Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board 62 A10 pistons

hi ....i have a set of .020" over AE11412 solid skirt pistons which i found where 9:1 cr.. once the engine is assembled it is a bear to start as you can hardly rotate the engine with the kick starter...bike does start and run ok (good) but it is just to hard to kick and not sure the next owner will be able to start it! plus it is probably tough on crankshaft and other parts! looking to put lower compression piston in and i am leaning to the lowest cr 7.25:1 since i am not sure( but think) the head , cylinder were milled/decked...can some one refer me to a good non split skit .020" over piston and part number and where to find them? is 67-1417 std bore? 67-1418 .020 over? any help comment would be helpful...thanks,joe

Hi,
On a recent A10 build, where the head had previously been skimmed 0.030 off square and then had to be refaced back to correct the issue
I came up with a solution of an 80 thou thick head gasket
I got this from "copper gaskets unlimited" in Arizona
http://www.coppergaskets.us/contactpage.html

9:1 should not be that hard to kick over?
Do you know how many teeth engine sprockett is fitted ?
I find the original gearing to be very low for todays roads
The A10 will easily pull a 22 or 23 tooth engine sprocket
This also has the advantage of making the engine easier to kick start

HTH
John

hi john,
it is unbelievably hard to spin the engine, if it did not start easily it would be impossible to start it..i have started and worked on many A10's but this one's difficult to kick over...figured it was time to address it and change all the rubber pieces that deteriorated while in storage last several years..
.....i have a 62 spitfire scrambler that i have been gathering pieces for so i will have to check it's cylinder and head to see what has been changed...i rode it on the highway several years ago and i do not remember it being geared too low..
joe.

How easy does it turn over with plugs out?

spins ok ......again bike runs,idles fine.
looks like head and cylinder may have had several thousands max material removed (resurface- lap to clean up )..
joe

hi,
i checked and engine has a 17 tooth front primary engine sprocket....so a 17 vs 20 tooth makes that big of a difference in kick resistance.....joe

Hi Joe,
Its good to find the cause of the problem,
17tooth is either trials or B31 road
Next question is what kind of use the bike is going to get?

For street use 20 will be very low, go for 22/23

John

hi john...
i will see what i can find as i have a 17,19 and 20 now....anyone want to trade for a 22 or 23? haha... i can not find part number for a 22 or 23 , any chance that some one has part numbers? ....hope they are not to difficult to find....it will be interesting to see how much it helps in kicking over.
joe

18T was standard A7 and sidecar A10.
Standard A10 was 21T.
I always found the 21T on the A10 as a pretty good ratio for side roads etc.
Just my two centsworth.

The part number for the 23T sprocket is 65-2541. Baxter's and Raber's have them on their parts list. I have been looking because my A10 is geared low for state highways here.

i found this number for a 22 t,45-2774...
thanks for all the help guys...appreciate it.
joe

Hi I came too this forum through searching the internet for BSA part number 67-1417 , the only reference to this piston on the whole WWW is this thread?
I'm searching for this part after My Dad found His pistons to be 67-1417 and the other coincidence is a 17 tooth primary sprocket was fitted making the bike
hard to kick.
The only bike we believe fitted with this sprocket were trials bikes.
Any one have a clue where these piston originate?

67-1417 is a number found cast into the underside of the piston, it is the raw casting number, for BSA's internal use only, not the finished machined piston number which is usually 1 or 2 numbers lower.
BSA typically machined 3 different sizes from each casting
The standard A 10 piston in your fathers engine is part # 67-1416 and the + 20 is 67-1418 and the + 40 is 67-1420
These are all 7.25:1
The Part number of the finished piston will be stamped into the top of the piston and generally will not be able to be read being scrapped or polished off over the years.

Hi Thanks for Your reply, 67-1417 is the number stamped on the top of the piston which is why we thought that was the actual part number, there is no other numbers to be seen.

67-1417 is the bare piston number for a STD 7.25:1 piston The Part No for the same finished piston is 67-1416 , 67-1418 is +20 and 67-1420 is +40 Not all BSA pistons have a cast in number on the inside but virtually all have a stamped number on the crown which is the number of the bare casting. Almost always, the part number of the finished piston with rings etc is one digit lower and will not be marked on the piston, only on the box if NOS.