MZ/MuZ Riders

After 30 miles on my first longer trip (excluding rides around the block, in which the bike ran well), i started to lose power. RPM increased but there was no power associated with the increase. The bike then died on me. I got it started again, only to have the same thing happen: loss of power followed by quitting.

I checked spark and fuel. There was spark and fuel, but the spark plug was covered in a greyish oil (looked like water and oil). Compression test showed 0 compression. I should note that i was absent minded enough to not check the spark plug before going on my ride, and when i took out the plug noticed the crush washer was not crushed. So, the PO had not torqued the spark in.

I took apart the top end and what do ya know the camshaft was broken in two pieces (see attached photo). Checking the valves, cylinder, and piston, they all looked fine.

In addition to what i should look out for before installing a new camshaft, does anyone have any ideas how something like this might happen? Any info or advise appreciated.

Thanks all.

Bueller

warped head ?? maybe

some cars are bad about this when they mill the head or block and TQ it back down
with out having an expert head shop do the work
the cam races are bowed

cams are just like people theydo not like there knickers in a TWIST

From the looks of that cam, I seriously doubt your head is worthy of saving. The bearing/bushing area in the center is completely hammered, and the head material is much softer than the camshaft material, so it's got to be toast. I'm surprised you didn't hear the bike screaming for help, or is that what the loss of power was?

Can you show pictures of the area where the camshaft sits in the head?

Thanks for the responses. I've attached a couple more photographs...Don't look promising. And she was such a gem for the first 40 miles...!

while you got it apart do check out the oil pump
and its drive train

Looks to me like you have a paperweight on your hands there. The colors on the camshaft and rocker arms alone tell me the motor has been horribly abused. The condition of the cam bearing surfaces tells me you may need some ear training. That didn't happen without the engine making all sorts of sounds, screaming for help from the rider/mechanic. Hopefully the bottom end doesn't look anything like the top and all of the destruction is contained. Poor bike.

To be fair, it is hard to hear over that Holeshot....

Luckily, the piston and cylinder and conrod all look fine. Even the valves are ok. I do know it was a track bike in its past life. Alas you win some and lose some when buying used and form a PO you aren't acquainted with.

Reading the forum, it looks like the standard 660 Raptor head will work? All years or just the early '01-'05?

Just for reference, here's what mine looked like after polishing it with nothing more than a green Scotch-brite pad after 50,000+ miles.

Just razzing you! My bike sounds pretty sick, the good kind, after the engine work and full race exhaust upgrade. I might have a hard time hearing a cam go south.

If it's a 660 Raptor, it should be the same head. I don't think it changed until the displacement changed but I could be wrong. Call one of the many specialty Raptor 660 machine shops around and ask them. I used Kenz Cycle Tech to do the build work on my head and he's very knowledgeable. If you do speak with him, tell him the guy from Austin with the MZ Skorpion is very happy.

Check the oil pump. Make sure you're getting adequate oil pressure at the top of the head. Your cam is overheating and welding itself to the registers.

Thanks all for the responses. Got a nice deal for raptor head, cam, jug, and piston from a Raptor. Just to confirm, only the head from the Raptor will work for our bikes, correct?

I'll be sure to check oil pressure to the top. A friend shared with me that the loose spark plug has the potential to set off a chain reaction...no seal means exponentially more air, variances in compression, heat, etc....maybe this could have caused the lack of oil like symptoms and ultimately the failure? Needless to say, the head is quite warped.

Best,

Bueller

Everything above the base gasket on the cylinder is compatible with our engine, including the piston.

And if you plan on running the snot out of the new engine, make sure to remove the auto decomp system and replace the cush drive gear in the balancer shaft drive. Both are known problems when running at sustained high rpm.