6 replies to this topic

[Blocky]

I am in the process of restoring a 241 progress 2 and am currently rebuilding the engine.

I was a little surprised to find that the piston that is fitted is stamped as a B whilst the cylinder is stamped E

Obviously the two should match but can anyone tell me what figures the letters actually refer to ?

[helloyes]

They refer to the piston to bore clearance, you should use an A piston with an A barrel and so on You could send the barrel and piston to langcourts and have the barrel replated, to suit the piston. If the barrel has an iron liner fitted it may have been bored and honed to suit this piston ? you need to find out what clearance you have measure the piston with a micrometer 10mm up from the bottom of the skirt (front to back) and note the size then measure the barrel bore with an internal micrometer and minus from the other which will give you the clearance you have check your manual to see if its in tolerance hope this helps and good luck

[Monty_Jon]

Blocky, on 25 January 2012 - 06:40 PM, said:

I am in the process of restoring a 241 progress 2 and am currently rebuilding the engine.

I was a little surprised to find that the piston that is fitted is stamped as a B whilst the cylinder is stamped E

Obviously the two should match but can anyone tell me what figures the letters actually refer to ?

Its probably been replated at some time, and the piston matches the replated size?

[Lee Harris]

Monty_Jon, on 25 January 2012 - 07:31 PM, said:

Its probably been replated at some time, and the piston matches the replated size?

MUST have been replated. I doubt a B piston in an E cylinder would even runwell when new

Tolerance (diameter) Piston to bore should be 0,035mm when new
0,05mm will rattle a bit
more than 0,07mm soulds like a rebuild.

Size difference per letter is 0,01mm

so could have been 0,065mm assuming both were new when assembled

would sound like a bag of nails or a TY 250! hahahaha

Edited by Lee Harris, 25 January 2012 - 08:04 PM.

[Blocky]

Thanks Lee... just what I needed to know.

The cylinder doesn't look as if its been replated but the piston looks too good to be original. I wonder if someone has fitted a replacement piston and mistakenly read the E for a B (easy to do when parts are dirty) when they bought the new piston.

Will have to measure things tomorrow.

[furse]

where is the B or E stamped on the cylinder?

[Rosey]

Lee Harris, on 25 January 2012 - 07:33 PM, said:

MUST have been replated. I doubt a B piston in an E cylinder would even runwell when new

Tolerance (diameter) Piston to bore should be 0,035mm when new
0,05mm will rattle a bit
more than 0,07mm soulds like a rebuild.

Size difference per letter is 0,01mm

so could have been 0,065mm assuming both were new when assembled

would sound like a bag of nails or a TY 250! hahahaha

But still much quieter than a 307!