Rotax 650 Engine Rebuild (BMW)

[divimon2000]

Here is how it ran with the breather tube disconnected from the airbox. It enters the lower engine around the sump area

[Kawidad]

[divimon2000]

OK, so we got it on the table and started on the right side with the stator, starter sprag gear, etc. It all came apart pretty quick.



Flywheel came off pretty easy with the puller (standard for a lot of bikes). No heat required, but when I took mine off my bike I needed quite a bit of heat (good loctite?) .



Double overhead cams off, flywheel off.



Hmm, how'd this happen we wonder?


Next installment: THE PISTON! WOO HOO

[Kawidad]

Originally Posted by divimon2000

Hmm, how'd this happen we wonder?

Has anybody been in there before? It looks like installation error. I've seen it before when someone installed the flywheel without proper care.

[larryboy]

Originally Posted by Kawidad

Has anybody been in there before? It looks like installation error. I've seen it before when someone installed the flywheel without proper care.

Looks like a sheared flywheel key, he did say the flywheel came off easy...sounds like it was loose to me.


OP, please tell me you're splitting the cases and replacing all the lower end and trans bearings that you can afford, you're almost there already.

[divimon2000]

Ah ha!

All the land pieces still rattling around in there.





Theory: Woodruff key breaks, advancing timing, detonation occurs for some time until lands cant handle it anymore. Question is why did the key break? I'll let the owner Eric talk about how hard it was to take the magnet off- seemed easier to me than mine in re: puller, but that may be a result of it already breaking loose. Threaded nut? Only he knows torque. I didn't reef on it.

Re: splitting the case: Yeah we will (did), we're not on crack. (yet) . Wanna see how the cylinder looks? Wait till next post

[divimon2000]

Might as well hit the swingarm, dogbone bearings while we have a clearer shot. No one ever hits these on the BmW since there are no nipples! Of course Eric looses the free needles in the parts washer

Glad it wasn't me.

Looks goofy with no rear lower and no engine.



This is one area you get no detailed pics since my hands were greasier than a pig at an alabama state fair (no disrespect, prob same here in VT).

[Emmbeedee]

Originally Posted by divimon2000

Hmm, how'd this happen we wonder?

You'll have to be careful when you install this - clean the inside of the rotor and crankshaft carefully and use a Loctite product on the shaft in addition to a new key. Often if a flywheel has been allowed to turn on the crankshaft it wears the crank so you can't get a tight fit and it'll keep shearing the key.

I once had a Bultaco that happened to - the crank was written off - it never held the flywheel for more than an hour before shearing the key.

It's a shame that engine was worked on by vandals. My '02 F650GS is still going strong after 110,000 kms and has never had anything but regular maintenance. It even still has the original water pump and seal.

[ericsbr]

the nut was tight and had threadlocker, i used an air impact to remove it. the flywheel/magnet was also tight on the taper, i used a puller with hand tools (no air), and it required some effort. sudden engine stoppage could have sheared the key.

[ericsbr]

Originally Posted by Emmbeedee

You'll have to be careful when you install this - clean the inside of the rotor and crankshaft carefully and use a Loctite product on the shaft in addition to a new key. Often if a flywheel has been allowed to turn on the crankshaft it wears the crank so you can't get a tight fit and it'll keep shearing the key.

I once had a Bultaco that happened to - the crank was written off - it never held the flywheel for more than an hour before shearing the key.

It's a shame that engine was worked on by vandals. My '02 F650GS is still going strong after 110,000 kms and has never had anything but regular maintenance. It even still has the original water pump and seal.

the flywheel/magnet only moved about 1/16-1/8 inch clockwise. the CW rotation probably had a tighteneng affect on the nut, which is good. it was tight on the taper and needed a puller to come off which is also a good sign, i will clean well, use a generous amount of loctite 648, and of course a new key. since it never "spun" on the shaft, im hopeful that it will be ok.

[Emmbeedee]

Originally Posted by ericsbr

use a generous amount of loctite 648, and of course a new key. since it never "spun" on the shaft, im hopeful that it will be ok.

When I did the rotor on my F800GS this Summer I found Loctite 620 is the right stuff for the rotor shaft. I think the manuals call for 648 but I was told it's no longer made. I ended up having to buy 36 ml of the 620. Wasn't cheap, but I probably have enough to last for the rest of my life.

[Royal Tiger]

Looks good so far! Keep up the good work.


I'm looking to possibly retire in the St. Albans area in the future. I'm only 42 so I have time.

[divimon2000]

Originally Posted by Royal Tiger

I'm looking to possibly retire in the St. Albans area in the future. I'm only 42 so I have time.

You'll have 10x more fun in Burlington or winooski, but I have friends up there, who seem to survive.

[Royal Tiger]

Originally Posted by divimon2000

You'll have 10x more fun in Burlington or winooski, but I have friends up there, who seem to survive.

We liked Essex as well. She really liked St. Albans though. I'm trying to remember the other places we went. Jeffersonville?

[divimon2000]

We're getting some Loctite 648, I think you can get it, just a big honkin bottle.

Not to hijack my own thread but, I used Permatex Red Permanent and am now thinking about re-doing it. Permatex says nothing about heat (although they say you need 500 degrees to remove it) and its "thread" locker not "cylindrical" locker. Big diff? Grrr. I was in a time crunch for my first big ride, and thats all they had locally.



Maybe I'll search a bit on the Loctite thread.