I just bought a 1991 350L 4x4. It wouldn't start or run worth a darn. Tore apart carb. It was full of varnish. Soaked in carb cleaner. Put it all back together, but it still doesn't run right. I have spent 2 days playing with it. It starts better now, but still runs like crap. It doesn't idle fast enough. It's sluggish off the line and dies once at full throttle. I have to tickle the throttle to get it to start running again. Pulled the tank and cleaned the screens. The throttle slide was in upside down. Flipped it over. The number on the needle jet doesn't match the number in my Clymer manual. The E-clip was in the second groove, it only has five, not six. Have tried them all. The idle stop doesn't keep it running fast enough. Maybe that is why they flipped the throttle slide and adjusted the idle with the throttle cable. Float level was too low. Adjusted so the float arms were parallel with the body. Then I got lots of gas out of the overflow on the bottom of the bowl. Lowered float level again. The idle mixture was out 1 3/4 turns, not 3/4. Tried it a bunch of different ways. The manual isn't much help. I'm about ready to give up. Any good advice on an easy way to get everything adjusted right???

 

It takes FUEL, COMPRESSION, SPARK to make a motor run. You have worked on the carb, what about the other two? Have you checked the compression and spark? How does your plug look after you get to run it a little bit?

As for your carb, it does sound like a hell of a mess. Varnish can be a nightmare to get out of some of the smaller ports in the carb. I have had my share of that. Are you sure that it is the right carb for your wheeler? If the needle jet isn't the right one, it kind of makes me wonder?

Your best bet would be to buy a complete rebuild kit for it. I would make sure it is the right carb, first. Also check the carb adapter(the boot between the motor and carb). I have seen one with a small crack that was giving the guy alot of problems. I have also seen it destroy motors.

Write back with some of the answers to these questions and I'm sure I could help you out some more.

 

Thanks DJE,

Spark is strong.

Compression seems good, but haven't checked with a tester. The starter motor is missing, so it feels like good compression when I pull start it and it has lots of power, when it's running.

I was almost ready to throw in the towel and take it to the dealer for repair, but I hate to admit defeat, and I'm afraid of what the bill would be. When I have time, I'll get a new rubber boot and a rebuild kit. I'm going to strip it down, again, and soak it some more before I put the kit in. I'll get the carb #, jet # and needle #.

What initial settings and float level should I start with? How can I tell if it is running too rich or too lean?

Thanks for your help. Updates to follow.

TN4ONFLOOR

 

I always start with the stock settings and adjust it from there. You stated that you have a Clymer Book. It should have all the settings in there.

I don't know if the carb will have any numbers on it that will actually tell you what it is. I can tell by just looking at it and measuring the bore size. I have never really looked for numbers, so I don't know if they are even on there. I just looked at the one off mine and thier aren't any on it that would tell me.(I actually have it off for other reasons right now.)

As for cleaning the carb, I always use Gumout. I make sure I shoot it into evey hole I can find. I usually go through about 2 whole big cans by the time I'm done(I like to know it is deffinately clean). If you have compressed air to use than this works really well to get the bigger stuff out of the ports. I hope also, that you didn't soak any of the O-rings in carb cleaner. This wouldn't be a good thing. O-rings probably wouldn't be much good after that.

This is what I would do for initial settings:
* Put the slide in, the right way
* E-clip in the middle position(their is only supposed to be 5)
* Air mixture screw- 3/4 turn out
* Floats should measure (.5 - .6 inch) This is measured with the bowl off. You measure the distance from the gasket surface to the arm that the float hits. Make sure you push the needle in then let it just spring itself back a little bit. There's where you measure.

Last, but not least. the spark plug can be read to actually tell you alot about how the engine is running, if you know what to look for. If the plug is actually wet or has a high build up of black suity carb, then this is usually a sign of it running too rich. If the plug has a white cast to it or kind of looks glazed, then these are usually signs of it being too lean. You should really only use a brand new plug to use for this. I will usually get the engine up to normal running tempature with an old plug before I put in the new one. Start up the motor, get on the machine and run it up to full speed. When you get going as fast as you can then, carefully pull it into neutral and shut the engine off. Now you stop the wheeler. Pull the plug out and see what it looks like.

Any more questions, feel free to ask us.

 

I had the same bike only a 92 model that started having problems similar to yours. How many miles does the bike have on it (mine had 4,000)? I also adjusted the carb, it helped some. Ultimately I checked the compression it was about 110 lbs. Talked to a Polaris mechanic and he said once they got to about 110lbs or below they start to have problems that you can't adjust out with the carb and you need to rebuild top end. I elected to sell mine instead as it needed more than just the top end rebuild. I would say you need to get a compression tester to rule this out.

 

Okay, I finally made it to the Polaris dealer. Discovered they don't sell carb rebuild kits, sooo, $72 later I walked out with an envelope containing the few new parts that I needed. Cleaned the carb, again, installed the parts and began a couple of days of frustration. Still can't get it to idle unless I adjust the throttle cable to hold the slide open further than the idle stop holds it. Still won't start, cold, unless I squirt a little carb cleaner or starting fluid in her. Still cuts out when full throttle under load. Carb overfolw vent on bottom of bowl still spits gas, sometimes, even after lowering float level and installing new valve and seat.

Archery season opens here next Saturday, but I guess I won't be saving steps by riding my mule. Damn!!

Still can't find my compression tester. (We moved, and it's in a box, somewhere. But where? I hate moving.) While searching other sites I've learned ALL sorts of info on Mikuni carbs. Never heard of a crankcase pressure test before. Need to make a tester and see if I have a leak. I think maybe I've got low compression AND a crankcase leak.

Now the questions.....
I have no hose hooked to the plastic overflow fitting on the bottom of the bowl. Where should it be attached to??
I have a small plastic tube coming from the top right side of the crankcase. What is it and where should it be hooked up to?? I get smoke and vapor out of it. I thought maybe it hooked to the carb, but the only place to hook it is the overflow. (I know the hose from the tranny hooks to the fitting on top of the carb.) Engine doesn't start with it hooked there. After learning about crankcase leaks on 2-strokes, I'm now afraid of having a crankshaft seal leak.

I really like my Trail Boss, but I don't want to invest more into it than it is worth. I got it cheap. I like fixing things so I know it is right and don't mind spending time to learn, and some money, but I don't want it to be a money pit. Should I put it all back together, get it running the best I can, sell it for whatever I can get, and then buy another one?? I'm sold on Polaris 4x4's and know better about what to look for next time, but I'd be happy with my old TB, if I could just get it running better.

Sorry this was so long. I'm just crying in my beer and need some advice. Thanks.[img]i/expressions/face-icon-small-confused.gif[/img]

 

ok first of all polaris 2 stroke engines vibrate alot and when you get some miles on them they tend to wear the needle valve assy. and that is the only means of comrtroling gas flow to the float bowl. this is why gas leaks out the carb when bike is not running. also it causes bike to run very rich and this is why it won't idle.(also check throttle lever safety shut off) get a new needle valve assy. polaris part #3130360. then adjust float levers parallel with carb body. Also remove main jet and push out needle jet. sometimes main jet shows it is clear but the needle jet under it is clogged. also remove the pilot jet and make sure it is clean. this jet is the only jet that the carb uses to idle on. if it is plugged it won't idle. also the jet needle for the 91 350 is polaris part #3130391 also order this. vibration also causes this to wear>--some indications of these parts wearing out is 1. hard on gas 2. you need to shut the gas valve off or the bike will flood itself while sitting 3. gas leaking on ground with bike shut off. one more thing it is better of to buy a new main jet (3.50)and pilot jet (2.50) if they are really varnished up. it you try to push something through them you will enlarge the hole size and screw up the mixture. also everybody that runs in a lot of dust make sure your air filters are kept clean. a plugged air filter will make the motor run rich .....I hope this helps

 

I hate to tell you this but I had similar problems with my 91 trailboss also. While you may be having trouble with your carb I'm thinking you might have a more serious problem. Pull the rubber boot between your carb and cylinder off and check to see if there are any cracks in it. Then pull your reed cage assembly out and take your flashlight and inspect your piston. This is where my problem was. Polaris has week pistons and they tend to break. Unfortunately when the pieces go through the bottom end they usually do more extensive damage. I ended up having to have my cases welded and a complete rebuild using a wiseco piston. Good luck!!

Tim...

 

Okay, I should have been more specific in my last post. I've replaced the jet needle, needle jet, float arm pin, and fuel inlet valve seat and needle. All parts were from my Polaris dealer. I'm not sure of the part numbers. Float arm is adjusted parallel with gasket surface.

I'll borrow a compression gage and make a pressure test rig this week. What else should I be trying??

 

did you check the throttle safety switch. It won,t fire if there is any slack in the throttle cable. when you say you have to hold the throttle open a little do you mean you have to give it throttle or are you just getting rid of the slack. as far as the starting problem the chock passage is blocked up or the chock plunger isn't lifting when you choke it (broken choke "T" in behind lever) or cable is broke.