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Ray Lovestead
Joined: 21 Dec 2011
Posts: 156
Location: United States, Colorado, Louisville
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 Posted: Tue May 08, 2012 1:10 pm Post subject: Loose Shift Lever |
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Has anyone has trouble with the CR125 shift J-arm coming loose at its connection to the motor? I'm starting to get missed shifts (15,000+ RPM!!) from it.
I am going to drill and tap the end of the shift lever to use a washer/stud to keep that J-arm from coming loose. Just curious if this is a common problem.
Ray
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Jeff DeMello
Joined: 13 Sep 2002
Posts: 2213
Location: United States, Pittsburgh Pa,
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| Posted: Tue May 08, 2012 2:07 pm Post subject: |
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I never had a problem with mine.. Use some loctite.
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Jeff DeMello
Emmick F125 Pavesi |
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Gary M Smith
Joined: 24 Apr 2007
Posts: 147
Location: United States, California, Fullerton
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| Posted: Tue May 08, 2012 4:01 pm Post subject: |
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After you tighten the J-arm, is it tight? Make sure your clamp bolt is installed the correct way, one side of the slot has a clearance hole, the other side has threads. Install the bolt through the clearance hole first, then the threads and tighten.
Gary
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Ken Schilling
Joined: 01 Dec 2005
Posts: 1345
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| Posted: Tue May 08, 2012 7:25 pm Post subject: |
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| Jeff DeMello wrote: | | I never had a problem with mine.. Use some loctite. |
^+1 (Blue Loctite)
Just a couple of other things to check & consider:
- The pinch bolt should be an M6 SHCS (socket head cap screw / don't use a button head as the head strips too easily!!!) and the proper length for full engagement into the 'J' arm. Use a good grade bolt, not the cheap low grade kind. When in doubt of the bolt condition, REPLACE!!! This holds true for the rest of the kart as well...
- I also use a "spring/wavy" washer under the bolt head to help maintain tension on the bolt "just in case"... I use these "spring/wavy" washers all over the kart, don't use split lock washers.
- Check the 'J' arm pinch bolt thread, run a tap through it to clean it up if necessary.
- Check the 'J' arm splines. You can use a small file and wire brush to clean them up if necessary.
- Check the transmission output shaft splines. You can use a small file and wire brush to clean them up if necessary.
- Check if the 'J' arm is too loose/sloppy on the transmission output shaft with no bolt installed. If it's too loose you will have a tough time tightening it enough. You can use a pair of pliers to close the spline gap if necessary. Use a blade screwdriver to pry it open if you've closed it too much. It should just "slide/slip" on. Remember, the pinch bolt is installed AFTER the 'J' arm is all the way on the transmission output shaft.
- Check the 'J' arm for cracks. This happened to me... I was missing shifts on track, I couldn't see any cracks but with the kart on the stand I looked at the 'J' arm with a flashlight while I both up and down shifted (without the engine running) and saw the 'J' arm open up at the crack while it was under tension.
- Check the shift rod for cracks.
- Check both ends of the shift rod to see if the rod ends are tight and have a jam nut. Most likely one of the rod ends will have a left hand thread. If so, most likely the jam nut with have some sort of mark on the OD of it to identify it as left hand, make sure to mark the same end of the shift rod as well to visually match them. If the rod ends are loose the shifter will have excessive play. Make sure to have plenty of the rod end threaded into the shift rod (IMO at least 1/2 of the thread length). You may need two (or more) shift rods in different lengths depending on your gearing and chain length.
- Check the shift rod for partially stripped rod end threads. You can run a tap into the threads to clean them up and/or tap the shift rod deeper.
- Check the rod ends for excessive wear & sloppiness.
- Check the shifter arm for chassis & steering wheel clearance as well as excessive play. You can bend the shifter arm by heating the bend area (with a torch / a hair dryer works in a pinch but takes a long time...don't ask me how I know) and SLOWLY bend the shifter arm using some sort of pipe, wrench or even an axle (stiff). You can do this while the shifter arm is on the kart if you get it hot enough. If not, remove it from the kart and hold it in a vise. p.s - don't forget that the shifter arm will be HOT (don't ask me how I know...). I mark the floor pan for reference with a Sharpie to mark the ideal location/angle of the bottom of the shifter arm.
- Check the connections between the shift rod/shifter arm and shift rod/'J' arm for tightness. I use nylocks, "spring/wavy" washers and jam nuts to help prevent loosening.
- The 'J' arm should be as close to vertical as possible to provide the best leverage and full shift action.
I think that's it... 
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Ken Schilling
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Chris Reinhardt
Joined: 29 Aug 2002
Posts: 2933
Location: United States, New York, Ossining
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| Posted: Wed May 09, 2012 3:33 am Post subject: |
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I had a J arm that was made from a shift lever where the pinch bolt was in the wrong position!!! There's a groove in the shift shaft for that pinch bolt to lay in, even if the pinch bolt is loose, you shouldn't be able too slide it off the shaft. Mine I could!!! I had to really crank down on the bolt to keep it secure.
As been suggested above, if the splines on either of both the shaft and the lever are worn, you might have to replace....
CR
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Bill Cox
Joined: 01 Dec 2003
Posts: 295
Location: United States, California, San Diego
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| Posted: Wed May 09, 2012 12:29 pm Post subject: |
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Like Ken, I use a socket head bolt; however, I use a longer bolt with a flat washer and deformed nut. Check the nut and bolt occasionally for tight. I've never had the J-Arm come loose.
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Ray Lovestead
Joined: 21 Dec 2011
Posts: 156
Location: United States, Colorado, Louisville
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| Posted: Wed May 09, 2012 1:21 pm Post subject: |
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Awesome - Thanks Ken. I'll get it apart this weekend and check it. The end play is most likely due to a worn part. But call me crazy, I figure these parts should last more than a few months. it was probably loose and worked itself apart.
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5765
Location: United States, California, Winnetka
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| Posted: Wed May 09, 2012 2:15 pm Post subject: |
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I've never used any of the methods described above and have never had a J-arm come lose. However the 18in guns have mangled many a J-arm.
Mike G. |
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Alan Sheidler
Joined: 09 Aug 2001
Posts: 471
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| Posted: Sun May 27, 2012 1:42 pm Post subject: |
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One more thing to check.
We had one J-arm that seemed to be correct in every way, except that it was always just a little bit loose on the shaft. Close inspection revealed that the pinch slot was just plain too narrow. When the pinch bolt was tightened, the two sides of the slot would meet, preventing a complete clamping effect on the splined shaft.
The solution was to temper it with a torch, (to prevent cracking) and open the slot to where the sides were parallel. Then it was mounted it in a vise, and a saw blade was run down the slot, taking material off of both sides. After that, a little more was taken off to form a very slightly v-shaped slot, and the arm was re-installed. Still in service, not loose anymore. +1 on the blue Loctite here. |
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Ray Lovestead
Joined: 21 Dec 2011
Posts: 156
Location: United States, Colorado, Louisville
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| Posted: Sun May 27, 2012 2:38 pm Post subject: |
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Thanks for all the replies guys.
I solved it by tapping the end of the shaft that the J-arm fits to on the engine. Upon further inspection, the threads on the J-arm were toast and my further and further tightening of the bolt on the J-arm was just bending it.
Once tapped, I could put in a washer or two and get a bolt to hold it down. I was then that I discovered the "real" issue, the side of the engine case was rubbing against the J-arm, forcing it away from the case. So, it appears the J-arm arm itself was the issue. I had to grinding some of the base of the J-arm so it would all fit.
Thanks guys.
Ray
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Alan Sheidler
Joined: 09 Aug 2001
Posts: 471
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| Posted: Sun May 27, 2012 2:54 pm Post subject: |
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| Ray Lovestead wrote: |
Thanks guys.
Ray
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Good times. Not sure how the lever could be that close to the case, but if it is working now, all is good.
Alan
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