Every now and then I find some time to ride or work on my quad. All prodjects around my house takes months to complete. I am still in the process of fine tunning my jetting on my Prairie 650. My current jet settings are 128fr/ 132 rear with needle on 4th notch. I have yet to notice any real improvement after 3 different jet settings( 132fr/136 rear, 130 fr/ 134 rear ). Air mixture settings are approx 3 1/2 turns out. My next move will be to check my needle clip placement. If they are both on the 4th notch( it should be unless I messed it up), I am considering moving them to the 3rd notch. My plugs remain black with all the other rejetting attempts. My choke was redone a year ago. Has anyone tried the 3rd notch on the needle to make it leaner on the first 2/3rds on the throttle? As a reminder I was never much of a mechanic before I bought my quad and not much has changed since!

 

Gosh that is lean. I see you have an HMF. I don't recall any really high elevations in PA, and can't think of any reason you would be so rich. I think something is funny. Different 650s shouldn't be that far off. I hate question your jetting technique, but it is either that or your 650 has funny busines going on. You really should be 5th notch and 132/136 with your mods and elevation. Maybe you didn't put the needles in the same way as the rest of us. Whatever it is, you have gremlins in there somewhere.

I have a "Nyroc" exhaust and am happily on the 5th notch (after being on the 4th notch without the exhaust mod). Runs like a charm, slightly lean on main jets but not much.

How does the machine run? Does it tell you that the needles are at fault for being rich? You can tell by the way it warms up in dire cold, if the needles are rich, it will run quite well. If the needle is rich, there won't be any coughing on a cold day, not much need for choke, and sluggish at 1/4 throttle on a warm humid day (humid from steam, etc.). My brother's Prairie is rich to the point of studdering on a hot day. But, it runs like gangbusters when you start it in the cold. No coughing, not stalling, starts without the choke unless it is below zero, then it only needs a little choke.

How do you know that you need 3.5 turns on the air screws, turn those in, then back them out 3 turns. I dunno, 3.5 works for a lot of people. I don't like mine that rich, I need the idle leaner in case water comes into the tailpipe, or steam at the inlet.

 

Haynes, I agree with nyroc, in spite of what your plugs are telling you you must be lean, I have the HMF ,DJ and 5 uni-vent;s and I'm useing 4th notch, and 134/138 DJ main's on mine, they were the biggest main's in my kit. with you having the snorkel, you have to be letting more air in than me! I think the snorkel alone warrent's a size up on jetting circuit's, I have the needle's one notch leaner than dyno-jet recommends and the main's one size richer, unlike nyroc, I could not get that hesitation to go away with my needles in the 5th notch, but with you Diamong g snorkel and pipe, I think you should be on the 5th notch and the mains the same as me 134 front 138 rear, as far as the air screw's,I didn't count my turn's. I warmed the bike up until the fan kicked on so I knew it was up to temp. let it idle, turned the rear carb air screw out(counterclockwise) until it idled down(rough) turned it the other way just until it smoothed back out then stopped, did the front carb the same, and your set. I think your getting a false plug reading because of your choke, loading the plugs with soot and raw fuel and not burning it off, It happened to me until I figured out the best way to get a plug reading, try this get a brand new set, start the bike and run it for just a few minute's, just long enough to where it will start and idle WITHOUT useing the choke, giving a little gas is ok, but let it start with the choke off, put the new plugs in, and ride for a minimum of about 30 minutes, different throttle, wide open, medium etc, pull the plug's after this.I 'll bet they aren't black now, this way you know for sure it's not the choke enrichment black fouling your plug's, If they are white or colorless, try my setting's and then do the same thing over again, and recheck the color, it should be tan then......sorry for the long post, hope we helped.

 

I haven't as yet rejetted my Prairie's carbs, but having experience with motorcycle carbs,
Could you be counting the notches on the needle from the wrong end? Just a thought.

 

Everyones help is greatly appreciated. I never attempted any type of engine or carb work before my 650 so I am very much a rookie. My quad runs strong at all the different jet settings. My concern is that I have not experienced any performance gains with installing a snorkle and trying the different jet settings, so I am assuming I am not jetting it correctly yet. When I pull out my needles I'll make sure I am on the 4th notch. I don't notice any true performance chances after trying different jets either. I am considering going back to the kawi needle and stepping up 1 jet size with kawi jets.

 

If I would go back to kawi jets, what are the stock size and what size should I rejet to with my listed mods?

 

have you got a full HMF

I just got my full system found one finally as they quit making them per HMF

I am going 140/144 one notch richer than stock and 3.5 turns out as that is the recommendation from big gun for theirs and both pipes flow about the same

 

No slip on Hmf

 

Haynes1111 - The stock Keihin jets are 138 - 142, front and rear. The next size up would be 142 - 145, front and rear. Just buy a 145 and move the 142 to the front cylinder. I think that's what HMF recommends anyway.

 

a question, I looked through every jet my dealer had, and they were not a 145 in the bunch, the only Keihn he had were the hex head and real long, are Mukuni main's the same cut as Keihn? would they work? also he looked under the 650 microfische and didn't have a 145 listed, the 650 uses Keihn 32mm CVKR carb's, I had him pull the Pra.400 it uses a Keihn 32mm CVK carb, not sure what the R stand's for but the 400 had a 145 listed and he ordered that one for me, should be in Tues. $7.05 for the one jet, will this jet work????