What to expect from these port specs?

I've actually cut out the transfer walls entirely before. it does really nasty things to your intake velocity but can make for one hell of a top RPM screamer
 
weee, everyones 5 c worth!

how you mounting em in the lathe? plain old 3 jaw in the bore and then...how to ensure its dead square?

expanding arbor would be ideal... any consideration of spigotting out the top so you dont need a head gasket?

then the port timing itself... have you started mapping them? worked out the time areas? done a template?

opened up the intake and transfer to allow extra flow? this is all before even considering tampering with the durations.

im with that theory of hacking out the transfer walls... they serve no purpose and make getting into the port itself a breeze.

allowing for manipulation of flow.
can always bog em up a bit with poxy or welding...

then there gets this really tricky bit.

i figured you could pull it off with spark flash photography, otherwise...

you want a perspex head, with the same combustion chamber shape as the head you run.

a source of fog or smoke on the intake...

a vacuum on the exhaust...

and to get a true dynamic idea of gas flows...

a high speed camera so you can spin the engine at near operating speed.


yep, a flow bench but rather than static, which means nothing...its dynamic. useful.

(at least thats what i think, though i never bothered actually doing it...)

its not just about "port timing"... its about flow...turbulence... and how else can you see that at 5.5k it suddenly stalls at the transfer? anyway...

then theres that whole subject of the intake, tuning that side of the engine...


and in the end...using el cheapo engines made from recycled beer cans...

the realisation that the hours of work involved, the nikhedonistic drive to get it done, was all in vain, and one should have gotten a morini/denardis in the first place.

hate to say it, but you will spend a LOT of money destroying parts before you get it "right".


hmmm...say you eat five cylinders...thats $200 at the price i find em at.

five pistons... another $100... youll always have one drop its keeper pin and destroy everything.

two engines... 400....

bearings, parts, time, labour... countless...

morini 50cc as used in a ktm50... about 5-600 last time i looked... virtually bulletproof.

i know it takes out the satisfaction of DIY but all ive found with these engines...is NO SATISFACTION!


PS...when you make a decent pipe, even for a stock standard engine, which you will end up doing because anything else is so much effort after the first three blow up, the gains are extraordinary ;)
 
Last edited:
don't discourage the poor guy. I was very satisfied with my engine after I did all the mods to it and put on a torque pipe. It started easy, ran smooth, had great acceleration, climbed hills like they weren't there. Only thing I hated was the rough ride because it was a bicycle.
 
im just saying its sorta easier to concentrate on the exhaust, intake for stock... only do a little cleaning of ports... the easily swapped bits that actually make it go...but dont spend tooooooo much time making mods that end up making anchors... sure, youll get em to go but are the results worth it? 9hp is sheer dreaming...

once you make a pipe for a 180 exhaust, 140 intake etc...youre stuck with having to make every new cylinder that way...


i read lathe.... check out chainsaws instead ;) the results are far more worth it. get a good one... then that 9hp is actually reasonable.
 
mine has 157 exhaust duration, 118 transfers duration. not pipey at all.
here's the big 6:
porting
pipe
carb
ignition system
compression
balanced flywheel
 
see, port durations mean nothing.

just measured up my stihl ms170 quickly... max rpm of 14000, working rpm of 8-9000...

approx 140 exhaust, 100 transfer. thats just rough, i didnt actually mount the degree wheel, but im pretty sure ive read them as being close to that, if even LESS. 136/96 im sure it was.

anyways...im sure that if i did a time/area map of them...theyd be pretty close to the "ideals" laid out in them books by jennings blair and the other one... the cross sectional areas are HUGE. couldnt be bothered. just verifying my info before rolling a pipe for it. the time has come!

so many things to modify, before even touching port durations... angles of port roofs and walls, areas, and flow capabilities always remain the most important.
 
"port durations mean nothing". wow, really.
please get off your drugs (or get back on them) and get back to reality.
you aren't revving up to no 14 thousand! you can fool others but not me.
'fess up man
 
MAX rpm 140000

this is max redline as stated in the workshop manuals. any more and they explode.

they will do it, unloaded.

OPERATING rpm...8000 to 9000 rpm... now thats LOADED...

do you ever read ENTIRE posts or just select the phrases that suit you at the time?


like the little bit about MS170....STIHL???? CHAINSAW???

what? you think im saying a HT POS gets to that? :ROFLMAO:
 
Last edited:
nsr150...

transfer of 126

exhaust of 196

find a steep hill and it still wont get past 11k. absolutely gutless at 10.5, max band at 10k.

of course, in this case, its the exhaust to blame. change it and suddenly they wind to 13k quite happily.
 
Back
Top