can high rpm damage flywheel magnets?

Hi Guys,

New Member here.. Got myself a 1980 KZ250 C which i'm in the process of getting on the road.
I'm learning more about bike mechanics but don't have a space of my own yet, so took it to a local Mechanic.

Having bought it (from interstate) without test riding, i was ready for a few surprises, but had a heap of unexpected issues.
Turns out that the whole top end needed rebuilding (bad oil leaks), including overbored cylinder, OS piston & rings, valves, valve seals & springs, rockers, camshaft, cam chain, new points & timing advancer... Basically the entire top end is now new.

SO.... I thought i'd be on my way with this done, but heading into the workshop to check it out I noticed that my (chrome) muffler had all this new heat damage on it. When questioned, the mechanic explained that he'd run the thing consistently at really high RPM to "Wear in the rings". To my understanding, this is the opposite of what you should be doing anyways. After this process, the mechanic took it for a test ride wher he discovered that it was also starting to have timing issues, despite the new points and advancer.

He's then apparently spent 10 hours, unsuccessfully trying to get the timing right, finding out that it's now got a really weak spark. Finally after all this time looking at the timing marks on the rotor, he's noticed 2 significant cracks in the flywheel rotor magnets, which look even more severe when we removed the stator coil.

Ok. now i've set the scene (thanks for bearing with me so far), my QUESTION is: Can this process of extended high RPM / redlining the bike (to wear in rings) have potentially caused the rotor magnets to crack? I've had a few people say yes and have found anecdotal evidence online about it, but need more proof before I go in there & challenge him on it.

To me, that would explain why this issue of low spark (as alternator stops working & battery begins being drained) has only just appeared after the rebuild & gotten progressively worse. Does that sound plausible?

Unfortunately, this would reflect a pattern of behaviour for this mechanic - they snapped my Fuel Tap / Petcock without telling me (using pliers) and hoped that i wouldn't pick up on it (i did).

Any help would be really appreciated. I've ordered a replacement flywheel (which was US$350) All i want is to get the bike out of this garage ASAP, without having to pay these guys the labour they've wasted on my bike, let alone the damage they've caused to it over th last 6 MONTHS they've had it!

Thanks everyone.

Jezz

Do you have a B.A.R. where you live?
Steve

Wow. I don't think extended high rpm should cause such problems with the magnets, but there is nothing in your story that justifies allowing that dude to own a wrench.
Perhaps if you can post some decent pics of the cracks, some of the more experienced folks around here can make an assessment.

swest wrote: Do you have a B.A.R. where you live?
Steve

Is that the Bureau of Azzhole Reaming? I think that is just what he needs.

Bureau of Automotive repair. he needs his license yanked. If nothing else they can make him pay for a complete rebuild.
Steve

Damn it to Hell, I hate reading things like this.
Somebody needs a serious, and merciless ass kicking.
I'd stop now and get a lawyer

Did he really say he held it at redline for an extended time? Does he know that all of the fins, on the engine, mean the bike is air-cooled, as in, it has to move to get cooled?

Below is you "mechanic" breaking in a new set of rings. Call a lawyer. Ed

Was he a HD mechanic by any chance?
Steve

Hi All,

Thanks for your feedback so far. I'm in Sydney (Australia) so we don't have a BAR but we do have an Office of Fair-Trading (government' Dept.) which helps resolve these kinds of disputes between customers & service providers.

I'm going in there today to challenge him on this & will get some pictures of the damage for you to check out.
Wish me luck.

Jezz

Luck
Steve

Been following this for a little and good luck for sure! A wrench is a dangerous tool with that level of stupid.