Currently in the design process for a high comp air cooled head for a stock vespa kit. Machining cast iron would be a bit more difficult, but I believe would produce a cleaner result than aluminum, at least from my experience from cutting the 2. I am looking for a result that won't warp easily and can be run without a head gasket, so I am looking for any input from people who have experienced both
Cast iron or aluminum head
Re: Cast iron or aluminum head
I'm trying really hard to thing of a single bike I can recall that has a cast iron head. Not a single moped off the top of my head. Typically you want alu because it sheds heat faster.
I would just turn down a stock vespa head, or run a decompless head and mill the cylinder down vs. the head.
Or, you could likewise start with a stock euro top end and be able to do much of what you're looking to do without milling/welding anything.
Re: Cast iron or aluminum head
Yeah with the stock head, there’s only so much compression you can squeeze from it from milling it down due to the decomp. All of the kits without decomps are for 43mm+ cylinders, with too large of a combustion chamber for what I’m looking for. I swear I heard of some derbi kits having cast iron heads, but I think I’ll go with Aluminium for what you said about heat shedding
Re: Cast iron or aluminum head
Also, do you have a good place to get a euro top end? Looking on Italian eBay, a lot of the results have the U.S style cylinders
Re: Cast iron or aluminum head
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> Also, do you have a good place to get a euro top end? Looking on Italian
> eBay, a lot of the results have the U.S style cylinders
Hit up Dos Cycles. I'm sure Blake and Tyler could find you a good dykes ring top-end.
Re: Cast iron or aluminum head
Kickstart heads don't have decomp. Kinetic heads are a different design, may get what you are after easier.
Here is a kinetic head compared to a piaggio, huge difference in design.
Almost certain I have a 10pin dykes ring stock top end I would sell.
Re: Cast iron or aluminum head
Aluminum duh but you're barking up the wrong tree if you think you need more compression. There are some pretty good aftermarket heads for Vespa. The malossi 43 is nice.
Vespa is 100% impossible to start without decomp
Re: Cast iron or aluminum head
I have been just fine push starting mine without decomp with my kitted variated grande. There is diminishing gains with more compression, but they are gains none the less. I am just playing around with my bravo and E85, its been decent so far but to run a fuel with less power per gallon, I need to maximize the advantages it does offer in timing and compression
Re: Cast iron or aluminum head
How high are you thinking? I've machined several hundred (thousand?) HC heads for mopeds and run up to 16:1 on e85. I'm all for experimentation and figuring it out on your own but two strokes don't respond as well to compression increases as other stuff. There are 50cc decompless heads that would get you pretty high
Re: Cast iron or aluminum head
I'm thinking about 14:1, since past then the gains wouldn't be worth the extra stress on the crank and needle bearings. I may go with a kinetic or euro head since that would be a lot easier. With running E85, what timing were you able to run at 16:1 before pre detonation?
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