mm side play and no up and down movement in the big end bearing. It moves freely with no visible signs of any problems.
My question is, is there an easy way to check the bigend and crank bearings without splitting the cases? And if one of the bearings started to make such a noise would it just go away? I still haven’t pulled the flywheel off to see if something underneath caused the noise. If a grab the flywheel by hand I can’t feel any movement such as excessive end float or up and down movement in the left crank bearing.
I don’t expect any miracle diagnosis over the net but I’m baffled that such a bad grinding noise just went away. I’m paranoid one of the bottom end bearings is gone and don’t want to throw in a fresh topend just to have a bearing let go.
Anybody with any knowledge or advise would be appreciated.
