Hello everyone. My project is coming along on my 1992 Yamaha 40 hp 3 cylinder thanks to all the help. I have a question. I’ve got a new portable fuel tank, all new fuel line from tank to carburetor with oem line under the cowling. New fuel water separator as well. Carburetors completely rebuilt with all new jets , everything. Pilot screws out 1 1/2 turn. Hard to start , rough idle and a sneeze after all this done. Tried adjusting the pilots 1/4 turn at the time but no difference in idle on any of them. Runs good at wot. Here’s my question I noticed the new connectors at the motor where leaking and bulb not getting tight. Only thing I can think of is they’re not compatible so I replaced both with the old ones. Bulb pumps up and holds prime now and no leaks. Problem is I have not had a chance to run it yet after doing this. Do any of you think this could’ve fixed my troubles? Was I getting air from the connectors while it was running? It’s driving me crazy not being able to run it yet since I found those fittings so I thought I would bug you nice people for opinions. Oh when it did idle it was kind of high at around 950rpms. I’m hoping this fixed it all after everything I’ve got in it with other repairs as well. Looking forward to hearing what y’all think. I’d really appreciate it.
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Question for the pros about a 1992 Yamaha MSHQ
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I would not think those connections would have anything to do with the hard starting, fast idle, or the lean sneezing.
did you follow the link and sync procedure in service manual after putting the carbs back on?
have you checked to see if timing is in spec at idle?
did you go thru the prime start system , making sure all the passages are clear, heater works, diaphragm and check valves all are in good shape?
is the red lever on the prime start in the auto/normal position?
did you try turning it to the open position to see if that helped to get it started and then turned to off or the auto position to run once started?
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I’m finally going to be able to move the boat back to the driveway where my water source is so I can see how it runs. If still the same problems I’ll go back to the manual for the link and sync again. It just has a manual choke and there all closing all the way and opening all the way. Leak is fixed and the carburetors where spotless with all new jets, everything. I must have cleaned the carburetor bodies 10 after soaking just because I didn’t want any dust that may have accumulated while waiting on parts. Unless something got in the system anyway. Anything’s possible. Timing should be good since it was actually running smooth until the carburetors started leaking which is why I opened them up and then found the mess. Lol I’ll let y’all know what happens. Thanks so much for the input. It’s greatly appreciated.
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Originally posted by Douglasdzaster View PostI’m finally going to be able to move the boat back to the driveway where my water source is so I can see how it runs. If still the same problems I’ll go back to the manual for the link and sync again. It just has a manual choke and there all closing all the way and opening all the way. Leak is fixed and the carburetors where spotless with all new jets, everything. I must have cleaned the carburetor bodies 10 after soaking just because I didn’t want any dust that may have accumulated while waiting on parts. Unless something got in the system anyway. Anything’s possible. Timing should be good since it was actually running smooth until the carburetors started leaking which is why I opened them up and then found the mess. Lol I’ll let y’all know what happens. Thanks so much for the input. It’s greatly appreciated.
maybe you have the wrong carbs on the motor if you say it has chokes
this shows it has a solenoid valve but it does not look like it has any linkage that attaches to it to close choke plates on the carbs
Yamaha Outboard Parts by Year 1992 OEM Parts Diagram for CARBURETOR | Boats.netLast edited by 99yam40; 05-03-2021, 10:18 AM.
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Originally posted by ausnoelm View PostYamaha carbs are very hard to clean, they are easy to make look nice, but cleaning requires a lot more than washing, soaking, spraying and looking at.
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Originally posted by 99yam40 View Post
maybe you have the wrong carbs on the motor if you say it has chokes
this shows it has a solenoid valve but it does not look like it has any linkage that attaches to it to close choke plates on the carbs
Yamaha Outboard Parts by Year 1992 OEM Parts Diagram for CARBURETOR | Boats.net
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Originally posted by ausnoelm View PostYamaha carbs are very hard to clean, they are easy to make look nice, but cleaning requires a lot more than washing, soaking, spraying and looking at.
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well, does this thing have the solenoid valve on the bottom carb?
what does it hook onto and what does it do when operated?
I have read a heated sonic bath cleaning is sometimes needed to get all passages cleaned properly.
I have heard in the past these multi carb motors are like several single cylinder motors tied together.
If you do not sync them properly they will fight each otherLast edited by 99yam40; 05-06-2021, 06:19 AM.
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Originally posted by 99yam40 View Postwell, does this thing have the solenoid valve on the bottom carb?
what does it hook onto and what does it do when operated?
I have read a heated sonic bath cleaning is sometimes needed to get all passages cleaned properly.
I have heard in the past these multi carb motors are like several single cylinder motors tied together.
If you do not sync them properly they will fight each other
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Originally posted by TownsendsFJR1300 View PostIf your guy isn't available with a sonic cleaner, a new one (decent unit) can be had for $125-$150.00 (About the equivalent of an hour labor at a Yamaha dealer).
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I finally got to run the motor today here at home. Double checked for any more fuel leaks while priming. All looked good and primed up tight. Took about 6 pulls to start then it sneezed and died. I fallowed the link and sync process in the manual. Started up and ran just a little rough so I adjusted the pilot screws and now it just has a little vibration which I think is expected (tell me if I’m wrong). I ran it quite a while and stopped and started it several times. Started first pull every time idled a little high for a sec then came back down to 800 rpms every time. Or as close as I can get to 800 with the portable tachometer I have. Tomorrow I’ll see how easy it starts while cool. I’ll know for sure when I can put it back in the water. Here’s a question, while adjusting the pilot screws the top two are the ones that made a difference. The bottom carburetor didn’t change anything very much when I’d turn it. What’s going on with it?
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