xt 125 x starting

[bumbaclartio]

so, after a lot of work and trial and error including valve clearances and more, i cannot get the bike to start with ease, it takes a while with me covering the air filter to form a vacuum for it to start up, and even then it kicks into a high rpm until a few seconds after, this problem is then resolved by a warmed up engine but when the throttle is twisted the rpm seems to stick for a longer amount of time.

I suspect a carb problem but thought id ask a few more owners for advice.

Edited April 16, 2020 by bumbaclartio

[Cynic]

(edit) 1st question, how old is the fuel, if its not stored in an airtight container it goes to shit pretty quickly. Only useful as parts cleaner past around 3 months old.

 

Idle jet or an air leak, outside chance of fuel flow from the tank or float height.

The engine will need a richer mixture to start, either your choke circuit is blocked. I don't know the carb on the bike but it will either block an airway or add fuel. Normally adding fuel. As the engine warms this need goes away. If it starts without choke the mixture will be so lean as to cause the engine to race away.

Idle jet could be more likely as:

Its part of the choke circuit as its the jet the engine starts on.

The initial pick up from closed throttle needs the idle jet to be good allowing the jet needle to take over the midrange. There is a chunk of overlap but you get the idea. If the idle jet is blocked probably partially, the transition from idle to revving will leave the engine momentarily starved of fuel.

An air leak from a split in the manifold seal or any of the inlet gaskets could do it, expansion could close the gaps depending on where and what the gap/crack was in. So fixing things when warm. 

Zapping all potential leak spots with wd40 would help there.

 

I'm going with a weak/partially operating choke and some obstruction of the idle jet.

 

Hope it helps..