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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

XR125L-5

The bike has developed a very erratic idle.
just standing ticking over the revs will build up alarmingly and then slowly reduce. I have checked the throttle cable operation and it has the correct free play and the Throttle valve hits the bottom of the carb body but still the best way to bring the revs down is to wind out the throttle stop screw. I have checked and cleaned the carb this afternoon but no improvement. Any ideas why?

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  • Posted 2 years ago (27 September 2012 20:56)

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jaffa90

Joined:

Mar 09

Posts: 8930

jaffa90 says:

tickover

Welcome geoff,obviously the fuel flow is ok,

could be a weak throttle slide return spring,

could be the choke plunger not seating,

could be the fuel level varying in the float chamber,

check float movement,

check needle valve seating and float shut off position (measurement)  by holding the carb upsidedown and try blowing air into the fuel intake.

Sounds like you may have crap coming from the tank preventing correct fuel level shut off. 

 

[This Reply has been modified by the Author]

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kcmc

Joined:

Jan 08

Posts: 7534

kcmc says:

Honda XR 125L 2005?

Hi 2012geofff and welcome to the site:smile

I think you mean its a 2005 model?

I think also that this could be a air leak,probably the O ring rubber seal at the carburetor face to the manifold or the O ring and gasket joint between the head and manifold.But probably the O ring, carb to manifold (as you have removed it,and refitted it)or just not seated or fitted properly?not tight enough allowing air through.Good Luck

KCMC:tongue:

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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

XR 125L

Many thanks.
It's a good point about the float in the carb and possibly an air leak. The bike has been used in some odd places during the summer and I gave it a full service on my return. Maybe it's my poor workmanship. I will remove the carb over the weekend and check all the points you have made.
Many thanks. Geoff

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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

XR125L

Would you be kind enough to give me a bit more help?
I have removed the carb and checked all the gaskets and 'O' rings. I have also removed the float chamber and checked the float movement. I have cleaned all the parts and reassembled with a smear of liquid gasket between the faces-just a smear.
I turned the fuel on ready to start and fuel ran out of the carb overflow. Sticking float me thinks. After rocking the bike the fuel stopped over flowing. The bike started well and ticked over better than usual but then up go the revs and the only way to get them down was to switch the ignition off. I eventually got a tick over again but then on the throttle after a blip the revs take ages to fall back to tick over. The clue may be the carb overflow event so my question is " if the float is sticking in the bowl would it cause the revs to fluctuate without me touching the throttle?
I have searched the full service manual for ideas but it offers no advice.


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jaffa90

Joined:

Mar 09

Posts: 8930

jaffa90 says:

tickover

As my first post really,the fuel level is varying.

Does the float, float:blink:?

Did you check the setting of the float shut off position?

Did you try to blow through the fuel inlet (carb upsidedown) to see/feel if  it was sealed?

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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

tickover

Thanks for your comments jaffa90.
I will remove the float and check that it does float.
The service book indicates that the float level should be 14mm so I will make up a gauge and check.
I did blow through the fuel inlet and all seemed OK.
There were some very small particles in the bowl and after cleaning I thought that was the fix but no.
I will go through the process again carefully.
Thanks for all your help.

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jaffa90

Joined:

Mar 09

Posts: 8930

jaffa90 says:

needle valve

I suspect the needle valve (operated by the float) has a hardened rubber point,if so check for any marks/wear.

Also if possible fit an inline filter inbetween the fueltap and carb.

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kcmc

Joined:

Jan 08

Posts: 7534

kcmc says:

Honda XR 125L 2005?

Hi again Geoff

You don't need to make a measuring tool for this model(but if you have one ,go for it:smile) if not,just fit a clear piece of pipe to the float bowl drain,then with the fuel tuned on(it hasn't got a diaphragm tap so no worries there) open the float bowl drain screw with the clear pipe held in a U shape,the fuel will only flow to the level of what the float allows.You use the straight edge of the float bowl jointing surface as a guide,if the fuel level if above this its to high and will flood the engine or even over flow out of the same pipe you are holding.If the level is below this line its to low and could cause fuel starvation at higher RPMs,can't find a picture of this,so i hope you get the idea?Good Luck

KCMC:tongue: 

As you can see this level is a wee bit to high.It should be level with the joint or at the bottom edge,not above like this picture shows.

 

[This Reply has been modified by the Author]

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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

eratic tickover

Spent today investigating the carb. After reassembly the bike runs a better but it still takes several seconds to return to tick over from a quick dab on the throttle. I will contact my local Honda dealer and ask if there is a carb service kit. Your point about the float valve is a good one so I will certainly replace that item.
Thanks for all your help I really appreciate the time you have given to suggesting a fix.
When I have replaced items I will let you know how it runs.
I will get and fit a fuel line filter. That foreign fuel running on reserve in the tank may be part of the problem.
Thanks again  

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2012geofff

Joined:

Sep 12

Posts: 8

2012geofff says:

eratic tickover

I like that idea Kcmc. I made a tool out of some thin ally but with your suggestion I will be able to see if the float is controlling the fuel level correctly. I will clamp the pipes in place and try running the engine.
I am planning to get a carb service kit (if such a thing exists) from my local Honda dealer but I will at least replace the complete float valve assy.
Thanks for taking the time to help solve my fueling problem.
Rgs G

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