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05-07-2007, 3:58 PM kracker Joined on 04-04-2007 sanford,florida Posts 11 Re: Mikuni Performance Tuning thanks for all the help....what do you use to adjust the fuel screw?i cant seem to find anything small enough to get under the carb...    Report

05-08-2007, 5:39 AM wwlknsn Joined on 04-09-2006 Memphis, Tn Posts 154 Re: Mikuni Performance Tuning There really isn't an easy way. Especially when running but a necessary evil regardless. I use a small round knurled screwdriver with a flat blade screwdriver bit that I ground down to fit. You need something relatively large to grasp as you are trying to adjust. Look at the last page or two of the RAIS pdf file and you will see the tool. ww   Roostin' Rhino RAIS Power Tube    Report

05-08-2007, 4:56 PM kracker Joined on 04-04-2007 sanford,florida Posts 11 Re: Mikuni Performance Tuning will ok i finaly got all three circuits dialed in between 12.5 and 13 on my air/fuel gauge.but.....as soon as i give it a little gas to take off it spits and sputters bad.once i finaly get it into the mid range it screems all the way through wot.i just can't figure out why it is doing that when my idle is dead on 12.5 to 13 as the book says is "ideal".i have the dj170 in for the main,clip on second notch and the air fuel screw is barely out.do i have another problem other than the carb since all three circuits are dead on the air fuel gauge???    Report

05-08-2007, 5:17 PM kracker Joined on 04-04-2007 sanford,florida Posts 11 Re: Mikuni Performance Tuning forgot to mention when i give it gas to take off and it starts choking out the gauge drops down to between 8 and 9....way rich    Report

05-08-2007, 5:56 PM wwlknsn Joined on 04-09-2006 Memphis, Tn Posts 154 Re: Mikuni Performance Tuning I'd like to mention that I have never tuned anything with an a/f gauge so my opinion about any of the readings that you may attain are pure speculation. I'm assuming you have the stock pilot jet installed. Define what you mean by your a/f screw barely out?  It's important to realize that an a/f gauge is a read of exhaust gas temperature. Consider that when you are sitting there at idle and punch it, the read from the air/fuel gauge is delayed from the pure fact that what is happening in the carburetor 'right now' is not what the a/f gauge is reading. It's downstream from the here and now and reads what happened 1/2 a second ago. Plenty of time for an erroneous perception. My opinion is that your a/f mixture screw should be out at least 1.25 turns and likely 1.5 turns minimum even if the a/f meter reads 2. Do a simple test. Turn the screw out 2 turns and see what that does to performance from the idle to pilot circuit. What you are describing is a lean condition from the stand point of the idle/pilot transition. Not enough gas to fire with the available air immediately off idle. Take it for what it's worth,...and that is free. Once things get right, it takes off like a scalded cat. Once again, pure speculation. No dyno, no a/f gauge. I appreciate that these items are out there for those that want them and wouldn't even think to speak negatively about their products or opinions. However, my Rhino runs like a champ from idle to an extended 1/2 mile and beyond wfo run with nary a spit, snap, crackle or pop repeatedly and it does so without the benefit of anything other than my free seat of the pants dyno. Let me know what happens. ww    Roostin' Rhino RAIS Power Tube    Report

05-08-2007, 6:14 PM kracker Joined on 04-04-2007 sanford,florida Posts 11 Re: Mikuni Performance Tuning i tried the a/f out 2 turns and it still chokes out and is very hard to get into the middle range where it runs fine....i'm about over it........i dont know one person around here with a rhino...even stock that doesn't choke out under stress......i just dont get it....    Report

05-08-2007, 6:52 PM wwlknsn Joined on 04-09-2006 Memphis, Tn Posts 154 Re: Mikuni Performance Tuning Personally, I couldn't stand for that condition. I do to much puttin' around and throwing up rooster tails. By the looks of your avatar, you obviously have a snorkel. Think about the off idle condition and define it a bit more. Does it gulp as if there is nothing there when you punch it or does it go into a stutter up and into mid range? Snorkel or not, you should be able to tune out just about anything unless the restriction is simply to great. What I would do (as opposed to removing the snorkel) would be to experiment with the pilot jet size and/or your slide spring tension. I would try 2 sizes smaller/larger than stock on the pilot jet (35 and 45) and determine what type of performance change is made. Do this first because I think it will give you the most immediate read. If neither change makes a difference, buy a couple of stock slide springs, one to stretch out to increase tension, the other to clip to decrease tension. WIth a snorkel, I think you are going to need to think outside of the a/f gauge to determine what works best. There are some serious delays and equalization points that are not present with the stock set up. What happens with the snorkel detached? ww  Roostin' Rhino RAIS Power Tube    Report

05-08-2007, 6:59 PM kracker Joined on 04-04-2007 sanford,florida Posts 11 Re: Mikuni Performance Tuning off idle it will run fine into the mid range but if i stop to turn around it sputters real bad like it wants to go but doesn't...jerks real bad then chokes out....i will try taking off the snorkel tomorrow and see what that does...i even have the same snorkel made in 1.5 so i will try that...i do notice some debis floating in my fuel filter but i have changed that thing out 3 times now in a week....    Report

05-08-2007, 7:24 PM wwlknsn Joined on 04-09-2006 Memphis, Tn Posts 154 Re: Mikuni Performance Tuning Given that detail, it sounds as though the engine is gasping for air on the low side of the mid range circuit and corrects itself as air velocity makes it way through the snorkel. It's a lot easier to draw air through a funnel than it is through a straw so consider that this is what is occurring in your engine. You're riding along ok and decellerate by taking your foot off of the pedal which closes the butterfly which causes your slide to lower due to the rapid loss of engine vacuum. But by the time that everything equalizes, which is what a CV carb seeks, you stomp on it, the slide has not quite lowered all the way and you introduce a big slug of vacuum by hitting the throttle hard. Technically, your carb thinks you are at idle condition but in reality your slide is positioned somewhere where it normally is in a normal mid range circuit run. The vacuum sucks a big gulp of fuel up around the jet needle from the main jet and chokes until it self corrects due to the restrictions of the snorkel. I have long thought that a snorkel setup would require a needle jet change to correct this type of condition but I have never seen anyone  make that suggestion. By needle jet, I am talking about the jet that your main jet screws into which is responsible for the lower range mixture of the mid range circuit. Some refer to it as the emulsion tube.  Your condition would require a leaner needle jet. Regardless, disconnect the snorkel for grins and see if something changes. My guess is that it will. Since you are doing all of this, try this for a baseline. Turn your a/f mixture screw out 2 turns, swap the thick and thin washers on the jet needle, put in a 155 main and disconnect the snorkel. Stay away from 3 foot deep water holes and ride a bit. Tell me what happens. I do believe that you can correct the condition with the snorkel but it is going to take a bit of work outside the normal realm of the a/f screw, needle position and main jet. ww Roostin' Rhino RAIS Power Tube    Report

07-11-2007, 7:04 PM wickedsportrhino Joined on 07-10-2007 Posts 1 Re: Mikuni Performance Tuning HAVE A QUESTION I HAVE A 2007 RHINO SPORT WITH TWO BOTHERS DUAL EXHUAST , DYNATEK CDI AND COIL , PRO COM RECTIFIER , MAGIC BOX , K&N AIR FILTER , POWER NOW INSTALL , RAIS POWER TUBE , TRINITY CLUTCH SHEAVE AND WEIGHTS , MIKUNI HI FLOW FUEL PUMP AND FILTER . BEFORE I INSTALLED ALL THIS I CALLED TWO BROTHERS TO INQUIRE ABOUT WHICH JET THEY RECCOMEND HE SAID FOR MY ELEVATION {MISSOURI} AND WITH THESE MOD A 170 TO 175 . SO I BOUGHT THE DYNO JET STAGE 1 KIT AND INSTALLED IT ALL LIKE THEY SAID AND PUT THE DJ175 IN . BUT FOR SOME REASON MY RHINO LOSES POWER AND STOPS PULLING AROUND 50 OR 51 MPH . IS THAT WHAT IT SHOULD DO OR WHATS  WRONG ? ANY HELP                                  THANKS JOE OTHER THEN THAT I AM VERY IMPRESSED WITH PERFORMANCE AND POWER AND GET LOTS OF ATTENTION WHERE EVER I RIDE . IT ALSO HAS 27" SWAMPLITES , MOTOSPORT BLACK TORX WHEELS , 2 6" PIAA LIGHTS , VENOM 4000 WINCH ,  BUT I STILL NEED A 3" LIFT KIT , IF ANYONE KNOWS WHERE I COULD BUY ONE LET ME KNOW      Report

07-16-2007, 4:35 PM wwlknsn Joined on 04-09-2006 Memphis, Tn Posts 154 Re: Mikuni Performance Tuning Every Rhino is going to respond differently to different conditions. It's simply not as easy as saying put in this size jet and it will run like a banshee. You need to assess the jetting needs for your Rhino under the conditions that you normally ride in with the modifications that you currently have. Thoroughly reading the detail here will give you a good idea of how to determine the efficiency of each jetting circuit and get yur performance where it needs to be. I think if you get it dialed in, you will realize better top end performance. Let us know how it goes. ww Roostin' Rhino RAIS Power Tube    Report

07-21-2007, 9:09 PM DesertViper Joined on 07-22-2007 Posts 13 Re: Mikuni Performance Tuning This is just my opinion, but I think Krackers problem is the combination of a 2" snorkel and a CV carb. As has been said previously, the diaphragm in a CV carb equalizes vacume between the engine side of the carb and the air intake side of the carb (and lifts the slide). I had the exact same problems he describes on my old '05 Rhino after we changed to an 11:1 piston and a mudbuster cam. I could not get the problem to go away with all the jetting changes in the world, but we finally got it to go away well enough by changing the size of the vacume ports in the bottom of the slide. It appeared to be a vacume problem and not a jetting problem. In my case I had increased vacume on the engine side of the carb by increasing engine compression. In Krackers case he has increased vacume on the intake side of the carb by installing a long narrow snorkel. Both changes would alter the difference in vacume across the carb and may exceed the CV carbs ability to react adequately. I believe we made the vacume ports smaller on the '05 Rhino I had. I don't know if Kracker needs to make his vacume ports bigger or smaller, but would suspect he has to make them bigger. If changing the size of the vacume ports does not help, then I would think the two easiest fixes to his problem would be to either remove the snorkel, or change to a non CV carb such as the Mikuni TM 45. Just my thoughts on this problem, because I had what sounds like the same problem. Excellent forum you have here by the way. DesertViper    Report

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