yamaha 2006 90HP hiccups at idle speed

itsfishy

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Nov 4, 2010
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I just bought this 90HP and found that it hiccups at idle speed. It also will start up fine but after 15-20 seconds it hiccups and shuts off. Restarts ok and when it is above idle speed it runs great. Only does this at low speeds around 800-1000 RPMs. Runs fine at top end.
*
I cleaned the carbs, which looked clean to me other than some corrosion in the middle carb bowl and around the fuel enrichment pump assembly. I*disassembled the assembly, cleaned it and tested the electrothermal*valve resistance and valve height per manual. All looked well.
*
I*adjusted the low speed jets and*put in new plugs. After putting it all together again I expected my hiccups to go away. That isn't the case. I still have the original problem. However I gained a*lot of experience with the Yamaha engines.
*
Does anyone one have any suggestions on what to do next?*
*
Rich*
 

99yam40

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Re: yamaha 2006 90HP hiccups at idle speed

still sounds like your carbs pilot (idle) passages have some restrictions or you are sucking air somewhere. Running too lean at idle.

Did you do the link and sync procedure in the manual after reinstalling the carbs?

Does it still have the problem after motor is warmed up?
 

itsfishy

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Re: yamaha 2006 90HP hiccups at idle speed

still sounds like your carbs pilot (idle) passages have some restrictions or you are sucking air somewhere. Running too lean at idle.

Did you do the link and sync procedure in the manual after reinstalling the carbs?

Does it still have the problem after motor is warmed up?

Runs better when it is warm, but still hiccups when I slow to low RPMs. Doesn't do it on a regular pattern. Most of the time when it is warm it isn't strong enough to shut the engine down. From a cold start it will be strong enough to shut the engine down once. Until it warms up. I didn't do the sync procedure. I didn't change any linkage so I by passed that. Doesn't seem to run any better when I make it richer. Where would it be the most likely to be sucking air? Would that not effect it at higher speeds? Or isn't it sucking enough at higher RPM to effect it?
 

99yam40

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Re: yamaha 2006 90HP hiccups at idle speed

Do the link and sync every time you reinstall carbs.
The carbs do not end up exactly where they were before and any little bit will cause the butterflies to be off just a RCH.
One open or closed just a little more than others can cause problems.

Some times it takes more than one cleaning to get all the passages completely clean.
Did this motor have the plugs covering the pilot screws and did you open everything to clean?
 

itsfishy

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Nov 4, 2010
Messages
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Re: yamaha 2006 90HP hiccups at idle speed

Do the link and sync every time you reinstall carbs.
The carbs do not end up exactly where they were before and any little bit will cause the butterflies to be off just a RCH.
One open or closed just a little more than others can cause problems.

Some times it takes more than one cleaning to get all the passages completely clean.
Did this motor have the plugs covering the pilot screws and did you open everything to clean?

I removed the plugs and valves when I cleaned the carbs. Disassembled the carbs and blew out all passages with air. I didn't soak then though. Some people soak them over night I hear. I will sync them and see how that does.
 
Joined
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Re: yamaha 2006 90HP hiccups at idle speed

Is this a 4 stroke? If it is the throttle plates probably need to be balanced with a vacuumate or equivelent using the manual, kinda complicated if you have not done it. They best way to clean 4 stroke carbs is to ultrasonic clean them, HF has one for about 70 bucks. Very small passages.
 

itsfishy

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Re: yamaha 2006 90HP hiccups at idle speed

No it is a 2 stroke. I have checked all that you have mentioned. Maybe I will have to clean the carbs again. This time let them soak.
 

takara

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Oct 27, 2010
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Re: yamaha 2006 90HP hiccups at idle speed

I have same problem with my 98 40hp, hope you do better than I have.
 
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