Author Topic: Plunger A10 pistons  (Read 1809 times)

Offline emilios

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Plunger A10 pistons
« on: 05.12. 2009 11:33 »
Hi
Im going to put the cylinder block on my engine(A10 cast iron head 1952) and im having two questions.
1. Haynes manual says not to put any cement on base gasket....is this ok or i will have oil leaks?
2. I bougth new pistons from TMS (+40 high compresion)..Haynes manual say that high compresion pistons have bigger cutaway for inlet
    valves..My new pistons have the same cutaway so it must not have correct position..
   Is that right??
Please advice cause im planning to put pistons and block tomorrow.
Thanks to all
1956 BSA A10 Plunger
1954 BSA B31 Goldstar Replica
1970 Honda cb750K0 project
Cyprus

Offline terryk

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Re: Plunger A10 pistons
« Reply #1 on: 05.12. 2009 12:26 »
I wouldnt put high compressoin pistons on a plunger unless you are using the thick flange cylinder barrells and square fin head not the small round fins. I think about 7 1/2 to 1 compression is safe with original cylinder barrels. Also I would run a 356 cam with any pistons above 7 to 1. Also a small amount of sealant is fine anywhere on the engine and gearbox as long as it doesnt block oil ways so not on the oil pump etc. Hope that helps you a bit.
1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline emilios

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Re: Plunger A10 pistons
« Reply #2 on: 05.12. 2009 13:45 »
Can you show me a foto of the flange i must use?
1956 BSA A10 Plunger
1954 BSA B31 Goldstar Replica
1970 Honda cb750K0 project
Cyprus

Offline emilios

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Re: Plunger A10 pistons
« Reply #3 on: 05.12. 2009 14:12 »
thats my cylinder head...if that can helps.
1956 BSA A10 Plunger
1954 BSA B31 Goldstar Replica
1970 Honda cb750K0 project
Cyprus

Offline emilios

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Re: Plunger A10 pistons
« Reply #4 on: 05.12. 2009 14:35 »
I asked TMS(supplier) if i can put this pistons and the anwer was:
"NO THE PISTONS WILL BE OK AS THEY ARE APPROX 8:1 COMP RATIO WHICH IS HIGHER THAN THE LOWEST COMPRESSION WHICH WERE ABOUT 7:1 BUT LOWER THAN THE LATER MODEL EXPORT SUPER ROCKET & ROCKET GOLD STAR WHICH WERE ABOUT 9:1 "
 
1956 BSA A10 Plunger
1954 BSA B31 Goldstar Replica
1970 Honda cb750K0 project
Cyprus

Offline emilios

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Re: Plunger A10 pistons
« Reply #5 on: 06.12. 2009 17:38 »
Anyway...today i fit high compression pistons in egine and im ready to set ingnition but i was reading manual when i saw riding that if you put high compression piston(7.25 to 1) to A7 or A10 the ignition setting is 3/8in  BTDC.
??????????
Does someone put high compression piston and set ignition like manual say?
Please advice
Thanks
1956 BSA A10 Plunger
1954 BSA B31 Goldstar Replica
1970 Honda cb750K0 project
Cyprus