Rotax 650 Engine Rebuild (BMW)

Discussion in 'Thumpers' started by divimon2000, Dec 11, 2012.

  1. divimon2000

    divimon2000 Been here awhile

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    Ah ha!

    All the land pieces still rattling around in there.

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    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) :wink:. Wanna see how the cylinder looks? Wait till next post :D
    #21
  2. divimon2000

    divimon2000 Been here awhile

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    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 :rofl

    Glad it wasn't me.

    Looks goofy with no rear lower and no engine.

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    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).
    #22
  3. Emmbeedee

    Emmbeedee Procrastinators

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    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.
    #23
  4. ericsbr

    ericsbr Adventurer

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    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.
    #24
  5. ericsbr

    ericsbr Adventurer

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    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.
    #25
  6. Emmbeedee

    Emmbeedee Procrastinators

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    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.
    #26
  7. Royal Tiger

    Royal Tiger Sd Kfz 182

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    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. :D
    #27
  8. divimon2000

    divimon2000 Been here awhile

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    You'll have 10x more fun in Burlington or winooski, but I have friends up there, who seem to survive.
    #28
  9. Royal Tiger

    Royal Tiger Sd Kfz 182

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    We liked Essex as well. She really liked St. Albans though. I'm trying to remember the other places we went. Jeffersonville?
    #29
  10. divimon2000

    divimon2000 Been here awhile

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    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.

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    Maybe I'll search a bit on the Loctite thread.
    #30
  11. divimon2000

    divimon2000 Been here awhile

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    Getting the starter gears off. This bike uses a couple plastic gears to get to the Sprag clutch embedded in the flywheel. Cool system, first I've seen (when my spring broke this spring).

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    Voila

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    The twins take apart the case. Eric on the right with the right side cover, Bill on the left. Me shooting.

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    Cool stuff. I think: Shifter shaft up front, then the counter shaft (output sprocket) then main crank shaft (magnet attached), then the counterweight shaft.

    Important to take this apart since the F650 GS engine is known to have blown counter balance seals causing the symptom we had (oil blowing out the breather). Not that we didn't find a better culprit in the piston, but....

    Eric decided to pull the bearings and seals here for good measure. Bearings did feel a tad grungy, but not much. Pulling is the next step.
    #31
  12. larryboy

    larryboy Chopper Rider

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    Paper gasket on the center cases? That's very strange, I wonder if that's why some of those engines grenade and others don't, hard to get a consistant torque/preload on the bearings with a paper gasket in the middle. I'd imagine that you'd want to be super specific on the torque values for the case when you put it back together.
    #32
  13. mcma111

    mcma111 Long timer

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    Paper gaskets are quite normal in most engine cases. What's in your motor??
    #33
  14. divimon2000

    divimon2000 Been here awhile

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    Pulling out the Counter Balance bearing with heat and a blind puller.

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    Some of the stuff:

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    With all that stuff floating around the piston, amazed to see a perfect cylinder complete with crosshatching. 35k miles.
    :freaky

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    #34
  15. divimon2000

    divimon2000 Been here awhile

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    Clean!

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    Before:
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    Hard to keep the workers on task. Eric checking to see what he's gonna like on the back.

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    Gettin the valve out

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    #35
  16. divimon2000

    divimon2000 Been here awhile

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    Getting the valve parts out

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    Valve stem seals: hard to get a grip on.

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    The adventure garage couch and viewers

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    Eric about ready to launch a valve across the basement. It faired AOK!

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    And lapping the valves

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    Eric can talk about the ordering of the parts now. What we need, where to get it, etc.
    #36
  17. ericsbr

    ericsbr Adventurer

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    I started a parts list before we even touched the bike based on what I expected to find and was pretty darn close. Piston and rings, seals, gaskets, counterbalance shaft bearings.. ended up needing a few small extras like woodruff keys, plastic timing chain guide, and a few misc hardware items.

    First step was an online bmw dealer parts search to get all the part numbers. Then googled the piston (most expensive and common part) to see whats out there. There didnt appear to be any aftermarket parts available for this engine. No problem since i really prefer to use OEM internal engine parts. Searching bmw part numbers returned mostly dealers and this place- http://www.2wheelpros.com They sell tons stuff (OEM and aftermarket) for many motorcycle manufacturers. Overall their prices seemed about 10% less than bmw dealers. Some parts were backordered but thats ok since this is a winter project.

    I did look into getting the C/B shaft bearings from a local brg supply place. BMW doesn't make bearings, they just repackage and mark up the price. These were standard size NTN brand bearings. After a long conversation at the brg supply place about brands and quality i ordered SKF brand (a huge worldwide bearing mfr). 2 days later i went to pick them up, and well, they just seemed low quality. Decided it was not worth using vs the cost savings. This engine will be 100% when im done and dont want any junk parts inside.

    Lastly the water pump. No leaks but have heard lots of talk about issues here. BMW only sells a kit including seals, impeller, and shaft. My impeller and shaft have no wear but the seals a bit hard. A little research found the same seals are used in rotax go-kart engines. Ordered seals from a rotax dealer in Mass.
    #37
  18. STisma

    STisma Been here awhile

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    #38
  19. thumpism

    thumpism Between bikes

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    I'm following this thread with interest because I found a '94 F650 near my house, and the guy tells me he might sell because the bike needs work and he can't afford it. He claims there's a knock in the engine and I'm curious about the extent of what needs to be done, how to proceed and the associated costs. What's a reasonable price for the bike in this condition?

    Keep up the good work.
    #39
  20. ericsbr

    ericsbr Adventurer

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    #40