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Yamaha 40HP idling rough

Even compression between cylinders is what you look for.--------------No actual numbers are published as there are too many variables.
 
Well Racerone,did compression test today starts good now but wants to shake and puff no smooth idle ? I am kind of fustrated but came out good on test each cylinder twice. #1 cyl 110psi,#2 cyl 105psi,and #3 cyl 110 psi also started with new batch of fuel so there was less smoke than usual.After engine came to operating tempature. Hey I did notice one thing that was weird to me a novice when i took tempature readings with my infared dot thermometer i found 31 plug 136 f,#2 plug around 130 f ,and #3 plug 126 f is this normal #1 is top, #2 is middle, and #3 is bottom cyl respectibly? So where do we go from here ? Carburetor problem or fuel pump. When it gets a little darker i will see with my plug tester how far they will jump. Thanks to racerone and anyone else with input.
 
If this motor sat for long periods of time then the small carburetor jets could be plugged.---------------If you have good ( 7/16" ) spark at each cylinder then I would take carburetors apart for cleaning.--------------Inspect fuel pump for hole in the diaphragm. Inspect reed valves while carburetors are off.------------Spraying carburetor cleaner at the carburetors is a waste of time they need to come apart for cleaning.
 
Thank you just in time just finished ordering rebuild kits for all three carbs,book says its moderate as non mechanic rating i have all the tools exept it says i need a thin walled socket to remove needle ? can`t think of name. Also is ti alright after removing all plastic and rubber to soak carb body in carb cleaning fluid? A smaall 2 cycle engine tech once told me you would destroy the stihl carb by soaking in carb fluid.
 
Thank you just in time just finished ordering rebuild kits for all three carbs,book says its moderate as non mechanic rating i have all the tools exept it says i need a thin walled socket to remove needle ? can`t think of name. Also is it alright after removing all plastic and rubber to soak carb body in carb cleaning fluid? A small 2 cycle engine tech once told me you would destroy the stihl carb by soaking in carb fluid.
thank you again let me know about the socket and the soaking please
 
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Racerone what am I looking for when I get the carbs of inspecting the reed valves ? Please. thank you your help has been indispensible.
 
i use an ultra sonic cleaner heated, you can use hot water
i use a vinegar and water and dawn soap
yes carb cleaner will eat throu some carbs

then i use carb cleaner in every hole then use compressed air to blow out
 
Took off all three carbs fairly easy, I hope the rebuild will go as easy, i have a tip for anyone, do not unscrew check valve screw all the way when inspecting middle carb fuel enrichment pump. 6H4-24413-00-00 i broke trying to get it off to immerse in hot water it is not pressed on but pretty near and difficult to get off. So i had to order another 6H4-24413-00-00 nothing but laughs today. When my parts arrive i will clean and reassemble.
 
Racerone ,and Justintime I sure need your expertise now.I rebuilt all three carbs and installed them found only small hose leak and repaired had engine running like new.purring then me the idiot stuck a bussiness card in front of top carburetor wich is #1 engine stalled now I can not get it to start. It turns over coughs and shuts off .Please help me what could I have done .The book said if alot of fuel showed on card there may be problem with reeds.Before putting carbs on i shined high intensity light thru intake holes and seen nothing broken or missing.:(
 
I do not think you did anything wrong.----------------Look for reeds leaking with a very strong flashlight shining into carburetor bores.----------------------Try and start it again tomorrow and see what happens.------------------Sounds to me that it flooded.---------------Try again tomorrow.----------What sort of book said to use a card ??
 
It was a seloc manual Racerone I think your right i think it just flooded but yall`s advice about the carbs was right on the money when i had it running it was smooth . Thank you I will try tommorrow to see. On a cool morning what shell do. Have to fix the wifes supper now.Thank you for your prompt resonse.:cool:
 
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