LC4 640 starter clutch fix

[exman]

Originally Posted by Tseta

Exman, the theory you have heard is very valid and I agree with it. I have heard something similar from a source which I consider highly reliable, who also deals with a lot of KTM LC4s.

I don't know about any bad consequences, but, for what it's worth, I have been both starting* and stopping my LC4 with the help of the decomp. lever for some while now. I think it will ease up the load on the starter as well as the sprague clutch and associated components. The sprague clutch itself, not to mention the hub or the 79T-gear, are quite expensive indeed and any action that can be taken to lengthen their service life would seem logical.


*Starting the bike while using the decomp. involves pulling the lever in, pushing the starter button and letting the engine gain some "momentum" and then releasing the decomp. lever, thus enabling the bike to start.

Cheers,

Tseta

That's the answer! All my doubts are gone! And Gunner completed the theory with his notice about how bad battery can contribute to the excessive wear of the clutch components. And what's more: after reading your posts, I checked Tseta's article about How to service suspension on LC4, and enjoyed all those beautiful landscapes of B.C. posted by Gunner. Not bad for a newbie in just one afternoon. Thanks guys.

[bmwktmbill]

The real deal from KTM



Red loctite, 95psi broke it, this is the wrong way to do things but it is quick.



Looks good.


Is good.



Put back in service.
Torqued with the air wrench, again the wrong way.
bill

[2wheelsrbest]

Sprag clutch is out
Boss picked up ring with teeth in it, which all fell out

anyone have a good picture/diagram showing which way the teeth fit inside the retainer ring?

I realize there are only two possibilities, but do enjoy getting it right the first time.

Thanks to everyone who...

pointed me to this thread
took a picture of what they were doing
shared their alternate fix experiences

[slackmeyer]

Originally Posted by 2wheelsrbest

Sprag clutch is out
Boss picked up ring with teeth in it, which all fell out

anyone have a good picture/diagram showing which way the teeth fit inside the retainer ring?

I realize there are only two possibilities, but do enjoy getting it right the first time.

Thanks to everyone who...

pointed me to this thread
took a picture of what they were doing
shared their alternate fix experiences

Crap, I should have taken a picture of that. I just fixed my clutch. I'll just say that it did take two tries, but that second try went pretty quick once I had some practice.

I just shortened the OEM spring by about 3/4", no need for a new one for me.

[2wheelsrbest]

Ok, I will answer my own question using bmwktmbill's pictures above.

The 4th picture shows the retaining ring and the teeth well enough. Retaining ring has two different edge patterns to the metal--inboard edge is different than outboard edge. Match it up with the picture and orient the teeth such that the notches/lips on the outer, grooved edge are all pointing the same direction. Pic is a little fuzzy, but shows it clear enough.

The 3rd picture, as well as losiu's on post #1 shows the orientation of the assembled sprag clutch to the motor. Put simply, the side with the snap ring (shown well in post #1) goes in, toward the motor.

I used an SKF 19992 spring, which was what I had available ($10, locally) and it works fine. It is significantly smaller in circumference than what came out, but I don't know what OEM looked like originally.

My recap--

97 Duke 620-E, <7k miles
33mm puller, Motion Pro #08-0390, M33 x 1.5 RH IT, fwiw Parts Unlimited or Tucker Rocky (I forget) had different part number of 158089, $40 Seattle Cycle Center (Yay!)
24mm left-hand crank nut @ 132 ftlbs
no crank lock bolt that losiu mentioned
puller provides anti-rotational holding power for pulling action
no new gasket needed, no oil lost
SKF 19992 seal spring used

*Same puller works on
Suzuki GSXR 1000 01-08
Suzuki GSXR 600 01-09
Suzuki GSXR 750 00-09

Yamaha WR450F 04-11
Yamaha YFZ 450 04-09
Yamaha YFZ 450 12

^In case you run into a mechanic who doesn't know he has a tool that will work OR have a terrible time finding a tool listing when trying to order.

[MNCherryinCA]

Hey All,i am going to attempt to put in a new sprag from KTM this weekend/week. I will take lots of pics and post a report on the LC4 index.

[shiftylukbast]

Hi, I know this is quite an old thread, but I would just like to say thankyou Losiu. Followed the excellent photo guide on my '05 640 Supermoto, came up with a sprag spring in exactly the same condition, put in the new oil seal garter spring and my starter sounds brand new.

[MNCherryinCA]

Hey All,
Check out my pics showing replacement of the sprag clutch on the LC4 index.

http://advrider.com/forums/showpost....postcount=2903

[DirtBikeDaddy]

Well I've finally sat my A55 down and put some time and $ into doing this repair...to tell you the truth I got tied of kick starting the beast...Grrr
Like all you fine blokes have told me, it was simple with the right tools.
I too have a 26mm flywheel tool for sale, hahaha, but the 33mm arrived friday!

No pictures sorry, but the spring is toast, not just stretched but flattened in multiple sections...
I'm going to pick up one of those SKF seals and give it a go.

I have one questions;
My spraugue assembly is showing signs of wear, the little bits have flats and rough spots, but the shaft is clean and smooth.

Would the sprague assembly work if I flipped the individual bits around, kind of swap the gouged/rough surface for the smooth ones so to speak?

I did note the unit has a directional arraow on the inside surface but I'm just being cheap, because the replacement part is listing for $107.00 CDN plus all the TAX, shipping, etc...etc...I'll be lucky to get it in my hand for under $200.00!

Thanks for ALL the help...this old newbe really appreciated it
Cheers
DBD

One last thing...details
KTM 2004 SMC 11,000

[gunnerbuck]

Originally Posted by DirtBikeDaddy

I have one questions;
My spraugue assembly is showing signs of wear, the little bits have flats and rough spots, but the shaft is clean and smooth.

Would the sprague assembly work if I flipped the individual bits around, kind of swap the gouged/rough surface for the smooth ones so to speak?

I did note the unit has a directional arraow on the inside surface but I'm just being cheap, because the replacement part is listing for $107.00 CDN plus all the TAX, shipping, etc...etc...I'll be lucky to get it in my hand for under $200.00!

Thanks for ALL the help...this old newbe really appreciated it
Cheers
DBD

One last thing...details
KTM 2004 SMC 11,000

It very likely would not work in any other way than the way it was designed.. The tumblers have a cam profile that wedge out to grab the drum while at the same time gripping the raised machined surface on the gear with the underside..

You could give it a try and see what happens...

The sprague is $65 at parts pit stop

[slackmeyer]

Originally Posted by gunnerbuck

It very likely would not work in any other way than the way it was designed.. The tumblers have a cam profile that wedge out to grab the drum while at the same time gripping the raised machined surface on the gear with the underside..

You could give it a try and see what happens...

The sprague is $65 at parts pit stop

I gave it a try (accidentally) Doesn't work, the cams don't grip. I knew it was a one way thing, but I didn't pay enough attention when taking it out. . . . live and learn.

[AEsco48]

Hello.... Does this sound like a sprague clutch issue? Bike starts up fine after a quick push of the e-start button...

In the below video I had run out of fuel.

http://youtu.be/rjISVTSAGYI

Any ideas?

[DirtBikeDaddy]

Originally Posted by AEsco48

Hello.... Does this sound like a sprague clutch issue? Bike starts up fine after a quick push of the e-start button...

In the below video I had run out of fuel.

http://youtu.be/rjISVTSAGYI

Any ideas?

Even on an empty tank yours sounds alot better than mine!

If your bike starts I'd say you have no problems, but if the noise gets louder or you hear any sliping it might become a problem.

Cheers

[DirtBikeDaddy]

Originally Posted by slackmeyer

I gave it a try (accidentally) Doesn't work, the cams don't grip. I knew it was a one way thing, but I didn't pay enough attention when taking it out. . . . live and learn.

Thanks for the info, I have a seal on order to replace the spring.
I plan to just file down the worst of the rough spots and give it a try.
My season is almost over anyways, along with my temp. license...lol

Now that I have the tools, it's not such a big deal replacing the assembly if the spring dosn't work.

Cheers
DBD

[5-0 BAIT]

So, I'd like to thank Gunnerbuck for showing me the light & sending me to this thread. I'll also post pictures of my little adventure, and let everyone know if this is the surgery my bike needed. Boy howdy I tell you what.