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Hi,
I rebuilt both the carb and pump, and set both idle mixture clockwise seat lightly and turn back 1 1/4 turn, if I wide open the throttle, then start, it looks fine, after I close the throttle, it won't stay idle.
I ever checked the 4 cyl compression, all around 110, looks fine, and gas is fresh.
Any suggestion?
Thanks.
peter
I hope you're using new plugs and they are gapped properly...you might try altering the gap by .005 to see if it smoothes the idle,you'd be suprised to see what .003 will do to an engine that rough idles,other than that have the coils checked to see if they're ok.
Oh that 1 1/4 turn on the idle screw is just a ballpark figure,each carb has to be fine tuned from there.
You also may need to reset the idle speed! if the barbs have been apart and the linkage disturbed, often it will need to be reset. Also look at the linkage for the spark advance. Don't know this specific model but the throttle usually controls the ignition advance.
When it won't start, after a few cranks, pull the plugs and check to see if they are wet or dry. Sounds like the low speed settings are off, but could be too much or not enough gas...
sorry, I think the throttle I mentioned should be a lever for quick idle.
When I lift the quick lever open, the outboard looks fine, when I put the lever back (because you can't change gear with the lever open), it stalled, no idle.
peter
As said above make sure to use new plugs, and I mean brand new out of the box. Its amazing what a new set of plugs will do for a 2-stroke.
The spark plus is new, and the gap is not adjustable.Quote:
Originally Posted by Marker
peter
As said above 1 1/4 is just a starting point. If you have a copy of the shop manual that would be a good reference but even then they are not 100% accurate. This is the method I used on my holley carbs way back in my younger days of muscle cars:
Start the engine and set the idle speed screw so it idles (not the air mixture screw that is next)
Let the engine warm up to get off the chock
Adjust the air mixture screws to get the highest idle, while doing so turn down the idle to where you want it
Repeat setting the air mixture screw at the low idle to achieve the highest idle, blip the throttle to test for hesitation and make further adjustments to the air screw to reduce hesitation.
If that does not work I test for a vacuum leak by starting the engine and spraying wd-40 around the base carb (not in the barrel), if there is a leak the WD-40 will act a fuel source and the idle will go up - you may need to manually set the throttle partly open to achieve a stable idle in order to test.
If that is not successful I would go through other diagnostics such as testing each plug for a spark (u tube is good for this), testing the plug wires for resistance using a multimeter (can get them cheap at CT), verifying fuel mixture ratio (could be too rich).
Good luck, let us know how you make out.
M.
Sucking air?
Check all connections from the fuel tank, through the primer bulb, both sides, then the connect to the motor itself?
I think that it is sucking air also. Perhaps the diaphragm is cracked in the fuel pump. Take it off and examine the diaphragm for holes or cracks. Also, there may be a fuel filter right before the pump and it may need to be replaced. Also, if you are using gapless plugs and they are not the recomended plug, I would switch them out for the Merc recomended plugs.
If you are able to run it for any period of time, you could look to see if the plugs are whitish which would indicate a lean burn - too much air. Only other idea would be that there is a piece of junk, varnish, rust etc stuck in one of your low speed jets, allowing it to run fast but not at idle. I do not know how many carbs are feeding the four cylinders of this engine.
PaulR is correct and to add to that my question is have you made any linkage adjustments?
Your engine advances timing when you move the throttle/fast idle lever first before it actually moves the throttle plate to add fuel.. So before we add more fuel we actually add more timing and that is what initially increases rpm.
Setting this up is called sync and link. Its very critical to the performance of your engine.
You need to qualify your ignition system. Do a simple spark test with a sealed spark tester..
If spark is good then install the proper spark plugs and when running do a drop cylinder test by using a insulated pair of plug wire pliers or suitable one's that will work and remove one plug at a time and if there is a change in sound you know that cylinder is working. If no change then you have a starting point.
If its all good.. go back to those carbs..
Did you clean the carb in a vibrasonic? Did you install a new carb kit? needle and seat?
Best of Luck