Just bought a pred 90 not running for 140bucks. Great shape just was not running. Cleaned the carb and pulse coil got it running has new gas in it Seemed to be running good. Adjusted idle speed and air idle set screw to best setting i could find. Took out for a ride and it runs great does dohnuts spins tires up untill you give it over half or full throttle it will bog. The only thing i did not clean in carb was the float needle cavity. I did not want to drive the pin out to take it appart. That and float level i hurd could be picky on these. It could probably use a new plug but thats on order. It has a ngk 6hs in it now should it have a 7hs? Maybe someone can save me some time with ideas!!!! Thanks

 

All it takes is a piece of trash or grit to get behind the needle to slow down fuel flow. Cheap as the knock off carbs are I'd just get one for 18 bucks.Carburetor Fits Polaris Predator 90 2003 2006 Electric Choke Carb | eBay The blamed oem needle and seat are over 50 bucks! Polaris Needle Seat Predator Sportsman 90 0451669 | eBay Plus takes a BPR7HS plug that most cycle shops would have.

 

Yeah your right to just get a cheap one one ebay or amazon. Atleast the parts for these things are pretty cheap aftermarket wise.

 

Crazy that even at cheaper online places they still want $325 for this little oem carb.

 

Did you ever get this running. I bought an 04 Predator 90 and it does the same thing. The carb that was on there was a cheap Chinese knockoff. I took it apart three times now and cleaned it plus pulled all jets and needles. Currently it bogs down around 1/2 to wide open. I have a new airbox and filter. Currently I am running 1.5 turns out on the fuel screw (or throttle slide screw) and 3/4 turns out on the air. 82.5 on the main jet, 22.5 on the pilot and #3 on the needle clip. Thise are per the manual and what was in the original carb as well. I also tweaked the float to allow as much fuel in as possible. (FasterATV) It starts and idles fine, but when I open it up it still bogs down. If you crack the choke open about a 1/4 there is no more bog. Everything points to the middle circuit and the needle and clip. For grins, I even moved the needle to the 4th clip and it is the exact same. I have adjusted the fuel screw every place between 1 and 2.5 with no difference.

From another forum (FasterATV) I'm being told to reroute the fuel lines as there was a service bulletin about that, which I'll do next and possibly check the petcock for debris, but it makes no sense that that when I go to partial choke it is getting plenty of gas. Someone also mentioned a plugged exhaust but again it goes against what seems to be happening when I open the choke and let a little more fuel in.

I also have an original Mikuni that really needs to be cleaned. I can try that and swap all the new parts over and see if that works. I was also thinking about hooking up some fuel to a hose and bypassing the tank and the petcock to eliminate that or even a fuel cap. I also replaced the old vent hose with a new hose that comes off the tank.

2 strokes are new to me.

 

Feel exhaust flow at an idle,should be pretty strong. If it's weak,the exhaust port could be carboned up along with the exhaust pipe itself. Found plenty of the little 50 and 90 machines like this over the years. You can clean an exhaust system up by plugging the tail pipe and filling it with kerosene and stand in a corner for a few days.I've had to also chip hardened carbon deposits around the exhaust ports. Another area on Polaris atvs that a lot of people over look is tank venting and the petcock itself for reduced fuel flow.Bulletins were on Eton based machines. Although similar Polaris youth machines are manufactured my Aeon. One other area people over look is compression. If it's below 115 psi,might be time to freshen up the top end.The Mikunis are better carbs and if you take the time to soak one over night in Berrymans carb cleaner, blow out all the passages including the small top and bottom orifices in the carb bowl you might have better luck with it also. See if this video can help.

 

Thanks for the reply. When I bought this machine lets just say I thought I was getting something better maintained and so far I have been disappointed turn after turn. Anyway, at least I'm capable of doing these things and I rather enjoy it in an odd way.

So here is what I'm going to do.

1. check the compression (have to run up and get the tool) If that fails I'll get a rebuild kit and replace the entire top end. (well I'll see if there is anything salvageable first)

2. I'm going to strip the used Mikuni I got from Ebay for this bike and soak it, bringing over all the new parts from the other carb and if I have to I found another more complete carb kit to work on this carb.

3. Still need to check the petcock.

4. Pull the pipe. I think it flows fine but what the heck, soaking it is easy and if I have to rebuild the top end, it can sit out a week while I order the parts and rebuild the top end.

Two additional questions, what type of injection oil should I be running in this thing or should I scrap it for a pre-mix instead? What kind of engine oil should I be using in the crank case? Is there anything recommended besides the Polaris brand stuff?

The last owner was running it around on partial choke and I have no idea how long it has been like this or what anyone has done to this thing since 2004. I know the carb has been replaced with the Chinese carb and a few parts have been changed on it.

For what I have changed already I'm approaching what I think is what the bike would have been worth if it was in great shape. However, I'm planning on running this for the next five to six years (maybe more) so to totally freshen this up to a solid bike where I know everything that has been done it is probably worth it in the long run. I'm pretty **** about my stuff. I don't like to abuse things but if I do break something then I will want it repaired correctly right away. I don't mind modding if done correctly but I don't want it hacked.

Oh yeah I have seen that video before plus he has a couple others where he is fixing that bike up.

 

Oil pumps are pretty dependable on these little machines. Any good brand of Synthetic 2 stroke injector/premix oil would be ok to use. One other area that causes problems is the stator. Mainly because of the open slots in the plastic cover designed for the plastic fan to keep the flywheel and stator area cool. It allows water,dirt and mud in also which is a killer of stators on these machines. Not a bad idea to pull this cover and clean the pick up coil and flywheel area. Usually compressed air will get rid of a lot of accumulated dust. Plus if dirty enough could be part of your problems. Good that you have the manual as I would check out stator resistance to rule out any problems there also. Cheap 20 buck stators for these are on ebay if ever needed.

 

I did a compression test, all though the engine was cold, I only got 30-35 psi, I could warm the engine up but I'm doubting I'll be getting 115 to 120 psi, unless those rings will expand that much.

I bought Berrymans this afternoon and I will probably strip the Mikuni later tonight.

If I'm going to be doing a top end, I plan on getting a complete kit, is there anything that I'll need that does not come in the kit? Most kits are the jug (cylinder), piston, head, rings, wrist pin clips and two gaskets. Anything else I should replace since the engine will be out?

Also now one other thing I'm noticing, when the engine is cold, the kick start doesn't come all the way back up and I have to raise it with my foot, it comes up maybe half way. However when the engine is warmed up it works fine.

 

Nope 30-35 psi doesn't cut it. The kits are pretty well complete for a top end job. Kick starters hang up mainly because of being dry and accumulation of belt dust. Pull the cover(leave the kick starter lever on) and blow out any dust from the ratchet area along with the clutches while you're at it. Spray a little penetrant to seep down shaft bushing and a thin film of grease on all the other parts.If the electric starter doesn't work or turns slow a lot of times dust gets in the idler gear assy. Cleaning and lubing this area up can make a big difference in electric starting. Once the cover's off you're there anyway.