We are planning another trip to CO this summer to ride Tin Cup, Hancock and Mt. Antero. Last time we were out there my 1988 Fourtrax 300 2X4 ran OK but not the best. It even sounded different when we got up to around 8000 to 10,000 feet. I still had enough power to run as long as I didn't get in a hurry or tied to run fast. I was told I needed to re-jet the carburetor. My question is will it hurt it if I DON'T re-jet the carburetor. I can deal with the loss of power because we don't ride fast anyway. Does it do any harm to the motor?

 

Your machine runs richer when going up in elevation, same as higher temps. You won't harm your machine if you don't rejet. You will waste fuel and possibly foul plugs but thats it. Now if you were jetted for higher elevation and ran at sea level, then your running lean and could harm the motor if done for longer periods of time.

 

Jetting is just another name for getting the ratio of air to fuel correct. One way is to change the jets, which control the flow of fuel...or change the amount of air. Either method is correct, but in your case, because youll be at altitude for a short while, and then go back down to lower elevations, the easiest way for you to 'rejet', is either remove the air box lid, when you encounter the sluggish driving from too rich, or prep the lid ahead of time, with a few 1 inch diameter holes. When youre at lower altitude, keep the holes covered by duct tape or nylon plugs, or both. Then as you go up, remove the tape, one by one, until it runs right. Then when you come back down, retape the holes, to prevent running too lean.

1988TRX250R, has it right...too rich will only waste money or soot up a spark plug (bring an extra, or use an iraduim plug, they resist fouling better).

 

[quote]
Originally posted by: hondabuster
prep the lid ahead of time, with a few 1 inch diameter holes. When youre at lower altitude, keep the holes covered by duct tape or nylon plugs, or both. Then as you go up, remove the tape, one by one, until it runs right. Then when you come back down, retape the holes, to prevent running too lean.[quote]

Very creative! That's such a great idea, that I'm going to do just that. I'll be riding locally from 5000' to 10000". Thanks hondabuster.

 

what they said....

Tin Cup and Taylor Res area is sweet,,,,,,have fun,,,,,i miss that place

 

Thanks for the info! I will do the air breath cover method. No more than we'll be riding in that area that will be best for me.

We REALLY liked the Tin Cup area. The last time we were there we rode from St. Elmo to Tin Cup and back. Then we rode to Hancok and on past quite a way. THEN we rode Mt Antero!! I loved that the best. We didn't quite make it to the top because we ran out of time. I had my ATV and we had also rented one and it had to be back that afternoon. This year we will Antero first so we can go all the way to the top!!

Again, thanks for the info on the air breather!!
[img]i/expressions/face-icon-small-smile.gif[/img]

 

i live in illinois, how high can i go before jetting problems

 

http://forums.atvconnection.com/mess...word1=altitude

Your 300 should have room in the lid for two TPI valves.......