High Idle at Start After Carb Cleaning

[LaRockMan]

I'm a new member to the forum although I admit I previously researched the Yamaha mid section corrosion issue here before purchasing a used boat a few years ago. My current problem relates to a 40 hp 1999 two stroke. It wouldn't start and having had dirty carburetors before, suspected that was the problem again. We removed the carburetors, cleaned and reinstalled them, cleaned the fuel filter, drained the fuel tank, added fresh gas + two stroke oil and replaced the hose from the tank to the engine. The engine started without much effort post rebuild, high idled for a few minutes and then settled down to normal idle. We let the engine run till warm then shut it down and re-started. At restart despite already being warm it went to high idle again. Now every time it's started, it goes to high idle for what seems to be a random amount of time before settling down to normal idle. Have not done the link and sync procedure yet (read about it here), but will do so. As noted above we have previously successfully cleaned the carbs with no issues. I would appreciate any thoughts on what could be causing the high idle problem!

[greasyshaft]

Is it prime start?

If so the engine will idle high until the fuel enrichment valve closes, completely normal.

[99yam40]

The CDI advances the timing at start up to raise the RPM and then drops down to normal once motor warms up.
There is a temperature switch on head that tells it when it is warm.
Even after warm it will idle higher at start up but should drop back down to normal fairly quickly.
Is it staying high for too long?

Maybe there is a problem with the temp switch

[LaRockMan]

It was high idling for a minute or more. Took the carbs back off and cleaned the jets under the plastic cap. Now it fast idles for 2 or 3 seconds at restart when warm which seems normal. Fuel enrichment valve in the "normal" position. Thanks for the responses.

[almetelo]

When you cleaned the carbs how did you left the A/F mixture screws?
I supose you removed the A/F screws when cleaned the carbs, or not?

What model is 40 2 strk?

[LaRockMan]

Almetelo A/F mixture screws were not removed-should they be? Motor is C40 TLRY.

[99yam40]

The Y means it is a 2000 not a 1999
To clean all passages the screws have to come out.
So always pay attention to where they are set before removing