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Help, 89 25 hp 2 stroke won,t idle

C

carbo12jim

New member
I got this motor from my brother earlier this year, ran good last year. I have rebuilt the carb,replaced the fuel pump, tank, and all the hoses, replaced no 1 cyl coil. If I give it a couple of squirts with the primer and advance the throttle it will start and keep running as long as it doesn't drop to idle speed. With a timing gun and turning with the starter motor the timing seems good and both plugs are firing. I have also gone through the carb several times and all passages seem open. I've run out of ideas. Any help would be much appreciated. compression is 120 on both cylinders
 
I have also gone through the carb several times and all passages seem open...it will start and keep running as long as it doesn't drop to idle speed.
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If it won't idle the small circuits are still clogged. Try this: drain the carb and fill it w/spray Seafoam and let it soak 24-48 hrs. while it dissolves the hardened fuel varnish. It'll smoke alot when it starts but should be able to idle. The throttle response will be greatly improved.
 
Thanks, I'll give that a try. All of the circuits have been cleaned and blown out several times. I can see through the idle jet and 3 small holes going into the top of the venturi and pressing the choke solenoid when it is running does cause it to bog down. Is there any way to measure vacuum on the intake
 
Have you tried adjusting the idle speed a little? Turn the mixture screw CCW 1/8 turn at a time to increase the richness of the mixture and let it settle for 30 seconds before doing it again. Start from 1&1/2 turns CCW from all the way CW.
 
I have tried after starting at 1&1/2 going 1/4 turn at a time. adjusting it seemed to make a difference in engine speed and smoothness but would not prevent it from stopping if the throttle was released
 
Is the engine losing spark when it nears idle speed? If you squeeze the primer bulb near idle speed when it starts to die will it keep on running?
 
I've tried squeezing the primer bulb, it is still firm and has no affect on it. Turning the engine with the starter and the throttle in the idle position, there seems to be good spark on both cylinders
 
Crank case vaccum??? how the suction in the carb?? iv seen the crank bearing seals leak air and not get enough vacuum to pull fuel thru carb this will not effect engine compression
 
There are two hoses, one from the side of each cylinder to the bottom of the plate holding the the reed valves in place. Can intake vacuum be measured from this hoseand if it can what should it be?
 
Pretty sure those two hose are oil return lines. I'm not sure of an official test for vacuum of crank case. How I found this problem on my engine was cranking it over with my hand on carb should have pretty good suck mine had pretty much none(I could not start my engine either) there are two seals one on top of crank one on the bottom under power head (have to pull power head to change) REALLY sounds more like a carb issues! what is rpm at idle?? What rpm does it hold idle?? What's the tip of the air/fuel adjustment screw look like? Smooth pointy no signs of wear
 
..."Pretty sure those two hose are oil return lines."

Correct. No way to measure vacuum on these since it pulses positive/ negative.

Either your carb low speed circuits are plugged (from not cleaning it properly), or your idle mixture screw is set way too lean.

How did you "clean" the carb? Spraying it with carb cleaner won't do: you have to disassemble it, soak it overnight in cleane, blow out all the passages, a rod it out at times.

Jeff
 
If the crank seal is bad than pulling the bottom plug wire off will tell you that #2 is not hitting because of the leak.
Those hoses are the bleeder lines and there are check valves in the fittings. That would cause a rich idle most times.
 
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Opti-man-808 said:
Pretty sure those two hose are oil return lines. I'm not sure of an official test for vacuum of crank case. How I found this problem on my engine was cranking it over with my hand on carb should have pretty good suck mine had pretty much none(I could not start my engine either) there are two seals one on top of crank one on the bottom under power head (have to pull power head to change) REALLY sounds more like a carb issues! what is rpm at idle?? What rpm does it hold idle?? What's the tip of the air/fuel adjustment screw look like? Smooth pointy no signs of wear
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the idle screw tip looks good, it will not hold idle. I have to keep playing with the throttle to keep it from dying, I would guess keeping it above around 1200 rpm to keep it from dying
 
timebandit said:
If the crank seal is bad than pulling the bottom plug wire off will tell you that #2 is not hitting because of the leak.
Those hoses are the bleeder lines and there are check valves in the fittings. That would cause a rich idle most times.
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I'm waiting on a gasket to come in then I will try pulling the bottom plug wire. After running it I pulled both plugs and they looked the same, slightly wet and black
 
Remove some of the bypass covers to inspect pistons and ring for scoring.-----------Water pump impeller was replaced recently I hope.
 
fastjeff said:
..."Pretty sure those two hose are oil return lines."

Correct. No way to measure vacuum on these since it pulses positive/ negative.

Either your carb low speed circuits are plugged (from not cleaning it properly), or your idle mixture screw is set way too lean.

How did you "clean" the carb? Spraying it with carb cleaner won't do: you have to disassemble it, soak it overnight in cleane, blow out all the passages, a rod it out at times.

Jeff
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I cleaned the carb by soaking it for about 4 hours in carb cleaner, blowing it out and rodding out all the passages with a copper wire a total of 10-15 times because I agree it acts like something is plugged. adjusting the idle screw seems to affect rpm as does holding the choke solenoid in
 
Here's one other thing to check: Is the "choke" plunger in the carb being pushed down when the "choke" is in the off position? If so, it tends to suck in fuel when it shouldn't. Readjst to avoid this.


Jeff
 
fastjeff said:
Here's one other thing to check: Is the "choke" plunger in the carb being pushed down when the "choke" is in the off position? If so, it tends to suck in fuel when it shouldn't. Readjst to avoid this.
Jeff
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that happened when I first rebuilt the carb. Found out it makes a difference which end of the spring is next to the ball
 
Change those plug black and wet both not good try new plugs sounds borderline fouled it's a cheap try

Idle screw can u c from outside of carb or have to remove from inside???? There should be a idle screw and a mixture screw the mixture screw will effect idle but richen or lean out carb at idle this tip needs to be pointy with out any Knicks this one should be like 1to 1 1/2 turns out from lightly seated to start and can be adjusted from there like fast Jeff and guyjg mentioned adjust idle screw so she hold high idle the adjust the mix screw and try to bring idle down once u got mix right
 
Opti-man-808 said:
Change those plug black and wet both not good try new plugs sounds borderline fouled it's a cheap try

Idle screw can u c from outside of carb or have to remove from inside???? There should be a idle screw and a mixture screw the mixture screw will effect idle but richen or lean out carb at idle this tip needs to be pointy with out any Knicks this one should be like 1to 1 1/2 turns out from lightly seated to start and can be adjusted from there like fast Jeff and guyjg mentioned adjust idle screw so she hold high idle the adjust the mix screw and try to bring idle down once u got mix right
Click to expand...

Good idea on the plugs. They are new but new doesn't always mean good. I will try jacking up the idle screw and see if I can get the mixture adjusted
 
First, thanks for all the ideas and suggestions. Sometimes it is hard to see the forest for the trees. I put new plugs in and adjusted the idle speed screw until I could keep it running while I adjusted the idle mixture. When the rpm gets down to around 1000 it slowly dies like it is running out of gas.To start it back up I have to give it 1 or 2 squirts with the primer and open up on the throttle, almost like a vacuum leak on a car. Any further ideas or the name of a good repair shop near Charleston, SC would be much appreciated
 
Did you ever find out what the issue was? Everything in your post matches my current situation. Even same outboard year and hp.
 
Thought of two things that can cause this:

1. The rubber gasket that seals the reed assembly is leaking. One half of the reed cage feeds one cylinder, the other side feeds the other. I've seen this gasket cause a leak and it would MURDER idle.

2. Excessive blowby (though your comp readings are reasonable). I've seen triples with born bores that would not idle below 1,500 rpm. If one tried, it would slowly idle lower and lower until it stalled.

Jeff
 
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