Yes, if your machine was jetted as close as possible, you should have to increase jet size. But most polaris two strokes are so rich that you can lean them out.

 

Rob,

I'm positive that you're supposed to go down in jet size with the Rad valve.

 

Don't misunderstand me, it very well could be that Boyesen tells you to go smaller on the main jet. All that I am say is that typically these performance parts, wether it be K&N, pipe or reeds, typically require richer jetting because they are designed to pump more air through your motor. You can't tell me that if now your going to add a K&N your going to go to a 180 main.

 

You're right about the K&N or Pipe. However, the manufacturers will tell you on those 2 products to go up on the size of the main jet. On the Boyesen Rad valve, boyesen specifically says to go down on the main jet 2 to 4 sizes. Find someone else who knows more about rad valves, and they can give you reasoning behind a reduction in main jet size. I'll try to find an answer for you tomorrow. I don't have Boyesen's 800 number with me right now, but their technical dept. will be able to answer the question.

 

I have to agree completely with Rob. As a long time drag racer and general car nut I can tell you for sure that "lean is mean", meaning that you can make more power by running a lil on the lean side but you can also burn a valve or a piston if it gets too lean.

I cant possibably see why Boyson would suggest that you go down in jet size.
Look at it this way..

Aftermarket RAD valves are supost to flow more air than the stock one..Right? So if you are flowing more air but still the same amount of fuel then you are going to run leaner. If you flow more air and run even less fuel, then you are going to run a lot leaner.

I agree with Rob that your power gains are more than likely coming from the leaner A/F ratio.

When I ordered my V Force from Rick Ritter I ask him if I need to rejet the carb to match the V force. He said that I wouldnt have to rejet it but he suggested RICHENING up the mix by turning in the mixture screw on the carb 1/2 turn. He said if it bogs are bucks under heavy throttle then to slowly lean it out til it clears up.

As far as reading the plug. Im not sure if you can do it like you can a 4 stroke. Since the 2 stroke burns oil in the cylinder I would think that it would look black all the time regardless of the A/F ratio...but thats just a thought.

Anyway this has been a great discussion!

Andy G

 

I installed my delta II's at the same time as a reed spacer, and had a significant gain in the crispness of throttle response. I did have the RCR Stage 1 Kit on the quad at that point, so I was moving alot more air & fuel than a stocker.

 

Andy... I am by no means a good ATV mechanic, actually I suck! But I did learn how to read a plug. On my 2-stroke it it easy to read at wide open throttle: Brown. But once I let it idle a bit it gets black again...

 

Andy,
What Chris at Boyesen explained to me was that an air filter or pipe flows more volume(as far as air is concerned), whereas the Rad Valve produces higher velocity, creating a higher vacuum in the carb(which in turn pulls more fuel), atomizing the fuel better, thus producing a rich condition. My Xplorer had a 200 main jet in it from the factory, and I went down to a 195 because with the Rad Valve, the bike was running too rich. And, I really don't care what anybody "thinks" is correct. If I'm using K&N, I'll use their recommendations. If I'm using a performance pipe, I'll use that manufacturer's jetting recommendations. AND, IF I PUT A BOYESEN RAD VALVE ON MY BIKE, I WILL USE BOYESEN'S JETTING RECOMMENDATIONS. If you sell a product, it is your responsibility to know everything about your product, and I believe Boyesen knows a little more about their product that the average mechanic "thinks" he does.
I don't mean to be rude about any of this, it's just that I'm getting tired of trying to explain that Boyesen knows more about their product than we do. It wouldn't make sense that if the rad valve created a lean condition that Boyesen would recommend leaning it out even more. How many engines would be toast if that were the case??? Would Boyesen still be in business??? I don't think so.

Sorry if I seem disgruntled--I'm not a postal worker!! LOL!!

Thanks for your responses, and I hope we have all learned something from this forum topic, as that is what we're all here for.

Later,

Waylan

 

I have a 00 400 Explorer and I have a modified air box, k&n filter and a Dynoport "cheater" pipe. The bike was set so rich from the factory that it would foul out plugs every 50-100 miles. After these mods it ran great with no more plug fouling and I did not rejet. We measured the settings with an exaust gas temp. probe to be completly sure. I then installed boysen power reeds and they said to go 1 to 3 sizes leaner on the main and to maybe raise the needle position 1` clip leaner. After installation I could tell it was running slightly rich again so I dropped the main jet from a 210 to a 200, and opened the airbleed screw from 1 1/2 to 2 turns out. These adjustments did the trick and the thing is now running great. I not sure why but Boyesen reccomends going 1-4 mainjet sizes leaner with all there products and it works. I talked to the rep at Boysen and he said if you do not do this you probably won't see all the performance gains that you could.

 

Walexa, I never questioned that you should follow Boyesen reccomendations, I'm sorry if I came across that way. I would also do what the manufacurer suggested. It just seemed odd to me. The more velocity does make sense, if it is true a higher velocity through the carb will pull more fuel as well. Now I wonder, did you gain any top end or just crispness and bottom end throttle response?