If anyone knows what might cause my quad to not start cold please throw me line. It will start easily w/o choke when tow started w/ 500 scrambler. After it warms up, even runs for 30 seconds, it will start fine. But i cant get it to idle since the day i got it. when it stalls it makes a clunk sound and sometimes pops through the carb.( replaced carb adapter boot 2 times due to this. I was thinking the problems may be related. Not really farmiliar with rotax motors.

 

I would check your valves and adjust if need be! Thats what it sounds like to me !

 

Valves, pinched vent line, choke at half choke and not all the way in. Start there first, then the vent tube, valves require a litle more time but we can walk you through it. Update us...

 

I agree, sounds like a valve adjustment is needed, and check ur spark plugs, prob need replacing after tryin to hard start it

 

My vote is the pilot jet! If it has a 40 in it, go to a 45 or 50. It is not getting enough fuel to run cold.


It is easy to tell though........

If it turns over and over and over but does not want to fire.........it is probably the valve lash.

If it pops right off then dies and you have to repeat this exercise a few times until enough heat has built up, it is pilot jet. Also, you won't be able to give it even the slightest bit of throttle while cold or the bike stalls. This is because opening the throttle introduces even more air which is not what the motor wants until it is warm.


The reason there are so many bikes out there that do this is because people add a pipe and intake and only increase the Mainjet. The Pilot often gets ignored and the new stronger vacuum signal draws more air and overwhelms the little pilot jet on cold starts.

 

Thanks for the info. I going to try the jets first, i believe they are stock( pilot and mains) Also might check for excessive valve lash. What is strange is sometimes it will fire up cold w/ no problem and doesnt seem to be staving for fuel ( bogging down when throttled). Do these engines have solid tappets with shims? Ill update you as soon as i change jets. thanks again.

 

If you have any valve lash issues they will be too tight.......holding the valve slightly open, bleeding off compression making it difficult to create enough heat to start when cold.


Do you have any mods like a pipe or intake?

 

the only mods that i know of is the e- series silencer( the one with the tuning plates)

 

My friend, you need a 45 starter jet and 45 pilot jet. Sometimes I start my engine at -25*celcius and I have to restart a couple of times because its frozen. When you start cold, pull the choke at second position and start.(Never touch the throttle) If it stalls, wait 5 seconds and restart......


The clunk sound when it stalls, its normal its the clutch-sprag (one way bearing) inside the flywheel hub.

 

amazing what a difference a larger pilot jet, makes.