What Fuel?

[wolfmanbean]

Ok so im having an issue, so I'm resorting to the forum. I am currently running a HMF exhaust with the K&N air filter. I have the HMF jets, just have not put them in. so my question is, what octane do you run? I ran 87 octane for about 6 months After I changed the pipe and filter. It ran just fine. Then one day I had the seat off and noticed on the air box that I should be running 91 octane. So I switched on my next fill up. I made it through about a half of tank of fuel and the plug fouled out. So I thought no big deal it happens. I put in a new plug and it did it again. Not sure if its the fact that its not jetted or the change in octane. I want to jet it but I'm kind of affraid to mess with the carb, and I really dont wanna pay the dealer a $100 to jet it for me. So should I switch back to 87 or stay with 91 (which sheetz only sells 92)? Or go back to 87 or stay with 91 and jet it? I have a trip planned in oct. to go to hatfield mccoy, and I dont want to have issues. please give me some insite. thanks

 

[08wolverine]

What color was the plug when you changed it? it may be running lean because of the additional airflow from the air cleaner/exhaust.

 

[aces3]

I would jet it first I have a 08 450 with all the same Jetting is easy to do. Hmf should have given you instructions and its only one jet the main. AS for the fuel I tried running 91 and it did the same to me. I usually go through a couple plugs a year any way 800-900 miles so I get about 400 miles out of a plug. Once it starts popping out the exhaust alot I changed the plug.So go back to 87 or if offered a 89 octane and try a little fuel stabilizer something that will help with the ethanol, not too much, or couple ounces of dry gas. I have been using a little seafoam because we have moisture issues in our gas in NY.

Jetting
remove seat
remove gas tank of course plastics around it.
disconnect choke cable,fuel line from carb, drain fuel out of carb bowl.
loosen both clamps on either side of carb
turn the carb towards you ( I do this on left side of machine)
remove 4 screws on bottom of bowl. tada
good time to clean it out with a little carb cleaner.
Main jet is right in the middle. switch to a 140
I have ridden several different elevations and never had an issue.


Last: let us know the outcome.

 

[wolfmanbean]

I cant remember what color the plug was. You make jetting sound simple, so I'll give a try. I'll switch to the 140 and go back to 87. I'll let you know how everything went when im done.

 

[wolfmanbean]

Wow changing the main jet was really easy. Oddly enough my jet kit didn't come with a 140. It's an HMF jet kit, which they reccommend a 140, but didn't include it in the kit. So i intalled the lowest one it came with, which was a 142.5. I also switched back to 87 octane. It goes from idle to rev limiter without any popping or stumble. I also tryed to take a high speed run. I could only get 45 mph. before I ran out of road. Not to many straights were I live. Thanks for all your help.

 

[aces3]

No problem thats wierd about the jets but I had thought about stepping up to a 142 several times.

 

[oldschool1921]

I live up north and only about 700ft above sea level and I run the 142 with 91 octane and have never had any problems. (with the HMF/K&N)

 

[07350r]

I highly recommend getting a Dyno Jet Jet kit and simply following the instructions to the detail jetted with your air box lid on. Very simple if you just follow the instructions, I have installed over a dozen and they are awesome, best on the market in my opinion. Also, never run less then 93 octane if you don't want carb problems, most atv manufacturers have a sticker on new machines that recommends only premium fuel in there motors. In spite of what some say, their is a big difference, especially with this ethenol crap which actually lowers octane to start with and absorbs moisture.

 

[Snowdog]

I have the DynoJets and only run 91 octane and have no problems. I would jet it correctly, run the highest octane and try it again and see if the plug fouls again.