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PostPosted: Sun Jun 23, 2019 11:01 pm 
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848cc
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Joined: Sat Feb 03, 2018 8:09 pm
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Hi All,
The primary gear of an engine I just pulled down has a chip / gouge in the rear top hat bush. This is the second time of seen that. What’s happening?
Anyway, is it ok to run - or does it need replacing (also some scoring on the inside)
Also, I read someone saying that ‘they don’t make em like they used to’ and new ones fail a lot. Is this a thing?


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PostPosted: Mon Jun 24, 2019 4:39 am 
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Joined: Fri Mar 19, 2004 6:19 pm
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Location: near Baulkham Hills, NSW
OK to run.
The scoring inside is caused by burrs on the c-clip slot during removal, they are not detrimental, will just hold a little oil.
These bushes are sintered bronze and brittle, that's why they can chip on the edge.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:


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PostPosted: Mon Jun 24, 2019 11:25 pm 
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848cc
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Good to hear, thanks Doc
What about the new ones being no good? Have you heard that before?


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PostPosted: Tue Jun 25, 2019 7:21 am 
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Frog Johnson wrote:
Good to hear, thanks Doc
What about the new ones being no good? Have you heard that before?

Years ago some locally made aftermarket ones had a gear machining problem, I haven't heard of current primary gear problems.

I have used floating front bushes on my 1275s with good results. Even in 998 gears machined out for 1275 use.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:


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PostPosted: Tue Jun 25, 2019 11:34 am 
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1275cc
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Joined: Sat Feb 09, 2013 5:44 pm
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Location: Camden
There was some talk on "mk1-forum" in UK several years ago regarding the bushings used in some new primary gears not being suitable for use with little lubrication as in minis. The main problem was with some new primary gears fitted with pressed bushes as per original, and not with the floating bushes.
The upshot was there had been some failures, but since then, there should not be a problem with gears from reputable suppliers.


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