Author Topic: Heeelllppp! Gearbox  (Read 2928 times)

Offline pedrochapala

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Heeelllppp! Gearbox
« on: 10.06. 2014 21:59 »
i've been down for 11 weeks now and done everything i can think of. replaced inside cover bearing on mainshaft and layshaft bush. took apart clutch and repacked the 18 roller bearings[looks like it could use 19?]. dificullt to get into neutral. once i do and it runs for a bit it pops out and makes a gawdawfull racket  and i can't get it back. tried shifting into third on a short run and racket. got it apart again but not the inner cover. ran it for a bit with primary cover off and clutch side seems ok but it popped out but not totally and made the racket. please tell me i just need to adjust the gear control plunger! i'm going nuts!
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Offline morris

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Re: Heeelllppp! Gearbox
« Reply #1 on: 10.06. 2014 23:01 »
Hi Pedro,
Could it be you lined up the dots on the selector lever and the inner casing to well?
I remember when taking my box together again after a rebuild, I hit about everything except the correct gear (or any gear at all). I had to take it apart again and put the lever a notch higher to make it work correctly.
Since then I'm still wondering why the dots are there. I think it's a trick from the Brits to confuse us foreigners! *smile*
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Offline pedrochapala

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Re: Heeelllppp! Gearbox
« Reply #2 on: 10.06. 2014 23:24 »
i didn't take the box apart so the blue dots wouldn't have been moved? i just removed the inner and outer case covers in order to change the bearing race and brass bush. the noise started before i did this and that's why i did that in the first place. i thought it was a con rod but definitely from the gear box. the noise is at low rpm and seems to go away at speed. but now did it when i shifted to 3rd.
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Offline duTch

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Re: Heeelllppp! Gearbox
« Reply #3 on: 11.06. 2014 05:46 »

   Heya Pedro, getting' all a bit excited hey…??   *conf*
Morris- it's a plunger, so there's no dots like on a S/A(I think they do work, except for foreigners-just need the right colour- who said anything about blue, try red they work better *smile*)- the shift mechanism is different, but the  main box internals are the same.
Can't say for anything for sure, but seems most have a whine in third gear, almost like it has a surrogate part number..! What kind of noise is it..??
 Is the flange on the new bush the same thick as the original?
End float on layshaft minimal no- more than a couple thou?
 didn't take first gear off the shaft and lose the inboard shim ?
 18 rollers is right- I think, S/A have 20...?
   Mine sometimes slips out of third under load- note to self...!

  I have a spazzo connection at the mo so'll have a think about it and get back later..maybe try the selector plunger, but can't see why that'd suddenly need a change...?


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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline muskrat

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Re: Heeelllppp! Gearbox
« Reply #4 on: 11.06. 2014 14:27 »
G'day pedro.
Sounds like a bent selector fork or badly worn cam plate.
To remove the forks the shaft they run on must come out. It's held by a grub screw best got at with the bike lying on it's side. The two forks are the same so mark which one comes out first. Put them back on the shaft and see if one isn't quite square to the shaft and other fork. It only takes a poofteenth to cause problems. If they look OK put them back in but swap positions. If the problem moves from 1-2 to 3-4 you can be sure one is out.
Hard hurried changes can do this. While it's apart check the teeth on the selector arm claw, they can chip or wear causing problems too.
Best of luck.
Cheers
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Offline pedrochapala

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Re: Heeelllppp! Gearbox
« Reply #5 on: 12.06. 2014 17:22 »
the noise in third is a clacking like teeth aren't meshing. as soon as i go back to second,it's gone. the noise when starting and idling is like a slapping con rod but as soon as i ride at higher rpm it disappears. when i stop i discover it has slipped out of neutral and i suspect into 3rd or 4th or something that doesn't exist[?] because one can still kick start and the bike won't run away or stall. actually, what i just said is strange-eh!
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Online chaterlea25

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Re: Heeelllppp! Gearbox
« Reply #6 on: 12.06. 2014 17:44 »
Hi Pedro and All,
In your first photo it can be seen that the outer gears have fallen out of mesh,
This would seem to indicate a lot of wear on the inner end bush of the layshaft (bottom shaft)
A full strip and inspection would be my recommendation

HTH
John
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Offline duTch

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Re: Heeelllppp! Gearbox
« Reply #7 on: 12.06. 2014 20:15 »
Quote
or something that doesn't exist[?]

Maybe you've discovered that elusive 'Warp Drive' that they've been searching for years for....?

Remembered I had a noise when putting my box together- had put the shim behind layshaft first on the outside my mistake... *eek*
 Usually they jump into neutral, rather than 'out of neutral...?
I agree with the other guys though, and you can pull the innards out for a look, with box in place, but if you need to do the other bush, it's engine out.
 Kinda hard to check play on the inner bush though however you do it...?
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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online BSA_54A10

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Re: Heeelllppp! Gearbox
« Reply #8 on: 13.06. 2014 00:47 »
I will go for a worn fork / sliding gear or cam plate as well.
Had this happen a few times to me with old leaky boxes.
the fork ends wear around the spot that they contact the grove in the sliding gear.
When this happens it causes increased wear in the grove so some times the gear will "flick" into full contact but light pressure will cause the gears not to mesh properly
The whine in only 1 gear also leans towards this theory as a dud bearing will tend to wine in all gears.
A dud countershaft bearing will whine only in top gear.
Selector fork scuffing ( and thus wearing ) will cause a whine in that gear only and oft it will be different depending upon weather you have up shifted or down shifted ito that gear.
A bad detent cam causing a mal alignment will usually make no difference up or down both will be bad.
So yes it is out with the box  time.
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Offline pedrochapala

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Re: Heeelllppp! Gearbox
« Reply #9 on: 14.06. 2014 04:35 »
there is no whine. read my description again please. i have it out now so what am i looking for?
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Offline muskrat

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Re: Heeelllppp! Gearbox
« Reply #10 on: 14.06. 2014 05:56 »
G'day Pedro. Your going to need whine and lots of it  ;D.
Do you have a parts diagram?
First check the camplate for fit on the bearing (not too much wobble), the grooves and the indents for the plunger. No nicks or rounded edges. Next the forks as described, square, no perceivable wear and fit on the shaft, also the pins that slide in the camplate grooves. With the gears look for rounded dogs and the respective holes and fit on the shafts. Check the two locating rings are in place. Check the selector claw for wear and chips and it's spring and plunger work. Check the constant mesh gear bushes for wear. If all that is good it should work.
Best leaving the whine till after it's checked.
Cheers
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Offline duTch

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Re: Heeelllppp! Gearbox
« Reply #11 on: 14.06. 2014 21:15 »

 Ok Pedro, there's no whine, but in your first post all we had was a "gawdawfull racket', which could have been clunks, clatters, rattle and hum or a whine.... which I'll say more about later...

 In my previous post, the noise I referred to was actually what sounded like your description
 
Quote
the noise in third is a clacking like teeth aren't meshing.
, but if this was your original noise, my remedy is n/a anyway, but worth keeping in mind on reassembly...  *ex*

 If you haven't already dismembered the box, check the shaft end-floats first, and if there's a gasket in the joint, take note of its thickness, as that affects the layshaft float (obvious).
I suggest taking photos at each stage for your own reference...
The obvious check for bent shaft is roll it on a flat surface..?
I can't think much else that hasn't been said until you update us.....enjoy the sangria...!

 Maybe not related to your issue Pedro, but just a thought on Trevs' post;-

 I expect any clutch drag, and mismatched revs will help the selector forks wear quicker ...?

Quote
Selector fork scuffing ( and thus wearing ) will cause a whine in that gear only and oft it will be different depending upon weather you have up shifted or down shifted into that gear.


 
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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline pedrochapala

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Re: Heeelllppp! Gearbox
« Reply #12 on: 15.06. 2014 14:30 »
my parts manual calls for a gear locating[c-clip] ring on each shaft. these were never on mine as long as memory serves. someone told me that they're only there to keep the gear clusters from falling of when you are servicing/inspecting. can i do without? it will take 2 to 3 weeks and maybe longer to get them mailed to me.
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Offline muskrat

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Re: Heeelllppp! Gearbox
« Reply #13 on: 15.06. 2014 15:21 »
G'day Pedro. I really can't say what happens if their omitted. I haven't got a spare box to try it. If it were mine I'd stick'em in. How did everything else check out?
Cheers
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Offline pedrochapala

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Re: Heeelllppp! Gearbox
« Reply #14 on: 15.06. 2014 16:52 »
i really don't wanna wait fer a coupla dinky parts that may not be necessary. it's been 12 weeks now. i hafta get then from abq, new mexico and if i use ups it will cost about $35usd. the layshaft rear bush is toast and i'm checking with a machinist here if he can make me one. i now know why neutral is so hard to hit on the cam. have any of you slightly enlarged the notch?
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