Riddle me this

[Copperhead1960]

1987 40hp vro

I have been chasing a lean sneeze at idle. Today with the motor in a tank running a little faster than idle. I placed my hand over the upper carb and had little to no effect on the engine. I placed my hand over the lower carb and the motor chokes out and dies instantly. The motor is running on both cylinders. How does covering the carbs have such drastically different effects. Can an engine run on one carb? If so would this cause a lean sneeze at idle?

 

[david_r]

Re: Riddle me this

you eng will run on one carb but youll burn those cyl with no lubrication from the mixed fuel

sounds like you have a dirty carb or an air leak

take some carb cleaner and start her up and spray the carb cleaner around the gaskets.......youll know if shes suckin air

also this is a good thing to look at

http://forums.iboats.com/showthread.php?t=244013
http://forums.iboats.com/showthread.php?t=167352

 

[DJ]

Re: Riddle me this

Can an engine run on one carb? If so would this cause a lean sneeze at idle?

Yes, and quite well under no load conditions.

You are not running on both cylinders. At least, only one is doing the majority of the work.

You have a dirty carb.

 

[tashasdaddy]

Re: Riddle me this

agree.

 

[Copperhead1960]

Re: Riddle me this

As part of the recommissioning of this engine I pulled the carbs ounce to do a rudimentary cleaning and then again to do more thorough cleaning and install a carb kit. I was thinking swapping carbs to see if the problem follows the carbs. Is this worth my time, Switching linkage and upsetting the link and sync? What steps would you guys recommend?

 

[CATransplant]

Re: Riddle me this

In the time it would take you to switch carbs, you could do a cleaning of the offending carburetor and get back to boating.

 

[Silvertip]

Re: Riddle me this

You do have compression on the dead cylinder don't you?

 

[Benny1963]

Re: Riddle me this

yes compreeion and spark test on that cyl .
i just built the carbs on my 150 with b12 and wire and sierra kits
it wouldnt run right ,
went to red rhino kits and pulled all jets and soaked overnight
then blew with compressed air
put em back on set my timeing and now it runs perfect
and i cleaned the hell out of them .theres no substitute for soaking welch plug removal and jey removal
and the sierra kits are not to hot wont use them again had one needle and seat on bottom carb that was leaking causing rich condition
went to the other kits and the needle and seat held fine
whatever you do soak them remove jets and plugs and use brp or better kits

 

[Copperhead1960]

Re: Riddle me this

Compression on both cylinders in 140 +/- 2psi.

Question about soaking carbs, My manual says do not soak because the sealant on the aluminum/porosity of aluminum? Whats the story.

 

[david_r]

Re: Riddle me this

i dont soak a carb unless its been a long long time before shes been run......carb cleaner, wire, and compressed air are your best friends when cleaning a carb

http://forums.iboats.com/showthread.php?t=244013

 

[samo_ott]

Re: Riddle me this

Do you have a good spark on the dead cylinder? that could do it also...

 

[Copperhead1960]

Re: Riddle me this

In closing, I pulled the carb that did nothing when covered and found a piece of s%@t the perfect size to clog that carbs jet.

thanks for your help.

Tim