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Gnaw banshee guy needing some info


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Hey guys, I'm a brand new Banshee owner,that is I'm new to Banshees I wish I had a brand new Banshee lol! I've owened quads since I was 17 and I'm 34 now. I'm mechanically inclined and catch on quick so here goes. After deciding to look for a project banshee I found one within a week,picked her up and brough her home. It's a 2000 model with a clean title and in pretty good shape chassis wise. It has new carbon fiber plastics, new pro elite bumper,new pro elite nerfs, new ITP hole shots on black SS wheels DMC exhaust a cool head and I believe that's about it. The engine is dead I pulled the top end and it broke a ring and trashed the right side jug and dome. I've decided to build a 421 4 mil serval after a lot of research. I think it'll work best for what I want to do with it. I mostly play ride with my sons,wife and friends but want to be able to readily spank some guys at the local mix park sand drag strip. My boys are 9 and 11 and both own 400ex's I also own a yfz450 with quite a few mods , a blaster ,TRX450 and a 660 Grizz.

The engine: I went ahead and pulled the lower end threw it on the bench and have it ready to split tomorrow (had to wait for flywheel puller). I want to open it up for 2 reasons I want to learn the banshee engine inside and out like my other quads power plants and I want to make sure there's no trash in the crankcase. I plan to go back with the stock jugs .060 over with a set of Vito's forged super stock pistons and run it like that until I save for the serval build. With all that out of the way, I have a few questions.

1.) what kind of horse power can I expect the 421 4 mil to make? I'm not asking for a human dyno here, I know a lot of factors come into play. It seems 2 strokes really make power easily so Imagine that it can just as easily be hindered by improper tuning etc. i want to run 93 pump gas most of the time and fuel when I take it out to play at the drag strip. I know that the DMC pipes will have to go I plan to run Shearer pipes on it.

2.) what jetting is recommended for the set up I plan to run first? Mods will be ; .060 over stock jugs,no porting, DMC,cool head with 20cc domes. My elevation is 86' and temps are between 40-60 in winter and 90-110 in summer.

 

3.) jetting increments, On my other quads the numbers are as follows for example 48 pilot,175 main.

I noticed when browsing jet kits the main sizes are 300-310-320 etc. Are all the banshee jets numbered this way, when I say banshee I mean the Mikuni carbs. If so is there some sort of crossover chart or something? if not can some one help me out with what stock jetting is for main and pilot jets so I kinda have an idea where to start.

 

4.) when I build the Serval is there any work needed on the cases like clearancing or anything? Also can I or if I have additional port work done on the Serval jugs or the cases will it adversely affect the low-mid range?

 

I think that's it for now, didn't mean to write a novel but this is my first ever 2 stroke and the only way to learn is to ask. So im askin. Thank you guys in advance. I'll get my profile sorted out as soon as I can. I belong to a few other forums and I know about the whole "use the search button" thing lol. I did trust me, I've been reading for a week. Just needed more specific answeres to my questions.

Edited by Project_banshee
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1. Tons of serval info out there. Check the dyno section.

2. Jetting section has a pretty sweet thread stickied to compare similar mods to jetting needed.

3. Difference in jetting you're spotting is mikuni vs keihin.

4. No case work needed for 4mm 68 bore.

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1. Tons of serval info out there. Check the dyno section.

2. Jetting section has a pretty sweet thread stickied to compare similar mods to jetting needed.

3. Difference in jetting you're spotting is mikuni vs keihin.

4. No case work needed for 4mm 68 bore.

THANK YOU Tricked carbine, you answered what I needed to know like a boss, answered in the order I asked, and didn't even need to insult me or make it an act of congress out of it.

No DEADBEAT IM NOT AN "ASKHOLE". Like I said at the end of my original post I did use the search function but a lot of the answers are "all over the place" as well. I figured I could ask you more advanced builders/owners For some quick info. That's is after all how anyone learns. Anyways I got what I needed. Thank you. I like to ask questions and will ask more, maybe I just need to simplify my Questions. Good day.

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Welcome to the banshee world and yes as Larry said this place takes thick skin but lots of good info here once you figure out guys are just going to ride you pretty hard when you first join up

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Why .060 over? Only go as big a needed. no real gains in boring over as big as you can. Used cylinders on low bore sizes are worth a little more.

Once you get used to how un pc this site is you will learn to like it.

it's .040 over now and it ate a ring trashed one cylinder. I want to build a 4 mil 421 but don't have 2k to dump into it right now. I just thought I'd see if they'd clean up at .060 and use some Vito's pistons someone pointed me at. Personally I was worried that it was gonna run warm like that but I was told it's be final what y'all think?

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1) Anywhere from 75-95hp seems to be the norm. 75hp being untouched, 95hp being ported on race gas.

2) With stock carbs, start with 320 main and 30 pilot for the winter. This wont be 100%, but it should be a good starting point.

3) A stock banshee has 200-220 main jet and a 25 pilot. Here is a link to mikuni jets http://www.jetsrus.com/a_jets_by_carburetor_type/jets_mikuni_VM_series.htm

4) No other work needs to be done, it is a drop engine kit. You can port the jugs and cases to gain more power, check out the dyno section to see graphs of the many different 421s out there to get an idea.

Awesome man thanks. ok if I were to have port work done on top of the kit would it adversely affect the power band range? I want as broad a power band as I can get, that's why I decided Servals were the way to go. I read that the cubs are pretty much an all out drag cylinder makin all thier power at the top.

One more,question(of course there's another questions right?) If my cylinders clean up at 60 over, I run 20cc domes,my DMC pipes and jet correctly and I run those pistons from Vito's that say "8 horses over stock" about what would that put me at pony wise? If I knew what the stock HP is I wouldn't even ask BUT.... I've asked a lot of people about the stock horsepower numbers and there seems to be a lot of controversy over it lol. One guys says "my title says 49", I read 39 on bluetraxx and 36 on some other site. Care to clarify this once and for all? My title don't say anything about horsepower,maybe mine didn't come with any lol.

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