How not to B33!

[Dan_B33]

Wolf!
You have light hand for writing! Thanks for documenting.
Ok I will have fresh spirit now. You did great job...that motivates me to become another "happy looser" putting fortune in order to have my BSA B33 running....

[Dan_B33]

Hello,
I wish I kept that bike under snow

[Dan_B33]

....close to nervous breakdown

[Dan_B33]

...piston and barrel are kind of a joke

[Dan_B33]

Any idea what author meant by cutting out barrel sleeve

[Dan_B33]

...and big end...

[Rog1]

Any idea what author meant by cutting out barrel sleeve

Do you mean the missing bits of the bottom edge of the sleeve/liner, front and back? I don't know the cause, but my M33's barrel is like that. The bike still runs okay.

[Dan_B33]

Yes Rog,
Thanks for shearing...I started to think it I some hack by previous owner....need to check if I have room for any oversized piston...

[neil1964]

Looks like a short rod piston (ie later model).
Obviously the bore will need a clean up of some sort due to piston nipping up.
I can't see if any deep grooves or if the top of the bore has a ridge above the top ring line.
If lucky might get away with hone and new piston and rings but I'd be surprised.
Those 'cut outs' on the bottom of the barrel are usually symmetrical fore and aft to clear the rod.
As long as they are relieved and blended without cracks/stress points and there is enough meat on the liner you might be ok.
Pistons for that version (short rod) are around (more so than long rod/early GS type).  I would always go 7.5:1 in one of these.
I'm more worried about the marks on the flywheels as harbingers of more badness in the crankcase!

[Dan_B33]

Thanks Neil,
I have checked barrel and looks like the scratches are not that deep. Still do not know if there is a room to make any oversize here ? +0.06inch?
Indeed what is inside crank case ....I have no idea. Changing sump plate I have not seen any bits....and crank spins ok no play up or down....

[Dan_B33]

...barrel bottom reading is as on the picture below need to switch
I inches with that measurement

[Dan_B33]

Ok some more news.
I've had a look at the cylinder head. So looks like home made valves here....but not machined no drill an grinder I guess

[Dan_B33]

....and head

[Derek996]

...barrel bottom reading is as on the picture below need to switch
I inches with that measurement

STD bore is 85mm + a small clearance, maybe 0.1 to 0.15mm. Your measurement of the piston and the bore reading of 86.4mm shows possible a 1mm overbore (+40 thou). There should be room for boring out to the max +60 (1.5mm)

[neil1964]

Hepolite 11744/060 would be choice if the bore will clean up with light hone (afraid a machine shop will be needed to see). I get you to 55thou over? 1.4/25.4 allowing for caliper vs micrometer!
New valves and guides are available from Alpha bearings.
Can't tell from your pics if seats are pocketed.