Started out as wanting to do a compression check, tried turning the wheels... yeah, right.. 30psi in 1-3, 36 in 4.  Realized after sitting for a few year it should be run, warmed up and then checked. With questionable wiring, and wanting to see if the engine turned over, we jumped started directly from battery, disconnecting main electrical wire to +.  Our question, should connecting power directly to starter at least turn over the engine?  We have a new AGM battery with 310 cca but the amps are 17.5.  What's happening is that the starter motor spins, but does not engage motor.  Pulled starter, and the sprag only turns one way.

+ on starter and - on chassis should make the starter turn over.

If the bike has been sitting a long time piston rings can stick but eventually unstick. Compression test immediately after a long time sitting unused may give a bad reading because of this. Ks are good engines and loss of compression is not usually an issue and if it does happen valve clearances and head gasket issues are more likely than ring and bore issues.

Also, compression test must be done on a cold engine but yes, you need to unstick those rings first. If you still have the sprag clutch out, make sure it's scrupulously clean because the non-enagement of the engine can only be a sprag problem.

You need to get the sprag clutch to engage. There are many home remedies for that process on the site. Once that happens, you'll be able to start it if the fuel filter isn't plugged, the injectors aren't plugged and everything else is able to wobble into action. Stuck rings from idleness can be contributing to low compression and failure to start as demonstrated in this video.

Thanks everyone for your input, all duly noted..  We split the cases, cleaned out the sprag with carb cleaner, finished up with diesel oil, put back together and same thing.. starter just spins.  What is perplexing is that when turning the sprag by hand it seems to be engaging clockwise and the starter turns counter-clockwise, which would mean it should engage the engine.  We've read many posts on this subject, one post had the starter going different ways by two different posters.. wondering at this point if the gears in the starter are the issue?  That video, btw, was hilarious!

SoCalK1P1 wrote:Thanks everyone for your input, all duly noted..  We split the cases, cleaned out the sprag with carb cleaner, finished up with diesel oil, put back together and same thing.. starter just spins.  What is perplexing is that when turning the sprag by hand it seems to be engaging clockwise and the starter turns counter-clockwise, which would mean it should engage the engine.  We've read many posts on this subject, one post had the starter going different ways by two different posters.. wondering at this point if the gears in the starter are the issue?  That video, btw, was hilarious!

Take out the starter.....if it goes back together easily its not the right way round and polarity reversed so it spins backwards. Putting the live onto to it to make it spin...it also spins wrong way. Its quite fiddly to assemble correctly. Put marks on it before splitting it so they don't go back wrong.

SoCalK1P1 wrote: What is perplexing is that when turning the sprag by hand it seems to be engaging clockwise and the starter turns counter-clockwise, which would mean it should engage the engine.

Clockwise when faced from the front of the engine or the rear?

I reckon the freewheel/sprag clutch assembly should be turning in the same direction as the starter gear because it's being turned by the countershaft gear between them. They both should be turning clockwise when viewed from the front of the engine.

Excellent pic Laitch.. OOOHHHH... so we cannot access the sprag clutch from the starter opening!!! What we are feeling is the countershaft... It's all beginning to make sense now!  Again, great diagram! Okay, so off come the cases and the sprag clutch.. instead of spraying inside with carb cleaner, we'll disassemble sprag.

One other question though.. when we did have access to the sprag and cleaned it with carb cleaner, it would engage in one direction and free wheel in the other.  does that mean it was working?

Yes.

thanks Arlina.. Well if that's the case.. back to amperage or starter? would a quick jolt from a car battery directly to starter to provide higher amps fry anything?

Don't get higher amps out of the car battery, the starter asks, the battery provides.
Works only with Volts.
Means; try the car battery.

Thanks, and makes sense.. tried the car battery.. no go, starter only spins.. The alternator cog does not move when starter spins.  should it? We don't mind splitting cases again, just want to make sure we're barking up the right tree.. Is the starter a possibility of bad gears?  We did bench test it and it did have lots of torque and the end gear spun.

SoCalK1P1 wrote: Is the starter a possibility of bad gears?
We did bench test it and it did have lots of torque and the end gear spun.

Which direction was the starter gear spinning when you looked at it—clockwise or counterclockwise?

Seems like sprag is slipping....
Is the sprag installed the right way?
Will be a bugger to take it out again

Laitch, Looking at starter from behind, it spins ccw.. Arlina, don't mind pulling it apart again, will be doing that any way to repaint everything..:-)  So it the starter is spinning, does that mean that's okay?

SoCalK1P1 wrote:Laitch, Looking at starter from behind, it spins ccw.. Arlina, don't mind pulling it apart again, will be doing that any way to repaint everything..:-)  So it the starter is spinning, does that mean that's okay?

This is an old thread.....same issue and seems it should be spinning the other direction...but read post 29 too. 

https://www.k100-forum.com/t5428-after-replacing-starter-motor-brushes-starter-only-spins

I am not going to name any names but yours is the second one this month!

SoCalK1P1 wrote:So it the starter is spinning, does that mean that's okay?

What it means to me is if it turns the intermediate gear in the right direction to turn the freewheel in the right direction to engage the sprag clutch to turn the crank in the right direction, it's ok and you're back to Square 1. You have an unreliable sprag clutch that you either try to clean with one or more of the home remedies on this site or you do what Alby did and overhaul the works.

If you can bump start the engine, you can steep it in diesel oil, Rislone or other concoctions—instructions on the site—in an attempt to rid the clutch of residue that's interfering with the action of the sprags.

Olaf, yeah, I had read that post before posting, I believe in that particular post someone said it should spin one way and someone else said it should spin another way.. maybe they were looking it at it from different views..?  So took the starter to a rebuild shop, they said it was fine.. okay, so eliminate that.  We split the cases, re-connected the rear drive to the bell housing, connected the starter and..... the sprag does not turn. This was after we already had it down to this point before, flushed with carb cleaner and followed up with diesel oil. The first time no noticeable particles came out.  This time, lots of particles came out when starting the carb flush.  We took a video of the starter engaging and the sprag just sitting there.  We soaked it again in diesel oil and we're going to let it sit for a while and then do the process all over again to see if anything else comes out.  So, Laitch, you're right on..

SoCalK1P1 wrote: We took a video of the starter engaging and the sprag just sitting there

Please post it on YouTube and post its link here.

For my own clarity, what you are intending to convey is that the freewheel gear was spinning but the auxiliary shaft gear wheel with the sprag clutch attached to it was just sitting there? It'll take a heap more cleaning if that's the case. If you could get the engine running, that might help loosen the sprags in the clutch housing.

While you're waiting for transfiguration of this assembly, buy some fogging oil at AutoZone or et. al. then soak each of the cylinders with it. If there are stuck rings in there, that should help loosen them. Starting, if it happens, will be a little stubborn and smokey.

Can you confirm whether you were trying to perform a compression test rotating the rear wheel by hand while the engine was in gear? I seemed to have gotten that impression.

We'll get the video on YouTube and post it here..  So AFTER the starter disengaged, the sprag "sorta" moved.. so yeah, more cleaning.

We had looked at a post where someone put in 10cc of motor oil into each of the cylinders.  We'll check the fogging oil out.

Right, we removed all the plugs, put it in 4th and spun the wheel. The reasoning behind the compression check was not knowing the mileage, should we look for a replacement engine.  Well, it seemed a compression test would give us an idea of the engines condition. Since it hadn't run in a few years, bump starting didn't seem like a good option.

SoCalK1P1 wrote: Since it hadn't run in a few years, bump starting didn't seem like a good option.

With oil in the cylinders, bump starting would be ok in my book, but that would come after replacing the fuel filter, cleaning the tank, and replacing all the tank and injector fuel lines.

Chris Harris was the 10cc guy. He has many useful videos concerning Bricks and Airheads. I use fogging oil because I like the name and believe it has superpowers.

We'll check into the appropriate fuel lines and clamps.. have a set of rebuilt injectors en-route.. have a new fuel filter, think we're going to have to replace the fuel sending unit.. pulled that apart and the piece that houses the wires and fits into the cone shaped threaded part was pretty toasted.  We gooped it up with Seal-All just to get the bike started.

After reading all of this thread I am going to put a tested good sprag clutch in my shed....4 Ks, [2 have the very early sprag clutch] and one is bound to need one so if the time comes just do a one day exchange.

Sounds like good oil, regular changes would prevent a lot of this from happening...

SoCalK1P1 wrote:Sounds like good oil, regular changes would prevent a lot of this from happening...

Putting plenty of miles on it regularly also helps.

Okay, soaked the assy in Gas/sea foam mix overnight. Next day more junk at bottom of the bowl. Seemed to be grabing very well when spinning by hand. Flooded the area with diesel oil, connected battery...just spins. So I put some resistance against the clutch gear and it seemed to want to grab. So we put everything back together, jumped the starter..it just spins. Does anyone know if too much oil would cause it not to grab? Well, at that point we decided to order another used working sprag to test it. In the meantime we’ve completely disassembled the bike to clean everything up and prep for paint. The plan will be to put it all back together before paint to make sure all the lines on the tail of the bike are the way we want them and then we can get it running and check compression at that point. To that point, is there a way to check electrical components to make sure they work, like the ecu, IM etc? PO did say it was running prior to sitting for a few years..

Time to get back to this.. we have had the sprag clutch out and in about 7-8 times, the latest was after a very thorough disassembly, cleaning and reassembly.  STILL just spins, does not engage the engine.  Battery has full voltage and 310 cca.  Starter was previously tested okay.  The engine is currently off the bike at this point and we have connected the battery to the ground strap and then applied power to the starter.  Under normal conditions, should this turn the engine over, or are there other things in place to prevent it from turning over? Pretty baffled as to why there is non engagement.  We have manually turned the alternator flange to simulate a "bump" both ways.. just spins. Are we missing something obvious?

I think the starter motor is spinning the wrong way.

From your video, it looks to me like the idler gear is turning clockwise. See in the picture from Laitch it should be turning anti clockwise. The post by Olaf has a link how to fix it.

SoCalK1P1 wrote:Time to get back to this.. we have had the sprag clutch out and in about 7-8 times, the latest was after a very thorough disassembly, cleaning and reassembly.  STILL just spins, does not engage the engine.  Battery has full voltage and 310 cca.  Starter was previously tested okay.  The engine is currently off the bike at this point and we have connected the battery to the ground strap and then applied power to the starter.  Under normal conditions, should this turn the engine over, or are there other things in place to prevent it from turning over? Pretty baffled as to why there is non engagement.  We have manually turned the alternator flange to simulate a "bump" both ways.. just spins. Are we missing something obvious?

Sorta sounds that way to me too.

Thanks guys, will confirm that and let you know

confirmed that the starter is turning clockwise.. as per the the post, turned the brush plate 180* and it still spins in the clockwise direction.  One of the brushes is barely touching the spindle, so I found a new non oem starter for $110.. will get it in 2 days..  Thanks for all the help on this!

Swap the ends like ki00lt mentions in his post #29 that Olaf refers to.

The rear cap that bolts to the transmission, turn it upside down, above the right side bolt hole are two lines.

With the main cylindrical body, the BMW label goes to the front of the bike. At the rear end is a squarish, slightly rectangular indentation, this lines up with the two lines on the rear end cap.

A square hole on the side of the front end cap lines up close to a front indentation. These two main body indentations are both in line with the two lines on the rear end cap. The screws bolting the two ends together will bring it all to the proper alignment.

Yesssssss,
Finally I can add a photo with my phone. Beer o'clock.

daveyson wrote:I think the starter motor is spinning the wrong way.

From your video,  it looks to me like the idler gear is turning clockwise. See in the picture from Laitch it should be turning anti clockwise. The post by Olaf has a link how to fix it.

The earlier posts say the sprag clutch only spins free in one direction meaning it seems to be performing correctly. The usual issue is that it can spin in both directions.

I see only 2 possibly issues then, one is that the sprag clutch is installed wrong way round [I don't think that's possible] or far more likely starter is assembled wrong way round and that's very easily done. Many have done that. Despite the manufacturing marks on the body its easy to do this and making marks as you disassemble can be problematic if you clean it up after to look like new. 

For bench test the live goes on to the starter electrical connection, the ground/earth is through the body into the engine and via the casing back to the battery through the earth strap lug on the gear box. I imagine this part is correct.

Oddly enough I've taken a sprag clutch to bits this morning. Not certain, but I think it'd be possible to install the sprag ring the wrong way round. I'll check later. This is not the early 3-pawl type.

Impressed by the lateral thinking btw

daveyson... geeeenius!!  A picture is worth a thousand words... When posters say swap both ends, in my mind, that's impossible because of the different surfaces that mate up to the ends.. What it seems "they" mean is to rotate both ends.. in any case, starter now spins in proper direction, which is, looking from battery connection to gear, CCW.  Sprag clutch of course works after all that cleaning...lol.  SO, with that out of the way, we tested compression...  from the cylinder closest to the starter.. 90, 90, 30, 20!  Looks like time for a new thread..

If left sitting the Bricks rings can gum up reducing compression and burning oil. Running a high detergent oil for a 1000 K's or so can often remedy the problem. Or just run it, a mates Brick took quite a few thousand K's for the rings to start doing their job.
Regards Martin.

I thought swap the ends too, but however you did it, if it now works, good.

A few of the US guys have had success with running MMO or Sea Foam.
Regards Martin.

good suggestions..and thanks again! Once the bike's ready to assemble, I'm sure we'll be back..lol

If the engine is out of the frame, position so it is sitting on the right side.  Put a tablespoon of Marvel Mystery Oil in each spark plug hole and let it sit overnight to work it's way past the rings.  Do this a couple times, then do the compression again.  

When you do the oil change, put a pint of the Marvel Mystery Oil (MMO) in the crankcase.  Save the rest of the bottle to add to the fuel in the tank once you get the bike running.  Depending on how long the bike has been idle it may take as much as 4-5,000 miles to get the oil consumption under control even after the compression comes up to where it should be.

Last, when you do the compression test are you holding the throttle wide open and running the engine for at least 6-7 compression strokes with all the spark plugs removed? Are the sealing seats clean so the tester is getting a good seal?

Thanks for the input .75, we actually had the intake ports taped off for paint..!  We'll take a couple of days to do the mmo treatment and then re-test w/o the intakes blocked!  We have new injectors to put in and are planning on modifying the air intake system. But for now, everything is off for cleaning/painting.  I'd post some pics, but not allowed to do that yet...

SoCalK1P1 wrote:Thanks for the input .75, we actually had the intake ports taped off for paint..!  We'll take a couple of days to do the mmo treatment and then re-test w/o the intakes blocked!  We have new injectors to put in and are planning on modifying the air intake system. But for now, everything is off for cleaning/painting.  I'd post some pics, but not allowed to do that yet...

I am surprised you got any readings at all.

Totally disregard the previous compression results and run the test again with the ports open. These engines have been known to still have the cylinder hone marks visible after 100,000 miles.

Laitch mentioned using fogging oil while it was sitting and we did spray some of that in the cylinders 6 or so months ago..  We'll use the mmo first and re-test.

Point-Seven-five wrote: These engines have been known to still have the cylinder hone marks visible after 100,000 miles.  

They're lined with Nikasil (Nigusil, depending on the process. One has slightly more nickel in than the other). Nikasil is very, very, very, (keep going), very hard; so much so that the recommended running in period for new rings in Nikasil/Nigusil lined bores is as little as 100 miles. No joke. Ask Guzzi - they use Nigusil. My V1000G5 was still showing hone marks after 170,000 miles.

I suspect that you will be pleasantly surprised at the compression reading after removing the masking tape from the intakes.  

If you fogged the cylinders you probably don't need any additional oil to check compression, just make sure the throttle is wide open and you get 6-7 compression strokes for each cylinder's test.  Even over 100,000 miles I would think you can get readings over 135-140psi.  Make sure the gauge is screwed well into the plug hole.

As far as rings, my experience is that if the bike has been idle for a long time the rings can get gummed up in their lands.  They usually free up to get good compression fairly quickly, but the oil control rings may take a bit, sometimes a large bit, longer before they begin to get good control over the oil consumption of the engine.

115, 115, 90, 100...  So.. improved? yes!  Enough to put together and run it for awhile or do I need to check valves?

With the amount of work already done checking the valves settings is a simple YES from me,remember Inlet tight Exhaust loose 

If you've got this far then yes, Moriati's right. Do it.