Wont hold an idle revs up and down

Has it been serviced recently? Check the basics for petrol engines. Clean air filter, clean fuel filter, clean oil and oil filter. Is the battery fully charged? Is there fuel in the tank? (Yes, I've done that one). If there is a fuel tap fitted to the bottom of the tank? Is it in the open/run position?
Yours sounds like a fuel supply issue. How old is the bike? Does it idle smoothly when it does run? A good starting place is the fuel pump. Some scooters use a vacuum system for the fuel pump and the rubber diaphragm inside the pump wears out. This doesn't pull the fuel through fast enough and leaks air into the fuel system. This starves the engine of petrol, causing it to stall.
A lot of older bikes also use carburetors which need to have the fuel jets and idle jets cleaned occasionally, especially if there has been poor quality fuel in it at some time. Newer bikes use an injector which can clog up as well but this is less common.

Clean the carburetors

could be a number of things so i'd start with a few basic checks , make sure the air intake pipes are in good condition and securely fitted and the air filter is clean, the vacuum hoses also need to be checked for condition and make sure they are pushed onto their connection as these can easily pop off,crank case vent to air filter/rocker covers must be clear remove and check as should have a wire filter that may be getting clogged with oil deposits etc ,if these are ok then i'd look at the fuel lines but would have noticed a leak by now,try a fuel addative as might just be a carbon build up somewhere along the combustion /exhaust process , follow the instructions carefully , i've found that when using these addatives it's a good idea, if possible, to go for a long drive maybe 100 miles at a highish speed so everything can get to the correct operating temp , is car mainly stop/start use keep me posted if you wish

the floats in the carbs need cleaning

under the bonnet on the back of the mechanical pump there is a unit held in by 2 bolts
remove this unit and on the end there is a tiny filter
this will need cleaning because when the lift pump brakes down tiny parts of it get sucked up through the pipes and clog the filter
it may be best to feplace the fuel filter aswell

Basically clean up before use like opening the plugs and adjusting the spark gaps, spray some carb cleaner at the intake & if The soud of the engine smoothens even slightly, then add some it to the fuel in the fuel filter & gun the engine a few time. Flush the radiator and fill in frsh coolant/water. Check the level of water in the battery and top up with distilled water. Clean the air filter and check fan belt tightness. After these small maintenace checks it should run OK.......sodeep

its either fuel or air, check the air box under the seat, clean the filter, then check the fuel filter. If this doesnt work I would say you have dirt in your carb main jet.

ALWAYS have a fire extinguisher on hand when working on carburetors.
Remove the water trap bowl at the bottom of the petcock, (gas valve). Is there any water or trash in the bowl? Drain a cup of gas from the tank. Is there any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Before putting the slide back in the throat of the carb, move the clip on the jet needle one notch lower. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. This process should get you back on the road.

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Hello roobar2009:

>>From your Description it Sounds like a Carburetor Problem, a Bad Fuel Filter or Bad Gas.
>>If you have Changed the Filter and the Gas and the Problem is Still happening, then
>>The Following is a Simple Way to make Sure the Engine is Getting Gas from the Carburetor to Run.
>>If the Engine Starts and Quits, then Check the Carburetor Solenoid.
>>If the Carburetor Solenoid is Good or has been Removed and the Engine will Start and Quit when the Gas is Poured into the Carburetor Throat, then Soak and Clean the Carburetor.
>>The Following is a Basic File I Made for Cleaning Carburetors. Any Input is Appreciated. Even though the Carburetor Looks Clean, the Internal Passages May be Restricted with Varnish that Gas Causes to Build Up over Time.
>>Spray Cleaners Remove this Varnish in Layers, so Soaking is the Only Sure Way to Remove ALL this Varnish.
>>I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning.
>>You Only have to Remove the Bowl (if Applicable), Float Pin (if Applicable), Float (if Applicable), Needle Valve.
Remove Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed.
>>If you are Able to Remove and Disassemble the Carburetor and Keep the Gaskets Intact, then Usually these Gaskets can be Reused. The Only Parts you May Need to Replace is the Needle Valve.
>>The Float Needle Usually is Not Replaced Unless it is Not Operating Properly (the gas flow not shutting off and the carburetor is Flooding). Do Not Remove the Main Nozzle. This is a Pressed Fit and Removal is Not Required for Cleaning. Soaking and Blowing the Carburetor Out After Soaking will Clean the Nozzle.
>>Once Disassembled, then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts.
>>Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air.
>>***(Do Not Use High Pressure Air for the Zama Carburetors, they have Check Valves for the Primer and these are Usually Blown Out of the Carburetor if Not Careful. Allow the Zama Carburetor to Set on a Drip Pan and Dry)***.
>>****All the Carburetor Adjustments are the Same for Lawn Mower and Trimmers. There are Several Location for the Air Mixture Screws. The Idle Air Mixture Screws are Usually Located at the Top of the Carburetor Bowl and the Top of the Carburetor Body.****
>>If the Main Air and Idle Air Mixture Screws are Side by Side on the Side of the Carburetor, then the Idle Air is Nearest the Engine. The Main Jet Air Mixture Screw is Located in the Bottom of the Carburetor Bowl or Beside the Idle Air Screw on the Side of the Carburetor Body.
>>Some of the Older Model Carburetors have the Main Jet Mixture Screw Straight in from the Top of the Carburetor Body (this is Rare anymore). If you have Cleaned the Carburetor (Disassembled and Soaked Overnight in Carburetor Cleaner (I Use Gunk). Then Blow Out the Passages with Compressed Air and Install a New Kit if Required. Now Setting the Air Mixture Screws:
>>****Turn the Idle Air and Main Air Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Holding the Throttle Full Open, Start the Engine. Turn the Main Air Mixture Screw Clockwise Until Proper Revs are Obtained. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs. Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required. Now Set the Idle Air Mixture Screw so there is No Hesitation when Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.****
>>If This Carburetor has a Single Air Adjustment (Except Tank Mounted 9200 and 100900 Engine Model Carburetors), Use the Section Above that Pertains to Full Throttle RPM Air Mixture Screw and then Adjust the Screw if Required to Eliminate Any Hesitation when Throttling from Idle to Full Throttle.
>>For the 9200 Model Tank Mounted Carburetor Adjust the Air Mixture Screw Full In, then Reverse 1 1/2 Turns. Set the Throttle Lever to Full Throttle and Start the Engine.
>>Now Carefully Use 1 Finger and Open the Throttle Plate and Over Rev the Engine Slightly. If the Engine Over Revs and Does Not Struggle to Over Rev, then the Carburetor is Set. If the Engine Struggles to Over Rev, then Turn the Adjustment Screw In 1/4 Turn and Repeat the Over Rev Test.
>>If you Adjust to 1/2 Turns In and the Engine Still Struggles to Over Rev, then Return the Adjustment Screw to 1 1/2 Turns Out from Snug and Turn the Screw Out 1/4 Turn. Do the Over Rev Test. Continue this Process Until you have the Engine Over Revving without Struggle.
>>By Adjusting the Carburetor on this Style Carburetor Until the Engine Over Revs without Struggle, you have Adjusted the Air Mixture to the Best Possible Setting.
>>This file was Intended to Give you the Basic Carburetor Cleaning Instructions and May Not Reflect Your Carburetor Components.
>>If you have Questions, Please Ask. The links above Provide Good Directions on Cleaning the Carburetor. Make sure you use an Compressed Air to Blow through all the Carburetor Passages to make sure they are Clear.
>>1- http://www.repairfaq.org/samnew/lmfaq/lmclctc.htm
>>2- http://www.cpdonline.com/692509.pdf .
Please, Do Not Hesitate, If I Missed Something or you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance.
Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Be Happy. Thanks.

Good Luck

Respectfully

jbridger (John)