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Old 07-14-2012, 03:08 PM   #2903
KTM Noob
Joined: Mar 2011
Location: Santa Clarita, CA
Oddometer: 577
Slipping starter clutch (Sprague) investigation

Hi All,I started the 625 SXC Thursday at work and the starter motor sounded like it was slipping and not turning the motor over. This is a common symptom that is all over ADV about the LC4 PPs out there. I posted some stuff about "fixing mine" a few months back when I had a pretty severe problem with one of the starter gears breaking some teeth off and chewing up the inside of the flywheel. Got that one fixed by Lior's Motoride in LA. Lior used some parts I got from a friend which saved a big Death Valley trip for me. However, I think the sprague clutch we used was a bit loose. Here is a little step-by-step on how I took things apart today. When I get my new sprague from KTM, I'll take pics putting it back together and update the post.If everyone has seen enough of this problem, maybe we should take the best of all the different posts and link it to the LC4 links at the front of this index.

Removed Seat

Disconnected battery

removed the plastic cover from the C/S area and the oil line from the top of the flywheel case.

Removed the bolts on the stator cover and pulled it off. I inspected the stator. Everything looked pretty good. No big chunks of metal anywhere. There were some small shavings on the magnetic area. You could barely see them on the rag.

The stator still looked very good. Thank God!

Here are some of the small bits stuck to the magnetic parts:

The flywheel itself looked good in the front and inside. Now to take it out.

Got the impact wrench out to remove the reverse-threaded nut from the flywheel

Used a 24mm socket. here is the nut and thick flat washer:

Got the special flywheel removal tool ready...

Used the impact wrench again and removed the flywheel. i just put the bike in 5th gear. Didn't need to even use the brake or anything. I was surprised the impact wrench worked so well!

Here is the flywheel.

Inspecting the back of the flywheel and the sprague clutch, everything was in place.

I inspected the surface of the gear hub that rides against the ID of the sprague clutch and it looked pretty good.
After using snapring pliers to remove the black snapring, I removed the sprague clutch.
Here is the sprague clutch removed from the back of the flywheel. All the bits and pieces were there, albeit a bit loose. however, i do not know how loose it SHOULD BE until I get the new one from KTM. Inspected the rotor hub that rides against the OD of the sprague and it looked good.

Now I took the outer shell off the motor to inspect the starter gears for broken teeth. good news! No broken teeth!!!

This is the one that was broken into pieces on me last time. Seems fine now.

Now for the really fun part! Putting it back together...I need to get the new sprague clutch and gaskets in. In the mean time, with all of these parts removed...time for some good cleaning!

A couple of things noted...

The impact wrench made this REALLY EASY. I highly suggest using one if you can swing it.
Removing the shell to get at the gears was just a little tricky. the bolts all came out pretty easy, but it just didn't want to come off where the starter motor comes into it on the upper left. I used a big long screwdriver and a hammer to lightly tap it from the left side of the bike. maybe that's what that little tab is there for?

I will report more about the new sprague clutch vs old when i post up the re-assembly.'s a few days later and I got the new sprag clutch in, so here is the reassembly.

First of all, I had to start out with some good hops

First I put a new "form ring" into the groove in the little cover that covers up the starter gears and installed the cover with one of the capscrews that doesn't go all the way through.

Now I used a new gasket to seal the flywheel cover.

I used Loctite 515 to dress the gasket on both sides before installing the gasket and the cover.

I had to jimmy the cover a little and use the threading of the screws to move the cover into its final position. Here it is installed.

Before putting the flywheel back in, I noticed the threads on the end of the shaft were pretty dirty. I cleaned them gently with a wire brush and then wiped the dust out.

Now to replace the old sprag with the new one.

Old sprag on bottom, new one on top.

Like I said before, the new one had a much tighter spring.

here is the new one installed into the hub on the back of the flywheel

I had to use a few taps with a rubber mallet to get the flywheel to get back onto the tapered shaft. It was actually pretty easy.

Now to thread the thick flat washer and reverse threaded nut back on...

I used the impact wrench to torque the nut down. I may be screwing up here in not using a torque wrench, but i have to believe the impact wrench is putting more torque on this nut than I possibly could with a wrench or even a breaker bar.

Now to use a new gasket on the stator cover, I also used Loctite 515 to dress this gasket on both sides...

I did smear the 515 on both sides of the gasket.

Cover installed!

Now to install the oil line

Hooked up the battery and said a prayer...

Turned the key, pulled the choke...hit the button....vroom!! Success!!! YES!!!!

This bike had not fired this quick the entire year+ I have owned it! The starter motor is DEFINITELY still good. The thing cranks the engine over with ease now! YYYYYEEEEESSSS!!! I only waited about 30 minutes after putting it back together, so when the engine heated up, I started to get some smoke. I think i had a little excess loctite goop that was not cured that was squeezed out of the gakset. I THINK that's what is smoking, but not sure...I looked for any hoses, wires, etc that might be resting against the engine and didn't see anything. I'll try again tomorrow after the loctite is fully cured/dried out.

I also noticed the 515 loctite said it was for 300F applications. Maybe it was the wrong stuff to use, but oh well...we'll see.

Good news is that the sprag clutch is fixed!!! Yahoo!

MNCherryinCA screwed with this post 07-17-2012 at 08:25 PM Reason: update with pics.
MNCherryinCA is offline   Reply With Quote