Help with Airsal BBK on 2003 People 50 2T

[sparky_ppl]

Bad tuning killed the Malossi, I'll post pics of the deceased later     

The stock carb had some shims to raise the factory needle. I have a 21mm Arreche carb and am waiting on a 20mm intake manifold.

The scoot is just a weekend warrior, not a daily driver. I don't want to race it but I'd like to squeeze every bit of performance from it without splitting the crankcase.
I bolted the kit on as is and it had nothing for power, that's what caused me to come here and learn about the squish gap (out of the box the kit didn't touch 0.062" solder when checking).

I chose the Airsal due to aluminum construction and the 3x thermal conductivity compared to iron (live in florida).

Will machining the top of the Airsal cylinder ruin it? The ports looked like they were where they need to be @BDC.

If I machine the head down then machine the combustion chamber edges back in, wouldn't that put me right back where I started as far as the squish gap is concerned? I know I would gain compression from this.

Thanks to all of you for the information, this is insanely helpful. scooterinvasion.com is also amazing in terms of information.

[Areomyst]

I chose the Airsal due to aluminum construction and the 3x thermal conductivity compared to iron (live in florida).

Will machining the top of the Airsal cylinder ruin it? The ports looked like they were where they need to be @BDC.

[/quote]Yes.  The cylinder is plated, so milling from the top of the cylinder will have a high chance of chipping the plating and ruining it.


If I machine the head down then machine the combustion chamber edges back in, wouldn't that put me right back where I started as far as the squish gap is concerned? I know I would gain compression from this.[/quote]
This is also correct, yes.  Which is why I would machine from the base of the cylinder.   This will lower your ports though, and can in many cases lower them so they are not opened properly at BDC.  It might work out okay to machine the deck on a plated cylinder, but I haven't tried it and it seems risky to me.

Some Airsal cylinders have really high port timings anyway.  If you've got some 196 degrees ex and 140something tx you are way more than safe to machine the cylinder down.   I'm going to go back and look at your pictures though, because I seem to remember that the piston did line up well at  BDC.  Mine did not:


This is my cylinder at BDC before turning the base down.  Yours might be spot on.


Have you considered changing the Next-R for the RSII?  You will notice a good improvement.  I would switch exhausts (honestly) before paying a machine shop to do all that work.  

Thanks to all of you for the information, this is insanely helpful. scooterinvasion.com is also amazing in terms of information.

I'm glad you like Scooter Invasion.  It's a lot more work than some people think to keep something going like that without advertisements, banners, etc.  

Best!

~Josh

[Areomyst]

I'd have to sit down and take a better look at those measurements.  Are you certain of your measurements of the port distances from the deck?

Here are a couple of port maps:

This is an Airsal 70cc for Liquid Cooled Super 9


Here is a Malossi for liquid cooled Super 9.

Those are the two that I have for Kymco. Keep in mind that your Kymco engine has 41.4mm stroke, whereas most other 50cc 2-strokes have shorter stroke.  (39.2 for mina, and 39.3 for piaggio) There are more port maps here:
http://www.scooterinvasion.net/forum/viewtopic.php?t=488

When checking out the port layout, measuring with a degree wheel, etc, it is best to torque down the head. You can use some old spacers or rollers or something to take up the slack that the head would normally take up that way you can still look into the cylinder and see that the ports are uncovered at BDC.  I would put the base gasket on, get true top dead center with a piston stop/degree wheel, and then rotate the engine around to true BDC.    This is more accurate (by far) than just turning the engine over by hand and stopping when it looks right.  

Hope this helps.  

~Josh

[zombie]

Very nice J. You (like always) are an asset to us all.

[sparky_ppl]

Just to let you guys know and give a follow up to this post:

The kit has been installed and been running amazing since the last posts. I ended up shaving off 0.030" off the top of the jug. The guy who did it runs a performance dirt bike shop and was impressed with the overall quality of the Airsal kit. He was able to sand down the very top of the coating after milling which prevented any chipping (had the cylinder apart recently to replace the head bolts with studs and everything look great). If i remember right, the squish gap measured at about 0.82mm after milling.

Once again, you guys are awesome and hopefully someone who finds this with the same problem now has a solution.

[wassonii]

Great to hear and some damn good infos. Thankin ya!