Author Topic: A10 Barrel Cafuffle  (Read 1165 times)

Offline Humble Pie

  • Tinkerer
  • A's Best Friend
  • ***
  • Join Date: Sep 2010
  • Posts: 139
  • Karma: 0
A10 Barrel Cafuffle
« on: 23.10. 2010 17:28 »
Having trouble understanding something.

I know stock 650 bore is 70...the top of the bore is just about 70 ( sorry non dial calipers )

the bottom however is just under and more about 69, now should'nt the wear of the cylinder make this the other way around ??

Here is a picture,,am I un aware of something ? The top almost looks like a sleeve comes up and stops as both sides are the same and there is no carbon build up.

or am I just really lost on this ?

1952 A7 Plunger

A10 Trike

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3108
  • Karma: 45
Re: A10 Barrel Cafuffle
« Reply #1 on: 23.10. 2010 21:12 »
Hi Humble Pie,
The bore should be parallel and circular!!
I would go and get some better measuring device or failing that  select a piston and fit it in the bore right way up
measure the gap between piston and bore at right angles to the pin,
Do this at several positions in the bore,
To measure near the top of the cylinder it may be easier to fit the same piston upside down!!
Maximum wear will normally be near the top of the bore a little below where the rings top out

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5342
  • Karma: 61
Re: A10 Barrel Cafuffle
« Reply #2 on: 23.10. 2010 21:30 »
Quote
The top almost looks like a sleeve comes up and stops

Hi Humble Pie
 
Think of the piston rings as the "Sleeve".
The darker ring at the top is the bit the rings don't reach, if there is wear on the bore then often you can feel it with a finger nail at the bottom of the darker ring.

Can't explain the missing mm at the bottom of the bore although there should be minimal wear down there as nothing touches that bit other than the piston skirt (hopefully not to often)
Difficult to measure bores accurately though without proper gear
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Humble Pie

  • Tinkerer
  • A's Best Friend
  • ***
  • Join Date: Sep 2010
  • Posts: 139
  • Karma: 0
Re: A10 Barrel Cafuffle
« Reply #3 on: 23.10. 2010 22:09 »
Thank you both,,who is a good source for pistons ? I want to get the stock  7.25-1
1952 A7 Plunger

A10 Trike

Offline A10Boy

  • Wise & Enlightened
  • *
  • Join Date: Jun 2008
  • Posts: 1075
  • Karma: 11
  • Solihull, Near Birmingham England.
Re: A10 Barrel Cafuffle
« Reply #4 on: 25.10. 2010 12:33 »
Try cake Street Classics.
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline Humble Pie

  • Tinkerer
  • A's Best Friend
  • ***
  • Join Date: Sep 2010
  • Posts: 139
  • Karma: 0
Re: A10 Barrel Cafuffle
« Reply #5 on: 25.10. 2010 12:50 »
Found out that one,,my calipers were not the right tool for the job,,also was not deep enough into the cylinder  so looks like it will need to be bored an 1st over pistons
1952 A7 Plunger

A10 Trike

Online BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 1876
  • Karma: 31
    • BSA National
Re: A10 Barrel Cafuffle
« Reply #6 on: 25.10. 2010 13:49 »
You can measure the wear in the bore by popping a ring in the top, square it off and measure the gap with a set of feelers.
Do it at right angles ( twice ) just to be sure.
Hold it up to the light and look for daylight between the rings and the bore, again rotating the ring in the bore 2 or 3 times .
if you see daylight in the same place every time then the bore is oval.

Repeat the same near the bottom of the bore (usually a smaller gap at the bottom ) .
Average out the readings then subtract them from each other.
If the difference between the top & bottom is more than 15% to 20% of the diameter of the cylinder then it is also time for a rebore.
So if you had a difference between the gaps of .012" or more then that would signal a rebore.
Bike Beesa
Trevor

Offline Humble Pie

  • Tinkerer
  • A's Best Friend
  • ***
  • Join Date: Sep 2010
  • Posts: 139
  • Karma: 0
Re: A10 Barrel Cafuffle
« Reply #7 on: 25.10. 2010 14:43 »
Neat trick,,thank you  *smile*
1952 A7 Plunger

A10 Trike