[tjworthen]

I had an ATV mechanic put in a Dynojet and remove the stock jet that came in it. Steadman's in Utah is where I bought the machine. I don't have the stock jet anymore and I was wondering what people on this forum think of Dynojet.

I live at 6700 feet in elevation and ride mostly between 4900 and 10000 feet.

I feel like the bike is running rich. It has backfired on me at times when coming off the throttle. I am not the best at tuning a carb, but would love to learn.

Any thoughts out there on this.
THanks,

 

[namniar79]

It could run rich if you don't have the increased airflow. The basics consist of high flow exhaust and air filter. When you jet all your doing is increasing the amount of gas to the engine which will make it run rich, with more air it will compensate for the gas and should solve your problem assuming the kit was installed correctly. Or maybe you could play with the air/fuel mixture screw and correct it. but the pipe and filter would bring out its full potential that is if you don't already have these.

 

[vettepin]

the pop will go away with a 1/4 turn out on the pilot jet screw , this will give you a richer mix when letting off and stop the pops.

 

[Sparkey]

QUOTE ("namniar79")

It could run rich if you don't have the increased airflow. The basics consist of high flow exhaust and air filter. When you jet all your doing is increasing the amount of gas to the engine which will make it run rich, with more air it will compensate for the gas and should solve your problem assuming the kit was installed correctly. Or maybe you could play with the air/fuel mixture screw and correct it. but the pipe and filter would bring out its full potential that is if you don't already have these.

I take issue with the statement that "when you jet you increase the ammount of gas."

If you are jetting for higher altitude you should use a smaller jet, thus decreasing the ammount of fuel to compensate for the thinner air at higher altitude. If you do modifications that increase the air flow then you may indeed need to go to a larger jet to increase the fuel delivery.

Jetting is more than just increasing the fuel, it is tuning the carb to suit your needs. The effects can be seen by reading the spark plug.

Black and sooty indicates a too rich condition, brownish color is good.
White indicates too lean.

Fuel ratio is determined by the main jet at 3/4 to Wide open throttle, the Jet needle taper and position from 1/4 to 3/4, and the angle of the cut away on the slide below that. The idle mixture is controlled by the Idle jet, or pilot jet, and the adjustment of the Idle mixture screw.

 

[tjworthen]

Time has passed

It has been a while since my intitial post. I have been hesitant to change the jets and so I have always resorted to adjusting the carb. Most of the riding on this machine has been between 6000 and 9000 feet with the occassional trip at 4200 feet.

The machine's is jetted with a Dynojet 118 and needle. I am at the point where I am tired of it running lean. I ordered a stock Honda Keihin carb rebuild kit. It is time to do so anyways. I will be either installing a 125 or 130 main jet, I ordered both.

I have not been impressed with the Dynojet setup. Everything else on the machine is stock. It has been hard to start, especially in the cold. It backfires either from letting off from full throttle to idle or from mid throttle to idle depending on how I have the bottom front jet screw set.

 

[rich450es]

so you have been having all these problems with the jet kit for 5 years and counting ?......WOW !!!!!!
if you change back to the stock jets you will also need to get a new stock needle also

 

[SSpeckerwood]

so are you still in utah?? i've bought all my bikes from steadmans and still live in tooele.

 

[tjworthen]

Yea & Yea

5 years....yep. It's condition has always been to me "tolerable" as the engine didn't run too hot, has never burned or used oil, and has been a reliable starter even if it has been my most stubborn bike to start and warm up in the winter compared to my other wheelers.

Anyway, I finally decided to work on the carb tonight even though my rebuild kit hasn't arrived yet. My 13 year old has recently decided he likes riding the machine and he rides it harder than I do so I thought it was time to tune it better. It really only took an adjustment to the slow jet needle (opened it up a bit) and then adjusted the throttle idle. I got rid of pops. I cleaned the carb too, that probably helped a bit, but it wasn't too dirty.

Steadman's huh!, that is where I bought this machine. I live just above Kamas. I never knew what size jet they put it in when I bought it and it wasn't long after I bought that I had the Dynojet put in. I'll tell you though, I agree with most people on this board that a Dynojet Stage 1 kit really doesn't do much.

Funny, looking back at my original post, I laugh a bit thinking that the bike was running rich.