jet size

[M1dwestF1sh]

I have a 2000 500 xcsp ves polaris and I took it out for the first time and it bogged like crazy. Did this towards the end of last year too. I put 1,300mi on last year and it started off running fine but it has gotten very bad. I took apart the carbs and noticed the main jets are 420. That seems a bit rich too me but I wanted you guys to throw some input in. Any thought? I cleaned the exhaust valves last year.

[fishersofmen]

Make sure the carbs are spotless. Is the 420 size main jet the stock size? If so it should run fine with them. Check the choke cable and make sure it is not sticking. Also check the carb intake boots and crankshaft seals for leaks.

[M1dwestF1sh]

I just went through the carbs. Soaked and sprayed every jet and air/fuel screw with carb cleaner and compressed air and it still is bogging. I'll have to check those later this week when I have time. Thanks for the ideas! Its too the point where anytime I'm off the had the sled bogs to the point it kills.

[fishersofmen]

I just did crankshaft seals in an older exciter. It was doing the same thing really bad bogging down. Cleaned the carbs twice with no improvement. Finally decided to check for leaks. Spray some carb cleaner around intake boots and both sides of crankcase where the seals are at. If it revs way up you have found your problem. I just put this one back together a few days ago and it absolutely purrs the seals on both sides were wasted......

[M1dwestF1sh]

Just sprayed down the seals and nothing. Ive been digging around on some snowmobile forms and I might have to post something on there. When I choke it to half choke it goes away for about five seconds then it starts to bog even with the choke on. I can keep it running if I keep flipping the choke on half and off.

[DANR]

My son had one that was doing that. Turned out that the torque stop was broken, allowing the torque of the motor to pull the carbs away from the intake boots - just another idea.

[leech~~]

Just sprayed down the seals and nothing. Ive been digging around on some snowmobile forms and I might have to post something on there. When I choke it to half choke it goes away for about five seconds then it starts to bog even with the choke on. I can keep it running if I keep flipping the choke on half and off.

Run a compression check.

Every year most of my sleds over the years are a little boggy after sitting all summer until I can get them on a good trail or better yet a lake and blow them out a bit!

[Macgyver55]

If it ran correctly with those jets before (assuming they are the stock size) there is no reason to believe they need to be changed.

Leaning it out with different jets is just masking the real problem and could result in disaster. Make sure floats, needle and seats are good and properly adjusted. Check the choke enrichment circuit carefully to make sure it is fully closing and the seals on it are good. Also check the air box to see if any critters have built a nest in it. As said earlier make sure compression is up to par with specs.

Whatever the case, rejetting is the last thing you need to look at, the problem lies elsewhere.

[leech~~]

If it ran correctly with those jets before (assuming they are the stock size) there is no reason to believe they need to be changed.

Leaning it out with different jets is just masking the real problem and could result in disaster. Make sure floats, needle and seats are good and properly adjusted. Check the choke enrichment circuit carefully to make sure it is fully closing and the seals on it are good. Also check the air box to see if any critters have built a nest in it. As said earlier make sure compression is up to par with specs.

Whatever the case, rejetting is the last thing you need to look at, the problem lies elsewhere.

Plus+ 1, there was one guy I knew who had the mice pact his muffler plum full of cat food during the summer. It took a while to find that problem out!

[fishingstar]

when was the last time the exhaust valves been cleaned?

[M1dwestF1sh]

I cleaned the exhaust valves last year but I did put on 1,300mi last year. I'll have to check the pipe and air box for critters tomorrow haha! I had it out the other day and got it going mid 80s a few times. It felt good as long as I didnt let the sled idle. After hearing you guys talk I realize it would have been pretty dumb of me to reject it! Would low compression make it bog bad at idle?

[Surface Tension]

Yes low compression can make it bog so check compression to eliminate that.

I can't tell by your posts where the bog is at. Coming off idle, mid, upper RPMs, or all the time.

You said you cleaned the carbs. Nothing personal but I've seen it more then once when someone cleaned carbs but weren't thorough.

What about the pilot jet, was that cleaned?

420 main jet is fine.

Air screw needs to be removed while cleaning, start out with 1.5 turns for tuning.

You might have a pilot air jet(at the opening of the throat) was this removed for cleaning and inspection. When this is done and you still have a problem you can move on.

Since it picks up with choke/enrichment we'll go with lean condition. Pull the spark plugs, what condition are they in. Do their appearance verify a lean condition?

When choking you get a momentary pickup. That could be because of low fuel level in the bowls. Causes could be weak fuel pump, check the impulse lines and connection coming off the crank and fuel pump. Blocked fuel filter if you have one. Incorrect float drop. Pickup line inside the gas tank cracked or broken. Bad connections of fuel line between the gas tank and fuel pump. Cracked carb boots introducing air between the carb and engine.

[M1dwestF1sh]

It only bogs at idle to about 1/4 throttle. I didn't think it'd be compression because I would have thought it'd bog all the way. I'll check though. When I clean the carbs I take out the jets spray carb cleaner through the jets and it the spot they go and compressed air. Now that you mention the pilot air jet though I didn't take that out last time and I'm almost positive my carbs have that. I have two screws on my carb which I thought were fuel screws I took out and cleaned as well and put them back and put them to 1 1/2 turns out.

I would think lean too but whenever I pull the plugs they are almost black. Far from being lean which I don't understand if the sled picks up when I choke it. I have some time tonight so I'll check the other things you mentioned and I suppose take the carbs off and clean the pilot air jet.

Thanks for the responses!!

[Surface Tension]

That info helps and wasn't what I was expecting on the plug. Mikuni TM 38 correct?

What position is the clip on the jet needle. You can drop the needle one notch by moving the clip up. Then adjust the air air screws again.

[leech~~]

That info helps and wasn't what I was expecting on the plug. Mikuni TM 38 correct?

What position is the clip on the jet needle. You can drop the needle one notch by moving the clip up. Then adjust the air air screws again.

Your getting some good ideas here from ST. Do you have a sled stand to get the back end up and track off the floor? Sometimes it helps when adjusting the screws to be able to rev it up and down. Also, check your oil injection pump to make sure it is adjusted right if your plugs look black, it maybe dumping more then you need?

[Macgyver55]

I would fully expect the plugs to be black if using the choke to make it run better. The only way they will clean up and be the correct color is when the machine gets running right and he is able to open it up for a spell. By the description it sounds like the pilot jets were not cleaned and probably where the problem lies. Sometimes just spraying them and blowing them out is not enough if they are varnished up and a jet cleaning tool is necessary. No sense messing with the needles just yet as they are mainly in play starting just below 1/4 throttle up to just above 1/2 throttle, and the fact that it ran ok before.

Here is a diagram to use while diagnosing that shows what each circuit does. Based on your throttle position when the problem occurs, that is the likely circuit or circuits you need to concentrate on assuming other external factors are in good condition. As Frank said, intake boots, fuel pump pulse line etc.

[Walleyehooker]

Did you take out and clean the pilot jet when you cleaned the carbs? Not real familiar with carbs on a Polaris but the pilot jet isn't real visable and gets overlooked if you don't know where it is.

[M1dwestF1sh]

ST yes that's the carb. I already have the clip moved up one spot so it sits in the second notch from the top. I cleaned the three jets on the bottom and the pilot air jet and fuel screws. Checked the oil pump last week and it was in line. When I cleaned the pilot air jet last night and put it together it ran great very snappy for about 30 sec then the bog came back. It might just be my optimism but it felt great for thirty seconds.

[M1dwestF1sh]

Just to throw another curve in this whole deal it bogs bad when just idling and it will die. I can rev it to 3500 or 4000 without the clutch engaging and if I hold it there after about 5-10 seconds it bogs down and dies unless I reach over and flip the choke quickly.

[leech~~]

You may just need to get her out on a lake or trail and burn it out a bit if you have done all what has been suggested so far.

[Macgyver55]

When/If you are confident the carbs and all jets are clean, then you may have to check the crankcase to make sure the crank seals are not leaking. Check all your fuel lines before the fuel pump to make sure they're not sucking air, especially the pick -up tube in the tank. Have you ever replaced the fuel filter? Have you done a volume or pressure test on the fuel pump itself? All things to consider but I wouldn't ride it much the way it is or you will do damage, but when you get it right you'll know it!

[M1dwestF1sh]

I had it running and sprayed all around with carb cleaner to see if it would rev up and it didn't so I'd like to think the seals are okay. Is there a good way to check that fuel line? I have never touched anything on the fuel line. Sounds like its time to...

[Surface Tension]

When it dies after running at the higher RPMs and before you choke it is when I want you to check the plugs. Wet or Dry? Go back to checking the impluse line form the crank to fuel pump. Then check the gas line from tank to fuel pump like I suggested in my fist post.

Dieing at high RPMs would indicate the pump isn't filling the bowls or your flooding out.

The plugs will tell you.

Also have you checked for moister? A can see that on the end of the spark plug or in fuel drained from a filter. Could be on small drop in bottom of the bowl.

If that all checks out and it were me I'd take the outboard gas tank and remove the end fitting.

Then go to the fuel shut off valve on the sled or directly to the fuel pump and remove that line and hook the outboard tank hose to it. Pump up the primer bulb and start the sled.

Doing so you bypassed the filter and the pickup hose inside the gas tank. Again that hose can crack and suck air. The end of the hose inside the tank will have a screen and sometimes on check valve or a combination of both. The screen can plug and the check valve can stick.

If the plugs are wet and the engine is flooding then the inlet vavles have crud in them or worn or the float level is too high. Both carbs having the same symptoms would to much of a coincidence though but possible one is bad. I'd probably at some point run the engine with a plug out of each cylinder to try and isolate the problem carb or cylinder.

Also if this engine was loading up with fuel your going to notice it.

[fishersofmen]

Could a bogging problem be something electrical? I just had my exciter running great and now when it gets hot it will bog so bad it wont even move? Cold it runs fine but after 10 minutes severe bog....

[Surface Tension]

Yeah assuming your not overheating.

Coil, stator, ignition component problems can show up after they get warm.

You need ohmmeter and values, get those off the manual or they can be found on line.

Open another thread with specifics on engine and year.