Testing clutch springs from this set with the stock clutch shoes: http://www.treatland.tv/polini-clutch-springs-set-for-piaggio-scooters-and-p/polini-springs-245.030.htm
Black springs (weakest): 5500 RPM stall. These springs slide right on by hand. Not much preload.
What are you using for calculating desired tuned length?
Calculations from Jennings 2 stroke handbook. 177 exhaust port timing and 11,500 RPM.
Cool, that's what I figured. There's some stuff out there about determining your own static coefficient for your own engine. I need to get a tach or a light with a tach on it
Now that I'm thinking about it, I don't remember if I checked the port timing on this cylinder...
If you don't want to take your cylinder off, I can check port timing on one some time tomorrow
Wow Beautiful bike
Swapped the green clutch springs in and 2.8g variator roller weights. Stall is just over 7k.
Took the cylinder off and did a port map.
Used this: http://concubidated.com/ignition.php?stroke=39&length=85
My piston stops about .5mm away from the top of the cylinder so I get:
Exhaust: 22mm = 178*
Transfer open: 31mm = 120*
Blowdown: (178-120)/2 = 29*
Made a fresh base gasket to match the cylinder.
Sounds like the connecting rod may be 80 mm, not 85. That may effect my timing numbers some, but it's not a big deal. I'm losing interest in the metrakit quickly.
Here's a teaser, more pictures will come later today.
Current state of the bike. Yes, the rear exhaust mount broke off:
So I picked this kit up. 20 HP!
NOTE: this kit will not fit in the cases without case boring and relocating studs. This is not for beginners.
http://www.sip-scootershop.com/en/products/racing+cylinder+polini+big_p1660110
Custom assembled small end roller bearing.
Checking stud locations. NOPE. Must relocate.
Need to weld/beef up the outside of the transfers and deck the cases/transfer match. No big deal, right?
Pictures of the cylinder/head/etc.
Goofy looking exhaust port, 3 flange exhaust mount (love this)
Everyone loves head.
Please post pic's of the relocating of the the studs please. Interested in doing the same.
Pulled apart the cases to mock up the kit before having the cases bored.
I don't think I can make it work without an 85mm connecting rod. With the stock crank/rod my piston is 7.5mm below the deck of the cylinder.
I'm debating having an 85mm rod pressed in my crank or trying to adapt a minarelli horizontal aftermarket crank with an 85mm rod.
190 exhaust port timing.
A few casting imperfections below the edges of the ports to clean up. Also need to make sure the top of the exhaust port is angled to prevent ring snagging.
To relocate the studs I am going to get 7mm x 1mm threaded aluminum bolts (or thread my own solid rod) and epoxy them in place, then mill them flat. After that I will drill and tap the new mounting locations.
Jake. i might have a metrakit 'stroker' rod that might work. i'll have dig in my pile.
Sent you a PM Marvin. :)
Yeah, Tyler if you're on amigosdesderbisvariants forum they have a bunch there. Also look for the "culmination" thread on here
Here's an example of moving the studs for a watercooled kit on a derbi.
This is going to be soooooooooooo good!
Minarelli cranks fit in there without too much work...
Granted this one is 45 stroke, and has a YZ 80 rod pressed in.
Tyler,
What does your variator spacing end up like? What's your ignition solution?
You can put the variator where ever you like because it is a splined crank (same spline as a the stock start3/5 cranks). So no issue there.
Same taper as Puch, just larger diameter. I cut an HPI for one, pretty straight forward. The revo seletra ignition fit right on as well.
RTFO!
@Tyler: you have to machine the throws/bearing saddle right?
This would definitely make it easier on my start 3 builds
i came to say ugh derbi motor on another non-derbi frame
just a travesty
but I do appreciate the work going into the motor
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