|
|
Post by 190mech on Sept 15, 2019 14:42:00 GMT -5
|
|
|
|
Post by 90GTVert on Sept 15, 2019 16:40:39 GMT -5
I've looked at those, but I don't think the square heads will match up to my round cylinder for the outer o-ring to seal. They have to be a PITA and make stuff just different enough that it wont work. EDIT : Actually, here's a post of yours from a while back where you can see how square these are. I think any kind of sealant that can stand 300F and be resistant to raw fuel would work fine,we are just filling voids here,the real clamping is in the machined area.. Scott gave me a LC 50mm Charmo cyl kit,note the lack of O-ring in the chamber area..   vs mine...  |
|
|
|
Post by 90GTVert on Sept 15, 2019 17:08:35 GMT -5
I checked the DRR head and it's about 9.6cc. That's as setup for a 49.5mm bore and no recessing of the chamber.
I just measured 10.6cc of the current head, but I have measured it at 11.1cc before. Not sure what I did different. Could be that i used the temp sender under the plug instead of the crush washer?
At any rate, if I add just the 54mm bore 0.7mm recess to the DRR head to try to get squish correct, that puts it at 11.2cc. Not sure how much different it gets when the squish band is cut for the 54mm bore instead of only 49.5mm. I'm already tight on squish clearance so I can't really do anything with that. Kinda hate to cut the head and then find out it's too big and I'm just out the cash.
This DRR head uses a long reach plug, which is not common to the 90s. Luckily I had one around for the 86cc so I could check.
I also measured the depth of the outer o-ring groove on the current head and DRR head. Current head is 1.5mm and I'd want to cut it back probably a couple of tenths. O-ring is 2.5mm. The DRR head is 2.2mm. I'd have to cut off 0.1mm just to get it level with the center, so prob 0.3mm off which would still leave 1.9mm. The current head at 1.5mm barely wants to hold an o-ring in to install it sometimes so I don't think I should go farther and then leave a gap using it.
|
|
|
|
Post by 190mech on Sept 15, 2019 19:09:24 GMT -5
While there are cyl kits that size and larger available for the Honda engines,all are designed for longer strokes than the Mina engines can run..A 50X50 would be an ideal engine,but the 100cc 2 stroke class engines left ages ago in racing,so the 50mm pistons have also dried up..Then again a Mina can only handle a 48mm stroke(try to find one today),so we are boxed in a bit more..Added to an engine designed for 50cc and expanded to 90+cc leaves shrouded transfer ducting and little gasket surfaces for proper clamping further complicates this project!I have been looking for years into readily available parts to fab a 100-125 2 stroke scoot and its getting harder to find ANY of them we had just a few years back,,The Gilera 125/180 cranks and cylinders are not on the market anymore,,so other than making a one off from casting or CNC machining,the big bore 2 stroke Mina engines aint looking good!!  |
|
|
|
Post by 90GTVert on Sept 15, 2019 21:34:22 GMT -5
I found some old numbers and at one point I was at 13.19:1 uncorrected compression ratio and 7.46:1 corrected compression ratio. That was with an 11.1cc combustion chamber. I think at some point I had done the math at 7.7:1 corrected, but I don't know where the numbers are for it. Anyway, I used that old info to get a ballpark. Just assuming it ended up at 12cc with the modified head (WAG), that would drop those numbers to 12.01:1 UCCR and 6.84:1 CCR. I seem to be doing better with 7-8:1 CCR. With this engine hanging around at least the mid 7 area, it's the strongest 90cc I've ever had. If I'm wrong and the chamber ends up larger than 12cc, it's definitely a problem. 12.0 is bad still.
Not really sure what I want to do. I almost feel like I have to chance it because I don't have a lot of options. I guess I could cut back the current head's o-ring groove and see what happens, but again it's barely able to hold the thing well enough for installation so I don't really see it being a viable option. If it were a totally round o-ring groove, I could prob make it deeper on the lathe, but that jut out for the inlet/thermostat ruins it. I could possibly cut the majority of the groove that's round on the lathe with the rotary tool attachment (the thing I used for cutting a keyway into the water pump adapter). Then maybe freehand the rest. That also doesn't strike me as having a very high success rate though.
|
|
|
|
Post by 190mech on Sept 16, 2019 0:25:43 GMT -5
|
|
|
|
Post by 90GTVert on Sept 16, 2019 22:04:16 GMT -5
Back to the 86cc... I got the CVT setup and found that there was contact between the kick start spring and the variator fan's fins.   Ended up taking the Malossi supplied spacer for the OR vari down from 9mm to 8.25mm and that fixed it. I had about 1.7-1.8mm of clearance behind the variator and I wanted to keep a little in case anything ever shifts or changes. I put the degree wheel back on and marked the flywheel so I could check ignition timing. Got the engine back in the scoot. I left the pump off and hoses so I could check timing. Got it fired up and it was at 27 degrees at first. Backed it down till it ended up at 20, which was almost all the way back to stock position on the stator. I'm guessing this flyhweel has more advance than the large taper stuff that I typically use, but it could be from various things.   When I cleaned the carb before it went in, I upped the main jet, pilot jet, put in a richer needle and set it more toward rich. It sounds pretty rich to me. I put in the 10g sliders that my 103 likes, so it's prob got too much weight there too. Most likely won't run worth a darn ATM. Just trying not to melt it right away. I just have to install the water pump stuff, connect hoses, etc... and it should be ready to start finding out if it will actually move. |
|
|
|
Post by Kenho21 on Sept 17, 2019 20:44:34 GMT -5
What are the silver discs on the back of your air box?
|
|
|
|
Post by 190mech on Sept 17, 2019 21:36:19 GMT -5
Ken,If you go back to page 227,you'll see a UNI vent was sucked into the reed box,,I'm guessing the plugs you ask of are is what Brent machined to block off those goofy snap in thingys...
|
|
|
|
Post by 90GTVert on Sept 17, 2019 22:47:38 GMT -5
Yeah, those are aluminum plugs to block off the UNI Filter Vent holes. I got the cooling system plumbed and filled. Then I went to mount the seat and forgot the joy of having a "big" carb. The cable ran into the seat bucket. I made up 2 spacers from aluminum round bar, breaking and fixing the lathe in the process. Then, after that ordeal, I decided that it was smarter to make a spacer from aluminum flat bar. That would let the seat make the same more more contact for support than it would on the normal front mount. Figured that's a good thing since I'm heavy. I later added a strip of 3M double-sided tape to hold it in place so it's easier to remove/install the seat, but isn't hard to get rid of at some point.   Then I could get to seeing if it would go or not. I started off in the yard, because I figured it wouldn't run well enough to actually ride. It wouldn't hit at all. It just stumbled and sputtered around the yard. So this is where it started: DellOrto PHBL 25mm Pilot : 64 Main : 122 Needle : D36 w/clip next to richest (4 spots) I moved down to a 118 main jet. It improved only very slightly. I moved the clip 1 position leaner. It started to want to hit at about 8,000RPM after struggling a lot to get there. It was just an abrupt hit and then immediately sputtering. I moved the clip all the way lean. It improved more. It would hit hard if it would hit. It picked the wheel up when it hit and then fell flat. I switched down to a 112 main jet. That's the jet that was in there when I first cleaned the carb from trying to get it in tune with the 103. I'd imagine sealing off those UNI vents prob helps to richen it up all around though. These carbs do ship with a 102 main and I think my first 103cc that revved high liked only around a 105 with the filter vents still. That made it finally able to hit with regularity. Still really sluggish though. I decided that it was finally ready to go down the road. Video below is from that ride. You'll see it take off WOT and lag and lag and lag and finally hit. Then if I hold it WOT it stumbles or sputters periodically like it's still rich. Right now it reminds me of when I first rode a GY6 150. When you feel the grunt, you think it's really gonna go. Then it just feels flat like something is missing (if you're used to the 2Ts at least). With this, when I feel the hit I'd think it's gonna take off and then it's not great. Temps are really low. Coolant temp was staying around the 1-teens for about a 7 mile ride. Max CHT that I recall seeing was 186F. That would be indicative of very rich, but I don't know how the under plug CHT does with this 2 piece head and the thick section with the long reach plug. On the 103, I was seeing 320s CHT with it running strong WOT. I went through a nightmare with this same carb/reed/intake on the 103 at first. Never could get it right. Swapped in the 21mm Dell and it wasn't that bad to straighten out. I recall that a light/small flywheel did a lot for the 103 with the big carb, but then we get into all that no-charging crap. Point being, I'm prob gonna be fighting way harder than anyone that just buys an inner rotor, the recommended carb with recommended settings, etc... At least my very next move is simple. I'm letting it cool overnight and I'll check some fasteners. Then it'll be back to tuning. Oh, and my cooling fan started going nuts. It hasn't worked automatically for a while now. Then today it starts randomly turning on and off with cool temps. A few minutes after riding, I could touch the radiators, the adapter for the cooling fan's switch, and even the cylinder and head so it's legitimately cool. I'll prob just unhook the thermal switch and stick with the manual switch for control. |
|
|
|
Post by pitobread on Sept 18, 2019 10:06:02 GMT -5
Dellorto need needles to get right. At least in my experience. If it's not right on the needle it will never tune out. Nowhere near as forgiving as a keihin.
|
|
|
|
Post by pitobread on Sept 18, 2019 10:10:36 GMT -5
Also I wonder if your shifting too early? To me it sounds fairly clean, but it's not pulling... lighter weights?
|
|
|
|
Post by 90GTVert on Sept 18, 2019 12:56:27 GMT -5
Lighter sliders are on the list. I know this pipe likes 10,000RPM with the 103 and it's there now with the 86, but I don't know where it may work with this setup. If nothing else, I should be able to get it moving better. This may be where an aftermarket clutch is nice too, but I think I've only got 1,000RPM springs in the stock lightened clutch ATM.
That's the joy of tuning something like this. It can be multiple things.
I've currently got a 108 main in there, from 112 (don't seem to have a 110). Gonna try that. Then I'll either see what I've got for lighter sliders or swap the needle or all of the above.
|
|
|
|
Post by 90GTVert on Sept 18, 2019 13:30:59 GMT -5
Just got back from the 108 main jet test ride. Might as well update while I let the CVT cool for a minute. That helped quite a bit. Doesn't sputter so bad now when it starts to take off. Max CHT of 196F, so I'm thinking the CHT may be less useful on the 2-piece head. I know ryan_ott told me that CHT didn't really work on LC when I first got into it, but it worked OK for me on the standard-headed 103cc. Now the same CHT setup is way cold. Don't know where this kit would like to run, but I'm sure it's above 200 to run even as clean as it has so far. I think Ryan now makes use of a CHT with his Polini Corsa, which is a 1 piece. Not sure if he was using a modular head before or not. Back to the test run. When I got in the garage, I watched the tach as I went WOT from a stop. It went to 6950-7270. The pipe doesn't want to hit before about 8000. I think if I can get the revs up there on launch, then it will probably be in the ballpark at least. I'm gonna try some lighter sliders first and hope that doesn't kill the top end. It pulled to 10,500 at 60MPH (with a good tailwind) just now. I was kinda thinking it might pull the revs higher on it's own if it were right, but maybe not. If that doesn't work, I can see if it will respond to stiffer clutch springs. That usually gets my belt shifting before the clutch engages though, so that's why I don't normally do it. |
|
|
|
Post by ryan_ott on Sept 18, 2019 14:10:16 GMT -5
My previous observation with the CHT on LC was with 2 piece heads, currently I’ve got a single piece head and it seems reasonable. With the 2 piece heads I was seeing 200 or less.
|
|
