Author Topic: Can't get a timing side main bush the right size...  (Read 432 times)

Offline Steverat

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After more than one try, the closest to my -0.010" mainshaft is actually -0.015" (from Feked, who sold it to me as -0.010"). So what do I have to do? Have Feked got it wrong, or am I supposed to ream out the last 0.005" myself? I'd rather not do it even though I have a biggish reamer - I don't have a suitable pilot for making sure its in line with the drive side. It really is too small - it won't slip onto the journal.

Please enlighten me!
Steve

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online duTch

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Re: Can't get a timing side main bush the right size...
« Reply #1 on: 28.10. 2018 21:21 »

 Generally accepted modus operandi is to skim the journal just enough to be round, and then install and line-ream an extra-undersize bush  to suit, so what  you have is probably usable. Also it'll probably shrink a bit more when you install it
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 coater87

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Re: Can't get a timing side main bush the right size...
« Reply #2 on: 28.10. 2018 21:32 »
 Your bushing needs to be sized to the crankshaft.

 There is no way around this.

 Lee
Central Wisconsin in the U.S.

Offline BSA_54A10

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Re: Can't get a timing side main bush the right size...
« Reply #3 on: 29.10. 2018 12:17 »
We just finished doing a main.
I poured som bog into a spray can cap, turned it down to be a stiff push fit into the drive side main outer then bored it out to suit the pilot of the reamer.
Shane did the actual reaming and got .0004" worked a treat.
Reamer was an arm & a leg but the guide was a couple of $ plus a few hours on the lathe ( not my fort'e )
0.005" is about an hour with a deceint hand reamer and 15 minutes in the hands of some one who knows what they are doing.
Bike Beesa
Trevor

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Re: Can't get a timing side main bush the right size...
« Reply #4 on: 29.10. 2018 21:52 »
That sounds like a good idea. What's bog; resin, lead, white metal?

Ah, I think it must be this stuff:
http://www.chemspec.co.nz/?page_id=324

Offline BSA_54A10

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Re: Can't get a timing side main bush the right size...
« Reply #5 on: 30.10. 2018 08:58 »
Body filler.
Stuff was about 10 years old so a bit suspect for using on an auto.
Plain pink pollyester resin with ground chook feathers.
We procrastinated about how we would do it for months then he saw a piloted adjustable reamer.
The outer of the rooler was alread in the cases so we thought the pollyester would not damage the running face of the inner.
A bit tricky but on the little lathe I could slip the case over the bed to do trial fits on the outer diameter.
After that it was just a case of drilling then boring the hole for the pilot.
I allowed around .0005" over size on the pilot hole.
Pressed the guide into place then dit a trial fit with the reamer and we had lucked in a slightly tight rotating fit so worked perfectly.
Warmed up the cases with an hot air gun & the pilot dropped right out..
Spray can lit just happened to be the biggest diameter that would fit in the 3 jaw chuck on the small lathe.
Bike Beesa
Trevor

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Re: Can't get a timing side main bush the right size...
« Reply #6 on: 30.10. 2018 10:18 »
As duTch says, usual to have to ream to fit. When they were new, a bush may have been supplied 'pre-sized' but the tolerance would necessarily have been wide, meaning a bit of an agricultural fit. With older engines, some  probably with unmatched cases (like mine) you really need to line bore/ream to get it right. Remember too that when you press a bearing into a housing it shrinks by almost half the interference ie a two thou interference is likely to close up the ID by around .001" so having a pre-sized bearing bush would make the clearance to crank guesswork. I must admit though, that .005" is a lot to allow. One would normally expect one to two thou for finishing.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

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Re: Can't get a timing side main bush the right size...
« Reply #7 on: 30.10. 2018 19:32 »
Hi Trevor and All,
Quote
Shane did the actual reamin g and got .004" worked a treat.

I'm puzzled by the above
0.004 is a lot if you are talking inches would be OK if millimeters  *????*
('' usually means in.)

John
1961 Super Rocket
1963 RGS (ongoing)

Offline BSA_54A10

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Re: Can't get a timing side main bush the right size...
« Reply #8 on: 31.10. 2018 08:20 »
Hi Trevor and All,
Quote
Shane did the actual reamin g and got .004" worked a treat.

I'm puzzled by the above
0.004 is a lot if you are talking inches would be OK if millimeters  *????*
('' usually means in.)

John
Well spotted John.
Missed a "0"
He measured it at .0004" just slightly tighter than the .0005 " minimum.
Crank spins fine so decided to leave well enough alone.
It has a fresh ground shaft so the engine should bed in the extra 0.0001" without any problems, if of course measuring with a mm micrometer & converting to inches was in fact correct.
Bike will not be ready in time for the National now as the big end bolts were wrong.
He ordered the bolts before we decided to toss the rods.
Some one had bored the little end eye so large that the rod broke through the thinnest part of the eye.
Never seen that before but there was just not enough cross section left to take the load.
And we won't mention the metric or Unified bolts where they had simply cut a British thread over the top of the old one.
Gone back & changed my post.
When we get back and the fram jobs that have been ignored in order to get the bikes ready are all done then we will do a photo session & article for the Banter and put a link on this thread.
Bike Beesa
Trevor