Help Please

[jrm312]

i just got my cylinders ported stage 3 port , i have a noss cool head,and timing plate, procircuit pipes modified air box, my ? is i still wanna run pump gas 93 oct,

what should i set my timing at and what size domes 22 or 21, i live in michigan so im above sea level but i dont know how much.

[Meat]

set your timing plate anywhere from +2 to +4 and if you use 22cc domes your almost gaurenteed to be safe. You could prolly run 21cc on pump too, alot of guys will tell you that 20cc is usually the lowest dome for pump. Your elevation plays a big part in determining dome size\cylinder compression. Any porting work will also play a part in choosing the correct dome size for using pumpgas. Go with the 21cc's and be happy that you have the peace of mind that you have a reliable motor that you dont have to worry about exploding on the trails.

[Ducman]

21cc will probably work with +3 timing, consult your engine builder on how the port work will affect the dynamic compression. 20cc is probably too small with any timing advance to be safe with 93 octane.

[jsekula]

Here is a link to a good chart for you on dome sizing... Joe

 

http://www.thebansheezone.com/Bansheezone/CoolheadChart.htm

[jsekula]

i just got my cylinders ported stage 3 port , i have a noss cool head,and timing plate, procircuit pipes modified air box, my ? is i still wanna run pump gas 93 oct,

what should i set my timing at and what size domes 22 or 21, i live in michigan so im above sea level but i dont know how much.

You know... Your gonna have problems with compression!!!!!

Have you checked it with a gauge?

I am running Stage 3 port jugs and 22cc domes at sea level; my compression is 105 psi...

My guess is your compression is about 100 psi for Michigan, about 500-600 ft above sea level. Your machine is gonna run like crap and foul plugs a lot. I suggest doing this:

 

1. Get a compression gauge and use it.

2. Change domes to around 19cc which should yield you about 140 psi.

3. Do no go over 160 psi on pump gas.

4. Remember temperature!!! Colder air... the more dense. if you shot for 160 during warmer weather, you'll be way above that when it gets cold.

5. ALWAYS Check your jetting after any changes...

 

We have about the same setup... I am going to 20cc to get me to about 130 psi. (2cc less @ 12 psi per cc) If you know where you at with 22cc domes, you can figure on gaing about 9-10 psi per 1 cc change. Use the chart along with a compression gauge... Joe

[MotulMonsta]

I was running 180 psi on pump gas. I belive stock is around 120-140

[jrm312]

i checked my compresion and im at 149 psi with 22 domes

so am i safe with pump gas it also col here about 35 degrees so does that change my compression from cold or warm.

thanks for all the info i appreciate it

[Meat]

hey thanks for the info, I checked my compression today its at 149 with 22 domes, so am I safe with pump gas? and what should I set my timing at ,im a +4 now should I lower it?

 

I checked my compression today its at 149 with 22 domes, so am I safe with pump gas?

I can give you my opinion, but you should really be asking this question to the shop\guy that did your "mild trail port". Your 149psi static cylinder compression number is only one indicator when deciding what octane gas to run. When the cylinder ports are left stock, then its relatively safe to say "149psi is safe with 93\94 octane pump gas"..... but once you alter your cylinder ports(mild trail port) the rules for octane requirements change. Determining your "Compression Ratio", not your "Static Cylinder Compression" is the true way to accurately gauge if you need race gas or pump gas. Stock "compression ratio" is 6.5:1, since this compression ratio is always the same on every stock ported Banshee, one could conclude that 150 to 160 psi of "static cylinder compression" is the limit for running 93 octane pump gas. Once you change your cylinder ports(via porting), you also change your "compression ratio". So with a ported engine, you can't say "150-160psi cylinder compression for pump gas" anymore.

Your elevation where you ride your Banshee also plays a part in determining octane requirements.

Since I don't know your porting specs, compression ratio or your elevation..... I don't feel comfortable giving you a "yes or no" answer on your octane requirements. Sorry. I don't want to tell you that you could run pump gas and have you contact me telling me you experienced detonation and put a nice hole in your piston. I will tell you this, on a stock ported Banshee, 150psi static cylinder compression is right around the limit for pump gas. Anything higher than 150, like 155 or 160psi I would definitely tell you to run race gas, or atleast a mix or pump and race gas. Am I making any sense ??

What should I set my timing at, im a +4 now should I lower it?

Well +4 advance is recommended by alot of engine builders for guys running similar setups as yours. The +4 works good for higher revving piped Banshees. There are some downfalls to running +4. The powerband will hit harder and the power will come on more abruptly. While this hard hitting powerband is fun and one hellava kick in the ass to ride, it will make the quad harder to ride. If your trail riding your Banshee, or if you do a lot of sit down cruising in the back yard kinda riding, or even MX racing... the +4 advance might not be ideal for you. Another downfall of +4 advance is added engine heat buildup. Your engine will run hotter. A cooler running engine will produce better HP numbers than one that is running hot all the time. Im running +2 advance on recommendation from my engine builder. The +2 advance was shown to produce lower HP numbers on the dyno compared to +4, but only slightly lower HP numbers. The +2 engine will run cooler and produce a more trail friendly powerband. That's the kind of power Im looking for, something that is trail friendly, doesn't tire me out, powercurve like a MX engine, and still pulls your arms out of your sockets if you give it enuf throttle. There's also that peace of mind, knowing your running a cooler running engine, that is less stressed than a similar motor running +4 advance. Since you have an adjustable timing plate, you should experiment. There's nothing better than learning from first hand experience and here's your chance.

[Ducman]

Yup, ask the builder that did the port work. When port timing gets changed the dynamic cylendar presure also changes so going off of static presures may not be a good way to look at it. With stock porting everyone is a lot more even and there is a lot more data and experience to base dome sizes and ignition advance off of static compression.

[MotulMonsta]

Try it. If it spits and knocks you know you need more octane. My head's milled .010 bored .60 over stock and running vito's power pistons. I run pump gas I hear you can mill off 20-30 thousandths and still run pump gas. I haven't checked the compression yet..but it's pretty damn good seeing as it kicks's over pretty hard and I can't hold the pressure in with my thumb. Remember try to find gas thad doesn't contain any cleaning additives as they will strip the cylinders of their protective oil coating and cause premature wear. It's hard to find good gas now-a-days. Chevron, Bp, and mose generic knock off uses additives.

[MotulMonsta]

The more extreme the port, the lower the compression is going to be. more air will slip through the exhaust before the piston covers it up. the stock banshee compression ratio is 6:1..pretty low. you can run pump gas up to 12:1 compression ratio before it will start to knock. Least that's what my engine builder buddy tells me. The stock z400 sizuki runs like 11:1 compression. You should be safe so long as you don't decrease your dome size by too much. anything 21cc and up should run pump gas..any lower and it's vp race fuel time. I've heard people usind 18cc on pump gas..don't know if they were bullshitting me or not.

[banshee76179]

I run a stage II port

Trinity stage IV head that was shaved 10thou.

20cc domes

80 over, msd igintion,+3 timing

Playing around I run 93 octane..

when serious i run 110

 

But, consult w/builder 2 see!