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Discussion Starter #1
well, I know most of you use the Airforce kit and all, but anyone who is a pro at jetting I NEED YOUR HELP PLEASE!!!!! Since this pipe is real new, testing is being done for best performance through Trinity one way and we are trying it another to try and get the best out of the pipe.....They are doing a drop in K&N jetting 157 no other adj. really neede(maybe the needle cant remember) kept the pilot the same they DYNO it at 51.8 HP...... We went with a K&N no aibox direct to the Carb getting is no where near the same!! ITs at a 180 and I dont think even a 190 will be enough, needle is set second from the top, still showing a white/grey in color plug... Isnt going to a 200 main just a little much? There is no air leaks, I have an outerrwear on so that should help some but this thing wants to BREATHE like no other.!!one says to mod the float bowl, then others say DO NOT. Trinity says maybe it might be that it needs to have a boot on both sides of the carb,its a fourstroke issue..But still in all, .a guessing game. They are going to do a test run with the mods that are on our PRedator to see what needs to be done to get peak performance with this set up..My local maintenace guy says it can be done...... Does anyone know the REV limit???? Isnt it like 8500RPMS???? It revs out VERY quickly its amazing how much extra it gives the quad, I may need a new CDI box eventually or a REV kit to help out with this.... so much to learn and being on a new machine and a new pipe, its fusterating..... Any help would be greatly appreciated........TINA :)
 

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Tina, they should've already provided you with jetting. There I go back to that inadequate testing pet-peeve of mine. Go by what the plug is telling you. It's your heart monitor. If it's showing lean, give it more fuel. This head flows extremely well...even before porting. There are exceptions to the rule, but in general, you want the machine jetted in such a way that the needle's clip position is one of the center-most, not a top or bottom extreme. Who knows, you might even have to switch out needles, or hand modify the existing one if you've reached a size limit. Spent a month perfecting that on my existing 400 race mod....you want to talk about a taxing experience. I've always found the time invested into correct jetting will always pay off in the long run. If you get frustrated, walk away for a while, then come back when you calm down. Take your time, you'll get it right.
 

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I'll agree with Ken on this one. I knew as soon as I rode my Predator on Sunday with the new filter that it would take some work getting it jetted right. Today I'm going to pick up another assortment of jets, and also dig out my DynoJet kit since it has a different needle and even more jets. Then I'll play around with it more on Thursday and again this weekend out at the dunes.

Too much fuel is always better than not enough, because too much fuel won't melt your motor. Like somebody told me, keep increasing the jet size until the thing starts to stumble/sputter at high RPM, then back off one size and that oughta do it, at least for the main jet.

Rob
 

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Discussion Starter #4
Mine already has the needle changed and I have a Dyno. Iv went up to as far As I can with there selection of needle. Trinity does have a jetting REccomendation they have tested, but its with a modded air box NOT direct K&N (157main)Moquad. :) I understand throery here, but dont you find it a bit odd to be going up into the 200's for jetting??????? Ive never heard of anyone running that big a jet.I dont worry about running fat,heck my 400ex is on the fat side as we speak,I could only get so lucky to have at fat,but its very lean... So if Ive changed the needle and the setting ,then where do I go from there??? I appreciate your suggestions guys......TINA
 

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Not unusual at all, like we both suggested, if it takes it, give it to it. That's a whole lotta "it's". :D I could go places with that, but...I better not. I think the one with wings just won over the one with the pitchfork.
 

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Hi Tina,

Glad to hear you like your new pipe set-up. I agree with Ken though, it is just plain unprofessional for ANY company to send our products that have not been tested properly. The whole idea for a company to sell an accessory product, for that much money, no less, without full testing is just BAD BUSINESS.

I know that I will NEVER AGAIN buy a product from any maker, without having fully discussed the performance/merits of the product with other end-users first. I'm going through that same situation now with the SKYJACKER suspension company over a lift kit part for my Dodge truck (I caution everyone who is contemplating purchasing a SKYJACKER product....DON'T!!!!! They are the very worst customer service providers I've ever dealt with.)

Anyway, off the box...your jetting issues sound like a normal Predator to me! I don't think there is a main jet too large for this thing! The Airfarce, oh I mean 'force'...kit uses very large main jets...usually in the 180-190 range at sea level. That should be about right on a well piped motor with a good clamp-on K&N. It is my understanding the the AF kit flows about 475 CFM at max, which is about the same as what my K&N RU-1770 flows. As you know, the main is only "on" at WOT, so all else is the needle and pilot.

I think the Dynojet needle is perfectly tapered for this quad. It has great adjustability...when you change the clip position (6 available), you can actually feel the change. I would try a larger pilot, up to #50 (if you're at #45). That helped my set-up. But again, I wouldn't be afriad to go all the way up to a 200 main. If that's too much, then step down a sie at a time till it's perfect....


Keep us all posted!!!

Good luck,


JJ
 

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I don't think Tina wants me to post here, cause I'm not an expert. (hehe) But I have a question. Now she said that her plug was white/gray, which I do know is lean. But my question is, Tina, was that while idling to warm it up? Was that directly after you rode it hard? I was told (maybe wrong, correct me if I am please) that if you let it idle to warm it up, you won't get a correct plug burn. I don't, however, know what to do in this situation. I'm still messing with my jetting with just the WB pipe, K&N and Uni-Vents. I'm at a 160 now and adjusted the needle clip one down, but I think I'm going to try a larger main.
 

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Knowing how the slide operates in this carb may help you understand it's operation better but won't neccessarily make the jetting process easier. The slide/diaphram has a pressure chamber above the diaphram that is connected to the carb venturi through ports in the bottom of the slide. Also in this upper chamber is a spring which closes the slide, the bottom of the diaphram is ported to atomospheric pressure. When you open the throttle plate a lower pressure is created in the venturi and above the slide diaphram causing atomospheric pressure to push up on the bottom of the diaphram against the spring pressure which opens the slide and raises the needle out of the mainjet allowing more fuel into the incoming air. The slide spring, slide port holes and the entire intake tract are tuned together so the slide will operate properly.

Now you are eliminating the entire intake tract and adding a filter directly on the carb. The free er flowing air doesn't cause as much pressure drop in the carb venturi therefore you have less pressure differential between the upper and lower slide chambers which will most likely not fully open the slide due to the stock slide spring pressure being to high now for the changes made. You will need a slide spring with less tension/rate than stock to get the slide fully open again, (don't ask me where to get the right one, no clue)This is now where your jetting gets to be a problem, if the needle doesn't pull all the way out of the main it won't matter how large the main is because the needle will determine max fuel flow not the mainjet. Try running it with no mainjet at all at wot and see it it will bog from to much fuel, if not you'll know the slide isn't fully opening. Try raising the needle(lower the clip) to the 4th and 5th grooves, this should help in the midrange/top end but the transition from the pilot to the needle may be poor. You'll have to try some larger pilot jets to help this area and use the fuel screw to fine tune the pilot.

On the float adjustment, if you raise the float level much at all gas will run out of the carb overflow tube all the time it's running. Your only option here is to plug it off but I don't recommend that. Stock float level is 13mm and with the onboard fuel pump I don't believe you should be running the bowl dry so I would stay in the 12 to 13mm range here.

You may now understand why I am just in favor of replacing this carb altogether, you may get lucky and stumble across a setup that's acceptable to you but I believe without a ton of R&D it won't perform to it's full potential unless the slide/spring combo can be retuned to the on-carb filter arrangement.

Of course this is just my opinion, I could be wrong lol...

Good Luck!!!!
 

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Hey Tina, I've heard of many other Predator owners having the same issues with a direct clamp-on filter and jetting. The guys at Trinity and Gary at The Superbike Shop say to leave the airbox use a drop in K&N and add vents to the box. I'm no expert but I agree with powerslider in principle. Here's an idea put the airbox back and give it a test ride, see if you can get it jetted with the box in place using a drop in K&N. I also ordered the Trinity set-up they made sure to tell a drop in K&N was the way to go. (Prower Pros has a 4-5 week wait for a pipe) so Trinity it is.
 

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Discussion Starter #11
Holy cow!!!!!1 My brain hurts just trying to absorb all the info here!!! LMAO No serious guys, I REALLY apprecaite all the help more than you know. It seems all of us are really the only ones out here that know what this machine is all about.(the dealers and most other aftermarkets are clueless it seems)We bought jets today all the way to a 200.Gonna give it a few more tries but for the wk end gonna put the lid on and run stock filter so can enjoy a nice wk end of riding. I have faith getting it jetted ok for that,maybe its just the challenge to push the limits and try to make the direct K&N I dunno,seemed like a good idea at the time, works great on my 400ex,but I know its a whole new ball of wax on the Predator...Im pretty confident it needs a pilot, when going down hillscimbs,it actually stalled out so I know Idle is off a bit,maybe a Rev box or CDI too...... ProExPerdator~~~ The reading is taken when ran at a shorter ditance(getting RPMS up a bit) then kill it and do the reading.. Thats how we tested the other three qyads of ours and . I remeber when we put the trinity on my Daughters mini quad the carb was taken off about 50-60 times before we finally got it right......Had to go 3 pilots, jetting went from a 85.5 to a whopping 125 and change out the roller weights and DBL sock the open air filer.. now it runs beer bottle brown.or a little lighter sometimes.~~MOQUAD~~...... LMAO!!!! I could out a twist on this topic but I wont,I wont go there..... hahaha. I needed a good laugh..
 

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Discussion Starter #12
Pismo Beach Bound... Congradulations on your pipe! :):):):)
 

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Discussion Starter #13
I did forget to mention one good thing so far is..... the fan dont kick on letreally Half the time it used to since its been piped.:)
 

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Hello Tina Thanks I can't wait to get the pipe. By the way here's Gary's opinion on the clamp on. It was posted on his board this morning at Esuperbikeshop.com

Re(2): Clamp on filter question
IP: 63.121.237.238
Posted on May 22, 2003 at 08:03:42 AM by GARY

GUYS, GUYS GUYS. we have covered this subject so many times. a clamp on filter will NOT help your horsepower. it does not provide the VOLUME of air an engine needs & it kills the Velocity. imagine that your airbox is sealed & waterproof. which would hold more water-your airbox system or the clamp on air filter. see where i am going? the horsepower fairy is lazy. you lose precious time & air trying to make the engine suck thru a clamp on. it can take in huge gulps from the volume of air in the air box, & the airbox also resonates acting like a set of lungs causing the airbox to refill itself. you can get more to drink from a long fat straw than you can a short skinny one.
 

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Discussion Starter #15
Trinity told me to set the clip to adifferent setting like 4th from the top, if its too lean still, then to the 5th setting. Tehn, if all fails to try stock filter and box and see how it runs. I may have to go with the K7N drop in .. Ill post when I run both settings.....
 

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I have a Jetting/Pilot question! Do you have to change the pilot when you rejet? I have a Bigun Exhaust with a 175 main jet, modified air box and drop in K&N filter. Thanks!
 

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You don't have to change the pilot jet, unless you get to a point that the plug reading with your present pilot jet isn't correct, and you've run out of adjustment. Hope that makes sense. I'd like to know the jetting variables the DS650 crew has been up to. I know speaking with Mikuni (the performance side) they don't like the BSR, and instantly switch to talking about the HSR.
 

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Thanks Modquad! I have one more question...how do you get to the spark plug? Do you have to take off the gas tank? Also, the jetting variables you are asking about, I'm not familiar with what your asking!
 

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Yes, you have to remove the tank. Pull off the seat and both side panels, then remove the front plastic (three screws). Then remove the single bolt that holds the tank on, and then it lifts off. The plug is directly under it.

Rob
 

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Also, along with what Rob suggested, I always keep a golf-tee in my underseat toolkit. There normally isn't much fuel in the line when you disconnect the tank, but it's something simple that helps keep spilling to a minimum.

Duner, that was kinda a funky statement of mine. I'm going to check with the DS crowd and see what they've found to be the limits of this carb....they've been able to tweek on it for a few years, and even on a larger machine to boot. I know a couple of local shops already have the change done, but confidentiality prohibits my comments. I'm sure with current testing, the limits, like were found on the 400 2-strokes will surface over time. When you figure they were able to develop 3X the stock hp from that machine, this thing should be even better. Especially with the top notch base head design.
 
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