2 Stroke Squish Area Ratio Test - Plus Bonus PIPE test

Hi, welcome back. I'm Dave, this is my Kawasaki AR50. I'm trying to get to 100 miles an hour. First of all, thanks, 500 subs now. In fact, a bit past. Thank you very much for everyone who has subscribed. So today, what we're doing, I've cut a couple of nuets. So I'm going to go through how I cut these. I've increased the compression, but I've got two different squish area ratios to try. I've also put a nice little o-ring in there for better sealing. And a spigot in the top of the barrel for location. And at the end, I'm going to try a short pipe. Just to see what happens. Just checking the compression ratio on what I've got at the minute. I know I've done it before, but I'm going to do it again just so I've got an absolute definite before I modify the head. So I'm starting with 36cc in there. And I'm going to fill it up to the bottom. Okay, I'm now down to 45.5. So I'm going to do some mathematics and get back to you. A bit of public maths. So that's 5. So that's 15, so that's 9. That becomes a 3, so that's 0. So 9.5, 9.5cc. It's a spreadsheet I made many years ago. So we add 9.5. Which gives me 11.2 to 1 compression ratio I'm currently running. Or 6.03 trapped. So let's get this apart and machine it up and see what we end up with. I'm going to double check the squish as well before I make any changes. Okay, looks like it's got it. So about 0.7, which is not too bad. Maybe a little bit closer. So if you look for KiwiBiker in the bucket section. And this is the Excel spreadsheet that I downloaded. The latest link is here, I believe. It's towards the end. It keeps updating it. And as you can see, it does all your porting. It does fuzz pipes, wobbly pipes. This is the head bit that I actually used. The sticks show the inflow angles. Give you a port map. It's really, really cool. Okay, so my setup. I use the centre in there. If you can see, there's a lump of metal. Which is 54.5mm or 55.5mm, whatever. 55mm. It's clamped with two of the four jaws. And then on the bottom of the liner with the other two. And I've got it to within about half a thou. Which I think is good enough. I'm going to then turn it. I have this centre in here to support it. It's a little bit out of balance, but I'll do it slow. And then I'll just take some of that off. Next up is the head. So I've got a little adapter that goes into the chuck. So the head screws on that. And then I can machine this out. Right, I've got the cross line set up 12 degrees. Just so I can do the squish band now. Right, quick polish up. So you can see there's a little spigot there. It's only about a mm high. I can't remember the diameter I made it. However, in both these heads, the corresponding diameter sits there. And there's a little bit of relief there. So these, put it on. And it's lined up. All was central. I was originally going to lap these in. But I soon saw it was going to take ages to grind that to a really good finish. So I decided to put my o-ring in. So I've o-ringed that now. And to assist with putting the o-ring grooves in, I made this little setting jig. So I've got that set. This fits onto my head adapter. 40mm spark plug thread in there. I can set my tool up. And then I know I can go straight into the heads and cut an accurate o-ring. Right, heads machined. So this head here was the original head I was using. I've modified it. I've reduced the squish. It's now 0.55 gap. Squish area ratio is 0.39. And I've reduced the volume. So I've increased the compression ratio. It's now at 13.8 to 1 geometric. And that's 7.3 to 1 trapped. This other head is another head I've got. I've got a 50% squish area ratio. I've got 0.5 squish gap. And it's also the same CC. So it works out exactly the same, given the same 13.8 to 1 geo. And 7.3 to 1 trapped. OK, quick and dirty again. Put on a new head. I've made less power. So, that is not good. OK, one last test. I've got a really short pipe I've borrowed. Down for an 80mm scooter, I think. However, it's short. Somewhat near the length that the original pipe was for the original test attempt. So, I'm going to give this a quick run to see what happens to the power. OK, test results. So, I had big hopes for this test. I thought, I've got a couple of horsepower here. Not to be. However, let's review it. Let's see what we got. I didn't record much at the dyno. Because, quite frankly, I was quite disappointed. Particularly when I did the first test. More compression. Roughly the same squish area ratio. Less power. What is going on? I then put the other head on. And, actually, I did pick up a bit of power there. And I did a retest. So, the best test I had for that 13.8 comp with the 0.5 squish area ratio. It did beat the previous curve. So, 15.1 versus 14.6. So, those that actually said half a horsepower on my little post. You won 5%. So, about 2 of you. Half a horsepower. That's all I got. And, additionally, I put another pipe on. That really short pipe. I thought, I may pick up a bit more power. But, it was still going. I had to shut it off. I think the soft limit came in on the ignition. But, again, no more power. So, I've been able to walk through some bits. I've got some portcasts here. So, this is the one out of my barrel. And, as I said before, I've got about 15, 16 horsepower at the wheels. Blown down in this. Which is probably why I'm not getting as much power from the compression as I would have liked. This is the cast of the exhaust port that Chris did for the original AR. And, as you can see from there, it's a lot bigger. There's a lot more blowdown area. And, I think that's probably limiting me at the minute. Another one is, Chris spent quite a lot of time. This is his inlet. And, that's my inlet. And, you can see where he narrowed it down. And, he spent quite a lot of time flowing it. Potentially, an area to look at. And, he has got a little bit more port window area as well. I've been digging through my files. And, I've found all my templates for the original pipe that I did. For the article. So, I want to make that again. This is quite a short pipe. I'm just interested to see how it works this time. So, I'm going to get my tin snips out. And, make the pipe up. Hopefully, we can get a bit more power. I need at least another 3 or 4 horsepower. I reckon maybe 5. Keep comments coming. Keep giving us those likes. Subscribe if you're new. And, I'll catch you next time.