piston bdc and exhaust port

[mickdale]

does it matter if there is 2mm of piston skirt still in the exhaust port at bottom dead centre on a ts1?

cheers
mick

[Ian Hepworth]

Yes, as well as suggesting your other port timings may be way out it also means that part of the piston may get really hot.

[rosscla]

You using a 60mm crank?

[mickdale]

You using a 60mm crank?

unfortunately yes - didn't realize it raised the transfers and ts1 transfers are already large when I bought it.....

[mickdale]

Yes, as well as suggesting your other port timings may be way out it also means that part of the piston may get really hot.

hello ian
if my barrel has 2mm piston exposed out the top of the barrel and 2mm showing in the exhaust port:
191 deg exhaust, 127/125.5 transfers (transfers not the same)

if my barrel has 1.5mm piston exposed and 1.5mm showing in the exhaust port:
193.5 deg exhaust, 129.5/128 transfers

if my barrel has 1mm piston exposed and 1mm showing in the exhaust port:
195 deg exhaust, 132/130 transfers

think I need to get the bottom of the exhaust port welded before re plating, but not sure if I need the transfers tweaking so they are exactly the same..........

cheers
mick

[camel]

You using a 60mm crank?

unfortunately yes - didn't realize it raised the transfers and ts1 transfers are already large when I bought it.....

im confused here....if increasing the stroke the piston CROWN(is that what you meant?)should be lower than the bottom of the exhaust port at bdc by 1mm so therefore you would in theory need a 1mm packer to bring it back(just thinking alloud and not trying to state the obvious)..i cant see with the set up why you would have 2mm of piston crown exposed at btc,has the barrel been shortened?has the exhaust port been lowered?

[Muppet]

mb road tune?

[mickdale]

erm........dunno - what is the distance between the top of the cylinder to the bottom of the exhaust and transfer ports on a std ts1 cylinder?

cheers
mick

[camel]

have you got a 110mm con rod on the crank?
ie 3mm more than a std rod?
think were getting warmer now....

[mickdale]

hello camel,
just measured the cylinder and put data in edens port timings calculator

tuner who spec'd engine originally was 60mm stroke and 115/116 rod - was supposed to stick out top of cylinder 1mm but was wondering about 2mm to bring down transfers......