I checked the plug and it is black. I will replace the plug, however because of the elevation difference from where I live (5500 feet) and where I ride (10000 feet), I expected the plug to be black because it runs richer at the lower elevation. The machine has been jetted the same since owning it and this is the first time I have had this problem.

Also on a side note, I have heard on the Rincons you can cut the spring down in the carb for quicker throttle response. Can this be done on the Rubicons?

 

Ok. Maybe not everyone and maybe not immediately (although I'd be willing to wager it's a high percentage of the time). I should have just said Propnut does. Sorry for the generalization.

But the job of the main and pilot jets are moot if the float isn't allowing fuel into the bowl. That's my whole point. I realize jet setup is critical in a 2-stroke setup but we're not talking about a 2-stroke setup. The poster asked about a Rubicon which is a 4-stroke setup I believe. Get fuel into the bowl if that's the cause and then look at the jetting issue. Oh, and I never suggested the wire brush and drill bit anywhere in my posts. A little cleaning solution can't hurt to try. A little trick we used to use on the metal parts of carbs was Vanish (yes, the toilet bowl cleaner). If this failed, then it was time to replace parts.

I'm not trying to make a pi$$ing match out of this thread and we're getting off the topic. Suffice it to say, I'd try the low-budget fixes before throwing money at a problem.

 

Larpy, the fuel mixture will be richer at higher elevations, not lower.

Given the fact that it dies in reverse but not in neutral or forward, it sounds electrical to me. One of my regular riding friends has a Rubicon and there was one time recently they had an issue where it wouldn't run in reverse. It didn't have much power in the forward direction either but it wouldn't go at all in reverse. However there was some sort of fault being displayed on the console at the same time as well (I can't remember what it looked like, but I think it involved some blinking or flashing on the LCD display).

Just for grins though, is your fuel resonably fresh or did the problem start shortly after a fill-up. Are you using gasoline that has an alcohol mixture in it?...

 

Well i had a Rancher AT, alot like your rubi. and mine did the SAME DAMN THING!!! aahhhh it was pissin me off. and only when i was plowing snow.
it was jetted to rich. my plug was black and in the right light i could rev it up and see black smoke out the pipe. and the back fire is unburnt fuel in the exaust system then it'll light and backfire. so..
what i would do is rejet 2 sizes down. (what i did) and it should fix the problem. if not it's only $6 for the jet and 20 min to install it. and a new plug.

rejet smaller you'll see.

HR.

 

If I see any more problems with these two screens names

JDQuadRider
propnut

in this thread or any future thread

I will shut you off.

 

I am going to empty the gas, change the plug, reset the ECM, and clean the carb. How do I clean the carb? Should I take it completely out? I am mechanically inclined but have never done it before on this machine. Any hints?

 

you may want to check the switch on the front right brake handle, mine was stuck "on" (not the brake, but the little switch) and it thought i was trying to drive with brake on and it speed limited the quad to 1mph, serious back fireing and mis fireing resulted. If anyone doenst believe me, pull in the front right brake while in netural, put it in drive and try to drive without letting off the brake and you will see what i mean