The place to come to share your technical expertise, or just find out what the little springy thing is that's just pinged out of sight under the work-bench.
Any advice guys. After a flat out blast a couple of weeks back my bike started running on 3 cylinders. Looked at the ignition system first. Changed the coils and leads. New spark plugs cleaned the pick up coil etc. But still not running on number 4 cylinder. Even replaced the exup servo and fitted another cdi
I get a strong spark on all four cylinders, but number 4 remains stone cold., so took the carbs off yesterday. These had an ultrasonic clean and new emulsion tubes around five years ago. Still very clean inside. Blew carb cleaner through the jets and compressed air. Put them back together and back on the bike. Fired it up but still stone cold on number 4
When you had the carbs off did you check for a split diaphragm, float issue or fuel inlet blockage/ jammed needle valve. Also are you sure that coil lead no. 4 is not arcing out when fitted. Hope its something like this otherwise you need to look at valve train components or head gasket.
Goshreally2 wrote:When you had the carbs off did you check for a split diaphragm, float issue or fuel inlet blockage/ jammed needle valve. Also are you sure that coil lead no. 4 is not arcing out when fitted. Hope its something like this otherwise you need to look at valve train components or head gasket.
Yeah first thing I checked was the diaphragm. Thats in good condition and the slide moves OK. The needle is true Didnt check float height but it looks OK and fuel is filling the bowl OK. Will certainly check the lead for arcing. Nice strong spark when I hang it out the side of the bike. Will cut the lead back and refit the can (you never know!!)
Wonder if there is a way of checking fuel flow with the carbs off the bike?
With the carbs off the bike if you remove the float bowls each carb can be checked by closing three of the carbs fuel inlets using the floats using string if needed but be gentle. The fourth carb inlet can be checked by blowing into the fuel line and operating the float.Also if you have a pressure gauge it would be worth doing a compression test to see if there is a difference on no.4 cylinder.
Goshreally2 wrote:With the carbs off the bike if you remove the float bowls each carb can be checked by closing three of the carbs fuel inlets using the floats using string if needed but be gentle. The fourth carb inlet can be checked by blowing into the fuel line and operating the float.Also if you have a pressure gauge it would be worth doing a compression test to see if there is a difference on no.4 cylinder.
Good advice
Got a carb rebuild kit from Yambits. Replaced the jets in number 4 carb . Running on all four now. Header gets hot again. Think the pilot jet must have been blocked. Still splutters a bit when pulling away, but think this may be down to Yambits supplying a #35 pilot jet in kit. It was a #40 that came out. Have ordered a #42.5 to experiment. Will get it into J&S to get the carbs set and balanced in the near future.
