Yamaha 130/140 Not quite running right

[Dscott2542]

Hello everyone,

I have a video of my Yamaha 140 (Aussie model) running as well as I can get it, https://www.youtube.com/watch?v=Jm3xI2Cuaxc and I do not think it is right as it has this issue with popping. It pops through the rev range and shakes a bit, but does not have any problems starting or idling, it is very responsive when throttles are opened it just keeps doing this pop thing, I have replaced the spark plugs and gaped them, replaced the power pack and cleaned the carbs four times and messed around with fuel ratios until it sounds as good as it does in the video. It did overheat once and have heard that this can cause damage to the coils, but every mechanic I have spoken to has said this is highly unlikely, can someone please let me know if this sounds like a coil, I have a spark tester and used it on the motor but I think the tester is faulty as when it is connected to the lead it shows a low constant light like which continues even after I disconnect it from the spark lead. I also tried removing a spark plug after testing it once while the engine was running... it threw my hand into the brick wall and left it tingling for an hour after so I am fairly sure this is not the problem.

Any thoughts would be greatly appreciated.

Cheers guys,

Dan.

[99yam40]

Your pop you describe sounds like a what is called a lean sneeze, but I do not hear it in the video.
you can use a timing light to monitor timing and the spark also.

A spark tester with adjustable gap that lets you see the spark itself is a good one to have

[robert graham]

1500RPM's is considered the safest maximum in neutral....I didn't hear any popping in your video....sounded pretty darn good to me!....

[TownsendsFJR1300]

Agreed, it does sound pretty good.

How's the motor run while underway? Can you video record (with some help) while its doing it underway? It should be much easier to hear without the exhaust tone..

Can you check the condition of the spark plugs (brown, black, etc) after running it some at its worst moment?

[robert graham]

My C90 clicks, pops and rattles a good bit...thought that's how they're supposed to sound!

[Dscott2542]

Hi guys,

Thanks very much for all the replies, I had also been wondering if I may have been a little paranoid about the popping, I have also been told it could be a lean sneeze, I have changed the petrol I am using a couple of times which did not change the popping so continued with the thought it was something else. I have not had it in the water since it overheated last time, so I might try taking it out today and see how it goes.

Thanks again everyone, I will try it in the water and report back.