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Banshee Carb Performance difference


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Hi All,

 

New to this forum but have owned my banshee for a little over a year now. Have also owned many performance Yamaha’s both MX and quads. 
 

I have a question regarding carb performance. 
 

Both me and my brother have banshees, he just got his and I always thought my bike moved out pretty quick however we have been racing and he can pull on my bike no matter what gear from a roll or a dig. 
 

before anyone says “driver mod” I have raced his against mine and I can beat him. we are both about 230 lbs.

 

Bike mods are as follows for engines and performance. 
 

My bike: 04 LE, DMC Aliens, Vforce 4, stock manifolds, stock carbs, stock air box, stock head. Pingel dual fueler. Jets are 280m and 27.5p. 
 

My Brothers bike: 06 SE, Paul turner mid range, Vforce 3, Rhino head, 33mm Keihin carbs, stock air box, stock port. 
 

My question is, do the stock banshee carbs restrict that much air? Is the bike that much faster with bigger carbs on stock cylinders? Is there any downside to upgrading carbs with stock cylinders other than fuel consumption? 

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Yes, when it comes to the Banshee it has always lacks in the carburetor performance category. There is also other factors that comes into play as well like sprocket gearing and or rear tire size. The exhaust also plays a huge role in performance as well. Every brand of pipe have a different power curve. I upgraded the carbs on my Banshee from the old stock to Keihin 28mm PWK and they made a noticeable difference over the stock carbs. 

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On 5/31/2023 at 9:39 AM, JerzOutlaw350 said:

Yes, when it comes to the Banshee it has always lacks in the carburetor performance category. There is also other factors that comes into play as well like sprocket gearing and or rear tire size. The exhaust also plays a huge role in performance as well. Every brand of pipe have a different power curve. I upgraded the carbs on my Banshee from the old stock to Keihin 28mm PWK and they made a noticeable difference over the stock carbs. 

Okay great, thanks for the info. Sounds like the reason his bike is faster is the carbs after all. I mean 33mm Keihins would definitely flow way more fuel than the stockers. Sounds like I need to upgrade me carbs!

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I honestly would do a cool head before carbs.  Stock carbs will flow enough air for something like 70hp.  Depending on what type of riding your doing, change your front sproket down a size, or if your not in mud, change the air box to pods. 

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It’s not about flowing more fuel. It’s about the air/fuel ratio that your engine likes. Hell your setup is nowhere near in need of 33s. Stick will EASILY handle what you have.  
could you go to 33s…sure, but you’re going to have to go down in jet sizes…..essentially giving the motor the same amount of fuel as you were with your 280 mains and stock carbs.

there are SO many variables here that it’s not even funny. 
-what’s the health of each engine?

-what’s his jetting at?

-sprocket sizes the same? Tire size?

-his has an aftermarket head…what domes is he running?

——hell…is your bike even jetted correctly? What’s the plug chop look like? Did you chop and check jetting right before racing? ………..

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On 6/2/2023 at 11:12 AM, Jereme6655 said:

It’s not about flowing more fuel. It’s about the air/fuel ratio that your engine likes. Hell your setup is nowhere near in need of 33s. Stick will EASILY handle what you have.  
could you go to 33s…sure, but you’re going to have to go down in jet sizes…..essentially giving the motor the same amount of fuel as you were with your 280 mains and stock carbs.

there are SO many variables here that it’s not even funny. 
-what’s the health of each engine?

-what’s his jetting at?

-sprocket sizes the same? Tire size?

-his has an aftermarket head…what domes is he running?

——hell…is your bike even jetted correctly? What’s the plug chop look like? Did you chop and check jetting right before racing? ………..

Hey Mate,

 

Thanks for the info. Lots of good stuff here. 
 

engine health both check out with good compression. My bros Is a little more compression I’m assuming because of the aftermarket head. 
 

Not sure where his jets are at. I haven’t been into his carbs. Previous owner just gave him a bag of jets with the bike. 
 

sprockets on both bikes are stock. 14/41  

tires are both the same sizes, front and rear  

My bike is jetted with the recommended jets that DMC suggests for the 916s. Didn’t really look into it further than that because of the limited mods. I did chop the plugs a few times and they were pretty good.

Sounds like I should give an aftermarket Head a try with some domes then go again. 
 

Just an FYI, in no way am I serious about caring who’s bike is faster. Just doing a comparison to see what some of the other members think I could do to squeeze some more horses out of this stocker before I get some cylinders for it.


Thanks

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Cheapest easiest mod to up it a little will be a milled head. 
 

But before you start throwing the parts cannon at it, do some SERIOUS research on jetting and tuning carbs. You would be amazed at the amount of medium built bikes that can just BARELY squeak a win against a properly tuned bike.

 

the most power a 2stroke will make is actually in the detrimental area for hurting the engine……a 2stroke when lean…is mean. 
ever run a piece 2stroke power equipment out of fuel? The moment before it dies, it runs stronger than ever.

 I’m not saying run it so low that it will hurt your bike….. I’m just saying that if you’re running too rich you may be hurting yourself. And if your brothers bike is too lean, it may just be hurting his motor too. That’s why plug chops and learning to read the plug are important.

also…those “recommended” jets are just a starting point…..don’t ever guarantee that they know what’s best….. hell they probably are not accounting for air temp/elevation, other mods, health of motor…..

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