|
|
Post by Kenho21 on Mar 17, 2020 13:06:26 GMT -5
Had to run up to the hardware store for some adhesive anyway, so I picked up a coupler and a bolt. Had to tap the coupler, but got a solution worked out. Thanks for all the help though folks!   |
|
|
|
Post by Kenho21 on Mar 18, 2020 0:15:04 GMT -5
Got the gears installed finally (was waiting for a seal in the mail), and the cylinder mocked up to start checking durations and took care of a few other small things. I set the degree wheel up and quickly checked my exhaust duration and where my piston sits at BDC in relation to the transfers. I came up with a 178 exhaust duration, which sounds really mild for a Corsa. I then realized my eyes were crossing because I was so tired, so I could have made an error as well. Also, the piston crown sits pretty proud over the transfer ports. I kinda thought by going with a brand matching crank/cylinder/piston all of that would have come out much more favorably. I'm obviously going to do a little port work after some more measurements, but I don't think there's much I can do about the transfers.  |
|
|
|
Post by 190mech on Mar 18, 2020 4:30:46 GMT -5
The edge of the piston crown should be even with the bottom of the transfers at BDC,if not the base gasket thickness should be adjusted till it is,then check your durations..
|
|
|
|
Post by Kenho21 on Mar 18, 2020 8:09:59 GMT -5
The edge of the piston crown should be even with the bottom of the transfers at BDC,if not the base gasket thickness should be adjusted till it is,then check your durations.. I’ll take pics in a bit, but if I were to add that many gaskets, I think I’d had a squish of multiple mm’s. |
|
|
|
Post by 90GTVert on Mar 18, 2020 8:20:05 GMT -5
Normally you'd do as John said and try to get the transfer floors basically level with the edges of the piston crown at the bottom of the stroke. Then check durations. If all of that looks good, then check squish clearance. The head or cylinder deck can then be shaved a bit if needed. I have no experience with the Corsa, but I've used multiple Polini Sport kits and those were always fairly close out of the box.
If it's way off, then maybe check your part numbers again to make sure you have what you intended to get. I don't know if there is even a Corsa made for another stroke that fits these engines, but another possibility would be maybe the crank has a longer rod. Sometimes cranks come with different lengths of connnecting rods and a long rod would make the piston sit higher at BDC and in that case you should also see that the piston is high at TDC. In that instance, a spacer/gaskets should be able to get it all in check.
|
|
|
|
Post by Kenho21 on Mar 18, 2020 12:19:18 GMT -5
Starting to wonder if this is because Dynoscooter shipped me a Dio piston since there is no 12mm Mina piston. Dyno said it works fine and I have a thread about the subject (link 49ccscoot.proboards.com/thread/26299/dio-mina-corsa-piston). After some discussion it seemed like the Dio piston would work fine and from what I saw, it looks like the piston would be sitting lower, not higher if the piston was my issue. I looked at it again and this is what I'm dealing with... This is how many gaskets I've stacked to give myself close to level edges on the transfers/piston crown at BDC.  Still not perfect, but pretty close.  And this is what I'm left with at TDC. Tried checking squish before this and it's greater than 2mm which didn't even register on the two strands of 1mm solder I had twisted.  |
|
|
|
Post by Kenho21 on Mar 18, 2020 12:31:38 GMT -5
if anyone would be up for a quick phone convo to help me out real quick, PM me please.
|
|
|
|
Post by Kenho21 on Mar 18, 2020 13:03:07 GMT -5
I talked to Scooter Tuning and they think that the cylinder was machined improperly. I'm going to reach out to Dynoscooter to see what they have to say.
|
|
|
|
Post by 190mech on Mar 18, 2020 17:38:03 GMT -5
You'll want to see the bottom of the transfer like my old 103 is here;  Another reality check on just what cylinder you have is measure the distance from the top of the bore to the bottom of the transfer port..Kinda looks like you have a 41.9 stroke jug and we have a 39,? on a Mina.. |
|
|
|
Post by Kenho21 on Mar 18, 2020 17:52:21 GMT -5
Yeah, that’s what I’ve concluded. This cylinder is not right. I mean it looks just Like every other Minarelli cylinder I’ve seen, so I’m wondering if the machining on it from the factory is the problem.
Are there other cylinders that look identical to Minarelli cylinders with different bores?
|
|
|
|
Post by ryan_ott on Mar 18, 2020 18:43:52 GMT -5
For reference I was using a .12mm base when I had mine together. I’d pull that case out and mount up the cylinder just to show how it sits but it’s all boxed up and packed away.
|
|
|
|
Post by Kenho21 on Mar 18, 2020 19:10:21 GMT -5
For reference I was using a .12mm base when I had mine together. I’d pull that case out and mount up the cylinder just to show how it sits but it’s all boxed up and packed away. Yeah something is definitely wrong here then. Our setups would be identical, aside from the crank, and I’m roughly 3mm off. [mention]190mech [/mention] was kind enough to chat for a few and he mentioned the fact that Piaggo cylinders are nearly identical aside from having 42.xx mm stroke cranks, which would basically be equivalent to exactly what I have going on with this cylinder. That’s my best theory right now. Waiting to hear back from Dynoscooter to hear what they have to say. In the meantime, this will be arriving tomorrow... www.scootertuning.ca/en/cylinders-sport-70cc-aluminium/100114-cylinder-kit-athena-sporting-70cc-12mm.html |
|
|
|
Post by Zino on Mar 18, 2020 19:38:09 GMT -5
Ken since you have the corsa head and you are getting the Athena Sport.
Zuma Forum guys have taken the polini head with gasket to tighten up the squish on the Athena to below 1 mm .
You get plenty of bases gaskets to work with on the Athena but to get the squish real tight you may need to use copper spray to get it close to 1 mm .
So if you get stuck with the Corsa keep that in mind.
|
|
|
|
Post by Kenho21 on Mar 18, 2020 20:57:45 GMT -5
Ken since you have the corsa head and you are getting the Athena Sport. Zuma Forum guys have taken the polini head with gasket to tighten up the squish on the Athena to below 1 mm . You get plenty of bases gaskets to work with on the Athena but to get the squish real tight you may need to use copper spray to get it close to 1 mm . So if you get stuck with the Corsa keep that in mind. Oh good to know! I didn't think that squish would be a problem on the Atehna cylinder since it seems to be more race oreinted. Dynoscooter said they will let me return the cylinder. Maybe I'll ask if I can keep the head though... So just to clear up any of my seeming negativity about Dynscooter, I talked to them and they said I can get a refund for the cylinder. Also talked to Eric at ST and he helped me verify that this is a Minarelli Corsa cylinder. The machining must just be way out of spec or something. |
|
|
|
Post by Zino on Mar 18, 2020 21:57:28 GMT -5
It was a trick a couple tuners used to really ramp up the athena basic sport cylinder to race specs .
The guy that pointed out was vaporz he posted on here and zumaforums.
Athena is a good cylinder they use a standard copper gasket gasket instead of a rubber gasket on their head .
That is the only weak point compared to other brands in my opinion .
I have one ready to go on one of my vino's .
It is good that Dynoscooter is looking out for you .
|
|
