Boxerworks.com

Gidday

Over the years I have attended a good handful of these "Tech sessions" at various locations around our southern wooded areas, actually I'm finding it a little difficult and blurry to recall any Tech Advice being given out which involved the moving parts of motorcycles. How to cook a steak, YES!! When a prostate should be checked and if so do you or don''t you take the doctor some flowers to the appointment, well there was mixed consensus about that one..

I have attended many tech sessions and given my share. All were mainly tech oriented with a few lies thrown in for fun.

Hi - thanks for that guys - I will join in for sure.

So. I got the bike fixed. It ended up one valve was 2.4mm out ! But how did that happen suddenly? They couldn't explain it. So they fixed the adjustment and balanced the carbs. I picked it up and was running very smooth but down on power.. just felt laggy on the bottom end and normal past 4k.
My buds had gone to Bright the day before and I decided to catch up so I could camp and ride falls creek, hotham etc... love that area !
Along the Hume it started running a little rough and stopped idling. I compensated the idle knowing it was masking a problem and power was right down. Got to Bright, filled up and decided to do Tawonga gap to Mt Beauty. I come froma sport bike background and love to ride spiritly. The beemer handled beautifully with 50mm extra fluid in the forks, progressive springs and preload adjusted. Stopped at the top for a selfie then went to start the bike and the Starter let go from the flywheel with a ping. That's strange I thought... well at least I can jump start it. Free rolled down from the look out, got some speed and the rear tyre locked, tried 3rd then 4th with same result.. SHIT, the engine is seized !!!

Lucky I have total care and got her towed back to Melbs while I drove a rental. I thought about it on the way home and came up with a theory that the starter gear had broken and jammed the flywheel. Is this at all possible or have I welded the bearings to the crank while riding a bike with an obvious 'issue' ??

I'll pull it down this weekend for a look - but just hoping there might be some theories that the engine has seized in another way that is unlockable

Staf

Pity you had a ride on such lovely roads shortened like that. Sympathy attached.

"... one valve was 2.4mm out". Do you mean that the valve clearance was open by 2.4mm? Very odd, especially if the adjuster locknut was tight. I'd want more information about exactly what the mechanic found.

You will be getting a proper introduction to airhead mechanicking now, and you are in for a treat if you have aircooled VW experience. You must realise that nobody but yourself is qualified to work on your airhead. This applies especially to BMW mechanics, who are mostly quite skilled at changing out black boxes on the modern bikes.

As to the current problem it's impossible to speculate - it could be gearbox related for instance. Tell us what you find when you are in there.

I think you have a wayward valve seat. I'll guess exhaust.

Valve seat moves 2.3mm out of valve pocket, but remains in pocket. That would give 2.3mm valve clearance.
Up on Tawonga, your valve seat jumped right out, and is now stuck outside the pocket preventing the valve from closing, and is causing the piston to hit the valve and/or seat.

Just my guess as to what happened.
If you remove your valve cover, I think you'll now find 1/2" of clearance on the offending valve.

That's a really good guess. If ME is right (and it's got my vote for most likely), then you managed to dodge a very expensive bullet, as dropping that seat while riding would have holed the piston and done lots more damage. Still, if he's right, it will be expensive - just not nearly as expensive as it could have been.

I'll guess that the valve seat has popped out when he hit the starter, and the piston has not been able to hit TDC due to hitting the protruding valve seat/valve. That will have put a ding in the top of the piston, bent the valve and may have tweaked the conrod.

I'll also guess there may be a severely recessed valve head that the 'cooled off' valve seat has 'grabbed' when Staf stopped briefly.
Hit the starter, valve head pulls the seat out. Funholiday scoffed at my theory a while back after this happened to me..

In my similar case, the engine immediately ran on one cylinder after hitting the starter. But my valve seat did not come all the way out of the pocket. Only enough to prevent or seriously compromise the valve opening.
That sucker seat got peened back in place! It happened right at the campsite when we arrived at the Alpine Rally a few years ago.

I think Staf's bike was down on power because the seat moved back into the pocket, and the previously set clearance now holding the valve way open.

ME 109 wrote:
I think Staf's bike was down on power because the seat moved back into the pocket, and the previously set clearance now holding the valve way open.

Yeah, that part of it was why it all sounded like such a plausible explanation to me: because it explained the entire series of symptoms.

ME 109 wrote:I think you have a wayward valve seat. I'll guess exhaust.

That was what I was thinking after the first few posts in this thread. I have far too little experience with the airheads yet, but the words " . . . put it on it's side stand for a minute while idling.. there was a pretty loud bang . . . " suggested to me the the damage was due to overheating.

Could be intresting to hear if Salty would comment if he think the engine was pretty warm already when allowed to idle, and if "a minute" means "a while", which may have been several minutes?