300/440/550 JS550 is a bitch to restart

WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
Replace the needle and seat,it is bad and is allowing fuel to be pushed out the low speed jet when sitting, get a rebuild kit while you are at it,you are going to need it.
 
the WaTeRhAwK

the WaTeRhAwK

fryin' up a/m electrics..
Location
okc
dean85gt said:
The flame arrestor adapter has 3 bolts that go onto the carb..I hope that helps a bit.
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it is a regular bn 38 mikuni.
turn both of the adjustment screws lightly closed, then open them both to one full turn. either one will usually tune in between 7/8 and 5/8 of a turn open (depending on the shape of the needles and seats.) with a nice shape and clean needles and seats you don't want to go past 5/8 of a turn closed, it will lean it out too much.

yes, you can get good compression readings with leaky crank seals.
 
D

dean85gt

Location
Ontario
Why am I backing out the adjustment screws a full turn when you just stated that they need to be open 7/8 and 5/8.

Anyone got any pics to help? LOL
I'm used to tuning holley double pumpers on my race car.
 
the WaTeRhAwK

the WaTeRhAwK

fryin' up a/m electrics..
Location
okc
dean85gt said:
Why am I backing out the adjustment screws a full turn when you just stated that they need to be open 7/8 and 5/8.

Anyone got any pics to help? LOL
I'm used to tuning holley double pumpers on my race car.
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because between one full turn open and 7/8-5/8 is where it's tuned. that goes for both needles. there is no exact setting, but it's within that range, unless the needles and seats are worn, then it may take you even more closed than that. I'm just giving you the ballpark of where to be with it.
 
D

dean85gt

Location
Ontario
Alright so I will thread in both adjustment screws all the way...and then back them out one FULL turn and go from there....Now backing the screws off will effectively increase the fuel mixture correct (making it run richer) or do I have it backwards?
 
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the WaTeRhAwK

the WaTeRhAwK

fryin' up a/m electrics..
Location
okc
dean85gt said:
Alright so I will thread in both adjustment screws all the way...and then back them out one FULL turn and go from there....Now backing the screws off will effectively increase the fuel mixture correct (making it run richer) or do I have it backwards?
Click to expand...


yes backing them out richens the setting, closing them in leans it.
 
D

dean85gt

Location
Ontario
ok I will tinker tomorrow...The plugs are almost always on the dark and wet side so leaning the mixture may help.

Thanks again
 
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cookerq62

cookerq62

Life's Been Good
Location
Upper Bucks, PA
If it's hard to start it's most likely a bad gasket and water is getting into the engine somehow. Out of the water run without hose shut it down and try to restart it. If it starts fine put it on the hose and run it and look for leaks. Kill the motor then try to restart it right away. If it doesn't restart shut the hose off and check the plugs to see if they are wet. It could also be a bad check valve on the fuel tank or an ignition component thats on its last legs and doesn't work when it warms up or gets shaken up.
 
the WaTeRhAwK

the WaTeRhAwK

fryin' up a/m electrics..
Location
okc
cookerq62 said:
If it's hard to start it's most likely a bad gasket and water is getting into the engine somehow. Out of the water run without hose shut it down and try to restart it. If it starts fine put it on the hose and run it and look for leaks. Kill the motor then try to restart it right away. If it doesn't restart shut the hose off and check the plugs to see if they are wet. It could also be a bad check valve on the fuel tank or an ignition component thats on its last legs and doesn't work when it warms up or gets shaken up.
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i was thinking the same thing. maybe a warped head causing it too. I had the same problem a few years ago with a 440. we were chasing gremlins around that thing for awhile.

an easy way to check for a warped head or leaky gasket when it's hot it to do a compression test right when you beach it and compare those numbers to the ones you have when it's cold.
 
cookerq62

cookerq62

Life's Been Good
Location
Upper Bucks, PA
Strong water pressure through a hose will find the leak right away. A pin hole leak in a head gasket won't show up on a compression tester but will throw just enough water in the cylinder to make it hard to start. Be careful I had a buddy who ran a ski with a bad head gasket on the hose and ended up sheering a woodruff key when he went to restart it. It filled with water in no time. He is lucky he didn't bend a rod. That ski had cylinders within 5 psi of one another.
 
the WaTeRhAwK

the WaTeRhAwK

fryin' up a/m electrics..
Location
okc
cookerq62 said:
Strong water pressure through a hose will find the leak right away. A pin hole leak in a head gasket won't show up on a compression tester but will throw just enough water in the cylinder to make it hard to start. Be careful I had a buddy who ran a ski with a bad head gasket on the hose and ended up sheering a woodruff key when he went to restart it. It filled with water in no time. He is lucky he didn't bend a rod. That ski had cylinders within 5 psi of one another.
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if his head is warped, when the metal expands from operating temperature, the head metal will move away from the cylinders where it's leaking and it will take a little while for it to cool down and retract. if there is enough space created between the two, enough to let the water into the cylinders when it's hot, it will definitely show up with a compression check while it's hot.
 
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