2 Stroke Carb Jet Cleaning

[Jason2tpa]

Yep, no fancy pictures, basic, easy to understand information...

It's amazing how well the motor responds when the carbs are dialed in. Now that the jets are clean, I made the adjustment to the 4 air screws as you suggested All 4 were way out of spec range. Each one was turned out 1.5, spec is 5/8 +/- 1/4. My fault for not checking these earlier when having carb issues, though it wouldn't have made a difference with the jets clogged up as they were.

And if you can recall, I previously had to turn in the throttle screw to bring the idle up to spec. Well after the air screws were at proper setting and started engine, the idle rpms were at 1100! Obviously the motor liked the richer mix, rather a normal mix. So I turned out the throttle screw bringing rpms down to spec. If this brutal wind stops blowing a gale ill run all day.

[TownsendsFJR1300]

Just a side note to the above.

When you cleaned the carb, all those adjustment screws should have come out, cleaner sprayed thru, etc.

Don't leave any orifice up to chance.

Good luck on your test run!

[Jason2tpa]

Noted, thank you. I tend to be one of those impatient people who need to know what's causing the issue immediately, whether I can fix the issue or not lol. I did get the carbs functioning correctly but at the time didn't have a new carb kit to install. I'll buy one of those complete kits that include floats and screws. The screw heads took a beating coming out due to the corrosion. When I install this kit everything will be cleaned, soaked, blasted, you name it.

Just a side note to the above.

When you cleaned the carb, all those adjustment screws should have come out, cleaner sprayed thru, etc.

Don't leave any orifice up to chance.

Good luck on your test run!

[TownsendsFJR1300]

Did you run the boat yet, weather clear up enough?

[Jason2tpa]

I did. Beautiful weather here in Tampa, but blowing a gale. Motor ran great. Now I gotta figure out the glich with the tach. It's so inconsistent. When I took the boat out briefly last night it worked perfect. Today not so much. Numbers on screen were barely visable along with reading false errors.

So Ive concluded it must be a connection issue somewhere cause if the tach module itself was the problem it would consistently fail. Ive unplugged the tach harness on both ends, cleaned it up, reinstalled. The fuse is good. What I haven't done is check the motor side harnesses.

Did you run the boat yet, weather clear up enough?

[TownsendsFJR1300]

Yep, it was breezy down here too.

Glad to hear it ran good, congrates!!

[Jason2tpa]

Yah it's running great. And turning 2-300 more rpms! Max rpms i get is 45-46, low end of spec. But Im happy with the speed, which with an empty boat and low fuel it tops at 41mph.

And guess what, the tach gauge worked perfectly tonight. I wonder what its function will be tomorrow lol.

[TownsendsFJR1300]

Max rpms i get is 45-46, low end of spec. But Im happy with the speed, which with an empty boat and low fuel it tops at 41mph.

Put the correct prop on there, pick up another 1,000 RPM's and you'll be REALLY HAPPY (5,500).

When I re-powered, they put the wrong prop on it. Max RPM, with the wind behind me was maybe 5,000. That F150 was flat out a dog, like I was dragging the anchor. It wouldn't pull a skier out of the water it was that bad..

Went to the local prop store, explained I needed 6,000 and went to stainless.
COMPLEATLY DIFFERENT ENGINE. It'd jump out of the water, plane very quickly.

IMO, I'd be re-propping that engine. You not getting you full horsepower and performance you COULD be getting. Just my 2cts..

[99yam40]

Stuffed the empty crankshaft holes (in single 125 and 250 Yamaha two strokes-YZ's, Motorcycles) back in the day too...

Off the subject, but what does this do for the motor and how & why did you do it.

The only empty holes I can think of on a crank would be where they drilled them to balance the crank

[99yam40]

Put the correct prop on there, pick up another 1,000 RPM's and you'll be REALLY HAPPY (5,500).

When I re-powered, they put the wrong prop on it. Max RPM, with the wind behind me was maybe 5,000. That F150 was flat out a dog, like I was dragging the anchor. It wouldn't pull a skier out of the water it was that bad..

Went to the local prop store, explained I needed 6,000 and went to stainless.
COMPLEATLY DIFFERENT ENGINE. It'd jump out of the water, plane very quickly.

IMO, I'd be re-propping that engine. You not getting you full horsepower and performance you COULD be getting. Just my 2cts..

I agree,
if you are only able to run at 4600 with a light load, once loaded as you normally run it is way over propped.
But then again it may not be running properly yet.
only way to tell is have it tested with the Yamaha test wheel to see if it can hit the proper RPM at WOT

[rodbolt17]

I second the test wheel test.
running overpropped can and will lead to wristpin failure.

use test wheel YB1611 for the 95-05 40 and the 98-02 c40.
should turn yb1611 to 4900-5100 rpm.
if it wont the engine still has issues.
if it will the rigging or prop is incorrect.

[Jason2tpa]

Ok guys, will do. I can't recall the props measurements so ill jot them today and post. Those numbers to yall will probably give yall a definitive yah or nah of being overpropped. Which by the way, what does that mean? Too much or too little pitch, cup, rake?

[99yam40]

I second the test wheel test.
running overpropped can and will lead to wristpin failure.

use test wheel YB1611 for the 95-05 40 and the 98-02 c40.
should turn yb1611 to 4900-5100 rpm.
if it wont the engine still has issues.
if it will the rigging or prop is incorrect.

Rod I looked again at the 1st post to be sure and this thread is on his 1998 S115TLRW

[99yam40]

Ok guys, will do. I can't recall the props measurements so ill jot them today and post. Those numbers to yall will probably give yall a definitive yah or nah of being overpropped. Which by the way, what does that mean? Too much or too little pitch, cup, rake?

too large, too much pitch and/or cup

Did you look at the Yamaha performance bulletins to find a rig like yours to see what prop they used?

[TownsendsFJR1300]

Ok guys, will do. I can't recall the props measurements so ill jot them today and post. Those numbers to yall will probably give yall a definitive yah or nah of being overpropped. Which by the way, what does that mean? Too much or too little pitch, cup, rake?

If you have a prop shop (and that's all they do are props, repair, rebuild, etc), bring your prop down there and explain what RPM's / speed, etc your getting.

If its a good shop, they'll get you the right prop the first time around. They did so for me.

Your prop is grabbing to much water, thus its not able to spin up fully...