I Need Some Help Understanding My Transmission. (RC24)

Here is a little pic I whipped up. Let me know if there are any mistakes.



My bike will pop out of second and back into neutral on rare occasions. I've already inspected the shifter mechanism and everything looks brand new in there so I suspect either:

1. A bent shift fork ("h" in my pic, factory calls it left shift fork).
2. A worn groove in shift drum for above shift fork.
3. Rounded off dog gears for second gear.

I may be getting ahead of myself, so can anyone tell me for sure that the left shift fork is the one that engages 2nd gear and that the dog clutches (d) are the ones that might be rounded?

I want tp pull the oil pan and take a visual look at the parts to confirm that's my problem before I go and pull the engine out and split the cases.

Thanks

 

If I'm correct about the dog gears for 2nd gear being "D", then the big one is 33 teeth.




The smaller one is 29 teeth.




Here are some side views.






It's not the typical dogs I expected, in fact, I'm really not sure there is a bevel where the 3 pegs go into the holes to hold them together. Does anyone know for sure?

 

The diagram looks good and the left shift fork engages 2nd gear and those are the dogs "d" that engage 2nd gear.

The dogs in the 29T gear picture are the 3 cylindrical rods of metal protrusions up from the plane that fit into those slots inside the web of the 33T gear.

There should not be a bevel on the dogs, if there is a bevel on either the sides or the end face of the dog teeth then the gear will want to slip out into neutral.

Maybe you can tell from inspection which of the 3 culprits is likely, but if it is jumping out badly then it will have to be split for repair. Thanks for sharing, good luck with your project.

 

Cool, thanks for the confirmation.

When I say bevel, I'm talking about a dovetail style bevel that pulls the gears together, not the kind of bevel that pushes them apart. I was under the impression that the factory designed all the dogs with a slight bevel so that the trans would last a good long time.

Surely Honda wouldn't make all the dog mating surfaces a flat 90* angle and rely on the forks, shifter drum and the spring loaded detent to hold the gears against each other? That wouldn't make sense to me as over time, the dogs wear slightly and that 90* angle will wear to 89.5*, then 89* and next thing you know the gears will be pushing against the forks, wearing them out. As those wear it then prevents you from fully engaging the dogs together which is a vicious circle of wear.

Does anyone know if the shift drum, forks and fork shaft can be slid out the side of the engine if only they need replacement?

If my gears and dogs are good I'd definetly prefer not having to split the cases.

 

If anyone is curious, I'll explain what my bike is doing.

When I upshift from 1st to 2nd my bike will sometimes (1 out of 5) pop out of second and go back into neutral but only if I shift it quickly with the clutch at high rpms and get back heavy on the throttle. (Like a drag race type of situation)

Now if I upshift real quickly without the clutch, just backing off the throttle, and then getting back on the power it will pop back into neutral every time.

So when I want to get up to high speeds really quickly I do a slow, deliberate 1-2 shift using the clutch and it will hold just fine and then I can do clutchless upshifts into the rest of the gears. That's my "work around" since owning the bike, but I want to fix it right. So if I sell it, it will last a good long time.

With normal acceleration I can upshift fast with or without the clutch (clutchless is smoother) and all the gears hold just fine.

I bet if I sold this bike to a person who never would get real aggressive with drag race style take offs, they would never see the 2nd gear problem that I see.

 

Have heard about this being more to do with the selector drum rather than the gears themselves.
You can buy a modified part to cure this.
I will endeavour to find the info.
Ps my bike does this.

http://www.factorypro.com/
Scroll down a bit to find gear shift kit.

Roger

 

Your thinking of the shift kits that replace the solid detent roller with a ball bearing type and swap the spring with a stronger one.

I already went through my shifter parts and that is not my problem. I wish it were, because it would be an easy fix.

 

It was worth a try..
My bike seems to suffer the same fate when gunning away from the lights.

Roger

 

It's not that difficult to check the shifter mechanism. I'd recommend you give it a go. Here's how I did mine.

Drain and save the water and oil. Unless you want to swap it for fresh fluids of course.

Rig up a way to securely lean the bike on it's right side. The water pump has the 2 hoses and then 2 bolts that hold it and it slides out. The sprocket cover has about 4 or 5 bolts. The kickstand needs a 30mm socket. Then the shifter cover has 4 bolts I think. Once I opened it up and saw how everything worked I could take it apart.

The detent rollers slide out and you can check them for play. Mine were like new with no play or slop. Check for grooves the roller might have made in the shift drum. Check the bearings in the shift cover.

Clean and paint if you want.

I used a very thin coat of rtv on the shifter cover so as not to have any sqeeze out and find it's way into the oil filter. I replaced the water pump o-ring with an exact match from the hardware store. No need to open the pump.

Put all the rest back together and refill with fluids. Takes a few hours, minus painting. I did mine over the weekend. Took my time.

 

reverse is definitely missing. As for the issue, how many miles? End play might be exccesive enough to pop it back to neutral under hard acceleration. Just spit balling

 

Reverse "gear"? Your being humorous?

My bike has 44k miles on it. Not taken care of by PO. Old nasty fluids, been down on both sides, damaged fairings, cowl, foot peg, etc... It might have been abused. I've put a lot of work in it and got it fixed up now.

Although I don't expect any problems with the gears themselves with only 44k miles, shift forks are a whole other story. Some of the Suzuki M109 bikes are wearing out shift forks at 2k miles! VFR"s are known to be well built so I'm hoping it's a shift fork and not the gears and I'm hoping the fork shaft can be slipped out the side after the clutch basket is removed. The fork swapped out and the shaft slid back in.

I think I can access the trans through the oil pan to look it over and check for slack in the parts.

 

yeah, reverse was a joke, funner to me I guess. I am an auto-tech and the trans I tear down have reverse. Anyway, to check end play would require a precdure and some specific tools, possible having the input/output shafts out, ie... full disassembly, a big deal. Could be the syncro/blocker ring being worn, too. Got to be better guys on this forum to help you. I think taking the pan off will yield little info with out knowing exactly what to look for.

 

The factory service manual tells you exactly what to check and measure to make sure everything is within tolerance. Access through the pan is surprisingly good. I'll post a picture soon.

You can reach in there and wiggle lots of parts. I can spin the back wheel, shift from first to second and see how much the dogs engage. If I can push on the fork and further engage the gears say another 3/16", then I know that's my problem. You can inspect the shift fork pin to shift drum groove clearance, the shift fork claw thickness, etc...

Obviously there are a lot of clearance checks that require the transmission to come out, but going through the oil pan should be easy. If I have a badly worn shift fork and it's causing 2nd gear to just barely engage, then I might get away with replacing that part without splitting the cases. A new shift fork will push the gears all the way together and stop it from jumping out of gear. Problem solved. I have my fingers crossed.

PS, there are no synchro's in motorcycle transmissions.

 

Here is pic looking through the pan of a VF500f, but it's the same view on the VFR700.



The countershaft gears (the ones I need to look at) are pretty tricky to see, but a small mirror should do the trick. I can definitely see the shift drum groove. If the groove is worn and opened up (not fully engaging 2nd gear) then a replacement shift drum should fix the problem.

 

No they can't

Unless you figure out some new trick...

 

Why not?

Here is a pic of the lower case. Now behind the clutch basket is where the shift fork shaft slides out. Can anyone tell me how it's held into place?



It looks like the shaft can be slid out the side, you could then rotate the shift forks away from the shift drum. Then you can slide out the drum on the left side. At this point the forks should be able to drop out through the oil pan area.

 

I found a pic in the service manual. It looks like the "shift fork shaft" is held in place by the mainshafts bearing holder. It also holds it in the correct position so oil can go into the shaft, feed the fork bearings and then squirt out into the grooves the fork claws ride in.



I'm assuming the "shift fork shaft" is sealed on both ends?
You can see an oil inlet hole on the right side of the shaft near that bearing holder.

 

You might be on to something...

If you don't mind experimenting and want to take a chance, maybe you could just pull the fork shaft oout enough for only the 2nd gear fork to drop free. Not sure that there is clearance to remove it, but if so then maybe replacement of that left fork is possible.

Or pull the fork shaft but leave the forks in, rotated slightly to release the drum, which then lets you pull the drum for inspection.

That hole below the mainshaft bearing on the right side is to drip oil on the sliding surface of the shift fork. The fork shaft is pressurized from the left side thru an oil port in the case.

 

Subscribed! Mine does the *exact* same thing, and I'm hoping for a quicker easier fix than splitting the cases. Keep up the good work!! :thumb:

 

Check the cases, the sprocket output bearing wears a groove in the cases and can cause trouble