2001 Yamaha 50hp tlrz 2 stroke with prime start system starts and dies

99yam40

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I will get the new CDI Box on Tuesday and check all the settings again and also check the timing setting needed to run the motor before I install the new CDI Box. Should know if the problem is fixed sometime on Wednesday. Thanks, Tom
hopefully you have a timing light to check this
 

tdave

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Using timing light in the bright Texas sunlight I read 2-4 degrees BTDC is where I can get the motor to run and stay running. This reading was done before changing out the CDI Box. The new box was not exactly plug and play because the metal pointer, needle arrow on the new CDI Box was flat and hit the hex nut as the throttle linkage was moved. Was able to use the old pointer by doing minor filing to the square bolt hole.

Installed new CDI Box and double checked all settings and fired the engine up. Engine fired right up to about 2000 rpm and after about a minute slowed down to about 800 RPM. It ran for about another minute then started to misfire or chirp every 3-4 seconds. Discovered the fuel bulb will not stay primed/firm (new issue since last time). Disconnected the new gas hose from motor and squeezed the bulb and it stayed hard/firm. Engine will stay running if you keep squeezing the bulb. So now I have an issue with what sounds like backfire and fuel pressure to the Carbs. Fuel pump was new last year. Could vacuum lines be an issue, I do not see much about them in my repair manual.
 

99yam40

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sounds like a lean sneeze.
and pump is not doing its job if pumping the primer bulb helps.
check to make sure pump is still good,
and the idle jets/passages are feeding the fuel needed for each cylinder
 

tdave

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I replaced the fuel pump today started the engine. It ran fine, idled down as it should and ran for some 35-40 seconds before some chirping, misfire noises and it died. I pulled the fuel line coming out of the pump and cranked the engine over and observed the amount of fuel it was pumping. It did not appear as a steady stream but somewhat bubbly and not enough to run through 3 carbs. Will try to bypass the fuel pump and get gas directly to carbs tomorrow.
 

99yam40

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there is a chance you have a leak between the pump and fuel tank allowing air to be sucked in,.
But then the pump runs off of the #3 crankcase so it just pulses ,so does not run a steady stream.

rereading your other post, if pumping the primer bulb helps then look for an air leak between the bulb and pump.
good chance at filter housing oring or quick disconnect or one of the other hose fittings
 
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99yam40

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you have not reported what the timing is doing with the new CDI box installed.
at start up my C40TLRX shows around 5 BTDC and idles high.
once warmed up it drops back to 7 ATDC.
what does yours show?
also post up a pic of your new CDI box hooked up.
I am not following the problem with the wiper arm hitting the nut.
Maybe you did not buy an OEM CDI box,
what did you get?

and I have no idea how by passing the pump will get fuel to the carbs, something has to pressure up the fuel lines.
 
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99yam40

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did you follow the link and sync procedure in your service manual after you put the carbs back on?

all 3 carbs throttle plates need to completely closed and tied together so all are contributing to the idle the same.
(not just set at idle position)
also the timing is part of the procedure
 

99yam40

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any updates yet on your motor

link and sync and idle timing is very important
 

tdave

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Been raining here on and off for the past few days but will get back to checking things. Plan on replacing fuel lines and clamps to begin with.
 

maineiac5586

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Been raining here on and off for the past few days but will get back to checking things. Plan on replacing fuel lines and clamps to begin with.
I have a oem used cdi box on ebay from a 2000 40 hp 3 cylinder in good working condition
Item number 186185638248
 
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