97 EXC jetting problems


I recently bought a used 97 300 exc from a friend. The bike was purchased new in 98, and ridden mostly in the 99 season. It set idle for most of 2000 and the first part of 2001. The problem I am having is getting the jetting set up correctly for me. My friend was an intermideate rider and had the bike set up to run quick all the time. I have been out of riding for almost 12 years and find the bike really quick in the tight woods. If the bike is ridden in the low to mid range it does good, but as soon as I hit the top end it lags for a second and kind of blows smoke out of the exaust. If I ride in open country where I can keep it open I have no problems. The bike has a fairly new top end, and I am using Golden Spectro at a 20:1 ratio. (12 ounces to 5 gallons). What I would like is to have the jetting set for bottom end and mid range power, but still have the top end when I need it. With my currnet jetting I have already fowled two plugs in two weeks.
Any help would be appreciated.


At 12 oz. to 5 gal. your at something like 55:1, definetly nowhere near 20:1.
3 oz. to a gal. is 45:1 and 3.2 oz. to a gal. is 40:1.
I run my '98 KTM 300 EXC at 40:1. I live in Ohio, about 300-1400' above sea level, temp ranges from 50-90 degrees F during my riding season, here is my jetting: 172 main jet, 42 pilot jet, N85D needle in the 2nd clip position from the top, 1.5 turns out from fully seated on the air screw.
Not much difference from '97 to '98. Go to www.holeshotktm.com, click on message board, click on jetting forum, and there you go, more jetting info for KTM than you can shake a stick at !
Do you have your owner's manual ? There is a good section in it on jetting.


KTM Mike

Mi. Trail Riders
I have a 97 300e as well. The suggestion to look at the holeshot forum on jetting will absolutely get you the answer you need!

Based on advice on the holeshot forum, I ended up going to a #7 slide and a 1369 (I think that was it) needle to fix all my low RPM jetting woes. 175 main, 42 pilot, clip in #3 ( i think... ) and air screw 1 1/2 turns out. I use Maxima at 40 to 1. Also - I found that golden spectro really caused the power valve to carbon up real bad - supposedly the maxima burns cleaner - time will tell. Good luck!


Thanks for the feedback. I did visit holehotktm.com the other night, and got some good information from it. Thanks for also clearing up the ratio issue with me. I don't have the owner's manual that came with the bike, but have considered buying a shop manual for it. My conern with that is it may be a bit technical for me. I still don't understand all this jetting stuff.
My way of thinking was that if I am fouling plugs, and the bike seems to be running a bit rich, it must be because of the amount of premix that I am putting with the gas. But now I am concerned, after finding out that I am using less premix in my gas than anyone on either site, that I may be causing problems elsewhere (?).
Seems like a bunch has changed since my 87 YZ 250.....:scream:


Sponsoring Member
It took me awhile to catch on to the jetting vs premix ratio thing. When it comes to jetting you are working with fuel (gas) to air ratio. When you add more oil you end up with less gas in the same volume of fuel mix. The more oil you add actully makes the jetting leaner since the oil does not contribute to combustion. By running a ratio of 55-1 your carb jetting may have been on the rich side (more gas, less oil mixing with the air). If you increase the ratio to 40-1 or 32-1 you will find the jetting will seem leaner. First settle on a premix ratio then work with the jetting. You may find going to a 40-1 ratio will make the bike run how you want.