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Old 08-01-2013, 10:28 AM   #1
motobene OP
Motoing for 43 years
 
Joined: Mar 2013
Location: Wichita Mountains SW Oklahoma
Oddometer: 1,019
GasGas Pro Shift Mechanism Eccentric Adjustment

Someone may have posted this already, but here it is again.

I adjusted the shifter mechanism yesterday on the 2010 280 Econo with a favorable result.

Once you understand the mechanism, it's a no-brainer adjustment. It can be felt and heard without disassembly of anything (for inspection purposes), but it's easier to learn this with the clutch assembly removed so you can look right at the centering spring and it's eccentrically adjustable centering position stud.

There is a YouTube on the click adjust method narrated by Dale Malasec, buried in a Jim Snell video. I just can't find it at the moment.

A marvel, this Pro engine is! Wonderful design with build quality! Believe my Econo's black painted primary cover is magnesium, not aluminum. Casting color and weight are right for Mg. Slick idea for a self-contained water pump that does not lose coolant when removed. The three water pump screws are the front primary cover fasteners. Smart. Clutch removes by one 5mm socket head cap screw and custom washer. No mongo torqued nuts! Beautiful. Can't wait to get in there deeper....

This particular Econo balked when shifting down from 4th if suddenly stopped on the loop without shifting down in steps while rolling. I wrote it off as an Econo thing (that assumption we can get that Econo parts are pulled blindly from dusty bins). Rode the bike in competition over a year, then found out just recently shifting can be adjusted, simply.

Pull the water pump and primary cover and clutch off: Drain the tranny oil, remove three screws and pull off the self contained water pump and pull it out of the way (don't drain coolant/don't remove hoses). Remove the kick start lever (5mm hex) then pulls off with tapping. Remove the rest of the primary cover screws (4mm hex). Work the cover gently off taking care to not damage the gasket (grease it and reuse it). Swing the cover out of the way (do not remove the clutch hydraulic line - watch for the kickstart shaft shim - don't let the clutch 'top hat' thrust washer and bearing drop out). Remove one 5mm socket head cap screw (4mm hex) from the center of the clutch assembly and pull out the clutch. Watch this video for visuals of this process (Note that Jim fails to mention the one screw to remove the clutch assembly):

https://www.youtube.com/watch?v=XgKLrVBn2O8

Raise the bike to raise the rear wheel off the ground. Sitting on the ground, rock the rear wheel back and forth in rotation with your left toe while holding the clutch transmission shaft with your left hand to maintain drag so the transmission will shift fully. Move the shift lever with your right hand. Shift full up and down. As the shifter very slowly returns from full upshifts and downshifts, listen for when the two shift pawls you can't see inside the center cases click home into a radial slot. Watch the gap between the returning centering spring arms and the little hard coated aluminum eccentric stud affixed with a 5mm socket head cap screw (4mm hex).

You should hear the pawl clicking home no later than right as the centering spring arms touch the eccentric stud in both directions. Ideally, there will be a tiny gap, spring arm to eccentric, in both directions.

My bike came from the factory with the eccentric 95% biased up, and needing to go further up, giving very little room for up adjustment. Perhaps this is where some Econo comes in? I had to use all the available adjustment to make the bike shift from OK to better.

Moving the lever slowly back to the spring centered position from an upshift, my bike had one pawl click home with the upper helical centering spring arm about 1mm above touching the eccentric. Coming slowly back up to center from a downshift, the other pawl clicked home happened with the lower helical spring arm hard up against he eccentric with zero slack. Sometimes the click would not happen until I pushed up a bit more into the centering spring. There was my balky downshift problem. Sometimes the downshift pawl wasn't fully resetting.

The fix was to loosen the eccentric's screw, rotate it max up against the upper centering spring arm, then retighten the screw with upward finger pressure on the eccentric. All the available adjustment was used. The upper centering spring arm still has ample slack before clicking, but now the lower return spring arm has a tiny bit of slack as the pawl clicks home... thus it can consistently reset.

Ride report: Shifting is now more accurate and a little more smooth, about 90% as smooth as my Raga's. It no longer balks when shifting stopped from 4th gear to 1st.

motobene screwed with this post 08-01-2013 at 10:54 AM
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Old 08-01-2013, 11:49 AM   #2
laser17
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Nice writeup Moto - Very easy to follow your clear instructions.

I had to dremel a very small amount off of the centering spring on my 1st pro as the eccentric was maxed on that bike as well. (not an econo) This helped on that bike until I decided to replace it when the bike started shifting funny again a year later. (wasn't bad - but I knew it could be better) The new spring was perfect and left me with some adjustment (maybe biased 85%). Never had any more problems. I chalked it upto differences in the spring. They did "look" nearly identical - nothing obvious, but I didn't measure the wire dia. or gap to verify the spec of each one. Was happy it worked and moved on. As sensitive as that adjustment is - Im not 100% convinced mfg variations (or vender to vender) on that spring are as well controlled as we would like. I get the feeling that its one of those things a old pro assembly tech may know to watch for vs a high school kid working part time. Just my guess though.
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Old 08-01-2013, 08:35 PM   #3
motobene OP
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Quote:
Originally Posted by laser17 View Post
Nice writeup Moto - Very easy to follow your clear instructions.

I get the feeling that its one of those things a old pro assembly tech may know to watch for vs a high school kid working part time. Just my guess though.
Thanks. A college prof in in `83 said I should be a technical writer. I didn't go that way, but rather into engineering and product design. I retain the love of writing, however.

It is a sensitive adjustment. Your comment about changing springs made me think about manufacturing of torsion springs. Probably a bit of a challenge for repeatability what with spring back before heat treat.

The transmission design is pretty far out, like the way the two pawls engage the shift drum. I'm so full of admiration for the team or individual that designed this motor. Truly elegant designs are few and far between. This is a shining example. Lots of assumptions were chucked, and they made the nuttier stuff work well.
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Old 08-02-2013, 11:00 AM   #4
ridenm
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Originally Posted by motobene View Post
A college prof in in `83 said I should be a technical writer.
Nowadays that's like saying, "You have just the right aptitude for a rewarding career in a call center."

DAMHIK.

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Old 08-02-2013, 11:13 AM   #5
lineaway
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Originally Posted by motobene View Post
Thanks. I'm so full of admiration for the team or individual that designed this motor. Truly elegant designs are few and far between. This is a shining example. Lots of assumptions were chucked, and they made the nuttier stuff work well.
It`s also been the most `SPLIT` engine ever made in a trials bike!
Some swear it is a hunk of junk, but when it runs it is a great machine!
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Old 08-02-2013, 12:41 PM   #6
laser17
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It`s also been the most `SPLIT` engine ever made in a trials bike!
Some swear it is a hunk of junk, but when it runs it is a great machine!
Its funny - every time i've split one, i've admired the design like moto mentioned. I think you either love or hate GG's. I love em - Not that there not a true PITA sometimes. Reminds me of a red headed girlfriend I had back in college, but thats another story...

Also - now that they have the removable shift shaft design, I suspect the most split title will go to another brand. Maybe...
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Old 08-02-2013, 12:54 PM   #7
Sting32
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Originally Posted by lineaway View Post
It`s also been the most `SPLIT` engine ever made in a trials bike!
Some swear it is a hunk of junk, but when it runs it is a great machine!
Goddang, some people bitch about being hung with a new rope? I split a montessa once, that is 1 time, after having it done several times and I watched... that was 25 years ago sure...

Beauty of the GGas is, the design is one of Marvel and almost any idiot, almost, can split the cases and repair everything but crank stuff, IMHO. what other bike is like that?

I can sell a couple people around me, an ANVIL, in less than a year, they'll have trouble with it, sooner or later, even with it and the rubber mallet they own.

My brother has to tear his "450" motcross bikes down every so many races, adjust valves, re ring, look for problems that; when they crop up costs big bucks. I don't see why once in a few years, a bearing goes bad (split bearing) happened to me on the 08 Raga, and once in a while I have had to change the starter ilde gear, and elephant ear gear (knock on wood, not since the 2010) though... compared to the hours and money my brother has gone through, I don't see the problem with a COMPETITIVE brand bike.

IF you all goto the nationals, ( I know you are Lineaway, go watch the guys around Dale/Lewis's trailers...) watch and see, the Gasgas guys come get a "stock" bike, throws some aftermarket parts (likely) he carried in his suitcase. Now, Beta and the others??? I don't know this to be true...

I know it was in 06 when dad went to the World round/Nationals in tn, he as so impressed watching world riders come get bikes, instead of having their "special" bikes shipped.

Maybe not EVERY sponsored GG rider, but damn near all rode what they sell TO YOU AND ME...
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Old 08-02-2013, 01:10 PM   #8
laser17
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Sting must love them too....you poor bastard. Welcome to the group buddy.

I always joke that a new GG is like a box of cracker jacks - you never know what the special prize will be.

Why do I love GG's should be a new thread...
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Old 08-02-2013, 01:17 PM   #9
lineaway
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I`m part idiot and have the press to fix a crank. Mitch I can remember when I marveled how many engines Dale would fix in one weekend! I`ll be giving him crap tomorrow. I`ve bought several world round Beta`s and never had a problem. Still have a couple complete top ends too!
Splitting an old Montesa is not a marvel. Now a Fantic is piece of art!
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Old 08-02-2013, 01:20 PM   #10
lineaway
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Lazer, you are like my son. He will not even consider another brand!
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Old 08-02-2013, 02:06 PM   #11
laser17
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Well then, you must have raised him well! I like him already.
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Old 08-02-2013, 02:18 PM   #12
lineaway
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Sorry, I`m easy. Two wheels, handle bars and a rock. TRIALS ON!
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Old 08-02-2013, 04:04 PM   #13
Sting32
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Sorry, I`m easy. Two wheels, handle bars and a rock. TRIALS ON!
Hey Line, I was hoping I was joking behind your back, were'nt you on your way to Sipp?

Ok you saw what you wanted to see when dale worked on all those bikes, from guys that bash into crap, or havent done maintenance for the last 8 months, roll up to Dale, and he is pretty damn nice and does things....

Now beta on the other hand, for a long time there were only 2 or three riders on them, so if you saw 2 bikes worked on, you ignored that it was 100% of the bikes on hand, while GAGAS if he worked on 30, there were 200 at the event!!!!

Plus how nice was the Beta guy? I know, just me right? (yeah I see what I wanted to see probably too! yes I like gasgas as much as I loved my 172 Cota, that saved me from never ever riding trials again, probably at the time.
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Old 08-03-2013, 08:11 AM   #14
motobene OP
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Originally Posted by lineaway View Post
It`s also been the most `SPLIT` engine ever made in a trials bike!
Some swear it is a hunk of junk, but when it runs it is a great machine!
Wasn't aware of the number of cases needing to be split. Maybe that was mostly due to the shift shaft vulnerability issue, now made externally accessible in `12?

The one-lump, hunk-of-junk comments usually come from technical illiterates like the fellow who thinks his Chevy is a god and a Ford is a demon.

I've done several major designs in my career where the mandate was the design must be much lighter and smaller than the state of the art. That lead to big design challenges, not the least of which was the lack of available purchased components (the lower cost and available stuff is typically mongo big). Challenging past assumptions and integrations of functions (parts sharing functions) is required. Modern 3D CAD design has made this process so much easier.

The Pro motor shocked and changed the industry. It pushed everyone into lighter motors. It was so radical in its details at the time that I thought at first they'd not pull it off. But they did.

All design is a compromise. A TY350 bottom end and tranny may be bomb proof, but I'd much rather ride a bike with that Pro hardware. As for all the other modern bikes, all are very good these days. No hunk of junk comments from me.
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Old 08-03-2013, 01:24 PM   #15
thegraydog
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Originally Posted by motobene View Post
The Pro motor shocked and changed the industry. It pushed everyone into lighter motors. It was so radical in its details at the time that I thought at first they'd not pull it off. But they did.
When was this?
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