Polaris ATV Forum banner

Carburetor woes with my 400. Opinions please.

9K views 44 replies 9 participants last post by  4x4dually 
#1 ·
Background. The ATV slowly started to run bad and loose power over a few weeks. Hills became a problem, etc.

Took it to the dealer. They said it needed a carburetor kit installed because the valve and seat was bad and it was leaking fuel and flooding. A few days later I went back and they had it idling outside ready for me. I threw my leg over it and it wouldn't even take off without bucking and jumping. I left it with them for further diagnosis. Now they tell me that they had to re-jet the carb with a 152 to make it run correctly. The factory jet is a 167.5 for the main jet on a Mikuni 34 used on a Sportsman 400.

I'm not sure if I'm comfortable picking up the ATV and letting it ride like this. I've discussed it with another dealer her locally as well as a buddy who works for the Polaris design team. I'm here for a few more opinions before I walk next door today and let them have it.

Why would the jet need to change after 16 years of service? Is the valve just set to high? I've read online that the float valve doesn't affect the jetting unless it is starved for fuel but that didn't make any sense.

Compression/leak down test was fine and so were the cam and the valves when they checked them...or so they say.

I have trust issues. And this is why.

What would you guys do in this case? Throw a fit or take it somewhere else to be corrected and pay out of pocket for it?

Thanks in advance for your opinions.
 

Attachments

See less See more
1
#2 ·
Carbs often need some tweeking after a rebuild. Not sure why the drastic change in jet size but I would not throw a fit and instead just work with them. Keep testing it there at the shop until you feel satisfied. A good shop will give you some sort of warranty on their work.

Guessing they swapped the fuel filter also?
 
#3 ·
I can't think of a reasonable explanation as to why the main would need leaned out so much.

Do you know what work was done? As in, the parts that were replaced, what brand those parts are, did you give you the old parts? That's SOP for a decent shop.

Float level does have an effect on jetting but I doubt it's possible for the float to be so far off that it would cause such a change in the main jet.

I'd be curious if they put some Chinese brass in there. Or, maybe the guy who gave you the info doesn't know what the heck he was talking about.

I'd get the real story from them before getting too worked up.

Sent from my SM-G930V using Tapatalk
 
#5 ·
Thanks for the opinions. I walked next door and had a civil conversation. I told them that I had a full week to think on it (which I have since I've been at the lake) and told them I wasn't comfortable without the factory parts and sizes in there and that something else had to be wrong. I told them I didn't want a 'bandaid' put over another problem. They said "sure, we'll take care of it." Now.....to trust what they do, I have no idea. I know for a fact the air filter is clean and the fuel is brand new. I don't know if they checked fuel lines, valves, the float breather tube, etc, etc. What I was told is that they put a carb kit in it because the needle valve and seat were leaking. I went to get it when they said it was done and it wouldn't even run. I was mad enough then. If you call me, test drive the dayum thing. Not that hard. Then I came back later and they told me that had to re-jet it to make it work with a 152. They said the didn't have a 152 but they drilled a smaller one out and made one. Sounds great don't it? I'm sure it is a precision instrument now. LOL

I just hate things these days. I'm getting old enough now that I don't want to fix every single thing myself. I want to drop it off and pick it up and write a check. I expect things to be done right for $100 and hour. Instead, they now have my ATV for the FOURTH week in a row for a simple carb kit. Freakin' ridiculous.
 
#7 ·
They told me the left the pilot alone. It should be a 40 unless it is messed up too. It idles like a champ. It's the mid throttle that sucks. They sat out in the parking lot revving my 16 year old machine to redline over and over again like it was going to fix itself. I was waiting for a rod to make a window.
 
#9 ·
I'm sure they didn't. When I get it back, I have to go through the fuel system and find out why the reserve doesn't work anymore. I'm sure either the valve seals are gone or the main straw is broke in the tank. Something. You'd think they'd have checked all that and would have called and said they figured it out and need to replace xxxx. I'd gladly pay to fix what is broken, but this crap of "just add octane to your fuel" or "let's just rev it to the moon and maybe it will magically start working" has to stop....where's the bullet in my head omoji? LOL
 
#11 ·
I'm a fast learner once I get the bawls to dive into stuff. I'm an electrical guy but mechanical is a close second. Got a buddy that has said if I get it back to just send him the carb and he will set it up properly....but the point is....I shouldn't have to after paying $365 for a rebuild.
 
#12 ·
Right, you shouldn't have to work on the machine after having it at the dealership...You can either stay on them until they fix it right but you have to be prepared to be a prick about it, or write it off to experience and bring it home.
 
#13 ·
....... or write it off to experience and bring it home.
I would image the latter will be the case. The Case/IH dealer in Kingfisher, OK has been doing a lot of rework from other dealers in this state and from what I've been told, everyone is very happy with their work. I called and talked to the service manager about my issues and he assured me that nothing leaves their shop until it is correct. He may get his shot at it shortly. I'll give these guys a couple more days.

They also told me "we didn't really have much info on the issue when we started working on it." I told them it "DIDN'T RUN AND LACKED POWER." How much more dayum info do you need. Drive it around the parking lot. It will do the same thing! Some people's kids.....
 
#14 ·
Just got an update phone call. I was told "man, this thing is daemon possessed." LOL They told me they have been back through the carb and everything is correct. They said it runs great for three or four trips around the parking lot. They will park it, and next time it starts, it runs like crap. They've tried it several times and they can't predict when it will run and when it won't. They are going to try a new ignition module. Anyone got any other ideas? It almost sounds electrical at this point.
 
#15 ·
Well, that makes me feel a little better about the dealership. At least they are really trying to find the problem. And I know from experience that intermittent problems are the biggest PIA there is. Especially ones that don't have any kind of specific pattern to the failure.

I would say you are probably right though, the issue is most likely electrical. I know some of the electronic components don't have any test procedures. Repair manual just says to change it with a known good one.
 
#16 ·
It could be your fuel as well. I live down here close to Corpus Christi,tx and we got lots of refineries. I have a neighbor who is a fuel engineer for Flint Hills, some cities have certain blends of fuel for summer and winter and some for emissions. Any ethanol is the devil for carburators. For one thing it does not stay mixed very well. Its murder on plastic and rubber and certain gaskets. You may not have problems for months or years but in the end your going to have some gunk in the carb somewhere most likely fuel bowl it looks like amber hard/sticky it just takes a bit to mess up some passage or a o-ring shrinks just a bit. Chainsaws, weedwackers, and lawmowers are the real victims due to the companies that make them are not going to upgrade their fuel lines or gaskets or rubber orings ect. Walmart is getting into the fuel business big time look for new pumps or fuel stations and they will have a dedicated pump with no ethanol. with ethanol you have less BTUs which is less energy less power per gallon vs no ethanol. I like the other post on the electrical module those things can be hard to diagnoise as well.

All fuel is made as one and at the very end going into the truck different additives are added to make the recipe of fuel for some counties or cities. Shell does make a higher end fuel but would only recommend that for certain vehicles and you have to use a lot to notice a difference and the only way is either with a camera going down a spark plug hole or pull the heads and it should be a whole lot cleaner no deposits than using regular fuels
Good luck
 
#18 ·
What year is it? Could it be a worn cam lobe? Some of the older (pre-HO) model 400's (425cc) and 500's wore exhaust lobes off the cam, causing them to run poorly and loose power!?!?

Good Luck finding the Demon!
 
#19 ·
Yeah maybe worn cam lobe or valves too tight (it'll run ok cold not so when warmed up and trying to start it). Easy to determine if either is the case. :cowboy:
 
#20 ·
Compression test and valve lift test were all said to be done and passed. They told me that some had cams that wore down, but mine was ok.

It starts and idles fine. It is the mid throttle that sucks. I'm wondering if it is the slide valve in the carb not lifting to let enough air in and it drowns itself. The machine never dies, it just looses power. No backfire.
 
#27 ·
Picking up the atv tomorrow. They've had it for four weeks and can't figure it out. It runs fine cold and starts running bad once it warms up. I'm going to ohm the pickup coil and ignition coil cold and hot. Any more ideas?


Sent from my iPhone using Tapatalk
 
#28 ·
I brought my ride home today. I test drove it around the pasture and sure enough, when it warms up, it runs like crap.

So I pulled the ignition coil, plug, and the plug wire out. I ohmed to coil, wire, and resistive plug cap. All were close to spec ( the spec doesn't give a tolerance.)

Then I checked the plug gap. It was .040". I set it back to .026" ( OEM range says .024-.028.)

Put it all back together and guess what......runs. Really good actually. Pulls harder with the throttle than it has in a while.

Dealer had it for four weeks. I think I've fixed it in less than an hour. I've drove it probably three miles so far and no issues.

I'll probably buy a new plug, wire, and plug cap. They can't cost too much.


Sent from my iPhone using Tapatalk
 
#31 ·
Still waiting on parts....but in the mean time....I've addressed the issue of having a shortbed and not being able to haul the ATV and pull the bumper hitch camper trailer at the same time. The angle has the muffler too low to close the gate so I'll either have to remove the gate or shore up the rear wheels a tad. Either way...I'm liking it.
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top