Sunday 22 April 2012

The search for the missing bearing

After my premature exit from the Rallymoto Sprint, I had to attempt to find out what went wrong with my CCM 604.

It felt like fuel starvation so first step was to strip down the carb. I thought I had solved it when I discovered a bit of grit lodged in the pilot jet but that didn't help and it was no better when I put it back together and on the bike.

So next likely culprit was electrics, I have an almost complete spare engine so swapped the stator and ignition pick up over but no joy. Next culprits were the ignition amplifier or the rectifier (both a regular failure on CCMs) but this would require borrowing the items off a friends bike to check them out and that wasn't posible for a couple of weeks.

So I decided to check some other things in the meantime:

First the cam belt, so after removing the cover the tensioner looked like it could do with a bit of tightening but nothing major.

Next, has it jumped a tooth? I could have marked the pinions and corresponding reference points on the back plate, turned it over twice and see if they still line up but decided instead to do it the way the manual says with a straight edge at TDC.

So I turned the engine over to what I thought was TDC and decided to remove the tappet covers to check.... glad I did!

There was about 8mm of play on the exhaust valve rocker

It turns out the roller/cam follower has self destructed!

And if you're still wondering what's wrong, here it is compared to the one out of my spare engine

So the exhaust valves were opening just enough to start the engine but obviously not enough to run.

So the question is what was between the roller and the pin? You can't see on the intact rocker, I was inclined to think a needle/roller bearing. which of course meant the rollers must still be in the engine ?

So do I have a poke inside the head, drain the oil and remove the sump plate and hope I find the offending bits, bung the intact rocker from my other engine in the head and hope for the best or do I strip it down and have a good flush out of everywhere.

Anyone who has ever tried to remove a Rotax motor (or replace it) from a CCM frame will know it's an absolute bitch. It took me two and a half hours to get the motor back in the frame last time I tried.

I decided to start with the first and see what I find!

So a few days later I had a fruitful "quest for the missing bits" in the sump of the CCM

First off I drained the oil, that turned up a few bits...

Then I removed the sump plate and found a few more bits in the strainer...

I then removed the smaller sump plug below the strainer, the one with the magnetic tip....

So that's where all the rest of it got to!

All looking good so far, next job is to flush the engine through from the rocker box to dislodge anything left behind.


  1. Those magnetic sump plugs are useful, aren't they? I once dropped a valve collet down the camchain tunnel. Eventually I gave up with the magnet-on-a-stick approach, and if the car hadn't been destroyed one night in a Wiltshire incident involving traffic lights, the offending collet would be wherever it ended up (probably the sump) to this day.

  2. That was nicely done. The finished material looks good too. hydrodynamic bearings