Engine problems

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A

a6lns

Well-Known Member
Messages
186
Location
Wellingborough Northamptonshire
Hi all have a fg Baja with a Zenoah 26 engine in it but it’s not running right keeps cutting out on idle revs slightly rise then cuts out Tried re running it changed plug but it’s not working if anyone can give me some idea what to try would be appreciated
andy
 
If it's increasing idle and dying richen low speed needle. Also if it decreases idle then dies lean low speed needle a bit so the idle stays stable then the low needle is set correctly.
 
You most likely have an air leak, or the carb needs rebuilt. Time to check a few things. First, are you sure your getting a good supply of fuel to the carb? Fuel.line didnt rot off in the tank, fuel line is still flexible, primer bulb full? Personally if I let something sit, I'll do a carb kit as power for the course. Next we have air leaks. The intake manifold is the most suspect, but your crank seals can be an issue as well. Theres basically 2 methods to finding an air leak. I prefer to vac and pressure test the engine as I have the equipment to do so. Next is, if you can get it to run at all, spray some brake clean around the intake and crankcase area and see if it picks up rpm. Depending on where you spray will let you know where its sucking air at. The manifold you can manually check. Remove it and set it against a straight edge and make sure its flat. Always worth checking is the carb and manifold are tight first. Then I would proceed to the fuel system.
 
Ok, so the short version is you need 3 things for an engine to fire compression (air) fuel, and spark. If your missing or not getting enough or too much of any it wont run. Were basing our suggestions off of what you've told us. Based on what you've said, I'm assuming you have good spark. So that means the air or fuel is the issue. Normally after long periods of sitting, the diaphragms in the carb get hard, so it wont pump or meter fuel properly. (This isnt the rule, just normally an issue) hence what I suggested going through the fuel system first. Next is an air leak, too much air and not enough fuel getting to the combustion chamber. This is less likely, but an issue non the less. As you've said you cant even get it to run at idle theres no way to check for an air leak, outside of a pressure/ vacuum check. So were back to starting with fuel and rolling out any issues with that end of the triangle. So to start. You would begin with going over your fuel lines, make sure they are not hard, amd the filter is still able to move freely in the tank. Next is the carb itself. If you don't feel comfortable tearing into it, buy a new one. When you go to check/replace the carb you'll be able to easily take the intake manifold off and check it for flatness across the flange surfaces that mount to the engine and carb. If you do a search I did a fairly detailed how to carb thread, that walks you through the basics of rebuilding your carb. There are numerous threads on starting issues, and leaking intakes in general.
 
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