Author Topic: Ruff idle/ missing thru rpms/black puffs  (Read 277 times)

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Offline Matty83

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Ruff idle/ missing thru rpms/black puffs
« on: September 15, 2023, 03:06:06 PM »
Went to go out today and did a shake down on boat and noticed ruff idle and it missing thru rpms and black puffs from exhaust under off and on throttle I removed the snorkel to get a better view of things and it all went away installed it again went to crap again I am assuming I am air starved or I'm to rich any help would be appreciated

Offline Painlesstom

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #1 on: September 15, 2023, 09:20:58 PM »
What are you referring to when you say snorkel? Factory plenum, or something your modified?
Tom

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Offline Matty83

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #2 on: September 16, 2023, 10:04:43 PM »
The factory installed air inlet for cooling fan/carb I was wondering if there is mod people have done to separate the two or make them more efficient to help with a problem like this

Offline Painlesstom

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #3 on: September 16, 2023, 11:53:52 PM »
The factory plenum won't cause the problems you describe, but it can cause off idle stumble by stalling the airflow momentarily during that period. Your problem is more than likely the float needle seat leaking, and that's causing a rich condition. Those Mikuni carbs were notorious for defective needle seats, I've fixed several dozen of them over the years. Feel free to send your carb to me to go through, I bench run every one I repair so it comes back tested.
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Offline Hillbilly

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #4 on: September 17, 2023, 06:44:39 AM »
It certainly sounds over rich, and the needle valve as Tom says is most likely culprit.  But it may just be a speck of dirt not allowing needle valve to seal.  You may want to take carb off and apart to clean the bowl, needle valve and both jets.  No cost and you get to learn more about the carb.  Good luck

Offline happul3

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #5 on: September 17, 2023, 08:25:41 AM »
Having experienced myself the issue with needle not working as it supposed few years back I was thinking that perhaps a pressure test would be a useful practice. Something along these lines: disconnect carb input line from fuel pump, jury rig a bicycle pump with pressure gauge,  build up 5 psi, observe how long it takes for the pressure to drop. This should also detect the dirt on the needle Hillbilly mentioned. One could also shake the motor vigorously to try and imitate the issue with needle seat unsealing due to vibration during operation.
   
And another simple check would be for a presence of gasoline at the bottom of air intake. After few minutes of idle, remove the airbox top, remove the foam airfilter, look straight down the intake. If it is wet with gasoline it is an indication of flooding likely due to one the issues Tom and Hillbilly pointed out. 

Offline Matty83

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Re: Ruff idle/ missing thru rpms/black puffs
« Reply #6 on: September 18, 2023, 07:28:00 PM »
Thanks for all the awesome replys I will do all the checks and give it a good cleaning and get back with you with the results