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F4 312r Gearbox Fault

5K views 35 replies 8 participants last post by  Donsy 
#1 ·
Having identified the part at fault , the question now is where to source the part and does it need to be a factory part ?

With the support, technical manuals and assistance from the good people of this forum I was able to remove the clutch and gearbox from the MV . Thanks must be given to Donsy for the straight forward step by step instruction he posted

The offending part stopping gear selection was found to be a small spring ( Part # 800071009 ) that pushes a sliding pin against a floating key at the base of the selector fork drum
(see page g11 of parts manual ) also on forum.

Shown below are photos of the two keys inside the gearbox . The first pin is not holding the key in it's proper place. not allowing it to lock into position and rotate the drum as the gear lever is rotated.
My iphone is fearless!

Auto part Automotive wheel system Rim Wheel


Auto part Rim Metal



Have not pulled this part yet but it sure looks small, can't cost more than $ 5.00 Right ?
 
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#8 ·
Thanks Noel, I originally joined in on another 312 gearbox thread,
Have to say some of the little things, comments posted may seem trivial to an onlooker but are important when it comes to passing on the the knowledge and therefore confidence.You guys are the kings , Thank you to all the Senior Members.
 
#9 ·
ratios?

Donsy;
is far as i know the only 'different' transmission is in the SPR
its +10 % on the bottom and -10 % on the top

i wish i had the money for one of JDS's transmission kits......but i don't:bawling:
my Brutale is too short on top, i'd like to change 5th and 6th
Chris;
i didn't use search, but i'm very familiar with transmissions

MV has the best stock transmission i've ridden.....and it does have the best shift mechanism......

as long as you don't put the little shift lever bushing in backwards, because it WILL fall out:jsm::jsm:
 
#10 ·
The EVO3, SPR and Senna 750, had different gearboxes Noel.
I think I might start looking at the Brutale ratios just for fun, but pretty sure they are the same as the F4's.

I found one bent fork, and two badly worn forks between the 2 gearboxes, so not bad at all for two highly abused gearboxes.
I will have a look next month to see what Andre wants for new forks, might as well get new one's, the gears in those boxes of mine are like new, testimony to what you said about it being good equipment.
 
#26 ·
The EVO3, SPR and Senna 750, had different gearboxes Noel.
Hi guys. Let me clear this gearbox shit up.

Donsy, I think your'e getting Evo3 confused with the SR final edition. It has the SPR/Senna gearbox. Evo3 is same as 1&2.
From the engine designer Andrea Goggi :"F4 EV03 engine is same as EV02, only with painted pick-up, clutch and sproket covers (same color as Brutale)."

I've got a complete Evo1 motor I probably need to part out....:naughty:
 
#12 ·
Donsy;
parts book 80009857 ed#2, Giugno 2003 page G17
shows only the SPR, AGO and Senna having the CR transmission

if others got one later, i don't know
AGO also Noel ? I didn't know that.
I do believe the EVO3 is different to the SPR, sort of in between the SPR and regular gearboxes.
I will look up the ratios, if I can find them all again somewhere Noel, thanks for that.
 

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#13 ·
Dons.. The AGO model was going to be a 750cc ( with EVO3 and Senna specs) before MV decided to make it a 1000cc based on the F4S..

Maybe the info out there is for a 750cc AGO which was never produced.. Only my speculation on this situation.

You need to do a bit more homework on this issue to confirm the above speculation..


.<O:p</O:p
 
#14 ·
Dons.. The AGO model was going to be a 750cc ( with EVO3 and Senna specs) before MV decided to make it a 1000cc based on the F4S..

Maybe the info out there is for a 750cc AGO which was never produced.. Only my speculation on this situation.

You need to do a bit more homework on this issue to confirm the above speculation..


.<O:p</O:p
Makes sense to me John, thanks for that, I will scratch around a bit more.
On a side note, you don't have any new gearbox forks lying around maybe :).
 

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#15 ·
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Sorry Dons.. I haven't got any gearbox forks in stock ( only a couple of new gears for the 750's)..

As you know, CAG or Mark is your best and cheapest bet for these second -hand parts, as long as they're prepared to split a gearbox unit .. I can get them new from MV with some trade discount, but I wouldn't know what the time scales on delivery would be..

.
 
#18 · (Edited)
Chris;
its on page G11 of the parts manual item #26, it fits over the pin on #22 and into the slot in #33

its the one in your 1st picture on the left

welding the hard chromed fork is a PITA and bending it isn't hard to do, accurately is
 
#19 ·
Donsy;
your transmission is too far to the right or the shift drum is too far left

it might be your quick shifter over shifting, is there play in the lever?

thats the kind of wear you see in automotive manual transmissions when people rest their hand heavily on the shift lever
 
#22 ·
Donsy;
your transmission is too far to the right or the shift drum is too far left

it might be your quick shifter over shifting, is there play in the lever?

thats the kind of wear you see in automotive manual transmissions when people rest their hand heavily on the shift lever
Thanks Noel, I will have a look at all these things.
It can't be the Q/S though, as you still manualy use your foot to shift, maybe my foot riding the lever a bit.
 
#21 ·
here is the tooth count (by CAG);
The gear ratios for the '03 750 and '04 SPR transmission

first gear: 13/38 - 14/37
second gear: 14/31 - 16/33
third gear: 18/32 - 15/27
fourth gear: 20/30 - 19/30
fifth gear: 22/29 - 23/33
sixth gear: 21/25 - 18/24

here are the ratios (by me)
1st 2.923 - 2.642 ~10% taller
2nd 2.214 - 2.062 ~7% taller
3rd 1.777 - 1.800 ~1% shorter
4th 1.500 - 1.578 ~5% shorter
5th 1.318 - 1.434 ~8% shorter
6th 1.190 - 1.333 ~10% shorter

the ratio spread in the 2 boxes
2.456 to 1.981 or ~20% tighter

so 1st gear will be 10% faster and 6th 10% slower.....

i tried going through my parts books but there are too many updated numbers to compare.....but a few of the numbers are the same on both the main shaft and the counter shaft

my bet is the F4 and Brutale have the same internal ratios

Ian; i don't think Brutales have a shorter 6th....it just seems so right:drummer:
 
#24 ·
gears?

thanks Ian i hadn't looked at a Brutale book

but i did find out with the F4 312 1st 2nd and 3rd were changed to taller gearing

1st and 2nd are the same as an SPR

14x37 or 2.642
16x33 or 2.062
3rd is different
18x31 or 1.722
instead of 15x27 or 1.800 in the SPR

4th, 5th and 6th are the same as the earlier bikes

Donsy; i'll start on the trail of MV gearing
as least now you know a 312 has the tall 1st
 
#28 ·
gears?

Donsy hold onto you head......

the 750 Brutales are geared
1. 2.92
2. 2.21
3. 1.78
4. 1.50
5. 1.32
6. 1.21
same as an F4 except for 2nd (2.12) and 6th (1.19)
primary is 1.72 (47x81)

910 Brutales are geared
1. 2.92
2. 2.12 same as 2nd in a 1000 F4
3. 1.78
4. 1.50
5. 1.32
6. 1.21 lower than a F4
but primary is 1.58 (50x79) like in 1000 F4s

feel better now?
 
#29 ·
Hahahaha
I will have to download all this info and have a good look at it sometime.

Very busy at the moment, bike on the back burner, and I have a massive head cold (it's summer?), and I have 3 MV's coming for mayor work.

Thank you for all the info, I think we'll have to do a Skype session soon !!!
 
#30 ·
There is a good side to having such a mechanical failure it is the great opportunity to inspect and do those things you always mean to get around to, Have serviced rear hub, found petrol overflow pipe not connected from last service ,found missing screw from underseat wire retainer in engine crevice ,found crack in exhaust weld at four into one,will probably give exhaust a polish while it's off "be rude Not to" generally clean and check over everything as you do. Tracking says parts have crossed globe and are now in NZ now watch them take twice as long to get across town!
 
#33 ·
Gearbox selector springs,Stop, read first

If you are suffering from a gearbox problem thought to be caused by a faulty gear selector return spring or the springs on the selector drum rotator you Do Not have to remove the gearbox to verify or replace these parts .
To access these parts drain oil and water, remove water pump from motor and allow to hang or tie back should you find it in the way , remove he gear selector from shaft and the three hex head bolts holding the select cover in place, from here you can inspect or replace the springs on the selector side of the gearbox . Although for me I was happy to remove and inspect clutch and gearbox and to gain the expierence But the simple replacement of the selector springs could be done in a comfortable hour or so

Have just finished installing selector rotator springs, refitting gearbox and repacking clutch plates , at time of removal the clutch and sprocket nut both were found to be only just seated only held in place by the lock washer on inspection the clutch nut is partially stripped from being cross threaded by factory and needs replacing.So for me the removal and inspection has surely been worth while.
 
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