Jump to content
Sign in to follow this  

I'm stumped. Four-Stroke keeps fouling plugs.

Recommended Posts

The bike is an '04 CRF230F. It has a decorked intake and exhaust, the carburetor was rejetted with a 132 [from 102] in 2007-8, stock pilot, and an aftermarket needle. I Haven't had a problem between now and when I did the mods. No indications were given that there was going to be a problem, I tried to start it one day and it would only start on full choke. Take it off and it dies. I took off the carburetor and cleaned it really well, and still nothing. I replaced the spark plug, and it ran completely fine after that. It ran for about a good 2 hours before it reverted right back, though. After spending almost 15 years on things with engines I have NEVER seen a four-stroke foul plugs like that. Considering that the jetting changes were made around 6-7 years ago, is it possible that could be the source of the problem? I was considering going down to a 120 as a I have heard 132 is not optimum. Or, could the rings on the Piston be defective, or possible something else where I could be getting excess oil leakage? 

Share this post


Link to post
Share on other sites

Can be mulitple issues, so you have to isolate

 

Compression test

 

Leak down test

 

If you have not cleaned the choke plunger, replaced the pilot jet, and adjusted the valves, do all that first.

 

There is NO REASON to change jetting as the years go by.  Jetting requirements do not change with time.

Share this post


Link to post
Share on other sites

Can be mulitple issues, so you have to isolate

 

Compression test

 

Leak down test

 

If you have not cleaned the choke plunger, replaced the pilot jet, and adjusted the valves, do all that first.

 

There is NO REASON to change jetting as the years go by.  Jetting requirements do not change with time.

I will perform those steps you suggested. The reason for wanting to change the pilot jet it that someone did Dyno/Air Fuel tests with stocks 230's and found the optimum setup to be a 120 Main, Accessory Needle, and 45 Pilot. These were changes I was considering before this happened. 

Share this post


Link to post
Share on other sites

Here is a Picture of the brand new spark plug after not even 2 hours ride time. It's one step 'hotter' than recommended for stock. EZf3c69.jpg

Share this post


Link to post
Share on other sites

I think you're right, put the smaller jets in it. Try it and report back.  Put a stock plug in it too.

Edited by Slackkinhard
  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×