The Sneeze

[RedRustler]

Well i finally borrowed some good spark testor's and the cylinder that i thought was droping spark at WOT is not. <br /><br />So do i know go back into the carb's? <br />And also i think my #1 cylinder is sneezing what does this meen?

 

[Silvertip]

Re: The Sneeze

Sneezing refers to the spit-back through the carbs (sort of like a back-fire on a carbureted auto engine). What engine, what symptoms, what's been done so far? Compression check, loose fuel fittings, loose carb mounting, bad reed valves, are some possibilities. Junk in carb for affected cylinder periodically clogging the high speed jet.

 

[RedRustler]

Re: The Sneeze

comp. between 105 and 112 115 lowest being #3 cyl.<br />yamaha 40 hp <br />i have changed the fuel pump,plugs<br />cleaned carbs. but i did not dip them. i only diped the #3 carb because that was the dirtiest.<br />I am thinking about ordering a rebuild kit.<br /><br />When i run the motor at 2000 rpm and it is sneezing i put my hand over the #1 carb mouth but not choking it. with the breather box off and it seems like the motor smooths out a little and it stops sneezing <br />So i am thinking since i did not dip the 1 and 2 carbs i should do this and blow them out.

 

[bigbrownbuku]

Re: The Sneeze

syncronizing three carbs is very important.<br />the first thing i do when i get a motor that has a lean cough is a quickie throttle valve sync. if that doesnt fix it, off they come.<br />my advice is to take it to someone that can do it.<br />its usually around a 2 hour job to completely clean a set of carbs like that then link/sync them. if it only needs to be set up you should escape fairly cheaply.

 

[Silvertip]

Re: The Sneeze

Your description is indicative of lean mixture. Carb cleaning means complete disassembly, soaking, ensuring each passage is squeaky clean, blown out with air, and new kits installed, and float level reset. As others indicate once that's done, sync & link (OMC term) must be done to properly sync and adjust the carbs. Finally, idle mixture and idle speed adjustments must be set (if mixture is adjustable).

 

[DCB2]

Re: The Sneeze

Is it true that when you run the gas out of of the crab bowls that it could dry out the rings? My mechanic told me to leave gas in the bowls when I winterize.

 

[Ray Neudecker]

Re: The Sneeze

One of the main reasons you are having problems with fuel restrictions now. If you drain the bowls, the fuel is still in the motor to keep enough lubrication to prevent the rings from drying out. Your mechanic likes to do carb jobs.

 

[RedRustler]

Re: The Sneeze

Ok well i just finished soaking all of the carbs and replaced all o rings and needle valve seats with o rings. <br /><br />i am going to run the boat in a canal tomorrow and see if is running any smoother<br /><br />It is still sneezing a little but i am going to have a mobile yamaha mechanic come by this weekend and sync the carbs and do the fine tuning for me so i will have my fingers crossed.

 

[bigbrownbuku]

Re: The Sneeze

Originally posted by DCB2:<br /> Is it true that when you run the gas out of of the crab bowls that it could dry out the rings? My mechanic told me to leave gas in the bowls when I winterize.

if its a "pickle mix" it shouldnt be a problem. probably your mechanic didnt want you to RUN the gas out of your carbs as opposed to DRAINING them. running a carb dry also burns internal lubrication as the engine gets leaner. granted its not much but for an engine that relies primarily on deposit lubrication, everything helps.