2 Stroke Carb Jet Cleaning

[TownsendsFJR1300]

Not even going to try.

I never worked for Yamaha (as a living like Boscoe) and don't have access to the documents Boscoe has with his years at Yamaha. His knowledge (and others) are way more than mine, that's how they made their living with literally years of experience specifically working on Yamaha's

I've worked on THREE Yamaha OUTBOARD engines my entire life, motorcycles (including Yamaha's) and everything else (cars, etc)over 42 years, self taught-NO schools. Yamaha motorcycles use alot of what the OB's do, FI, OHV's, water cooling, besides having a built in transmission(doesn't drop off like a LU- you have to split cases)

Just basic mechanical "hands on" knowledge. There's few things I can't fix once I get my hands on it. Over the net, somewhat more difficult as folks don't always give the whole story, something rigged wrong(that you won't know or ask about), etc. Motorcycles, Yamaha's specifically I'm MUCH more knowledgeable about...

Re you question about your carb, I've never seen two LS jets, especially on yours which is a larger engine (not like a 9.9). I do know most (95%) customers gas engines I fix are fuel related with jets clogged with varnish. That's why I mentioned clean all jets and you must see light thru them as varnish can hide on the sides. That's also why I push the RingFree, I know it works as I use it on machines with fuel issues.

BTW, the career I retired from (25 years), was Law Enforcement. Mechanic's was / is my hobby... And I'm still learning here re outboards

[Jason2tpa]

Well you're dam good at helping others with their mechanical yam issues. So keep it going my man.

Not even going to try.

BTW, the career I retired from (25 years), was Law Enforcement. Mechanic's was / is my hobby... And I'm still learning here re outboards

[Jason2tpa]

Alright boys, here we go again. Re-read this earlier post of mine concerning:

1998 S115TLRW

I experienced power loss as rpms approach 3300. Sounds like it's flooding if i throttle up. Because the carbs are due for a good cleaning im fairly sure the jets are gummed up. As a quick fix, what are your thoughts if i were to dump the 4 bowls, spray compressed air using the straw directly into the main jets, then some B12 carb cleaner into jets.

If the issue is the main jets I would think this works

Then this:

Update:

Yep, it did the job. But time to pull the carbs for a complete clean job.

Experienced the same issue today. Motor sounded and ran great crossing the bay, a 15min ride at 3/4 throttle. Loaded up the baitwell (adding approx 130lbs of weight to stern). After I throw net I bucket wash the deck down, open the self bailing plugs and motor at a high idle to empty the water. As you can probably imagine, this high idle along with the extra weight in the back puts engine under a significant load. After deck wash was done I throttled up to head to my fishing spot and got the same power loss as my quotes above note....power loss with a throatier sound. If i give more throttle, sound gets deeper and will kill unless I back down.

But this time around I did something different....I'd push the key in (choke) and release. When I did this the engine seemed to breath life, then lose power again. Then I tried rapidly pushing key choke in-out, and if I timed it right, the engine would remain running around 3k rpms. I didn't continue this of course, didn't seem such a good idea.

Recall that I've pulled both the main jets and slow bleed air jets. All clear. I have not pulled the pilot jets simply because I didn't have the time last week to pull out the carb assembly. Well, now I've gotta make time.

Your thoughts? My plan is to pull the carb assembly, check the pilot jets, open the bowls and check the floats and needle valves. Anything else I should look for while I'm in there?

FYI:
--fuel is new
--fuel is flowing through the primer bulb
--spark plugs are brand new

[TownsendsFJR1300]

Perhaps check your fuel pump per the manual and also for any vacuum/fuel leaks.

IE, transom mounted fuel filter, the O-RING there, under cowl filter(same), etc.

When your hitting the choke, your obviously making the mix richer. IE, it sounds like its leaning out for some reason..

Your "throatier sound" sounds the carb's opened up, BUT the RPM's are not. Kind of like an old 4bbl Rochchester carb. Have the secondary butterflys too loose, its a bunch throatier (WOT) until the engine RPM catches up..

[Jason2tpa]

Fuel filter is inline under cowling. I'll check it, thanks. Other than opening the fuel pump, how else do you check its function? The primer bulb remains full, flow through it. If the pump had failed wouldn't the bulb be compressed? Engine idles in gear ok, so it's getting fuel (though maybe not enough once the throttle opens, obviously).

Do you agree it's a good idea to open carb bowls, check the needle valves and floats? I mean, this definitely sounds like a fuel issue verses a compression or spark issue.

Perhaps check your fuel pump per the manual and also for any vacuum/fuel leaks.

IE, transom mounted fuel filter, the O-RING there, under cowl filter(same), etc.

When your hitting the choke, your obviously making the mix richer. IE, it sounds like its leaning out for some reason..

Your "throatier sound" sounds the carb's opened up, BUT the RPM's are not. Kind of like an old 4bbl Rochchester carb. Have the secondary butterflys too loose, its a bunch throatier (WOT) until the engine RPM catches up..

[boscoe99]

Knowing that the jets provide fuel to the motor, knowing that the jets have not been cleaned, believing that the motor appears to not be receiving sufficient fuel, as evidence by the choke being applied makes the motor run better, I would suspect the carburetors might be the problem.

[Jason2tpa]

I would suspect the carburetors might be the problem.

Help me out a bit boss....I know the word "carburetor" to be a term used to describe the entire carburetor. As in, I need to pull the carburetor and give it clean. Speaking to an amateur, what exactly do you suspect might be the problem...jets?

Thanks bud

[boscoe99]

Yes, the jets. Fuel flows through them. If they are clogged up a bit with deposits then less fuel will flow. With the same amount of air and less fuel the engine will typically bog down.

Another test is to spritz a bit of gasoline into the carburetor inlets when it starts to bog down. If it picks up and runs momentarily that is a sign that it is starving for fuel.

[Jason2tpa]

Gotcha thks. Ive got both crabs off. The pilot jet plug screws on the lower carb are corroded bad, to the point that they're very difficult to unscrew. Need to get a flat head wider than the head so it wont strip. This might be a good indication the pilot jets are also corroded. We'll see.

[TownsendsFJR1300]

In post #4, first page, I mentioned pulling the jets, making sure you can see thru them, etc..

As noted previously, fuel, carb(s) are easily 90% of issues on a carbureted engine...

**You'll likely end up using a wider, thicker screwdriver (for the correct thickness at the jet) but it won't fit deeply enough in the hole. Grind off just enough of the wide edges of the screwdriver till it fits...

Then soak the jets with PB Blaster or similar over night. Gently clamp (or have a helper hold it solidly) before you lean on that screwdriver. That jet will want to break apart.

I have put pin point heat at carb bodies before for VERY stubborn jets..Helps break them loose usually.

[Jason2tpa]

**You'll likely end up using a wider, thicker screwdriver (for the correct thickness at the jet) but it won't fit deeply enough in the hole. Grind off just enough of the wide edges of the screwdriver till it fits...

I have put pin point heat at carb bodies before for VERY stubborn jets..Helps break them loose usually.

You're spot on about the screwdriver. The one I have is wide enough but doesn't completely seat into the slot. I don't have a grinder. Hoping the heat will break it free. The upper carb's lower pilot jet screws came undone no problem. But the lower carb jet screws are corroded pretty bad. And like I mentioned in last nights post, my guess is if the screws are corroded, so are the jets, which is the reason or at least contributing to the power loss. We'll see.

Any advice when inspecting the floats & needle? The manual really doesn't provide much, other than height spec and to look for cracks.

Thanks again for all your advice!!

[99yam40]

corrosion is a sign that water/ bad gas was in there.
so no telling what all you will find.
ultasonic cleaning may be in you future to make sure you get every thing cleaned properly

[TownsendsFJR1300]

Any advice when inspecting the floats & needle? The manual really doesn't provide much, other than height spec and to look for cracks.

I use a brake bleeder vacuum gauge and try to pull vacuum from the inlet with the float/needle closed.

I doubt you have that but another option (besides physical inspection, seeing any distortion on the needle) is to simply leave the bowl OFF, put the carb in the normal upright position. Hook up an auxiliary tank to the carb intake line. Lift / close the valve gently and watch for any leakage. There shouldn't be any when lifted/closed. Lower the float, fuel should come out.

You also want to make sure the float does NOT have fuel soaked inside /leaking (or it won't float!)

[Jason2tpa]

A little pin point heat loosened up the screws. The bowls aren't as bad as I thought they would be. A little copper color dusting, but no heavy deposits. The floats, which are black, do have that copper color dusted on the tops and sides 180 degrees from the needle. Those pilot jets did have a lot of deposits though. I could barely see light through each. As soon as I put them in a glass filled carb cleaner solution i could see black grains come out. I'll give them a good soak.

[Jason2tpa]

Update:

It's an amazing mechanical experience when carburetor jets are clean and functioning properly. It's almost like that's the way they are suppose to function all the time lol.

As y'all can tell from my sarcasm the engine ran great. Just to be certain, I filled the baitwell to replicate the same engine load I had yesterday. Engine responded by having a better low end pick up than ever before. So yah, I'm pleased.

I had been using seafoam once every 3 or 4 tanks. But more as a shock treatment, not consistent with every fill up. I know each of you has their own method for treating your fuel. And I certainly don't want to start a hot debate. But if y'all have a moment, share with me the product you use and frequency. I think I recall reading townsend uses yam's ring free.


Many thanks as always townsend, yam40, and boscoe.