a little bit more done over the last couple of days.
First thing with any engine is to check that the ports open evenly
i.e. do the ports on the left side of the barrel match the ports on the
right side? answer yep. and make a note of the port timings
also see if the bottom of the ports are higher than the piston at B.D.C.
with this kit the transfers are about 1.5mm below the piston crown at
B.D.C. this helps to keep the piston cooler.
the exhaust port has a fair radius to the top and bottom of the
port this helps to prevent rapid ring-ware and helps to stop the ring
snagging in the port. At B.D.C. the center of the exhaust port is about 1mm
bellow the piston crown, again this helps to keep the piston cool.
I measured the port timings, what i have is 120 on the boost port and the two
additional transfers, the main transfers are 125. Exhaust port is 172 and if
needed it could be opened up by another 3-4mm extra.
i will be using a DRT 105 rod (still 51mm stroke) with the 8mm packer so the
timings will come down by about 1 degree.
i was quizzing a more experianced tuner for his opinions as i am considering
raising the exhaust port to about 180, his wisdom was to see how it works
first,
he also reminded me that my old watercooled needed de-tuning as it was
a crank buster (the timings on that were about 130 and 185) as he said i can
always come back to it if it`s too slow. so i`ll follow his advise
(why ask if you can`t listen).
so starting the work, first thing was to cut an 8mm packer.
then dowel the packer, case and barrel (i used 3mm drill bits for this
as they are a common size) to ensure all parts line up at the
building stage.
then rough out the packer to nearly match the barrel, the transfers on
this kit as it arives have a lip at the gaket face, this is so that if
you do not get the welding and milling work done the kit can still be
used but less extreme opening of the case would be needed
for me to remove this lip and rough out the packer only took a few
minutes with a die grinder and rotozip.
then do similar with the transfers on the case. i have marked the area to
be ground with some blue marker. the reason that one side is so different
to the other is that the mag side is a falk half case and already has a bit
of the work done at the casting stage.
as you can see i have scrubbed a part of the case with the collet of the
digrinder. naver mind it won`t make any differance.
the blending is just about finished at this stage
the welding that i had done on the piagio half case isn`t too bad there are
a few pin holes in the weld but nothing to worry about.
i could have opened up the transfers at the case by a lot more if i had taken
them to the limit. i think that would make sense if i raised the exhaust
to anything over 185 and then needed the transfers to feed the barrel at
really silly rpm. as it is i still have that option and i still have
enough of the case left for any future kits (early yZ125 or KTM125 for example)
in the mean time i can get a bag of bicarb and clean up the dirty half of the
case. i was impressed with the results of my attempt at DIY soda blasting
it had a small effect on the lawn, but that`s recovering now.
so now i wait for some spare cash, and then more bits can come through the letter
box. such as a rod kit, a circlip or two, a couple of grommets, gear trunnion and
taper pin, longer cylinder studs, kickstart buffers,possibly
a new selector. then it should be just about finished.
the flywheel cowel is in the post so in the next couple of days i will have a play
at being a thin sheetie
wonder what i`ll forget to order.
"O"rings, bound to be something else
...................................
just for comparison i took a pic of the barrel with a standard gasket placed on it
i think this shows why the case needs welding and milling even though i didn`t
go extreme on opening out the transfers