The carburetor on my bike is feeding petrol back into the air intake, recently I've put a new piston in and I was wondering if it could be a slack in the barrel, or maybe the carburetor itself, if no
Basically, my son ditched the bike in a river, I've stripped it all down and blew it all clean with an air compressor, I noticed the piston had a crack on the side and I replaced it, but now I've put it all back together and it starts and runs fine, other than throwing petrol back into the air filter intake on the carburetor.
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This indicates that you have carburetor or intake setup problems. If the saw had sat a long time then most likely your going need clean and rebuild it. Please note that cleaning these with carburetor cleaner and especially the drip can destroy the carburetor. It is best to use an ultrasonic cleaner on these carburetors.
Also check intake gaskets placement as you may have installed either out place or backwards.
Check there are no air leaks around where the air intake rubbers are at your carburetor. It sounds like your bike is running too lean or weak which means your air/fuel mixture is running on too much air and not enough fuel. This would explain it running smoothly when you put the choke on as the choke "chokes" the majority of the air from the carburetor and allows more fuel to flow through the carburetor creating a richer mixture. There will be a mixture screw somewhere on the carburetor which will allow you to either richen (more fuel and less air) or weaken (more air and less fuel) by turning the screw either in or out. Only adjust this by a small amount (about a quarter turn at most) at a time and try the bike to see how it rides each time. After adjusting the screw each time let the engine idle for about 30 seconds or so to let it settle to the new mixture setting before riding. There will be another screw on the carburetor which is your "idle" or "tick over"speed adjustment screw which adjusts how high your engine revs while the engine is "ticking over". Turn it in to increase idling speed and out to lower the idling speed. This will probably need adjusting as you change the fuel/air mixture. I hope this helps you and good luck :o)
To remove your carburetor, remove the air filter cover, the filter element, and the backing plate. There are two large socket head bolts that hold the backing plate to the heads as well as three small screws that hold the backing plate to the carburetor. On the other side of the bike, remove the fuel line from the petcock and take the choke control cable loose by loosening the nut on the backside and removing it from it's bracket. Loosen the adjustment of the throttle and idle cables at the throttle twist grip getting as much slack as you can in the two cables. Pull the carb out of the intake manifold seal. You may have to wiggle it a bit from side to side to get it out. Then, disconnect the throttle and idle cables from the carburetor linkage. Guide the choke cable out as your take the carb off the engine. There may be a vacuum hose connected to the backside of the carb that goes to the VOES switch. When you reinstall the carb, put a new manifold seal on the opening of the intake manifold. If you remove the intake manifold. leave the four bolts loose and temporarily reinstall the carb and the backing plate. Then tighten the bolts. This aligns the carb and the intake so that everything fits together and you don't have a vacuum leak.
There are of course many possibilities as to what the noise could be. It is troubling that a mechanic listening to it could not make a better diagnoses other than piston slap. Early Suzuki four strokes often had some piston slap probably due to larger tolerances. This sound generally will go away or lesson as the pistons get warm and expand. With out being able to hear the noise , my best guess is pre-ignition. Start by doing a compression check, both cylinders should be over 110 PSI and with in PSI of each other. If compression checks out, install new spark plugs and more importantly new NGK spark plug caps (about $5 each). Next take off the carburetors, inspect the intake manifolds for cracks or separation (air leaks), clean remove the carburetor tops and inspect the vacuum diaphragms if damaged or pin holed replace them (about $152 each)(a used set may give you the needed parts for less), thoroughly clean and reinstall the carburetors. If the problem was just a lean condition on one cylinder this may bring the cycle back to its original glory. If the damage is deeper in the motor (crank) perhaps a donor cycle or engine would be the best option. Unfortunately, the only way most of these options will work is if you are willing to put in the sweat equity your self to save the labor rate.
cud be a combo of both-running rich from carb or weak spark--chec plug and cable for wear and resistence or test ign unit--may need jet ajust--breakin procedure is the same as new bike--get a maintenance manual-sayonara
hmmm, a few posibilities, might well be split cab diaphragms but overhaul should have spotted that. sounds like either too much gas or not enough, either flooding/gassing up or fuel starvation. could try running it without the aire filter too see what happens. it should run weak so if bike is better then you have too much gas, if bike worse then runnig weak to start with. I have seen this before with one particular cause.... petrol tap was leaking, gas runs past pistons when bike not running, soaks past and into crankcases. as breather recycles vapour back in to air box, when bike warm it's as rich sas hell. take of oil filler cap on engine and have a good sniff. you should smell only oil, if it's a strong smell of petrol, change oil and filter, dump petrol tap or see if new seals available.
hi do not worry the carb pistons are stuck if you can remove the petrol tank and the air filter bracket then you will see the top of the ca-rb there are 4+4 screws on each ca rb try and remove care fully and remove the piston s by giving very littel force then clean it with sumca-rb cleaner and check for free moment by sliding if it is free put back the piston and covers and give a try it should work because just know i have don it it worksmassage from india