So I have a Rancher 350 that I acquired several months ago. When I first got it, it appeared to run fine. After sitting a couple weeks with little use, it began to stutter at low speeds, such as making a u turn after a long run straight run. Over the next few weeks it got so bad it made it un-drivable. It seemed like it was running very rich.


Since the motor did not smoke I decided it was probably something in the carb. I took the original carb apart and cleaned it out and all and put it back together. It seemed to work better for a short time but returned to its previous state. Then I ordered a new carburetor. After installing it I tried running it and it wouldn't even idle. I then decided to get all new gas as well so I pulled the gas tank and took it apart and cleaned everything and put in a new fuel filter. Before putting the tank back in I ran some new premium gas and sea foam into a jar and ran that through the engine and it ran fine at idle and some elevated rpms. I then installed the tank back with a new filter and put the rest of the premium gas in. It now does not like to idle very well and once again bogs down like before.


Also, I know the valves are close to spec as I checked on the them and they were slightly too loose so gave them a 1/8 turn in for good measure. I also pulled the plug when I had the gas tank out and it was very fouled, confirming my thoughts that the bogging down was originally a rich condition. A new plug was just installed as well. The idle fuel screw has been checked to be the factory 1 3/4 turns out as well. The choke being stuck open does not appear to be the problem either.


The bogging down will also happen just in neutral reving it up too. If I hit the throttle all the way, it runs perfectly with no bogging. Its only if I get on it gently and the past idle-1/4 throttle sounds terrible and rough running and boggy. After that it runs perfectly fine.

The new plug was also obscenely fouled of about 20 minutes of letting the engine run and attempting to drive it as is once again showing it is running way rich somehow.

I have refrained from opening up the carb to see if something is clogged already because it is new and the warranty on it will be void if I open it up.


Anyone have any ideas of what it may be?


Thanks

 

Stick the original carb back on, you can alter the needle height etc, on that. You mentioned adjusting the valves then giving them 1/8 turn in, bad idea, too tight and you loose compression, too loose and they are just a bit noisy. If the bike is misfiring due to an electrical problem, it will appear to run rich, so don't assume the carb must be set rich.

I have a 350 in at the moment that runs OK sometimes, and sometimes won't idle, I recon a valve seat may have come loose, but the owner has decided to get a fresh bike, so it will have to wait until I have some spare time to investigate.

Sorry to have widened your investigations, but that is fault diagnosis.

 

Do you have an inline fuel filter? When I got my AC 500, the tank was full of crud. Caused me a lot of grief, until I found the problem. I'm with merryman, clean the old carb, blow out the pilot jet and try again. You might want to try a Dynojet stage 1 kit. Around $25 on eBay. I really like the tunable needles.

 

I tore it apart again and set the valves to spec for sure this time and left the new carb in. Put it back together and it seemed to run fine for a time and then it started acting up again worse than before. Going to let it cool all the way down and try again to see if it being hot has anything to do with it.


Is there a specific part of the electrical/ignition system that you think could be causing thins issue. It seemed that when it was running fine that it wouldn't idle well either.


Yes I do have a new in line fuel filter and I have cleaned the tank out as well.

 

Alright I am pretty sure you were right about it being an electrical issue. The thing is though that it keeps happening intermittently. Is it possible for the timing of the ignition to get off somehow?


For what ever reason, it wont start at all now. I checked to make sure there was a spark and there still is but maybe it is not firing at the correct time?


I tried testing the trigger coil/pickup to see if it puts out at least .7volts as the service manual calls for but my multimeter did not want to save the maximum spike value it saw for some reason.

 

Voltage regulator is real common on these atvs. of going out..Is it charging okay?

 

Hard to beleive both carbs doing the same thing

 

It has to be charging ok because it has not died in about the 2 months I have had it and been working on, riding it no matter how badly it ran.


So I decided to put the old carburetor back in because as far as I could tell all the electrical ignition was working at least most of the time and it was not starting up at all this morning. It cranked right up with the old carb. It still has the original problem from before the new carb but at least it started back up.


Its back to the original issue from when I started all this of it idling fine, but when you get on the throttle, it bogs down and dies. The thing is, if I get on the throttle and pull the choke out proportionally, it runs perfectly. Also remember it seemed to be running excessively rich before by looking at the plug but the above trick would make it seem like it did not have enough gas....


I'm not sure what to do at this point.

 

The 1 3/4 turns called out in your manual is a starting position, adjustment from that point will probably be needed once you can keep it running. Get a spark gap checker and see how hot your spark is, a yellow spark is weak, a good strong blue spark is needed, one that will jump a 3/16" gap at least. You might also want to check and see if the flywheel key is sheared while you have it apart. Other wise you might be looking at a electronic ignition box problem if your machine has one.

 

Now you have it running again, check the voltage at the battery with the engine running, if it goes over 15v at any revs, you have a faulty voltage regulator. Clean the old carb out yet again, something has blocked the new one, so you must have a problem with dirt or water in the fuel. If the plug is fouled again, drop the needle one notch and see if that helps or hinders. You haven't mentioned the choke, a common problem on 350s is the choke plunger stuck partly open, but not likely to occur on the new carb, could the cable be sticking?

If you still have the fault it could be the coil, CDI or trigger coil, although theoretically these can be checked electronically, I go for substitution, cheapest first.