F650 Engine Misc FAQ

compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.
Last Updated: 15 June 2007, by Winter #1935

Also see the following FAQs:


It is highly recommended you get the second DVD, as this contains loads of hints and tips on how to drop the engine out of the frame, and pull the whole thing apart (if you need to do that of course).

Engine Failures

Strange Engine Noises?

Q. Knocking engine, melting plastic.

Yesterday, I noticed that there was a knocking when in neutral, clutch engaged. Very scary. Moderate knocking, and I could feel it in the handlebar. Maybe from engine, but I think transmission, since it happens only with clutch engaged. I opened the clutch, because I was in there two weeks, 400km, ago to extract a broken clutch spring screw (which I had broken myself). I couldn't see anything out of order, inspected all the friction plates and clutch plates, all seemed well and in spec except one friction plate had chips in ten of the friction bumps, and I could smell burned oil when taking off the cover. When reassembled, the knocking was present but much diminished when I started up.

Went for a five minute ride to visit a friend, by which time the knock had reasserted itself (when in neutral, clutch engaged). Further, when I got home after only five minutes ride, the right engine cover was melted where it passes nearest the exhaust pipe.

Other recent work includes going to smallest shims on intake ports, so that one is now in spec and the other is almost in spec. They had been way out for a 12000km. Inspection reveals that the tachometer boot over the tachometer connector on top of the clutch is wet with oil, though it may have been before; the oil tank line from the top of the engine case near the oil pressure switch is wet with oil for a few centimetres, though it may have been before; there is a minor leak in the oil seal at the countershaft, which has been there for 7000km. There is no detectable knocking when riding or when the clutch is disengaged. By clutch engaged, I mean the clutch, not the lever. That is, clutch engaged = engine connected to transmission, the lever is at rest. Idles at 1350 cold, 1500 warm. Just to cover the point properly, I went out now and tried gradually raising it to 1600 (engine is cold right now), and the knocking merely got faster, not in any way diminished. I forgot to mention that there is a ticking, but it's always been there. Sounds like valves, but I've read somewhere that it's the chain, and it's normal on the F. In my investigation this morning, I had the clutch fully open. Inspected all the plates, found on friction plate with small chunks taken out of ten bumps (little friction pads on the plate). Small enough pieces to have been filtered out, I believe. Otherwise, all parts appeared to be okay and torqued up properly. I did not remove the clutch nut. Is it worth removing the clutch nut to look around behind (real PITA, that clutch nut)? Do you know how far can I go without pulling the engine out? Aleksander in Dubai 98ST

Complete New Engine?

by Steve #417, Richard #230 and Kristian #562, June '02

If all else Fails does BMW Supply Complete New Engines ...?

A: Sure they do.

Are you crazy?

Actually, there is such a thing as a Complete New Engine: It is Part Number 11 00 2 343 231, it is listed as 650ccm and retails for US$5190.00. It is a valid part number.

Caution this is for the classic and not the GS.

The motor along with the carbs weighs something like 85 lbs.

Here is what it looks like:


How much does the engine weigh?

Catastrophic engine failure

Rotax 654 failures are rare!
The Rotax 654 engine is generally considered bomb-proof. Many people will put more than 200,000 miles (320,000kms) on an engine before it needs any serious maintenance. As such, major engine failures (such as shown below) are very rare for the Rotax 654. Don't panic reading this story - your engine will not explode unless you do something really really stupid. However if your engine does explode, please let us know why, and take some pictures!

My engine locked up on the highway, and it look really bad. As it look like I'm going to have to trash the bike I'd like to understand what could have hapenned, so I'm calling to the expertise of this forum for advices. First of all, my bike: It's a blue '97 F650ST. I bought it used two years ago, with 10k kilometers. Since then I've added 30k Kilometers without any problem whatsoever. The 10k, 20k, 30k and 40k maintenance were done by a reputable dealer near Paris. This bike has been trouble free, the only things I had to change were two rear tires (one used, one punctured), one front tire, the chain and sprockets (twice) and a battery.

The friday before last I brought my bike to my dealer for the 40k maintenance. They changed everything, all the fluids, brake pads and so on. It hurts: 430 euros... But I got a new bike back, with smooth controls and perfect driving. I drove it home. Mileage at that point, 40360 Kms. This friday I took the bike to go to a family reunion. What was supposed to be a simple 2 hours drive turned into a nightmare. After and hour and a half and something like 160 kilometers I stopped at a gas station. I refilled, with the usual 95 octane version, and spend some time tightening up the damn right hand mirror. Total stop time, around 20, 25 minutes.

I then restarted and drove another 30 kilometers. At a steady 130/140 Km/h. And then sudently, without a warning, my rear wheel locked up. After a chilling ride, rear wheel sliding left and right I was able to finish onto the shoulder. In retrospect I should have pulled the clutch, to regain a rolling rear wheel, but to be honest at that point I was thinking the less stuff I was touching the better!

First inspection of the bike showed water everywhere, and pieces of shaved metal all over the place as well. Not good... After freezing for a while on the side of the road (yeah, it was cold, 5 celcius degrees out) the bike was towed to the nearest dealer, and he looked at it today:

In order to understand what could have hapenned, and potentially quote me a price for repairs, they need to open the engine completely, remove the cylinder, and see which parts need a replacement. At this point it doesn't look like the dealer did any mistake and it's already looking really expensive, read it will cost more than the price of the bike...

So, what is your best guess? What could have happened? Anybody know of a good engine I can buy? Anybody interested in a bike for parts :^( ? James, Paris

Catastrophic engine failure - Part 2

First of all the bike is back on the road. I bought a used engine from a used parts place in Alsace for 525 euros. The engine is one year older than my bike, with 52000 kilometers on it. The guy had a trip planned to the Paris suburbs so he delivered the engine not to far away from my place. The day before I had brought the bike back from Troyes using a friend's trailer and car combination (Thanks Christophe!). All was left to do was to take the whole bike apart to swap the two engines.

It took me a while to get everything off and on as it was a first for me, but with adequate documentation (Moto Revue Technique) anything is possible. the two engines are somewhat identical except for two parts: the way to put the output sprocket and the sensor for the neutral.

A week or so ago I got to the point where everything was mounted back, but when I pressed the starter all I heard was a loud crunch... After a frightened check it turned out that when the engine blew something must have been thrown with great force on the starter as one of the magnet inside it had crumbled into multiple pieces. Well, nothing than a call to the used place can't solve. 70 euros and two days later the starter was there, I plugged it in, and on the third try the engine started.

The bike smoked a lot, but after 10 minutes idling (and me checking everything) the smoke subsided. I took the bike for a ride, and after 35 kilometrers brought it back. I've put 200 kilometers on it so far, and all seems well, minus a couple of oil leaks I have to track down.

What about the old engine you ask? Well, I opened it today. Tell me your thoughts, the pictures are here. I stopped just before opening the oil pumps, I figured if one of them failed it could have been the cause. And so far, the upper pump turns, but the lower one seems to be locked... I'll see to it tomorrow. James Bond

First of all a general view of the damage, right behind the starter.

You can see that the cylinder is all cracked...

...in multiple places

note also that the carter(Crankcase) below is also touched, at this little pin is out.

To open everything, I stated by the top, removing the cam cover.

Then removing the cams. So far everything looks okay.

Well, removing the head shows that something actually hit it, damaging the valves pretty badly

Look, no piston! Where did the piston go? This is what I saw when I opened the head...

Turns out the piston has been reduced to little chunks of metal. See it down there?

I fished out this little piece and put it on the haed to give you an idea of size.

Let's look at the cylinder now, it's cracked all the way. I had to hold it together to take those pictures as the front part just fall appart. This picture is from the top...

...and this one from the back of the engine, looking forward.

It all dropped on the floor when I stopped holding it together.

nice hole huh?

Removing the cylinder, well, what's left of it.

A look inside the engine. See all those piston chunks in there?

They're everywhere...

I opened the side of the engine, to see if something stuck on the distribution chain could have caused this

Well, no. This is actually an area of the engine without metal pieces all over it

Engine Rebuild?

My '99F with 19k miles has been running progressively worse for several months now (details below). I recently took it in to the San Francisco dealer for a Level II service (at 18k) and hoped that that would fix the problem. Instead, its been in and out of the shop 3 times in the past month, yet the problem has only gotten worse. Today the dealer said that he found "65% leakage" in the leak down test and therefore I need a head rebuild for $1300. Ouch!

I'm no mechanic so I can't really say, but they've gotten the diagnosis wrong twice already. In their defense, they have been very apologetic and will refund what I've paid to date but I'm not sure I want to pay for a $1000 guess. I'd appreciate any suggestions or cheaper alternatives.

Here's the history:

I bought the bike used 3 years ago with 10k miles. I use it primarily for city riding with the occasional (once a month) long highway ride. It ran great for about a year but since then has gradually gotten worse in performance and gas mileage.

In the last several months it has gotten significantly worse, especially when the weather is cold or wet. Its taking increasingly longer to warm up and I can't just let it idle to get warm. The engine seems to have to be working in order to overcome the problem. Right now it takes about 10 minutes or more and until its warm it will not go above 3500 rpm (while moving). As soon as it hits 3500, it stalls, stumbles, surges, bogs down, and sounds very rough, until I pull in the clutch or upshift. I've almost dumped it several times when it bogged down in a turn. After its warm it seems to run ok. lessikos

Blown Cam Cover Gasket?

Recently I braved 20 degrees or so to warm up the oil for another month and test my new polar hands (enclosed handgrip covers for you flatlanders). After about ten minutes of riding time, I apply a moderate amount of right wrist (about 5g's in fourth). There's an audible PFFFT!, my right calf is covered in warm oil and I'm followed momentarily by a large blue cloud which subsides to a small blue cloud. I aim for home watching the oil and temp lights and being very careful. No further problems, other than the persistent small blue cloud following, a little more noise than usual from the valve gear, and a very dirty bike on the right side.

Inspection at home shows that the cam cover gasket is blown out of its recess on the right side, just above the exhaust pipe. I have not touched the valves in about 3,000 miles and nine months, and I believe it was carefully torqued when I did the last check. So what happened? I'm assuming something caused a LOT of pressure to build up in the cam cover. A clogged breather? something frozen (doesn't seem likely or it would have happened earlier)? I still have the carbon cannister in place, a la stock. The bike is always garaged, generally above freezing. bugsy

Rod Bearings Failure

compiled & edited by Kristian #562
by Gottfried, Team Pami, 29/11/01

Team Pami have had a couple of engines with these problems:

Other Symptoms

The bad rod bearings that I have heard keep knocking when the engine revs up. My daughter's bike made more of a knocking noise at higher engine speeds than it did at idle. Richard #230

If the rod bearings are bad then it may be that the water pump may has let the coolant into the engine and diluted the oil. This could explain the oil light flicker at low idle. This happened to my bike 32,000 miles ago but did no damage to the engine. Check your coolant tank and It will be empty. Let us know what you find. If this is the problem probably all you will need is the water pump kit installed and a couple quick oil changes to flush the engine.

See also the FAQ on Counter Balance Shaft Seal Failure.

This is not intended to be comprehensive at this stage as there isn't enough detailed information from older bikes. As the bikes all age and these problems surface, hopefully more details can be added. Hopefully it won't be from my bike. Kristian.

Snapped Bolts

Removing snapped / sheared bolts is not easy
While this section may help someone unfamiliar with removing snapped or sheared bolts, it is highly recommended someone experienced perform this sort of work. You can end up with a very expensive mess if you get it wrong. However if you are in the position where you must do it yourself practice first on something other than your bike. Even if you have to spend $20 at the local junk yard, it is far better to waste that $20 than pay $500 for a replacement part.

Method 1: Drilling (cylinder head to lower engine bolts)

This method was suggested by Flash for removal of a snapped bolt. The bolt in question is one of those holding the cylinder head to the lower engine. The bolt was rusted, which made if difficult to remove and resulted in it snapping...

Method 2: Using EZ Outs (other bolts)

In most cases you can use this method...

Once you have gotten the bolts out, you can use a helicoil or a timsert:

Can I ride my bike without a valve cover bolt?

Misc Questions

Ring Gaps

I came across a reference to Duane Ausherman's site on BMWMOA.org/Forum. Duane was an old hand with BMWs when I came on the scene. I have a LOT of respect for the man and his experience. There is a LOT of great stuff on his site. Then I read this... this...

Ring gaps for the BMW motorcycle

The Myth
Everybody "knows" that ring gaps must be placed away from each other. The fear is that the compressed gases would leak out if the gaps are lined up. Many suggest placing them at 120 degrees from each other to reduce leakage. If you are using the BMW ring compressor, that makes it a bit slower to reach around and under the piston to shove those ring ends into the cylinder. Let's think about this for a moment.

The Reality
Each time the crank makes one revolution the piston also travels up and down one time. For easy math let's use 6000 rpm. During one second the piston makes 100 trips up and down. True, only 50 are compression strokes, but for this discussion of time it matters none. Half of the trip is downwards and there is no compression. The half going up is now happening in 1/200th of a second. That isn't very much time. If all of the ring gaps line up, how much compression do you think is lost by gas going straight through them? Nothing worth considering.
Now lets think about another issue. The rings don't stay in one place. Proof is twofold.
1. A two stroke engine has pins to locate the rings to prevent them from rotating and getting caught on the open ports.
2. Set your ring gaps anyplace you want. Ride the bike 1000 miles and remove the cylinder. You won't find them in the same place.
This means that you must accept rotating rings, redesign the pistons to locate the rings or remove the cylinders very often to put them back where you have decided that they belong. I think that the first one is the best one. Forget about the ring gaps.

Anyone want to discuss it? Flash 412 (CO)

Ported and Polished Intakes

Has anyone ported or polished their own intake on a classic or a fuelie? damalden #1598

Countershaft Differences

I am putting a pre-97 motor in my 99' classic. It has the old countershaft sprocket circlip/crappy way of mounting the sprocket. Has anyone every switched that out with a currrent one? Can everything switch between a pre-97 and a 99' model? XtreemLEE #1188

Will a GS engine fit in an ST frame?

Does anyone know, or have experience with a swap of a newer F 650 GS engine into an older ST frame? Will it fit in as a simple bolt in with the same mounting configuration? Specifically, I am interested in fitting a 2001 gs engine into my 1999 ST. ddishman

Compression Release Mechanism

Can someone tell me what part this is and what it does? And how come there is not one on the other side? Educate me. billmallin #1629

The paint on my engine is bubbling?

This currently only appears to be a problem on the GS's. APPARENTLY, (and AFAIK this has never been confirmed) BMW or their subbies, put the paint on TOO thick OR the 2nd layer on TOO SOON and it never dried properly, remaining soft, which when heated by the engine, simply allowed gas expansion to form the bubbles. Kristian#562

Minor Instances

Minor cases can usually be identified around the small plastic plug on the RHS of the engine case. You can also find evidence around the coolant hoses on the LHS of the engine case. [Look closely and you will see small "bubbles" in the pictures].

Major Instances (Chicken Pox?)

These are some major cases of paint bubbling:


Frankly, I can't see a remedy as such, except for "remove, strip off teh paint and repaint" I was thinking about a new cover frankly, but (a) It's expensive and (b) what guarantee do I have that it won't happen again....none. It's annoying, and it certainly doesn't help when you go to sell it (so keep it!) but I do think it's largely cosmetic. Kristian#562

Is the Rotax engine (used in the F650) interfering or non-interfering?

Does anyone know if the motor ('01 GS) is interfering or non-interfering (ie - does the piston hit the valves if the timing is way off). I had the cams out and put them back with respect to what I thought was the hole that you thread a bolt into to lock the engine. maybe it was the wrong position hole on the flywheel. It doesnt really sound or feel like the engine has compression anymore. Is the hole supposed to lock the engine at true TDC? I can find tdc but I am not exactly sure what position the cams should be at this point and there was no hole at this position when I started. petes101

Where do I find the engine number?

What is Desmodromic valve actuation?

Gouge in cylinder-head?

ok so on my newly aquired f650 my friend had me listen to it with my helmet off and wow, was loud coming from header or exhaust up front. only had it 4 days pulled the exhaust and no gasket in connector? just sitting in there! omg did i buy a basket case?????? so i pull both header pipes and start removing the ring gaskets left one came out easy other wouldnt budge.. so after 30 min trying to get this thing out i start hammering my screwdriver under the gasket, ouch i gouged the surface pretty good what do i do.... saswok

Valve Guides

Performance Improvements

Most of the performance improvements for the Rotax 654 engine are for Classic (Carb) models. The reason for this is changes to the engine on Fuel Injected models will likely cause problems with the Fuel Injection system. And since BMW does not let us know how to change / adjust the FI system, there is not much choice.

Ron Woods Kit (Classic Only)

MSD Cams

Web Cam Racing Cams (for the DS650)

BoonDockers NO2 (Nitros Kits!)

Increased Alternator Output