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michaecal121

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Got a Chinese pitbike 110cc and I can't seem to get it to run... it has spark compression and the timing is setright... I have cleaned outthe carb 3 times and hve tried tuning it about 6 (resting needle clip) i have tried a lot of things and this is what I have found out... itwont start at all when on choke... when the choke is off I have to hold it wot in order for it to start but then just sputers out and dies... I have cleaed both jets and still having the same issue... anyone know what's wrong?
 

Cordogs

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Ok sounds like you've covered most basic bases, what kind of carby have you got. Have you checked the fuel tank for blockage? Is your valve adjustment correct?

Usually it's something simple mate, check these things^^ and if your not sure what your carby is take some pics of it, one of the boys will know what it is.

Cheers
 

my67xr

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with the air filter off the carby, look into the through the inlet of the carby, can you see the slide sitting a couple of mm off the bottom
 
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rotn50

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You got good fuel flow from the fuel line and carby bowl mate?
 

zwebx

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did you check for airleaks?
take the intake manifold off, leave the carby on the manifold removing the fuel line of cause... cover the head end of the manifold (airtight your hand should do) and blow into the carby... you should be able to hold a bit of pressure... if you cant try to feel where the air is coming from and seal it up (as straight sanding of the carby is not uncommon if there cranked really tight)
 

headsmess

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aye. check carb for leaks firstly. obtain intel on fuel flow by unscrewing drain or having carb pee on foot when removed... is all good? hmmms.

pop carb apart. check that there is some sort of passageway from float bowl chamber to the atmosphere... a kinked hose or blockage will stop air pressure pushing down on fuel in bowl which is what pushes fuel up the jet into the lower pressure area in the venturi.

remove any hoses except fuel line, blow with air in both directions.


spark plug.

what happens when you pour a couple of cm3 of petty down the intake and kick her over? an easy start with a quick revout then die indicates good engine, bad carb/fuel issue. nothing but a sore foot points to something nastier...
 

michaecal121

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Choke is a twist type? Nota push. Gas tanks and all lines have been cleared and cleaned. The cylinder is getting gas. I haven't checked the vales I'm not sure how to do valves on a dirtbike (if anyone has a link please post) I will check for leakage when I get home.

If ithelps the spark plug was covered in gas I cleaned the plug and took the carb ff and cleaned it aoutand since then thhe plug has nothad any gas on it annd seems to be running lean

Hope this info helps will keep you updated on anything I find out.
 

michaecal121

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Well found oout that the valves weren't the issue I ended getting it started and rode over to my buddies house to have him figure it out.. he told me it has low compression but not super low compression so he runed it up and got it working amazing. Now about 3-4 hours. Later i can't start it choke on or off it won't start! It has started to shoot blueish color smoke out the Carb about every 4th or 5th kick.. the spark plug looks fine its getting tje right mixture but idk why it wont start?

Does anyone have any ideas??
 

Cordogs

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Bluefish smoke usually means oil rings bud, just curious what was the valves set at? And what colours was the spark plug showing?
 

rotn50

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Still got spark lad, if so have you tried another one? Magneto terminals aren't arcing onto the frame?
 

michaecal121

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Soi got the bike running and everything but now 3-4 hours later I can't get the bike ti evven start!?! About every 5th kick with the choke off it blows back through the carbi..

Does anyone know my issue??
 

michaecal121

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Yes I stiill have spark haventt checked the magneto cuz it hhas had spark.. I don't know what my valves are set too. I did notice though that when I would put my hand over the carb intake and kick it over it would spit the "bluish smoke" it left gas all. Over my hand.. Im not. Sure what this means... any one havee any ideas??
 

michaecal121

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Yes I will check them when I get home from school. How could the valves be the problem? Is it just cuz! They won't seal? Or?? Could youu explain what it is the valves would be messing up.?
 

needapitty

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Yes I will check them when I get home from school. How could the valves be the problem? Is it just cuz! They won't seal? Or?? Could youu explain what it is the valves would be messing up.?


Because the valves get out of spec over time. The valve adjustments ensure the valves continue to open and close properly and at the same places. If they begin to drift out of spec and are not dealt with, you'll prematurely kill your engine.

Tight valves will have a tendency to "cup" their edges. Common in intake valves. Tight vavles are being pulled upward into their channels harder than they should be and the result is the edge of the valve will be bent inward as the pressure over time takes its toll. When put back into spec, it is too late. You now have this open gap around the edge of the valve that no longer seals. Loss of compression, blowback, etc.

Loose valves hang down lower than the should. Too loose and they won't seal properly causing gases to escape prematurely or worse, hang so low that the piston actually strikes the valve even as it attempts to close. Very destructive.

The tolerances we are talking about here are very fine.

What a valve adjustment does is compensate for changes in spring tension over time.

Valve adjustments are just preventive maintenance to ensure your engine will survive.
 

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