Plug fouling

Glider Boy

Member
Jun 30, 2001
1
0
Plug fouling on brand new bike

I have a new KDX. Every time I ride it I end up with a fouled plug. I have taken it back to the shop that I purchased it from and was told it was the type of oil that I was using. I therefore changed from a standard to a semi-synthetic. At the same time I adjusted the fuel/oil mixture to 40:1. It didn't improve the problem. This is a new motorcycle, should this happen? Should I go to a hotter plug or rejet? Help, I need advice.
 
Last edited:

David Trustrum

Subscriber
Jan 25, 2001
1,396
0
No it should not happen. New bikes are usually set up too rich as it is the safe option. If you are using a decent oil at the ratio recommended on the bottle then it will not be the problem, ever.

Once a plug is wet fouled it may never recover properly so change it. Use the recommended heat range.

I assume you are not leaving the bike to idle for minutes at a time & the bike is run in by now. Start playing around with the jetting particularly at low throttle positions (Pilot etc). Use the recommendations from the website & various threads as a starting point.

PS by going to 40:1 (assuming you were using more before) you have made the jetting richer as there is more fuel increasing the need to rejet.
 
Last edited:

BRush

Lifetime Sponsor
Jun 5, 2000
1,099
0
Fouling the plug is more of a jetting issue than it is an oil issue. I run Mobil MX2T at 40:1 and I almost never foul a plug. The KDX as it comes from the factory is jetted way too rich. Read through this jetting article. Recommendations are give under "Starting Points" at the end of the article:

http://justkdx.dirtrider.net/carbtuning.html
 

OLD-N-SLOW

Member
Nov 21, 2000
168
0
Go to the just kdx web site and rejet as it says. Also lots of good info there.
http://justkdx.dirtrider.net Go there and learn.
Yes, rejet it makes a huge difference. As far as oil and ratio goes, do a search
on the subect and prepare to be overwelmed by posts.
I would say a large percent of people use a synthetic between 32 to 50:1.
I do not mean to start a long oil post, just search and make up your own mind. And yes, by changing your ratio from 32:1 to 40:1 you made it richer.
Less oil ,more gas=richer.
The 200 and 220 are both jetted verry rich from factory.
Steve
 

David Trustrum

Subscriber
Jan 25, 2001
1,396
0
I use the brake to slow. I think you mean you type too slow.

Sorry an incarnation of an old school teacher must be channelling through me.
 

Canadian Dave

Super Power AssClown
Apr 28, 1999
1,202
0
Yes glider boy you do need to rejet. Once you've checked out the carb tuning guide on the JustKDX web page get back to us if you have any questions. While you are there be sure to check out the section on new bike prep. You'll want to grease your suspension bearings soon.

David