Holy 2 Stroke (piston)
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- čas přidán 8. 09. 2017
- A question asked by a viewer - and I draw on the board and bla bla bla for a bit
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"That piston hole is called a cylinder" lol
Good Job Matt Glad to see your subscriber list growing 20K very close
on my cr500 i did this and relieved the exhaust bridge to give it a bit of room for expansion under high load and it has worked a treat yea i probably loose a bit of power but id much rather not be cutting a groove into the exhaust side of my piston from the bridge over expanding lol
Aren´t the port bridges also for keeping the piston rings from popping out of their grooves too much and catching on the port edges?
When I was a teenager (a very long time ago) another kid had a Garelli moped that had a hole in the piston crown. The thing had bugger all compression and needed bump starting in order to spin fast enough to actually start. The weird thing was that it was unusually fast, not what you'd expect at all.
At high speeds the the hole will be too small for the enough charge top leak through the hole quick enough. Not only that but the expnading gas passing through the hole could be used to force charg through the transfer, but its a delicate balancing act. And like with everything the hole size will only 'work' at a certain RPM
You are likely right, certainly would not advocate someone doing it deliberately. As you say at some specific RPM it may have had a positive effect, possibly raising the crankcase pressure...
Makes me wanna try
Another reason to have a bridge is to prevent the piston rings from falling too far into the exhaust port, this creates more wear and in a worst case scenario the piston ring can snag and break the piston. Regular ports wear hard enough on rings and cylinders, another thing that's bound to doom the two stroke.
I read in the " 2 stroke tuner´s handbook" that a port´s width , be it a transfer or an exhaust port can be only about 50-60% of the cylinder bore to avoid the rings popping out too much.
I just thought it was interesting. Great vid Matt, as always :D
My polini evo has 130cc has 68% exhaust, i think 70 is Max on no bridge
Yes, the handbook is quite old. And of course there are exceptions like with everything :)
That is just what I read.
I just did some reading from the "handbook" i was talking about earlier and you are right. I will quote from there: "one should never simply and arbitrarily widen a port out to the 70-percent limit, the safe and sensible approach is to begin at 62-percent, with a shape that is as nearly an ellipse as is possible". :) interesting stuff this is...
@@Sahkopekka200 who published it and when would be interesting to see whats bewn proved or disproved in that
Matt have you heard of stihl 2mix 2 strokes chainsaw engine they have a seperate port about intake that only lets air in air fills underneath piston and seperates exhaust and fuel air mix its supposed to stop fuel going out exhaust unburnt
Yes - its on the list
Ha ha I got a problem with my exhuast 👍
wow, what's that song? sounds really nice
I’m rebuilding a Yamaha GP1200 PWC. The original pistons have a hole on the skirt and two more holes above the wrist pin on both sides. The wiseco pistons I ordered are missing the two holes above the wrist pin. Should I have those drilled or no? They’re beefier and a lot thicker there compared to the originals. So if I drilled it the oilers/air mixture would have to flow through a longer passage...I’m not sure what to do. I messaged wiseco but haven’t heard anything back. Any help would be appreciated thanks
Run the pistons as they are. If they fail then its wiseco's fault. If you modify then and they fail its your fault
I made one small 2mm hole like this in the piston. I did it to have more lubrication on that wall. But as the pston goes up , the small hole, gets straight in the middle of the exhaust port hole, just when the piston is in top d centre. I did not start the engine yet. It is a 180cc 2 stroke piaggio . What do you think will happen? I will loose the under piston vaccum /compression, or the exhaust pressure will level it out?
Ffs
The Windows are on the intake side .the engine ran fine before the whole blew in the center of piston
And 2StrokeStuffing goes like: Nah.. The thin Wall between the 2 Ports (called T-Port) are actualy there to prevent the Ring poppin out. On Cylinderkits without those cooling/oiling Holes in the Piston, the thin Wall is carefully grinded back to equalise the heat expansion.
And no, Matt, i don´t want to be nit picking :-)
Anyway, great Video :-) Will you do a Vid of different Portdesigns (2t & 4t)?
Cheers
Kai Müller cant it fill both purposes? Keep the ring safe and support the exhaust port?
Message approved by 2STROKE STUFFING 😂 Great video Matt!
Communist Hippie Keeping the ring intact is the purpose, but as a side effect it adds to the cylinder integrity too. It can't not do both...
2STROKE STUFFING ok
I believe its the other way. There are ringless nitro engines that are bridged - explaine that one bastards! LOL
Matt, have you ever played with any honda Odyssey 350r s?? I believe it would greatly benefit with some ..
Nope
The Wiseco pistons state to drill they yourself as someone previously commented. I have a Polaris 800cc 2 cylinder without an exhaust bridge and as I stated before the pistons have no holes. Many of the other brands of pistons offered for this engine have two holes to either side of the exhaust port, four holes in total. Do you see any benefit in drilling these holes in my Wiseco pistons?
If you are having ove-heating scuffin issues in that area - then yes
Thank you!
The Workshop so u don’t need to drill holes
Go back to the OEM pistons and then look at the replacement parts, some wiseco pistons come. With drilling instructions some don't without knowing what youve replaced or changed and what the oem part was like its hard to. Say yes or no without the thing in front of you.
Any idea why my 80" cc engine is only four stroking when I put a brand new window piston in it?
Cause it ain't tuned
simples
I think it was the 2 stroke stuffing guy said only to drill these holes on a forged piston and not a cast piston?
You shouldn't be drilling these holes at all
Wiseco replacement pistons come with instruction on how to drill the holes
Does it? Can you send me a link or picture?
I,ve downloaded the pdf,where do i send it too{i,m just a dumb aussie]
matthew-hudson@outlook.com - cheers dude - will be a good read
mine has 1 hole on the inlet side
Is it more of a window than a hole?
Actually this was what I thought you were going to talk about. On my freshly installed cylinder kit I have a hole on the inlet side. I always thought it provided some extra lubrication for the piston pin etc. New video coming up?😉
ninth