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knocking sound on start up(won’t start)

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Old 12-17-2023, 09:10 AM
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Default 350 big bear(won’t start)

just changed carb and intake to fix runaway. what’s up with it? looks like the carb isn’t sucking any fuel. is it the petcock? i put a video in comments

1991 yamaha big bear 350
 
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Old 12-17-2023, 09:25 AM
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Old 12-18-2023, 04:05 AM
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Sounds a bit like timing is out. Check the piston is at top dead centre, through the plug hole, when the timing mark on the flywheel says it is. If it is, check TDC mark on flywheel and camshaft either agree or cam mark is 180 degrees out. If you want to check the fuel tap, take the pipe off at one end and see if fuel runs out with the tap turned on.
 
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Old 01-09-2024, 12:50 AM
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Any update?
Spoiler
 

 
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Old 01-12-2024, 02:53 PM
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Originally Posted by merryman
Sounds a bit like timing is out. Check the piston is at top dead centre, through the plug hole, when the timing mark on the flywheel says it is. If it is, check TDC mark on flywheel and camshaft either agree or cam mark is 180 degrees out. If you want to check the fuel tap, take the pipe off at one end and see if fuel runs out with the tap turned on.
Originally Posted by JosefaRippin
Any update?

How do i pop of black cap to check cam mark. fly wheel is off mark as seen in pic

edit: just realized i didn’t check if piston is tdc. where is the crank? how do i move piston to top dead center? is it the bolt on the flywheel?
 
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Old 01-12-2024, 06:18 PM
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Black cap screw out also the center bolt in the cranking bell[recoil] is used to rotate the crankshaft after you remove the black cap look inside you willbe able to see timing marks on flywheel rotate to the T mark[for timing] here in the south we put a drinking straw in spark plug hole to gauge locate piston cycle when TDC both values should be closed an piston at the top an the T mark shouldbe align with arrow inside case and the camshaft sprocket key way and mark on the sprocket should be align with arrow on the head[shown in photo] if the engine has been rotated with the mark like in photo may have bent a value.
 
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Old 01-12-2024, 06:25 PM
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If you have to retime loosed chain tenisioner and sprocket bolt rotate sprocket and chain to the correct location
 
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Old 03-04-2024, 05:22 PM
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Originally Posted by merryman
Sounds a bit like timing is out. Check the piston is at top dead centre, through the plug hole, when the timing mark on the flywheel says it is. If it is, check TDC mark on flywheel and camshaft either agree or cam mark is 180 degrees out. If you want to check the fuel tap, take the pipe off at one end and see if fuel runs out with the tap turned on.
Originally Posted by JosefaRippin
Any update?
Spoiler
 

Originally Posted by papa hogg scoot
If you have to retime loosed chain tenisioner and sprocket bolt rotate sprocket and chain to the correct location
i got the piston tdc and the timing mark lines up but the gear that’s holding the chain is off, how do i go about fixing that? release tensioner then spin the gear under the timing chain?

 
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Old 03-05-2024, 02:51 AM
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Rotate the crankshaft by exactly 1 turn and the timing marks should line up.
 
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Old 03-05-2024, 10:15 AM
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Originally Posted by merryman
Rotate the crankshaft by exactly 1 turn and the timing marks should line up.
Should i get a new tensioner or chain?
 


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