Re: 1990 125 Force has 2 Mechanics Stumped
If it indeed is getting good spark on all four cylinders, and if it is getting adequate fuel to the carbs, Then lack of top end power is still probably related to fuel problems. Of course, with duct tape ingested into the reeds, there is a smoking gun which needs investigation. Reeds must lay flat on the vee blocks with no pre-load or concavity. They are, however, allowed to stand open a maximum of .010 inch at rest. If they look good, they are good and are not causing the problem. Check and replace the reed plate gasket. a broken or defective gasket allowing air to bleed between cylinders will affect power. ALSO: BE CERTAIN to tighten the vee block mounting screws and use loctite on them. These screws can loosen, allowing the vee block to move in and out with the crankcase vacuum and pressure, significantly affecting power.
However: You must define "Lack of top end power better." If you have the engine on a 18 foot hull and are expecting 50 or better, then the problem is not with the engine, but with your expectations. Hard numbers here would be helpful, ie. It used to go 40 MPH but now only tops out at 30 MPH.
Tachometer readings would be helpful too.
Actual compression ratios on the cylinders also would help.
One person's "good" is another person's "lousy."
That said, since the carbs were cleaned and possibly removed during the process, they may be out of sync. You need to remove the black covers and verify that the venturi butterflies are opening equally and fully at full control handle movement. They also need to be synchronized with the timing and you must ensure that timing is 30 degrees btdc at full throttle. Significantly retarded timing will cause lack of top end power. If your engine has an enrichment valve instead of choke butterflies be certain that the valve is not leaking, passing fuel even when not energised. As fuel pump pressure goes up with speed, the leak will get worse and cause rich running at high speeds with loss of power.
Float level is another critical area. With the carbs inverted and the fuel bowls removed, the floats should be level, or parallel to the carb casting, with only their own weight pressing on the needles. Floats set too low (with the carb in running position) will cause lean running and loss of power'
Low speed needles need to be somewhere around one turn out from lightly seated. Less than that will also cause lean running at full throttle, loss of power, and subsequent melting of pistons due to detonation.
Finally, check to be certain that the correct gaskets are installed on the bowl bolt and the correct high speed jet is installed in the carb. Lack of or incorrect gaskets can cause rich running at high speeds and loss of power. Missing jets or jets with the orifice enlarged due to rough cleaning will cause rich running at high speeds and loss of power.
At this point, you must assume that anything that can be out of adjustment is, and set all adjustable items back to factory specifications.
Hi,