Jump to content

Xr400r gordon mods jetting and needle.

Recommended Posts

Hello, this is my first post. I recently did the gordon mods, grinded out header welds to about .906", 6 holes in the baffle, pulled the snorkel and replaced with a coarse uni prefilter and replaced stock filter with uni filter. I use 92 octane ethanol free fuel. I'm close to sea level at about 90 degree weather at the moment. 

I've been playing with the jetting trying to find that magic combination. I haven't had any outstanding issues but I want to see if I can improve upon what I have. 

First I tried 58/158 and it seemed to like it better with the mixture screw turned real low(less than 1 turn). Then I tried 60/160 and I couldn't get it to start. Then I did 58/160 and it would start but it would run like crap. Then I went to a 54/154 and the bike seemed good. Then I dropped the clip on the needle down 1 size to raise the needle (richen the midrange) and what is odd is when starting the bike the idle was really high with choke off but low/surging idle at half choke. Turned out the fuel mixture screw from 1/2 to 3 turns and the Half choke idle became high like the no choke idle. I then loosened the idle screw a bit and all seems good. 

I just think it's strange how the bike acts like it wants more fuel after I richen the needle a slot. I'm thinking of experimenting and doing the 60/160 jet again to see what happens. 

Any suggestions?

Also since I'm using ethanol free fuel and ethanol has 33% less energy than gas, I would need 3% less gas than someone using normal pump gas not that it's a big difference.

Share this post


Link to post
Share on other sites

Are you sure the float needle valve is working and stopping the fuel coming in? I had the same kinda problem on my old CBR600 and the thing would run great but then flood out if i left it idle for more than 10 secs.. the float needle valves had a tiny bit of crud in them and it was over filling so much that fuel was coming out the the main needle at idle.. this of course messed up all the other setting as i was chasing my tail.

Share this post


Link to post
Share on other sites
13 hours ago, courior said:

Are you sure the float needle valve is working and stopping the fuel coming in? I had the same kinda problem on my old CBR600 and the thing would run great but then flood out if i left it idle for more than 10 secs.. the float needle valves had a tiny bit of crud in them and it was over filling so much that fuel was coming out the the main needle at idle.. this of course messed up all the other setting as i was chasing my tail.

The carb was recently cleaned and I inspected/adjusted the float. I don't have any outstanding issues at all. I have re-jetted to a 60/158. Bike handles fine. This jetting is probably slightly rich but I like it like that because it keeps the bike cooler when trail riding and makes hot starts much easier than before. My only complaint is the throttle is very sensitive after raising the needle up one notch(richening the mixture). Makes turning around on tight trails much more difficult. I have to ride the clutch more than I should.

Edited by John Deer

Share this post


Link to post
Share on other sites
6 hours ago, John Deer said:

The carb was recently cleaned and I inspected/adjusted the float. I don't have any outstanding issues at all. I have re-jetted to a 60/158. Bike handles fine. This jetting is probably slightly rich but I like it like that because it keeps the bike cooler when trail riding and makes hot starts much easier than before. My only complaint is the throttle is very sensitive after raising the needle up one notch(richening the mixture). Makes turning around on tight trails much more difficult. I have to ride the clutch more than I should.

This is all worthless without location.

I can help if you're high altitude. I also raised my needle 1 notch. and love it.

Others will be able to share their combination if you're at sea level.... midwest, northeast, etc...

We need to know your local climate and style of riding.

 

One thing I did notice in your post is that you had your fuel screw at less than 1 turn out and decided to go RICHER? That was the wrong call. Does your bike now cold start with no choke by chance? If it does, you will be caking the cylinder and valves with carbon when you ride.

Set your pilot size and idle speed (correctly) FIRST. Then worry about the needle and main. You should not be changing both jets at the same time.

 

P.S. You sound like me a while ago..

Edited by Jack the Dogg

Share this post


Link to post
Share on other sites
32 minutes ago, Jack the Dogg said:

This is all worthless without location.

I can help if you're high altitude. I also raised my needle 1 notch. and love it.

Others will be able to share their combination if you're at sea level.... midwest, northeast, etc...

We need to know your local climate and style of riding.

 

One thing I did notice in your post is that you had your fuel screw at less than 1 turn out and decided to go RICHER? That was the wrong call. Does your bike now cold start with no choke by chance? If it does, you will be caking the cylinder and valves with carbon when you ride.

Set your pilot size and idle speed (correctly) FIRST. Then worry about the needle and main. You should not be changing both jets at the same time.

 

P.S. You sound like me a while ago..

I'm at sea level. About 300 feet. I trail ride through long forest trails. Lots of turns mostly 1st and 2nd gear. 

Specifically, I live in Houston and I ride at sam houston national forest.

Today I adjusted my clip back to the middle position which fixed my sensitive throttle after reading that this was a common side effect of a overly rich needle.

So now I'm at 60/158 middle notch on clip. Mixture screw is 1.5 turns out and if I richen more or lean the screw by turning I can hear the rpms decreasing so I am confident the pilot is adequate. I cold start it with full choke. It will sputter for a couple seconds and then I switch it to half choke and it typically starts after a few kicks then if it's been 3 days.

I have checked my spark plug but I don't spend long periods at wot on my rides and I forget to check before letting the bike idle for a short period. When I did check my spark plug it was pretty dark. The bike could also be consuming oil though as the bike hasn't been riden regularly since 2005 which is why the plug may be dark. I'll have to check my dipstick next ride to confirm.

Edited by John Deer
  • Like 1

Share this post


Link to post
Share on other sites

Sounds like you're on the right track. 

Mine will actually start and idle on full choke though. I usually drop it to half within a few seconds, then off after about 20-40 seconds... temperature dependent.

Good luck, and keep it between the trees!!

  • 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:


×
×
  • Create New...