'93 25hp 2 stroke Spark Plug Issue??

[Dashunde]

Try this...

Disconnect your dead-man, block off the air intake for both cylinders at the front cover, seal it up tight with your hand if you can get it in there and pull the cord 4-6 times, not hard like your trying to start it, but hard enough to draw fuel in.
Reconnect the dead-man and try to start it without using the choke.

The idea is that at least both cylinders will be treated the same, instead of one being flooded by its choke and the other is left empty.

When you hold the throttle WOT when pulling, your clearing out excess fuel(working against your self).

Not if the choke is in place, opening the throttle allows a more acute draw from the bowl. Throttle plates seal tighter than chokes.
In his case your right, one cylinder is clearing out while the other is flooding.

If this motor is in any kind of good overall condition and (evidently) worth messing with, you really should track down a replacement carb with a working choke.

[99yam40]

I recon when its full choke it's really half choke cause only one flap. So at best only half choke is possible to start. If needed, I guess I could remove the vent cap and hold my hand over the carb with the missing valve. Though thats a pain in the ass. Let me try properly starting engine with the sequence you recommended. If it consistently starts on one then I dont have to replace the carb. Fingers crossed. Thanks for all your assistance.

As said, each cylinder is fed by its own carb. there is no crossing over in the crankcase, there are seals on crankshaft
That is no half choke , one cylinder is getting absolutely no extra fuel when pulling the choke knob with the choke plate missing

[Jason2tpa]

Hadn't thought of that. Makes sense thanks

As said, each cylinder is fed by its own carb. there is no crossing over in the crankcase, there are seals on crankshaft
That is no half choke , one cylinder is getting absolutely no extra fuel when pulling the choke knob with the choke plate missing

[Jason2tpa]

It's a good running motor once it starts of course. It's the inconsistent starting that bothers me but now I know why. Thanks again for all of your assistance.

Try this...

Disconnect your dead-man, block off the air intake for both cylinders at the front cover, seal it up tight with your hand if you can get it in there and pull the cord 4-6 times, not hard like your trying to start it, but hard enough to draw fuel in.
Reconnect the dead-man and try to start it without using the choke.

The idea is that at least both cylinders will be treated the same, instead of one being flooded by its choke and the other is left empty.


Not if the choke is in place, opening the throttle allows a more acute draw from the bowl. Throttle plates seal tighter than chokes.
In his case your right, one cylinder is clearing out while the other is flooding.

If this motor is in any kind of good overall condition and (evidently) worth messing with, you really should track down a replacement carb with a working choke.

[Jason2tpa]

Dead-man? Kill cord, i assume? The only way to block off the air intake is to remove a plastic cover that's screwed into the frame of the carb (4 screws). It's no big deal to remove this. I assume this cover is meant to keep debris within the engine compartment from being sucked into the carb? Because its not a air filter, just a cover.

[Dashunde]

Humm... you really ought to find another carb then.

[zenoahphobic]

Dead-man? Kill cord, i assume? The only way to block off the air intake is to remove a plastic cover that's screwed into the frame of the carb (4 screws). It's no big deal to remove this. I assume this cover is meant to keep debris within the engine compartment from being sucked into the carb? Because its not a air filter, just a cover.

The cover also acts as a noise suppressant (directs sound backwards away from boat in front)

[TownsendsFJR1300]

If your REALLY GOOD working with thin SS or aluminum and have the tools, you could make your own choke plate. Actually that plate may be brass, much easier to work with.

You have another one there as a template (if needed), get the correct metric screws and loctite them in when re-assembling..

*But agreed, you do need that choke butterfly in any case for consistent COLD starting.

[Jason2tpa]

I have the choke flap and the two screws, given to me by a local yamaha service store. However, and I might have mentioned this before, those screws flare at the distal end. Once removed they cant be reinserted. So why not get new screws, right? This became a very arduous task when I was searching. Thry are so small with a specific thread pitch and length. Yamaha doesn't list these screes in a parts manual. Actually they dont even list the choke flap. If i can locate replacement screws then this choke issue goes away. Suggestions?

If your REALLY GOOD working with thin SS or aluminum and have the tools, you could make your own choke plate. Actually that plate may be brass, much easier to work with.

You have another one there as a template (if needed), get the correct metric screws and loctite them in when re-assembling..

*But agreed, you do need that choke butterfly in any case for consistent COLD starting.

[Dashunde]

Look for similar screws at a remote control hobby store... RC cars, planes, copters, etc... they all use very small metric bolts.
Pick stainless if you can, cut to length with a little left over, clean up the threads, install the choke, clamp a punch in a vise, carefully feed it through the carbs throat, then lightly wack the head of the screw with another punch to mushroom the threaded end so it never backs out and gets sucked into the motor.
Brass would be easier to mushroom...if you can find it.. maybe with the parts for the rc boats?

Can you not clean up the threads of the old ones by chamfering with a Dremel or file and reuse them?
(Of course, mushroom them again too)

I'd like to see a picture of what you have to work with...

[Jason2tpa]

Im at the boat ramp now at the wash station to see if i could get it started. No luck. Pulled the plugs. The plug to the carb that can be choked is soaked, the other one a lil wet. I have a spare set of pkugs. Tried those but the same outcome. A couple pulls it almost got running. The next pull after that one though was dead. This is really frustrating cause once its running its great. I assume cylinders are flooded? Is there a quick solution to unflood while im out here or only time dries up the cylinders?

Look for similar screws at a remote control hobby store... RC cars, planes, copters, etc... they all use very small metric bolts.
Pick stainless if you can, cut to length with a little left over, clean up the threads, install the choke, clamp a punch in a vise, carefully feed it through the carbs throat, then lightly wack the head of the screw with another punch to mushroom the threaded end so it never backs out and gets sucked into the motor.
Brass would be easier to mushroom...if you can find it.. maybe with the parts for the rc boats?

Can you not clean up the threads of the old ones by chamfering with a Dremel or file and reuse them?
(Of course, mushroom them again too)

I'd like to see a picture of what you have to work with...

[TownsendsFJR1300]

I have the choke flap and the two screws, given to me by a local yamaha service store. However, and I might have mentioned this before, those screws flare at the distal end. Once removed they cant be reinserted. So why not get new screws, right? This became a very arduous task when I was searching. Thry are so small with a specific thread pitch and length. Yamaha doesn't list these screes in a parts manual. Actually they dont even list the choke flap. If i can locate replacement screws then this choke issue goes away. Suggestions?

Heck your 7/8's there!!

Pull the carb and as noted, bring it down to who ever carries small metric screws and find what you need.

Either flare or use RED loctite. Its good for over 400F degree's. Flaring would be safer but the loctite isn't going anywhere.

With that butterfly already off, you can just bring the shaft with you...Should just slip out the side of the carb (un-less there's something bolted up to the other side)..

If the screws you already have are long enough, as noted above gently grind off the flared part. If they use all the threads, again, loctite, OR at least you can use them to help find new screws..


Just a thought, I wonder if a "jeweler" can clean up those tiny screw ends for you. They work with super small stuff... Worth a try..

[boscoe99]

To get a flooded engine to start advance the throttle to the wide open position. Engage the starter motor. Be ready to come back on the throttle as soon as she lights off.

[TownsendsFJR1300]

Is there a quick solution to unflood while im out here or only time dries up the cylinders?

Yep, leave the choke OPEN AND hold the throttle WIDE OPEN and pull.

That'll dry out the cylinders. When it fires, its going to rev very quickly so be prepared..

[Jason2tpa]

Throttle wide open....in neutral im assuming or talking bout in gear WOT.?? Sorry just want to be sure.