G2 crankshaft sprocket spacer distance piece

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Richard Hyatt
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Joined: Sun Jan 27, 2019 8:52 pm
Location: Dorset

G2 crankshaft sprocket spacer distance piece

Post by Richard Hyatt »

Hi all , 1962 G2
Does anyone have the distance piece that goes between the backside of the crankshaft sprocket and the main bearing please ?
It is used to space out the sprocket to align the crank sprocket with the clutch basket sprocket.
Thank you
I have a single row chain by the way , I did the clutch hub up snugly against it's shoulder on the gearbox shaft , so I'm pretty sure the clutch baskets in the right place.
Just need to align the front crank sprocket and allow end float on the crank
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clanger9
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Location: Chester, UK

Re: G2 crankshaft sprocket spacer distance piece

Post by clanger9 »

There shouldn't be a spacer there - occasionally there might be a few thou of shims (at the most).
The sprocket sits directly against the main bearing, but you have to fit it the right way round. Something I found out the hard way...

Here's a diagram:
http://www.jampot.com/forum/viewtopic.p ... 04#p194020

Here's a picture (duplex sprocket):
http://www.jampot.com/forum/viewtopic.p ... 20#p184422

Here's a thread with all the gory details:
http://www.jampot.com/forum/viewtopic.php?f=15&t=17322

Summary: my bike originally needed a spacer (even with the sprocket the right way round), but that was because the main bearings weren't fitted correctly. With the main bearings in the right place, no spacer was needed.
1989 Moto Morini Dart 350
1993 Ducati 750SS
Richard Hyatt
Posts: 113
Joined: Sun Jan 27, 2019 8:52 pm
Location: Dorset

Re: G2 crankshaft sprocket spacer distance piece

Post by Richard Hyatt »

Thank you for the thoughts,
Certainly our sprocket was on the wrong way round, and we've corrected that (thin boss towards the bearing track)
Now I need to align the primary chain by bringing the crank sprocket out a bit by this 041091 or similar.
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clanger9
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Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: G2 crankshaft sprocket spacer distance piece

Post by clanger9 »

Hi Richard,

Check the full thread. Despite being mentioned in the manual, 041091 doesn't seem to exist.

If your sprocket is definitely the right way round, your main bearing is in the right place, you've got the right gearbox mainshaft and the sprockets are still misaligned, then you can pad the crank sprocket with some DIN988 shims:
http://www.jampot.com/forum/viewtopic.p ... 10#p155684
1989 Moto Morini Dart 350
1993 Ducati 750SS
Richard Hyatt
Posts: 113
Joined: Sun Jan 27, 2019 8:52 pm
Location: Dorset

Re: G2 crankshaft sprocket spacer distance piece

Post by Richard Hyatt »

Thank you for this,
Hopefully thin boss to the bearing is correct! It looked that way round in the drawings I found.
As far as I know the gearbox shafts are ok , I wouldn't really know if they were or weren't, it hasn't been on the road for ages by the previous owner , so I'm hoping it's correct.
We have a single row primary chain , your picture shows duplex , hope mines correct !
I'll explore those shims , that's all I can do.
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clanger9
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Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: G2 crankshaft sprocket spacer distance piece

Post by clanger9 »

Richard Hyatt wrote:Thank you for this,
Hopefully thin boss to the bearing is correct! It looked that way round in the drawings I found.
As far as I know the gearbox shafts are ok , I wouldn't really know if they were or weren't, it hasn't been on the road for ages by the previous owner , so I'm hoping it's correct.
We have a single row primary chain , your picture shows duplex , hope mines correct !
I'll explore those shims , that's all I can do.
Yes, simplex is fine! Mine just happens to be duplex.

How far is the misalignment? You can correct up to maybe 3mm with shims - beyond that you'll start running out of thread on the output shaft...
1989 Moto Morini Dart 350
1993 Ducati 750SS
Richard Hyatt
Posts: 113
Joined: Sun Jan 27, 2019 8:52 pm
Location: Dorset

Re: G2 crankshaft sprocket spacer distance piece

Post by Richard Hyatt »

Probably about 1/8" which is about 3mm so should be ok with thread , thank you for this.
It certainly is a voyage of discovery , this bike !
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clanger9
Posts: 1165
Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: G2 crankshaft sprocket spacer distance piece

Post by clanger9 »

Excellent. Hopefully it will all go together correctly!
These Lightweights are tricky, aren't they? ;)
1989 Moto Morini Dart 350
1993 Ducati 750SS
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