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Broken gearbox?

5K views 25 replies 11 participants last post by  theknurl 
#1 ·
Hi guys,

I have read a few threads about F4 gearbox issue and think it might be the "Recall Shift return spring" issue I have but wanted to check with you.

I have never had any issue with the gearbox (or any gearbox on any bike) except a few false neutral but more due to me, until yesterday as I took the bike and after less than 1 mile started to realise that I could not go back to Neutral (I was in second gear), simply nothing happened when I was pushing the gear leaver down. I tried to re-engage the second gear by clutching and try again to shift one gear down to neutral, but it did not work. I then tried to go into 3rd gear, this worked. I then tried from 3rd to go down to 2nd, but this was impossible. Then I tried to go to 4th, which worked but still unable to go down... and I continued up to 6th gear where my gearbox is now locked in... Unfortunately by trying to push too hard on the leaver, this leaver is now completely soft, apparently not connected to anything...

What do you think it could be? the shift return spring could be an option, but could I also have broken the forks?

Thanks for your help.

G.
 
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#2 ·
I am not to sure about the spring recall being on the F4's, but I might be mistaken. I do remember it being a recall on the Brutale 1090's though. Your problem does sound like the spring return, not sure if your bike is still under warranty, I would return it to the dealer ASAP.
 
#3 ·
Hi Donsy, Thanks for your quick reply,

The bike is not under warranty anymore so I was wondering whether this would be classified as a recall (hence whether under warranty or not has no impact) or whether this would fall under warranty and therefore would not be covered in my case.

How many hours of labour do you reckon it would take to change the spring and even maybe the forks? It is just to get a rough idea and not to be told 5h by my mechanic if it took only two hours.
 
#5 ·
It is a cassette gearbox as I understand it so thought it might be easier/quicker... but spoke to a garage and they said that assuming 4-5h would probably be a good assumption... :eek:( and apparently this is not a recall, just a warranty claim, hence 100% in my face as not covered anymore...

Is this kind of things common? Shall I assume it is a one-off or this could happen again as it is a design fault? I just don't feel like fixing it with the same piece of junk if something more reliable (or reliable at all) exists...
 
#8 ·
Where are you located? I don't think that it's as simple as a return spring in your case. The return spring, as I understand, returns the shift lever to a neutral position thereby centering the shift mechanism so that it can perform the next function.

You either cannot move the shift lever to the return position...by foot or by spring...or the shift mechanism is going back to return, but not engaging with the ability to reduce gear. However, it can raise the gear.

This leads me to believe that it is a broken shift fork or broken shift dog.

The $2.00 US Spring you refer to requires at least an hour of disassembly once the bike is on a work stand and would not cause the issue you describe.
 
#10 ·
Well, I do believe the way the shift fork works is one side up shifts and the other down shifts. The spring just centers the mechanism.
 
#11 ·
There are 3 forks in every gearbox I've ever pulled apart. They move left to right in grooves on the selector drum, 2 on one shaft (eg inlet) and one on the other (eg outlet). Each movement makes a gear engage or disengage.

When the fork is bent it will generally only affect a single gear, noticeable as a gear being difficult to engage or popping out under load. The bend generally prevents the gear moving far enough to engage correctly, damaging the engagement dogs on the gear itself. In the opposite direction the gear over engages causing additional friction and blueing of the parts. This is one of the things you look for for bent selector forks.

Additionally a bent fork rod, the rod the forks are located on can cause problems too. Inspection by rolling on glass usually shows this up.

All of the above i have only ever seen after a heavy crash.

Hopefully that helps eliminate something.

Sent from my GT-I9100 using Motorcycle.com App
 
#12 ·
You are right Chuck, not arguing, just trying to figure it out myself.
When my quickshifter died earlier in the year, it caused me to bend a fork, this only gave me a sometimes stuck in 4rd gear effect, or hard to go into 5th and back into 3rd again.
The way he could keep on going up to 6th, and not come back down, makes me think it's the spring not centre ring after each selection, meaning it will keep going up the box but not back down.
Like I said, I might be wrong, but I would love to know also.
On the gearbox, you have three forks, divided between the gears ...etc, and having no prior gearbox experiance, I had the manual and a few Bourbons as my only help to figure my things out.
It all worked great last weekend untill the brake rotor broke up on me, but that's a different story.

Be good to hear what was wrong with the gearbox in the end.
 
#17 ·
You are right Chuck, not arguing, just trying to figure it out myself.


Be good to hear what was wrong with the gearbox in the end.
Never have I thought you to be argumentative, Dons...PISSY, yes...argumentative, NEVER!:smoking::naughty:

Shift fork was the wrong term, but it eventually got the diagram out.

He said that he, initially could move the shift lever down with his foot.

That would recenter the mechanism (#1) spring or not.

The shift drum is not rotating in the down-shift direction(counter-clockwise in that diagram), implying a problem with mechanism #8.
The spring return lever, with the round wheel, that engages the star shaped wheel would be my bet.

On the Brutale 1090RR, the problem is with the lever return spring (at the end of #1) which results in a floppy lever:jsm:

Remember this, I am never wrong, but I am not always right!:cross::wave:
 
#13 ·
3 forks Chuck...It's the shift mechanism. May not be the "centering" spring, may be in the arm/pawl that rotates the drum.
 
#14 ·
Auto part Steering part Automotive window part Axle part


Number 1 is the rod that disappears into the engine that your gear shift linkage attaches to. The spring on that makes the lever 'centre' for your foot.

The star and spring at number 8 are what set the rotation. Each indent is a gear (or neutral). If the spring here's broken the little arm will be locked on an angle and is likely the problem.

3, 4 and 5 are your selector forks. 7 is the selector drum, you can see the grooves the back of the forks ride in. 6 is the rod the forks slide along.

Re-reading the symptoms i reckon your issue will be as indicated by donsy, and be the shift star/arm and spring not being in the right location or damaged. I also concur with donsy on how long it should take. Drain oil, remove cover, inspect, replace and reassemble. 2-3 hours. Shop might charge more though.

Good luck and please post the final diagnosis once known.

Sent from my GT-I9100 using Motorcycle.com App
 
#15 ·
?

transmissions are very simple;
MVF3_40; there are 2 shafts the forks slide on

it up shifts but doesn't down shift......
probably not the lever centering spring #800072826
because it won't recenter

my vote;
spring #25 p# 800071009
or a POS in there blocking dog #23 p#800071007

on the down shift side

PS;
NOTHING will put your ass on the ground faster or harder than a transmission......

my buddy Barry;
http://t1.gstatic.com/images?q=tbn:ANd9GcTOTrsUsp9zEHTQfzWsHG3Ytx6wxZK7Jwq_cI_TazlypdfmdIY1

i hate this picture.....
http://t3.gstatic.com/images?q=tbn:ANd9GcSTYO0QcAA0vEj2tEohWb-aUVdaN3o2jLiDvr2WkdAznXKE1__b

his back is broken

i know of worse pictures......i don't go there
i breaks my heart, they're my friends
 
#16 ·
Just looked at the F4 schematic - something I couldn't do on my phone earlier. Interesting lay out with the two rods.

Knurl what is the advantage of making something that complicated - looks to me like over complication with many moving parts (more parts more opportunity to go wrong). They surely didn't do it for nothing, got any idea?

Glad to see the F3 is more 'typical' in layout!
 
#19 ·
Hi Ho Donsy!

It could also be the upper fork of item #1 snapped off....or myriad other possibilities.
 
#22 ·
broken?

Carl.....:)
MVF3_40;
the schematic you posted is not a <'10 F4

the bike won't down shift, it goes up but not down
to shift again up the lever must recenter for the ratchet to work

I like the MV shift mechanism....it has internal dogs instead of Japanese style external hooks which require the eccentric centering stud as found in Japanese transmissions

my vote is still the downshift dog/spring being broken/blocked
p. G11 in the parts manual
bet its a simple cheap fix (other than pulling the trans):drummer:

RJ;
i don't think its forks....it went up 5 gears

i rebuilt transmissions for years (mostly in cars) and i'm very gentile on them....most of the time:naughty:
the Muncie in my Chevy still has its original syncros at 327,000mi
 
#25 ·
I didn't get a chance to go through all the posts but there is a recall on the spring. I called the dealer after experiencing issues shifting down. I was told about the recall and after the spring was replaced the issue was resolved. Funny enough, I had the same problem with my Ducati and it was also fixed under a "recall". They must all get the springs from the same supplier.

I am in Canada.
 
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