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201Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Fri Jul 23, 2021 5:35 pm

Danish biker


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@Point-Seven-five wrote:The sprag locks onto the smooth part of #9.  

The friction between the sprag cams and the smooth part of #9 cause them to lock onto the smooth surface.  They grip the smooth part the same way the wheels of a train engine grip the rails under it.  Because of the way they are shaped, the more friction there is the harder they grip.  Once the engine starts the sprag is moving faster than the #9 gear and the cams release.  

Have you ever seen the type of door stop that flips down and holds the door?  The harder you pull on the door the harder it grips on the floor to hold the door open.  The sprag works on the same principle.  Each one of the cams in the sprag is like that door stop.


Sorry for my total ignorens 😂😂

And Viking (I don’t need no BS) 😂😂

Do the teeth on my picture in last post, with the 3 red arrows lock on the blue arrow or the red arrow part on the drawing??????

And i ask in this rude no BS way, because I just don’t understand many of the technical explanations (sorry my bad).

But keep it KISS. Blue arrow or red arrow?????

Starter or Sprag clutch failure  - Page 5 D63a5f10

    

202Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Fri Jul 23, 2021 5:46 pm

Point-Seven-five

Point-Seven-five
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The red arrow part.  The teeth of the blue part are connected to the starter.

The sprag is being driven by the smooth part of #9 to turn the shaft that drives the alternator and the crankshaft. That shaft runs through the center of #9. Once the engine starts the sprag floats allowing the #9 gear to stop turning and thus causing the starter motor to stop turning when the power is disconnected.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

203Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Fri Jul 23, 2021 6:12 pm

Danish biker

Danish biker
Platinum member
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@Point-Seven-five wrote:The red arrow part.  The teeth of the blue part are connected to the starter.

The sprag is being driven by the smooth part of #9 to turn the shaft that drives the alternator and the crankshaft.  That shaft runs through the center of #9.  Once the engine starts the sprag floats allowing the #9 gear to stop turning and thus causing the starter motor to stop turning when the power is disconnected.  

I’m actually so sorry but I just don’t get it.

I understand the teeth on #9 join the starter, but still have absolutely no idea where these teeth go (see picture)??”

And PLEASE don’t explain in technical terms just post a picture (even better with an arrow showing where the teeth on my picture in this post lock on to???”)

Starter or Sprag clutch failure  - Page 5 12e19b10

    

204Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Sprag Fri Jul 23, 2021 9:10 pm

daveyson

daveyson
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Starter or Sprag clutch failure  - Page 5 Img_2042
.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

205Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Fri Jul 23, 2021 9:23 pm

Laitch

Laitch
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@Danish biker wrote:
I’m actually so sorry but I just don’t get it.

I understand the teeth on #9 join the starter, but still have absolutely no idea where these teeth go (see picture)??”

And PLEASE don’t explain in technical terms just post a picture (even better with an arrow showing where the teeth on my picture in this post lock on to???”)
Here's a little something to expand on daveyson's description.

Those are not teeth at the points of your red arrows, so quit calling them teeth and quit thinking of them as teeth. They don't bite into metal. It is the curved surfaces of the sprags that wedge against the hub of Gear #9 and start it rotating Gear #3. Gear #3 rotates the crankshaft to start the engine. Sprags are designed to pivot inward hard against the hub when the starter rotates Gear #9 and pivot away so they just contact the hub when the engine starts. Their curved design allows them to exert force and relax force. 

It's like pushing a large truck with tall wheels out of the mud. There are guys in the rear pushing on the frame and guys on the sides pushing on the wheel tires. The guys on the side pushing the wheels are the sprags. They aren't biting the wheels; they are pushing on the tire tread and sidewalls trying to rotate the wheel. When the truck gets traction, those guys fall away from the wheel into the mud and then get up to walk alongside the truck to push again if it gets stuck. Likewise, when the engine starts to crank, the sprags fall away from the hub by pivoting to create less friction but they are still in light contact with the hub if the engine stalls and the starter uses them to push against the hub to rotate the gear assembly again.

We're failing here using picture with circles and arrows to explain this to you. Certainly, the Danish Army should have experienced mechanics to explain this in your native language but I'll try a couple of photos. These are from Alby's brilliant post. I linked you to this post way back in Post #17 of this thread when I reckoned you'd end up here sloshing an ocean of solvents at the problem.

Starter or Sprag clutch failure  - Page 5 18_oil11

Starter or Sprag clutch failure  - Page 5 21_all11


__________________________________________________
1995 K75 81,000 miles
Starter or Sprag clutch failure  - Page 5 Usa-lo10
    

206Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Sprag Fri Jul 23, 2021 9:54 pm

daveyson

daveyson
Life time member
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Here's something else to look at before looking at a complicated clutch. Starter or Sprag clutch failure  - Page 5 Img_2043


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

207Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Sat Jul 24, 2021 3:51 am

Danish biker

Danish biker
Platinum member
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@daveyson wrote:Starter or Sprag clutch failure  - Page 5 Img_2042
.

That is the best freaking drawing I’ve ever seen 👍👍👍👍👍👍👍

That really clarifies e everything.

My brain just could not understand why my sprags have “cuts” (teeth) if they where not supposed to lock down (with the cut) on a teeth of a gear. In my wildest imagination I could not understand it would lock down on a total round (flat) smooth surface. I thought they where actually engaging something that with “clicks into the fine cut.

Sorry for my ignorance but until a few days ago I didn’t even understand it was the outside of the sprags that was turning the outer ring. I thought it was the inside of the sprags that turned something.

    

208Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Sat Jul 24, 2021 4:00 am

Danish biker

Danish biker
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@Laitch wrote:

Starter or Sprag clutch failure  - Page 5 18_oil11

Starter or Sprag clutch failure  - Page 5 21_all11

You guys are incredible 👍👍👍👍

As mentioned above my problem was I didn’t (till a few days ago) understand that it was the outside part of the sprags that in fact turned the outer ring and thereby starting the engine. I thought the inside turned something.

So I’m assuming that my spinning can be caused by:

1. Ware on the outside of the sprags.

2. Ware on the inside of the sprags.

3. Ware on the inside of the sprags cage.

4. Ware on the surface of the hub.

5. All of the above or more then one of them.

If I’m right I should get a new complete sprag but also #9 so the hub would be without ware.

    

209Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Sat Jul 24, 2021 6:20 pm

Shep

Shep
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Wow!
I have not disassembled or rebuilt a sprag clutch but with all the relevant descriptions, pictures and diagrams in this thread I am now well informed.
Thanks to you all for the detailed Sprag Clutch Technical Thread.
Shep


__________________________________________________
Model        Production Date/Serial Number
K100RS      1984 July/ (F0040448)
K100RS      1986 Dec/ (H0142581)
    

210Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Sun Sep 19, 2021 6:18 am

Danish biker

Danish biker
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Update

I’ve been riding 3.000 km with out any failure 👍👍👍

So what has changed?

The 75% diesel fuel and 25 % engine oil in the bike running at 2.000 rpm until the fan kicked in, didn’t do anything (when reading this I am thinking I must have been a wild man to dare try this).

The riding for 50 km, with 3.000-4.000 rpm, with 50% diesel fuel and 50% engine oil didn’t do anything (still thinking “wild man”).

So after taking all advice and trying it out no matter how dangerous it sounded, I decided to do one last think before taking everything apart and spending lots of money on a new sprag.

I took the sparks plugs out.

I took the crankcase cover off. Turned the crank till the first of the 3 holes in the sprag housing was visible. 

Then sprayed and sprayed flammable (only type I could get) carburetor cleaner into each hole.

Crankcase cover on. Hit the starter, with plugs still out.

Plugs in. Ran engine at 1.500 rpm for 5 minutes.

Drained oil and took filter out.

Put in a thin engine oil. It is a multiple oil used both for diesel and gasoline engines I got from a friend of mine who is a auto mechanic but also ride bikes and know about them.

I’ll keep riding on this oil the rest of the season and next spring go for 15x50 Mobile 1.

Starter or Sprag clutch failure  - Page 5 698d9810

    

211Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 10:34 am

moriarti

moriarti
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OK now its my turn, My mates 1993 75s developed this problem, crankcase off, turned engine over to access holes in sprag clutch, ONLY ONE HOLE FOUND is this right or do i need new glasses , comments and advise welcome scratch scratch


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

212Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 10:49 am

92KK 84WW Olaf

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@moriarti wrote:OK now its my turn, My mates 1993 75s developed this problem, crankcase off, turned engine over to access holes in sprag clutch, ONLY ONE HOLE FOUND is this right or do i need new glasses , comments and advise welcome scratch scratch
Shoulda gone to Specsavers........ 2 other holes blocked?


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

213Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 11:46 am

moriarti

moriarti
Life time member
Life time member
Eye test booked and probing tool ordered thanks for the reply Very Happy


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

214Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 12:00 pm

92KK 84WW Olaf

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Imagine my feeling, seeing NO holes......

Then found out early ones have no holes!! Change to mineral oil solved it.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

215Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 12:14 pm

Danish biker

Danish biker
Platinum member
Platinum member
@moriarti wrote:Eye test booked and probing tool ordered thanks for the reply Very Happy
 
😂😂😂😂 

Actually they (the holes) can be hard to spot. Two of the are actually harder to see, since they are placed further back as I remember.

    

216Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 12:15 pm

Danish biker

Danish biker
Platinum member
Platinum member
@92KK 84WW Olaf wrote:Imagine my feeling, seeing NO holes......

Then found out early ones have no holes!! Change to mineral oil solved it.

Yes that would have been “bad luck” for me. Luckily mine had the holes.

    

217Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Tue Sep 21, 2021 4:28 pm

moriarti

moriarti
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Thanks for the CLUE on finding them D/R. Being a Mining Engineer (retired) you would think finding HOLES was my forte Starter or Sprag clutch failure  - Page 5 44271 Starter or Sprag clutch failure  - Page 5 44271 Thanks for all advise from you all and NOT one sarcastic note of humour, YET Starter or Sprag clutch failure  - Page 5 214585


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

218Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Thu Sep 30, 2021 9:06 am

moriarti

moriarti
Life time member
Life time member
Up date Found all 3 holes, sprayed loads of cleaner through to no avail, Stuck solid no joy. A few hours later sprag on bench, you would not believe the crud in this thing all  rollers stuck solid. SO SCRUB A DUB DUB needed, a good hour cleaning then overnight soak in THINNERS,now looks like new. The bike was due a new clutch anyway so not much of a bind to go that extra bit for the sprag. NOTE to all, would it be a good idea to do an annual clean of the sprag via crank case access. Thus deducing the risk of failure. The amount of work/expense to reach this little bugger is considerable to say the least. Milage on this 75 is 88000 miles.What do you think Chatter


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

219Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Thu Sep 30, 2021 1:06 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I would guess that sometime before you got it, your bike went a l-o-n-g time without an oil change and probably was running on crap oil.  Just curious, what does it look like under the valve cover?  My bikes all have clean top ends and no sprag problems.  There is nothing in the sprag that will make it load up with sludge before the rest of the engine.

Bottom line, I am pretty sure you don't need to do anything special to service the sprag as long as you are doing oil changes in less than 10,000km.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

220Back to top Go down   Starter or Sprag clutch failure  - Page 5 Empty Re: Starter or Sprag clutch failure Thu Sep 30, 2021 1:27 pm

92KK 84WW Olaf

avatar
Life time member
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I agree on that!

Frequent oil changes seem to solve the problem. My Ks about to get their end of summer oil change.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

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