Overdrive 5th gear - Dropping/Slipping Out to Neutral

I like your perspective TooMany. All of this checking that I've been doing has at least had the positive result of me understanding the transmission a lot more than I had. I loved the service bulletin of "finger printing" the shift drum on vellum. Don't hear about vellum much these days. It was the common thing in my early draftsman work days.

I also lean toward the engineering solution #2. I driven to figure out what is really wrong here especially being starting work as a mechanic and now an old mechanical engineer. My family and friends know this well of me. My neighbor across when I was with my ex said, "you can fix anything", yeah I told her, except relationships! Option #1 is good when you want fast and sure and someone is paying for labor and parts.

Your conclusion is same as mine I believe. everything is pointing toward the new 5th gear OD. I'm thinking that it is a sloppy over size ID bore on it. I think the vibration gets it walking on the shaft and causes the decoupling.

I just closed the side case and am going to run it for a couple of more months this way. Hey maybe it will heal itself, LOL! I expect that I will split the cases, measure and compare the ID bore to my good original 5th gear. Most likely the old gear will go back in and I may change the gears and go to a 520 chain to get a little higher ratio.

Thanks for all your help. You and a number of others here are super in that regard.

Best,
Glenn
 
glennpm said:
... All of this checking that I've been doing has at least had the positive result of me understanding the transmission a lot more than I had...
Click to expand...

Great! Then one last thought.

Maybe this will make sense, just an experiment to ponder.

If you were to grind a notch, maybe 0.010"-0.020" deep, into the final pin, back where the stopper wheel rides, then:

-The stopper wheel would plunge just a tad deeper, giving a little more holding power.
-And this would advance the shiftdrum just a tad more clockwise, possibly getting the shiftfork's pin past the shiftdrum's slot's ramp.
-And nudging the shiftfork just a tad further into 5th.

Of course, the upper stopper wheel spring would need to continue tensioning the arm. In this pic, it looks like it's almost at coilbind.

The outer part of the pin, where it engages the claw, would remain the same. The spacing of that pin to the rear claw shouldn't be adversly affected...
 

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Damn it lost all the typing I did with the "your submission can't be accepted ..."

Short response is that I now understand why you wanted me to see if I could over rotate CW, i.e. the position in the slot.

Regarding grinding the last exposed pin OD, the stopper lever wheel sits between adjacent pins. It does this for all gear selections. The only way to make it a little more stable would be to decrease the OD a little but not so much that it drops through the pins. The spring anchor points would also require spreading, maybe change the end of the arm with another hole a little to the left, CCW.

PS A couple of nice rides today on other bikes. This afternoon headed out to the mountains on my Ulysses and the clouds were looking a somewhat ominous. Felt a couple of drops and looked up and saw at least 5 lightening bolts simultaneously ... decided to turn around ;-)
 

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Following up on DADDYG's comment on undercutting gears:

Here's a closeup pic of the dogs of the 3rd slider that enter and engage the adjacent 5th (driving, spindle) gear.

3rd-Slider-5th.jpg


Not the best image, but if you look closely, you should see that the dog has an undercut profile of about 5°. The Overdrive 5th MUST have a undercut profile to match those dogs. Otherwise, it may indeed tend to slip out of engagement.

So, I'd recommend closely inspecting the Overdrive 5th's engagement slots for the required undercut profile.
 
Yes, I noted DADDYG's comment about that. I noticed the undercut on mine but no way to see inside my OD 5th. It would be interesting if someone has one out, new or especially one that was pulled out, to see it the slots are undercut.
 
I have a new OD gear and best I can tell there are no undercuts, but I can't think of a way to be certain about that.

One thing I do see, I have one with a missing tooth and the original one from my transmission (see http://www.xs650.com/forum/showthread.php?t=41783) and the OD gear fits noticeably looser on the shaft than the OEM gear although in 46K miles I never had a problem with it popping out of gear. I checked the clearance with a feeler gauge and with the OEM gear it appears to be about 0.002" while the OD gear it's about 0.003".

I wonder, would it be a good idea to try and undercut the new gear before I install it?
 
dps650rider said:
...I wonder, would it be a good idea to try and undercut the new gear before I install it?
Click to expand...

Since you have an OEM gear, an older OD 5th, and the new OD 5th, could try a simple test.
Dry fit the 3rd slider onto the mainshaft, followed by one of the 5th gears. Engage the dogs, apply some twist to the gears, and try to pull them apart. You should be able to feel some resistance and counter-torque during separation if they're properly undercut. The non-undercut gear(s) should separate more easily, you should be able to feel this...
 
Yes small dremal Is used to match both sets and you would be surprised how much can be taken out. On Drag bikes they lock like fingers so they can't come out. I would think that the stock 5th gear that is being sold is not cut in anyway and is depending on you having a good gear to match. If it was my motor I would be going back in and replace the match also with a new gear. 30 plus years on a trans is going to put some wear on all those gears and miss shifts don't help. Sometime it can be so SMALL of a difference that you cannot see. I had a trans in a KAW 1000 and they are known for 2nd gear jumping out just like old Suzuki's and I back cut the trans and it still did it under big power. I got fed up and put another in and all was good. Sent that trans to FAST BY GAST and the next gear was the problem . They were just not working together to switch and 2nd would hang up and pop out. They cut all the gears and that trans went low 9"s in quarter mile and NO Problem. So sometimes it cannot be seen by the eye....
 
Appreciate these recommendations guys.

During one of my awake in the middle of the night times this week, I kept going over what is causing this problem and other causes I may have missed. I kept going back to perhaps an oversize ID on the OD gear which with vibration is walking the 5th OD out of position. Last weekend, a short ride of about 20-25 miles and it slipped out once. Saturday I went out for maybe 30 to 35 miles and it did it four times. Seemed to happen more each time as I was out a little longer leading to maybe heat expansion increasing tolerances or slacker chain causing vibration on drive axle ... A tight chain causes it to slip out more often though.

The undercut gear matching makes LOTS of sense. I could paint Dykem on and do the check you mention Steve and also look at how the stock 5th and new OD 5th are meshing. The surface hardening on these gears though could be compromised. I'll have to see what I can find on the web. I'm driven with these issues and hope I can restrain myself from tearing this apart until winter. I'll very likely put the stock 5th gear back in and dump the OD.

I also made a conscious and firm shift each time to 5th thinking maybe I had perhaps been a little sloppy. Once it jumped out, I also just tried to apply clutch to see if that would get it to re-engage. No good which is as suspected. The 3rd gear must be disengaged from 5th and cogs between 3rd and 4th not engaged with, i.e. smack in the middle with neither gear engaged. I guess I need to hook up a bungee cord to the shift arm when I want to stay in 5th ;-)

This takes the fun out of the bike ...
 
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The OD gear I bought has the small hole and I think I am going to need to bore it to fit. Will that cause a problem with the surface hardness?
 
I'm not sure if it would. The body of the gears need to be "tough" and not "hard" so they can react well to the loads applied to them and not be brittle, i.e they need to have good impact toughness properties. The tooth mesh surfaces need to be hard to prevent pitting and wear.

The 5th gear OD rides on the shaft and is not or should not be sliding. It is not be subject to the same wear and forces as the meshed teeth. I don't see an issue with boring/grinding the ID. Let's see what TooMany and DaddyCycles have to say.

Can you please look closely at your 5th gear dog pockets? Are they undercut and I think I read hear that the dogs are by around 7°?
 
Hard to tell but I'm just about positive they are not undercut. When I measure them with a caliper it looks like the opposite is the case by a couple thousandths.
 
Good feedback and thanks. You should be able to see it visually if you put the end of a steel rule in the pocket adjacent to the ends of the groove pockets. You would see a small gap at the root if you're following me.

Take a look at post #44 above from TooMany. the end of the grooves should be similarly undercut.
 
The metallurgy of that OD 5th will probably remain a mystery. My knowledge of MIM manufacturing is quite old. Basically powdered iron packed into a mold/form, followed by very high pressures and heat. Like making a diamond. Not aware of any post-process heat treatment. Basically considered it as thru-hardened, so post-process grinding was not an issue. Modern processes may be different, Asian processes may be disturbing.

I can visualize a setup with the OD 5th mounted on a rotary table, under a drill press or high-speed mill. With proper offset, the undercuts would be more precise. Would need to custom-trim cylindrical stones to the appropriate angle, like a shallow dovetail cutter. I've seen a project/mod done by a hobby-machinist where he fitted a high-speed pneumatic pencil grinder (56,000 rpm) to his mill spindle, to do this kind of precision grinding...
 
Wow, love it when tools are multi-purpose.

" ... where he fitted a high-speed pneumatic pencil grinder (56,000 rpm) to his mill spindle, to do this kind of precision grinding... "
 
Then again, I suppose the better path would be to have a way to positively confirm that undercutting of the OD 5th is missing, and push the problem back upstream, onto the supplier....
 
Yeah looks like that's the case from what dps650rider mentions. Just waiting to confirm that he checked the ends of the slots.
 
Hi dps650rider,

Just wondering if you've had a chance to check the ends of the slots to see if there is an undercut similar to the dogs shown above? You don't need it in the middle of the slot and really only one end. If there isn't, and straight in. it would be a lot easier for the slider to slip right out.

Thanks
 

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