Please help, cylinder not firing...

W

Windburned

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I have a 50 yamaha EJRP. The motor starts right at the turn of the key. When I throttle up only 2 cylinders are firing and the third starts kicking in, after about 5-10 seconds it finally fires the way it's supposed to. I replaced the fuel pump when I first got the motor that was shot. Carbs are clean, new plugs, I just don't know what's going on, any help will be greatly appreciated!!! Thanks in advance, John
 
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99yam40

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Re: Please help, cylinder not firing...

Which one is not firing properly?
Sounds fuel related, clean the carbs properly and then do the link and sync as the service manual says to adjust the carbs after reinstalling them.
 
W

Windburned

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Re: Please help, cylinder not firing...

Not sure which isn't firing, all plugs look exactly the same. It's got a jet on it so it's not like I can muff it to run it.
 
W

Windburned

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Re: Please help, cylinder not firing...

All carbs open fully and at the same time. After the initial sputtering and that third one kicks in, it fires and doesn't miss till I throttle down, then it starts all over again.
 
W

Windburned

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Re: Please help, cylinder not firing...

99yam40 said:
Which one is not firing properly?
Sounds fuel related, clean the carbs properly and then do the link and sync as the service manual says to adjust the carbs after reinstalling them.
Click to expand...

It's the 3rd or bottom carb that's missing, did a spark test all cylinders are getting spark... Took air filter off and then covered each carb with our hand to see which one wasn't affected... #1 carb cover it and engine bogs down, same with #2 carb.... #3 cover it.... Nothing no bogging down no change in rpm... Did the same test with spraying carb cleaner into each carb, bogs down in 1and 2 when we sprayed it in, #3, no change. I hope this sheds some light and gives you more info that you can use to help me. Thanks in advance,
John
 
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99yam40

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Re: Please help, cylinder not firing...

Check the fuel pump , if it has a hole in it it will leak fuel into the crank case for #3 and cause this type of problem
 
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