Rotax 650 Engine Rebuild (BMW)

[divimon2000]

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).



Voila



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



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.

[larryboy]

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.

[mcma111]

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

[divimon2000]

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



Some of the stuff:





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

[divimon2000]

Clean!



Before:


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



Gettin the valve out

[divimon2000]

Getting the valve parts out



Valve stem seals: hard to get a grip on.



The adventure garage couch and viewers



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



And lapping the valves



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

[ericsbr]

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.

[STisma]

Water Pump seals on sale at AF1 for $11.99ea
http://www.af1racing.com/store/Scrip...idproduct=2318

[thumpism]

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.

[ericsbr]

Originally Posted by STisma

Water Pump seals on sale at AF1 for $11.99ea
http://www.af1racing.com/store/Scrip...idproduct=2318

Good find STisma!

The rotax dealer where i ordered my W/P seals sells them for $5.82ea. heres a link- http://www.crg-america.com/kart-part...20(FR%20DD2%20...

[divimon2000]

Originally Posted by thumpism

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.

94? Not much if it needs engine work,, maybe $600-1000 and throw in a used engine for $600. You could part it out for 1000 and break even! Plus the nightmare of storing parts, mailing boxes, etc. hard saying until you know the problem. Carb cleaning could be the issue!

[20Fingers]

Originally Posted by divimon2000

Anyone here do this? (I'm sure, just haven't searched yet) Too bad for you, here is another one. I have rebuilt a bike before, but never had anything to do with an engine. Buddy has (Eric). My rebuild thread is here.



Buddy and I find a BMW F650 GS '07 with 35k on it for a REALLY good price. Been looking forever. Finally. Engine is pretty much toast , but thats what we do- buy other peoples junk (if its cool) and get'er going. We have more time and beer than brains and money.

Symptoms.

Oil out the breather tube into the airbox. So much so, the PO attached the end to a bottle of coke and drove it around. After a couple of checkouts by local dealers, Max BMW gives him the bad news of something serious. My guess is they said a new engine or work totaling close close to that. They did a decent diagnosis with compression test and leakdown test.

We started it and checked it out as well and found it may have less power that the other 650's we've rode, had some sort of clanking unlike the cam chain and a lot of oil coming out when starting. It decreased to a mist when driving.

All in all the bike is in supergreat shape and we're psyched. I have a Dakar and a rebuilt 650GS so we're up to a posse if this thing gets running. We figure we have a few thou to spend and still make money on it so its all downhill from here. (uh huh)

Coming home from Maine (Or, Post a pic of your bike in a trailer in front of a train! thread)



In the Adventure Garage


Tune in.

Its going to be my first long trip destination when the snow clears this spring, have to come out n see you and my old beast! It's amazing that she was till running with the broken piston! BMW quality! Happy to know that you don't have a bottom end issue as we thought, upper end rebuilds should be a bit easier but then again, were did the broken bits end up??? Cheers, and look forward to seeing more as you go! MC aka 20Fingers

[divimon2000]

Hey, glad you checked in, the bits were riding along with the piston and we have it all! Post a pic of the replacement bike here!

[20Fingers]

Originally Posted by mcma111

By any chance did Max say the piston and rings are shot thus the blow-by, pressurizing of the lower end?

Hey Steve,
I sold this bike to the boys at ADV Garage...also, I was the one who took the 650 to Max for some help! Yes, they indicated that only three reasons could be causing the loss of oil through the breather tube, on top of their diog, I spoke to ROTAX in Germany regarding the problem (out of frustration with not getting help at another NON-Max dealership) A five minute conversation with the tech at Rotax indicated that ONLY three reasons for the oil leak:
1) over fill, which is something of a common problem with these bikes and new owners...judging oil capacity and need for more oil. YES, I did over fill it about a year ago, discovered the problem, dumped the oil and refilled before 2 miles got on the odo.
2) Seal failure on the counter balance shaft, leaking oil from the crank case into the right side housing that has the vent tube on it.
3) Compression leak issue, causing a pressure build up in the crank case. Which was the problem ADV Garage discovered when they broke down the motor! AMAZING to me the bike was still running at all!

In retrospect regarding the money I spent on a dealership (NOT MAX), time, effort, and frustration with getting ZERO answers, ONE email or phone call to ROTAX could have saved me $600 in diagnostics and run-around! ADV RIDER was instrumental in my eventual success in finding the right help! I accessed the Thumper pages and found the right advice which led me to contacting ROTAX. Just wish I had done this prior to visiting the cheesy dealer who took my money (happily I might add) and sent me home with no real answer and no results. One stinking call-email, could have saved me a bundle!

Can't wait to see her back up and on the road this summer, or winter, depending on when ADV garage gets the job done!

[20Fingers]

Originally Posted by divimon2000

Hey, glad you checked in, the bits were riding along with the piston and we have it all! Post a pic of the replacement bike here!

Here's what I am riding now...however sweet she is, I will ALWAYs miss my Thumper! Maybe we can swing a deal to buy it back...when I win the lottery, that is!