Gila Guidelines: Porting to the Extreme

I first encountered Hollaendaren on a Moped Army thread a few years ago.  He was building a ZA50 for sprint racing.  He was looking to modify his clutches and saw some of my stock modified clutch.  He eventually ended up with a modified treats clutch 1st gear and hybrid custom clutch 2nd gear.  He shared some of his runs on the thread:

I always was in awe with that ZA50 build.  Especially how his ZA50 shot out of the gate like that.  And the sound!!!  Two-stroke at its best.  His basic set up was a 75cc Gilardoni cylinder, Mikuni TM28 carb, and custom pipe.  He gave some details about his modifications in the Moped Army thread but not enough to attempt to replicate his mods.  So I reached out to him via Instagram @hollandaren to fill in some blanks:

Moped Luau:  I remember you from moped army. You were asking me about my clutch work in my za50. Do you mine sharing your port work and overall engine setup on ur m36 bike?  That engine is so awesome!!  I would love to see it on ur YouTube channel as well. Thanks.
 
Hollaendaren:  Hey! Yeah I remember that :) I'm on there in periods I guess. Too many different kinds of projects, I haven't really done much to mopeds lately.  What do you want to know about it? The porting is pretty simple but I'd have done it differently today if I had a new cylinder.  Exhaust is around 196 degrees iirc, 70% width and a pretty straight top edge for hard pulses. Too wide and straight for cheap pistons with bad quality rings, I've broken a bunch of rings with it before I switched to a Wiseco piston with steel rings and no problems since.  The piston is a PW80 one, it has the ring gaps on the intake side so no problems with exhaust width on those. It's a lot higher than the stock Gila piston so I needed an 11 mm spacer.  Intake is widened and lowered way past the bottom of the cylinder, which is where the spacer came in handy. I put a large hole in the intake skirt for 360 degree intake.  I've widened the transfer passages a lot, they are too narrow stock. And I've widened the boost port quite a bit, it's like on the Athena cylinders now.  Reworked the head for about 14.5:1 CR, which just about works on pump fuel.   I think that's about it :) Feel free to ask though.

Moped Luau:  Thanks for the info!!  Anything special you did with the pipe? Also what gearing were your running? And lastly carb size?  Thanks again in advance!!

Hollaendaren:  I designed and built my own pipe for it. I had Simonini copy first but my own worked better, wider powerband. If you promise not to share it with anyone else I can give you the specs for the pipe :)  Carb is a TM28. I made a custom intake for it.  Gearing, not really sure but it tops out at 108 km/h and 13500 rpm on a 1/8th mile race :) First gear pulls to about 70 km/h. I have the regular 2 hp internal gearing.

Moped Luau:  Thanks again!!  I meant what external sprocket combo did u use?  I plan to share this on my blog so no pipe specs needed. Haha

Hollaendaren:  My sprocket ratio doesn't really matter because no one has the same size wheels as me anyway ;)  That, and I can't remember off the top of my head.  But I have 24" tires so my gearing is lower than everyone else's.

Happy Tuning Everyone!!