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Discussion Starter · #1 ·
I have this posted in another thread, but the info is somewhat burried amongst a bunch of other posts / info so I thought I would start a thread with just this info to keep it cleaner and make it easier to find.
Hey guys... Just thought I would share a little info about Gear Undercutting and what it means / does.

First off though I want to say thanks to JR, Crazyspeed, Carlos, and the others who recommended R&D Motorsports to me.
They are the company I used to do my undercutting, and their work is absolutely top notch.

Here is a quick pic of the package I received back from them. Everything was marked with Joes initials, and all of the replaced parts were sent back and tagged with what was found wrong with them. They even sent back the old snap rings they replaced.

the top of this pic is all of the old parts, and the bottom is the new parts.
Drive and Driven Shafts with undercut gears, NEW modified shift forks (You will notice where the fork rides in the shift drum that these forks don't have that trailer hitch ball to them. That ball is the design problem in the stock shift forks), and new SOLID fork rods. (Stockers are hollow and will bend over time with missed / grinding shifts. Both bikes I have in my garage had bent rods)



And now for the actual undercutting info...

Without going into a great deal of how a constant mesh transmission works, just keep in mind that the shafts are always turning / engaged and there are a couple of gears that are splined to the shaft, but can slide side to side and engage with their adjacent gear, which was free spinning, and change your gear ratio. Also, each gear dog / slot set has an accel side and decel side...

In the picture below you can see where the gears dog and slot mate together (this is the accel side). If you look at the surfaces which are touching in the photo you will see that the mating surfaces are cut at an angle with respect to each other. This angle forces the dog / slot to pull together. The more tq that is applied, the harder they are forced together. Stock gears do not have this angled cut to them.

If you look at the OTHER side of this particular dog (the decel side) you will see that the base of the dog, where it protrudes from the gear, is more rounded or curved. This shape actually helps to push the dog / slot away from each other. Basically leaving your shift fork and rod the task of keeping things mated together, under heavy torque.

Note: On this set of gears we did not back cut the Decel side, as it typically is not needed.



Here is a little video I took that shows the difference in slot / dog engagement - mating on the UnderCut and Stock cut sides of the dog.

http://video.google.com/videoplay?docid=-75611953187057122&hl=en

Note how on the decel side the gears try to push away from each other. Keep in mind this is under no torque, but merely me just pushing them together by hand. This is what causes the problem in the 109 transmission 2nd gear. Under heavy torque you have HUGE forces pushing these gears together, and the shape of the dogs / slots tries to push them apart on the initial engagement.

Now note the Accel side of the gear that had been undercut, and how the dog / slot lock together.

I am not sure why Suzuki doesn't just manufacture the gears on the 109 with an Undercut to them... but undercutting the transmission is definitely the cure for the 109's transmission woes.
Unfortunately it is not a cheap fix.
 

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Discussion Starter · #5 ·
I'll start putting it back together Saturday night, after I get home from our concealed weapons permit course... :D

If all goes well, some of the other Engine parts I am waiting on will come in for the weekend and I can finish the build... otherwise it will probably be closer to weekend after next.

I will certainly post up my take after I put some miles on it.
 

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JUtah,

What was the total bill for the work you describe above? Whats the thewarranty from the re-builder? I assume you have now void Suzukis warranty with respect to your transmission?

Tom
 

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What kind of money are we talking to have this done? I don't need specifics, just a ballpark would be nice.
 

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Discussion Starter · #10 · (Edited)
JUtah,

What was the total bill for the work you describe above? Whats the thewarranty from the re-builder? I assume you have now void Suzukis warranty with respect to your transmission?

Tom
My bike is still under extended warranty, and no... up till now has not been voided. All of my OEM parts are being replaced by zuk for free. (Including 2 new front rotors, a new clutch hub, and all of the stuff revolving around the tear down for the tranny)

As far as the warranty for R&D's undercutting, I didn't even ask about it. They are a performance shop that does TONS of this work for professional race teams and amateurs alike... I am not in the least concerned about the quality of their work. You could give Mark a call though and ask him.

If your question was about warranty from the person rebuilding my bike... well... that would be me.

I can't give a "Fair" price for everything I am doing to my bike because I am doing a 100% complete rebuild... new bearings, everything... and I am putting in a good bit of performance goodies as well... I also don't pay retail for my OEM parts...

Here are some figures...
Tranny $600 to $700 (Magnaflux, Back cutting, Forks, and Fork Rods)
Orings, bushings, fluids, gakets, etc $300 to $400.

The following is a "Guestimation" of what the average person will be charged:
Piston Rings $140
Crank Bearings $52
Rod Bearings $52
Clutch Steels $110
Clutch Fibers $140
Brake Pads $90
Spark Plugs $32

So figure $1,500 to $2,000 to do it yourself... (If you do a complete rebuild) This figure does not include any performance upgrades.
 

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I didnt know you were doing all this work yourself, or all the engine work. I am more interested in the transmission work only. The cost I really wanted to know was if I brought a stock M109 to R&D and they provided and installed all the fork rods, shifting fork, etc and undercut the gears, what would they charge. I can check with them if you dont know.

Thanks
 

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Discussion Starter · #12 · (Edited)
I'm not sure if R&D would want to tear your bike down for you. I believe they just want you to send them the gear sets...
But to be honest since it wasn't even a consideration for me I didn't ask that question, so I am not sure.

the GEAR work is $600 to $700 for R&D.

The rest would depend on who does your work for you.
 

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I didnt know you were doing all this work yourself, or all the engine work. I am more interested in the transmission work only. The cost I really wanted to know was if I brought a stock M109 to R&D and they provided and installed all the fork rods, shifting fork, etc and undercut the gears, what would they charge. I can check with them if you dont know.

Thanks
I am having the transmission rebuilt in my bike right now at the dealer. The bill is at $2900 with all the labor and new parts. So if you had a dealer teardown your trans and then you sent out your gears to R&D your looking somewhere around $3500 + or -
 

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My bike is still under extended warranty, and no... up till now has not been voided. All of my OEM parts are being replaced by zuk for free. (Including 2 new front rotors, a new clutch hub, and all of the stuff revolving around the tear down for the tranny).....I also don't pay retail for my OEM parts.......
You have must a great relationship with your dealer.:bigthumbsup::super:
 

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Discussion Starter · #15 ·
I do...

I have spent a great deal of money with them, and brought them a TON of business from friends / family, etc...

They are a company that appreciates my business, and the business I bring in, so they take care of me.
 

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wow rich great write up!!!!! i think i need to have that done also. you are the man. oh yeah thanks again for all your help over the last week buddy.
 

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Discussion Starter · #19 ·
I got to start putting Joe's bike back together this evening....
This new Tranny sure is a thing of Beauty!!



And the cases ACTUALLY back together again... LOL (lining the shift forks back up while you drop the lower case is fun!!)


Something interesting I found when I was cleaning some pics off of the Camera...
Here's a shot of Joe's 3rd gear, and what happened to it from the shift fork riding against it. I never saw it with the naked eye... (2nd and 3rd gear were both replaced before back cutting)

Note the Discoloration on the teeth of 3rd gear, as well as how beat up they are at the edges.
 

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Has anyone purchased or seen the new shift fork;(35F11) and made a comparison with the old ones. Are there any differences that can be seen?
Wondering if they changed the tolerances, type of metal etc....
 
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