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Ported cylinder or Serval


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so i just tore the engine down that i will be using for a snowbike/banshee build, turns out that the "fresh" bore and pistons were done crap and one pison and jug is scored. So.... i will likely be using a custom 2-1 pipe, lets not debate that too much, i will be replacing the crank so probably go a 4 mil, and the reason i used a banshee engine is because i may turbo it in the future and did not want to turbo a single cylinder bike engine. What are the opinions on three different setups, cleaned up and re-bored the allready bored stockers OR send them away for a port job OR buck up and put a set of serval cylinders on it? the obvious differences in price will have to be made up somewhere else likely me not having it done and riding this winter :(

 

what would the differences in power output be between these different options? and if i do turbo it later would the extra money now be wasted?

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If you're planning on boosting it later, you're not going to want to screw with port timing much. To do a 4 mil stock cylinder right won't be much less than serval cylinders, with that being said, a boosted 4 mil serval would be wicked. I think matt shearers turbo 7mm serval is in the 170 range turned down.

 

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when did mat get a turbo serval? i know his buddy tom had a turbo 421 cub making 200hp (mat built it)

 

 

and a 4mil stock cylinder is cheaper than a serval.

It might be his buddies, Matt's name was just attached to it. I'm fairly certain it was a serval though.

 

I guess I've thrown so much money at mine that another 3-400$ for a serval over a stock cylinder doesn't seem like much.

 

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I did a ported 4 mil stock cylinder and kind of wish I went serval. But the money thing got me too. Do you know what size your jugs are at right now? If you throw another $200+ at buying some virgin cylinders to port than I would just pony up the other $500 for a serval if I had it. Then sell your cylinders and head for $100 on Ebay. Now you're at $400 difference. But you also picked up the $200 head with FAST serval kit. So really only a $200 difference. BUT if you have a failure the serval is more expensive to rebuild.

 

What other mods are on your bike?

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as of now there are no mods, i was planning on using the stock cylinders because they were just bored and new pistons. But because the job was done poorly i now have another decision to make. I haven't measured the cylinders yet but i think it might only be the first oversize. I guess another question is what a cleaned up serval 4 mil with a 2 into 1 pipe would make for power? if it makes enough i might just not need a turbo for a while. gotta remember its going into a 300 pound bike.

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a 421 serval cost like 1500+ new

on FAST site it is 1723 for everything

"We also have our Complete kit (421cc) that comes with: 421cc 4mm Serval cyl., Pistons, Stud extenders, Water plugs, base gskt, 2x ARP Cub base nuts, F.A.S.T. Head and domes (set up for your altitude/fuel), "Hot Rods" 4mm crank Trued/welded, Ready to bolt together! $1,723.00"

 

 

http://farmandsandtoys.com/partdetail.asp?partid=403

 

same site

for a ported 4mil

$450 for crank

$255 for head

$350 for porting

$1055 for a ported 4mil stock cylinder engine.

 

that is a lot less than a 421 serval.

You going to run your stock cylinder with an open bore? Another $200 for pistons/gaskets. If you could get $100 out of your stock cylinders the difference is only $350=not much in my book.

 

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another consideration i just thought of is the size of the cylinders and head, since this engine will not be going into a banshee (dirtbike frame) i do have some tighter clearances to think of. Can anyone comment on if there is a different height of the cylinders or height of the cylinder head required for them?

 

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