My mcculloch 600068c starts and idles but when given gas it sputters and stops what is the problem? I replaced fuel line rebuilt the carbuerator new sparks plug. It has been suggested that there if a reed valve but where I don't know. It just acts like it is not getting enough gas
Garden - McCulloch
Answers & Comments
Hello. Generally, this problem is caused by a little gunk somewhere in the carb. or the engine. Get an assistant and a can of aerosol starting fluid. have your assistant squirt some fluid into the air intake to keep it running for a minute or so to clean the problem. Joe
Hi and welcome to FixYa. I am Kelly.
Start your carb adjustments by doing the following. Turn the LOW needle jet closed until it just closes. Then open it 1.5 turns. Make your adjustments on the LOW needle only for the moment. The goal is to adjust the LOW needle so that as you apply the throttle that it does not stall. Make your adjustments in less than 1/8 th turn increments. If it gets worse as you adjust the carb reverse the direction you are turning the LOW needle.
Once you start to notice that you no longer have hesitation increase the engine speed to max and adjust the HIGH needle until it just stops missing at FULL speed.
If by chance none of your adjustments make any difference... Open the carb base and check the position of the float needle tab on the diaphram. Bending it slightly DOWN (in 0.002 increments) adds more fuel and bending it UP causes less fuel flow.
Most of the time fuel starvation is caused by air being introduced into the fuel system or just not enough fuel through the float needle valve on the top of the diaphram. It can also be the fuel tank pick up tube / screen is clogged. Most of the time if there is a pick up tube problem it will lean out at high rpm.
Watch your fuel lines for any signs of air bubbles. If you see ANY bubbles at all after initally bleeding off the air there is still air being introduced into the the fuel supply and you wil have to find out why.
Lastly...I have seen loose fuel manifold tubes on carbs cause this problem. It is really really rare but it does occasionally happen. Make sure the tube on the side of the carb that mates the fuel tank line to the carb is tight and not introducing air into the carb.
Here is a fair dissambly video for a walbro carb:
I do not believe you have a reed problem at this time. If you did have a reed problem it would not even start.
And here is the re-assembly:
Here is a note about the float needle setting:
Float, Needle & Seat Setting
This critical setting is the primary way to adjust mixture on some Walbro carbs such as the WG8 used on Top 80 motors. Apparently Walbro offers a setting gauge to properly set the height of the lever for each model. Without that gauge you'll have to use trial & error which is a pain since you must open up the carb for each adjustment. In general, the lever will be parallel to the carb base. If the lever is too high, the mixture will be rich, too low and it will idle ok but be lean at midrange and above. It may also run the float cavity dry at full throttle and die, regardless of your highspeed / lowspeed needle settings.
Take good look at this picture:
If you have for sure tried everything in both of my posts and your sure that no air is being introduced into the fuel system; the only thing that I can think of that would make any sense at all is that one of the needle jet tips has broken off in the carb from being closed to tightly. Remove both jets. Inspect the tips of each jet to make sure that the tip is intact. Then with a bright light inspect the fuel metering orifice deep in the jet hole to make sure that a piece of the tip is not lodged in the orifice.
I've been doing this for many many years.
http://blog.fixya.com/index.php/2010/05/...
Kelly