stylecouncil wrote:
Thanks for the info fabio. Sorry to be a pain but getting a bit confused as to what's causing with the old girl..... do I need to block off the open ended pipe?
Also you can't see in the picture but underneath the vacuum hose are 2 x what I would describe as nozzles similar to the one the vacuum hose sits on that are empty ie nothing attached to them..... Is this normal?
Have bought some carb cleaner today and will have ago at dismantling and cleaning that tommorow also got some new fuel in a can so will empty the old stuff and replace with new. Also just wondering if giannelli has anything to do with it. Only had bike since fri so I'm clueless with!!!
Blocking it off is the usual practice but only from a cleanliness point of view and it should run ok as it is.
The 2 unused nozzles are for carb cooling/heating and on a 2 stroke they aren't usually used.
IMO 1st job would be to drain and change the fuel if you haven't already done so, this eliminates one of a series of potential problems, do the easiest things first.
Here's a bit of a checklist of things to look at after that, not all of these things apply to you but they're good info to know (I've pasted this from one of my Wiki articles).....
Engine does turn over but won't start - If the scooter does turn over but still doesn't start you should check for a spark and make sure fuel is getting to the engine. To check for a spark, remove the spark plug from the cylinder and re-attach the spark plug cap/lead back onto the spark plug. Hold the tip of the plug against the cylinder head and crank the engine.
You should see a blue spark across the gap, the spark should be strong! If you don't, there's possibly a problem with the ignition. This could mean that you have a faulty coil, CDI unit or electronic ignition module which will have to be replaced, or it could just be a loose wire. If the spark plug is fouled up/oily/overly blackened then it is very likely that it is the cause of your problems and you should consider replacing it as statistically, the second most likely fault with starting a scooter is a faulty/fouled up spark plug.
If you do have a strong spark, you next need to check that fuel is being delivered to the carburetor. Make sure there is fuel in the tank first and if so you can move on to checking the fuel valve. Most scooters use either a gravity fuel feed by locating the fuel tank higher than the carburetor, or some use a vacuum-fed petcock (on/off tap) controlled by the vacuum created at the carburetor. The carburetor has two fuel-related pipes connected to it. One is from the fuel tank and is for the fuel supply, the other provides a vacuum to suck the fuel from the fuel valve. If you disconnect the fuel supply pipe from the carburetor, fuel should flow out when you crank the engine (be careful to catch the fuel if you do this and don't do it with a hot engine), if fuel doesn't flow out then the fuel valve may be faulty. You can try applying a vacuum to see if fuel flows by sucking on the vacuum pipe(but make sure it's the vacuum line, not the fuel line if you try this!). Another Tip: If there is a spark but you are unsure about fuel supply... squirt a little bit of fuel (a spoonful) into the spark plug hole and then replace the spark plug and try to start the engine.....if it starts and runs for 5 seconds and then dies then you can check for fuel flow to the carb, or blocked jets.
If you are getting a strong spark, fuel supply to the carburetor is good and the engine is turning over on the starter, it's possible that the electrically operated automatic choke has failed. It's supposed to operate when the engine is cold, but if it's stuck or burned out, the mixture will be weak and the scooter probably won't start. The automatic choke is usually a black cylindrical object attached to the carburetor with a couple of wires coming out from it. It's the only electrical powered component attached to the carburetor, so it's usually not too hard to spot. If you have a meter you can measure the resistance across the leads of the choke, you should see around 10 ohms or less. If it's an open circuit its likely to be burned out and will need to be replaced. If it seems to be OK it may simply be stuck, or the wiring to it may have a problem/loose connection. You can also check to see that it's getting voltage across its terminals. A final check...remove the choke from the carb and plug the wires into a 12V source for about 5-10 minutes. The choke body should get warm and the protruding mechanism should extend slightly. Measure the length of the protruding choke mechanism - it should have increased in length by around 5mm more than when it was cold.
It's also possible that there is a problem with the cleanliness of the carburetor and if so you may need to remove it and clean it out. If the scooter has been sitting for a few months with fuel in the carburetor, the fuel may have evaporated and left behind a sticky "gum" that will prevent the carburetor from working properly and which must be removed. Statistically, the biggest problem for a scooter not starting is a gummed up carburetor/ blocked carb jets.
A very common problem is blocked jets in the carburetor. The jets have tiny holes in them that the fuel passes through to supply the carb and these become gummed up with fuel residue. You will find three jets in the carb (Main jet-used for Wide Open Throttle, Idle Jet-feeds the carb at idle/low revs, Choke/Power Jet-gives extra-rich fuel supply when starting from cold) and its easy to remove the jets and clean them out with a spot of Carb Cleaning Fluid and/or with compressed air. A tip is to blow through the jets with your mouth and then hold them up to the light to see if you can see clear daylight through the jet's bore. Whatever you do don't be tempted to prod the hole in the jet with a bit of wire or a needle as this will enlarge the jet's bore and be the cause of tuning problems at a later stage.
Setting the idle mixture screw - You could also be experiencing too rich or too lean fuel/air mixture to your carb. To set this you should screw the idle mixture screw fully in.... (Before you screw it in...look at where the screwdriver slot is at... then count how many turns it takes to go all the way in gently... 1 and 1/2 turns for example, and remember the number of turns for later)..... then unscrew it out by the number of turns that it states in your handbook - for my scooter it was 1 and 1/2 turns out.
If the automatic choke is problem free, the starter cranks the engine sufficiently, there's fuel at the carb and there's a strong spark then there may be an engine problem and you need to check the cylinder compression. To do this accurately you will need a compression tester. It screws in instead of the spark plug and measures cylinder pressure. When you crank the engine you should see a reading of approaching 125-150 psi. If it's 100 psi or less then its likely that you have an engine problem (probably failed piston rings) and you will need to remove the cylinder head to gain access to the piston rings. A trick to try if you haven't got a Compression Tester is to hold your finger tightly over the spark plug hole with the spark plug removed to see if your finger is forced away strongly when you try to turn the engine over - it may just indicate that there is very little compression if the force is very minor. Another tip is to add a teaspoon of engine oil through the spark plug hole and try to crank the engine again. If you then get a better compression its likely that the piston rings are shot, as the oil you added sealed the rings for a short period of time and hence temporarily gave you better compression.
Hope this helps
Fabio
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