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- Fuelling and Intake ( https://www.xt660.com/forumdisplay.php?f=207)

- - Fuelling Fix ( https://www.xt660.com/showthread.php?t=55)

Yes that can be a solution but please make sure you consult Kev fully as there are many items at play that determine surging and snatchy behaviour, the four main culprits usually are:

1) incorrect idle speed (tickover) which should be set between 1450 to 1500 rpm.

2) incorrect TPS angle, too close and it will shut the fuel prematurely, too open and it would flood the engine.

3) the least suspected one and often one of the main causes is: the level of wear in your rear hub dampers, otherwise known as cush drive rubbers, when they are worn they allow too much play and with that I would also check for a correct chain tension and wear of both chain and sprocket.

4) the one which nobody bothers to check is the side stand switch, if yours is mucky and dusty, it may causes it to stay in the open position or flick between open and close and makes the engine cut off automatically at random, so it's always worth keeping it clean and protected with WD40 or similar preserving lube.

Thought I would post my observations.
Just bought a new 2009 XTR.
No obvious surging but very jerky/lumpy? at low revs.
Factory CO 13
Increased CO to 20 - no change
Increased CO to 25 - much smoother
Experimented by 5's up to 40 with very slight changes and have settled on 38.

My observations too (changing CO and effect on RPM at idle):
TPS 16 , CO 11 (from factory)
CO RPM idle
11 1240-1270
15 1240-1270 much healthier sound, smooth low end
18 1350-1390 less pops
19 1310-1350 less pops
21 1310-1350 no pops at all
For now, I left it at 18, planning to rise RPM up to 1400 and read plug for final decision.
And maybe changing TPS to 17.

Effect of altitude on standard C01 setting

I have a 2008 XTR. The standard C01 setting on my particular bike is 12. I assume that this setting is based on the assumption that the bike will be run at sea level. I live at 1600m above sea level, should I reduce the C01 setting to compensate?
Also, I have had issues the engine stalling at idle speeds when trying to accelerate. Would lowering the C01 also remedy this issue?

Cutting out and running rough!

I have just done the hold select and reset thing on my XT660X and bumped the CO level from 6 to 15 and what a difference, no surging, no cutting out and much smoother running. How many people have sold the bike because of this problem or Yamaha agents made ripping owners off for a simple 60 second fix?

Cheers for the fix.:eusa_dance:

Free advice off likeminded individuals! Brilliant. Adjusted my xt sumo from 8 to 16. Stunning difference when plodding around town. This bike is perfect for 90% of the roads where i live on the isle of man. Wearing my boots out is the next issue.

Quote:

Originally Posted by JMC (Post 174)

DISCLAIMER: YOU DO THIS AT YOUR OWN RISK AND MAY VOID THE MANUFACTURERS WARRANTY.

Step 1. Before turning the ignition on press and hold Select and Reset buttons, turn the ignition on and keep holding both buttons until you see the Diag screen appear.

Step 2. Press Select once to toggle to the CO MODE

Step 3. Press both Select and Reset together. Hold for about 3 seconds to enter co mode. The number displayed is the cylinder selected (genereric computer for all Yamahas) You need to select 1, Press select to scroll up and Reset to scroll down.

Step 4. Press both Select and Reset simultaneousley for a few seconds to see the setting for the selected cylinder. This number will be different on every bike and has no relationship to the mixture its just a number it can range from -128 to +128. Write down the number and keep it in a safe place in case you need to return to your original settings.

Step 5. Pressing select will increase the value (richen the mixture), pressing Reset will decrease it.

I initially increased my setting 5 digits from 10 to 15. This smoothed the bike out but still had a little surging. After reading what Alan and others have said it should be safe to increase your original setting by up to 10 digits. I will now adjust mine up another 3 to 18.

Step 6 To exit CO mode, turn off ignition.

Noticed benefits. The bike is now very smooth to ride and on my 1st adjustment took out almost all the surging/jerkiness. This has made the bike much easier to ride through corners where i can now get on the gas earlier in the corner increasing the mid corner speed.

More info can be found on the forum: fueling fix.

Hi, can this fuelling fix be used on o7 xtx models with the exhaust sensor? deffo want try it as my bike is almost unrideable at speeds of 30mph and below.

Quote:

Originally Posted by bigTrev (Post 153803)

Hi, can this fuelling fix be used on o7 xtx models with the exhaust sensor? deffo want try it as my bike is almost unrideable at speeds of 30mph and below.

These XT's are very lean for emission control. Up your CO & fit one of my fuel mods, this will help with the surging. The CO can only adjust the fueling at part throttle, my fuel mod can adjust the fueling across the rev range.

Well i experimented today with the co level, standard setting was 13 so i upped to 19. didnt notice any difference, so upped again to 23 and still cant see any improvement. Next step, remove snorkle?? or "the Kev mod" or both?

Quote:

Originally Posted by bigTrev (Post 153864)

The results would differ depending on what ECU you have on your bike.

http://www.xt660.com/showthread.php?t=8546