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XR100 Carb Issue

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Hi all, new here, have searched thoroughly before posting however unable to find the advice I need.

My mechanical knowledge is sound, however I am reasonably new to the Keihin PD carbs that are on the XR100's.

My issue is this, I have started the bike after about 18 months of non-use. It went after about 10 kicks, and ran adequately, almost well, although at half choke. The bike would not idle/run with the choke off, and would bog out under full choke, but at half choke ran like a dream - I figured a carb clean was in order.

After taking the carb apart, removing the jets and thoroughly blasting everything - including the insides of the jets with carb cleaner, cleaning and testing the spark plug, and refuelling with 98 octane premium fuel, the bike starts first kick with no throttle, and idles at a good speed. However, the idle is very 'poppy' and blows a somewhat high amount of smoke. The bike runs like a dream from zero to about half throttle, however past halfway the bike will just bog completely. It will not turn off as if the kill switch has been hit, but is just absolutely non responsive.

I am familiar with the main jet, idle jet and i think what is the pilot jet?? which acts according to the fuel screw which is on the underside-front of the float bowl, but unfamiliar with the needle jet/needle clip. All these parts are stock and have never been modified, bar potentially the fuel screw, which should affect my seemingly rich idle, but not the death under high throttle. The engine will not rev with gentle >1/2 throttle, nor instant >1/2 throttle.

I am sure the float bowl was sitting so that the top edge was parallel with the seam in the float bowl/top carb, could this be an issue?

Have heard that the main jet may need changing, however it is the stock jet that worked beautifully prior to the carb clean, albeit under half choke. The gasket between the engine block and the manifold I believe maintains a perfect seal.

Any help would be appreciated.

Drew.

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I'd measure the float level and set to spec., and make sure needle clip is in groove to spec.  Are the valves (and cam chain) properly adjusted.....?  Fuel is fresh....?  Tried a new spark plug....?

Another little trick.........  With it running, shut the gas off and see how it runs and takes throttle as it runs out of gas (leans out).

Old School Al

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Also I should have mentioned........  Make sure you have a clean air filter.  Make sure the choke plate is working properly and staying clear open when the choke is in off position...........and closed in choke position as well.

Old School Al

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Thanks Al, I have just realised that my float measurement was taken with the carburetor level with my benchtop, not when the float just began to touch the needle valve, so this needs addressing. Spark plug is new. Air filter may need to be cleaned. I do not believe the needle clip has ever been changed, however I am unsure of how to adjust it, could you spare any advice.  Same with the valves and cam chain. 

I seem to have solved my spluttery idle by adjusting idle screw with pilot screw in tandem.

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Yep, need the float to be set correctly.  Make sure it isn't racked (twisted) also.  Best to get a manual before you dive into this project ............ it will be well worth it!:thumbsup:

Old School Al

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