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I realize it has something to do with air/fuel mixture not being set correctly. Is there a way to rejet the motor without taking it to the dealer? I am mechanically inclined so i know i can do it but i need someone/something to show me what to do. I'd rather not have to take the darn thing to the dealer everytime i'd like to fish a mountain lake. Advice?.....There is nothing in the manual that came with the engine pertaining to this subject.
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So it runs fine at lower altitude and then runs poorly at higher(?) altitude?....What exactly is the poor running problem?....how high is the higher altitude?....Originally posted by renegadeangler View Post -
I have run it twice at 1300 ft and it ran great
I hauled the thing to Utah and tried to run it at 8300ft. It started initially and then stalled within 30sec to a minute and wouldn't restart. So obviously it was flooded. I live in the greater LA area but haven't taken it to the local mountains which are 4000ft-5000ft roughly. When it ran near my home it ran beautifully.
So, in summary, it starts but doesn't run at all at 8300ft and starts and runs like a beaut at 1300ft. I have know idea how it does anywhere in between.Comment
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Two things come to mind when operating at high altitude. Idle and main jets would need to be adjusted (smaller size) and a propeller of a lesser pitch would be needed.
Even with the proper high altitude jets installed the motor is going to make much less horse power at high altitude. So, if you were properly propped at sea level you will be over propped at altitude. A pitch change is needed.
It is not a difficult job to change jets. Once the carburetor is removed from the motor the float bowl is removed. Four screws. The idle and main jets are then simply unscrewed and new ones installed.
The jets in your motor are a number 45 idle jet and 108 main jet as I recall. The jets from an F40 will plug and play with an F25. Look at the jets from an F40 model. The sizes have changed over the years but they are both smaller. Whether the are exactly what you will need at 8300 feet only you will be able to tell.Comment
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So I'll have to rely on trial and error
once i get the jets from the F40. Is it logical to assume that the higher the altitude, the more need for jets from a higher horsepower motor? so if the jets from the F40 don't help then i'll need jets from the F50 or F60? The larger the engine the smaller the jets?
As for the prop, the pitch ranges from 8-14. I'm assuming 8 being the lowest pitch and 14 being the highest right?
Thank you for info and time.Comment
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No, it does not work that way. You can't go by the size of the motor in horse power to determine anything about the jet size, or even if they will fit. I just happen to know that F40 and late model F25 jets are interchangeable. I was using F25 jets in an F40 to cure an idling issue because the F40 jets from the factory were too small. Thanks to the EPA.Originally posted by renegadeangler View Post
Once you look at your jets you can go on the internet and find non Yam jets of the same type. They are made by Keihin. Jetrus.com is one supplier. Maybe get some smaller than what you need and drill them out with a microbit until you determine the size that works best for you.
Www.jetsrus.com
Yes, 8 pitch is probably what you may need at 8000 plus feet. That is way up there.Comment
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Ok
***. Thanks for the great info and the time it took passing it on..............Screw the EPA.Comment
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