25 HP Nissan (2 stroke NS3) Carb Clean Question 200

[TwoRivers]

Hello all got a question or two? Started the Nissan up yesterday getting ready for the opening of PA Walleye season. Started up OK but is idling a little rough. RPMs jump 40 - 60 range. Is that normal? Anyways, after reading many threads here on carb cleaning, I'm convinced that I need to clean the carb again. Do I need to remove the round plugs on top of the carb to clean something underneath? (see pics) Also what about the BB shot, do they need to be removed?
I bought a carb kit the last time I cleaned the carb but I don't remember if it came with new plugs and if it did I can't find them. If I have to remove them (the plugs) can I put some JB weld on them and replace them?
I do have a (Tohatsu) manual but can't find this info there.
Many thanks
rob

 

[Sea Rider]

Rob,

Don't remove any piece that's casted like plugs & BB pellets placed at upper or lower carb halves. Just clean both halves properly, remove all plastic parts if any aside from float, remove jets, middle tube, sometimes won't come off and soak carb in carb dip for some time. Finish with generic carb spray. Give a overdose of carb spray inside mixture screw passage after finishing soaking time.

If measuring rpm at idle with a digital tach jumping that rpm range and more is normal, rpm will stabilized once throttle is opened up. Plugs and BB's don't come included in carb kit.

Happy Boating

 

[TwoRivers]

Rob,

Don't remove any piece that's casted like plugs & BB pellets placed at upper or lower carb halves. Just clean both halves properly, remove all plastic parts if any aside from float, remove jets, middle tube, sometimes won't come off and soak carb in carb dip for some time. Finish with generic carb spray. Give a overdose of carb spray inside mixture screw passage after finishing soaking time.

If measuring rpm at idle with a digital tach jumping that rpm range and more is normal, rpm will stabilized once throttle is opened up. Plugs and BB's don't come included in carb kit.

Happy Boating

Thanks for your response SR. I've cleaned the carbs as you suggest many times and still can't seem to smooth this motor out. Idle and low speed operation is much rougher than any of my Evinrude/Johnsons? I've got good compression on both cylinders (150) and both cylinders are getting spark, new fuel lines under the cowl, new gas tank hose and bulb, good gas. Just seems like I'm missing something?
rob

 

[TwoRivers]

Before I took up boating I rode dirt bikes. I had Honda and Kawasaki models with kelhin carbs and it was necessary to remove the "softplugs" to properly tune and clean the carb? What's under those plugs?
Anybody?
thanks
rob

 

[Sea Rider]

How old is the 25 HP ? Is the fuel/air mixture screw properly set ? Does engine work ok passing fast idle towards wot ? Get a 30 HP carb gasket and pass that 25 into a 30. 30 HP gasket being wider in middle will deliver more air and probably better the rough issue. Retorque all intake bolts, probably bit loose ?

Probably under plugs are air/fuel passages. who knows. Don't think that anybody has taken plugs out to see what's inside. The issue is that Tohatsu carb and crankcase plugs are not available as spares....

Happy Boating

 

[TwoRivers]

How old is the 25 HP ? Is the fuel/air mixture screw properly set ? Does engine work ok passing fast idle towards wot ? Get a 30 HP carb gasket and pass that 25 into a 30. 30 HP gasket being wider in middle will deliver more air and probably better the rough issue. Retorque all intake bolts, probably bit loose ?

Probably under plugs are air/fuel passages. who knows. Don't think that anybody has taken plugs out to see what's inside. The issue is that Tohatsu carb and crankcase plugs are not available as spares....

Happy Boating

Thanks Louis,
The motor is a 1998 and it has the 30hp gasket and the timing is set correctly for a 30 horse. Motor runs great mid to wot. Runs ok at low speed but not as smooth as I'd like. I just put it back together and won't be able to get the fuel air correct until I get it out on the water (hopefully tomorrow?). I'll try re torqueing the intake but the last time I tried that (Suzuki DT30) bolts started snapping.
I've seen guys drill holes in the plugs (evinrude/Johnson), pop them out, clean out the passages then jb weld the holes shut and pop them back in. Seems to me that if there are air/fuel passages under the plugs they'd need to be cleaned out?
I'm gonna start looking around for a carb off of a junk motor and see what's under there.
thanks again
rob

 

[Sea Rider]

Compared to my beloved 18 HP the 30 is not smooth at idle/fast idle speed, probably that's the nature of that beast.

Happy Boating

 

[TwoRivers]

Compared to my beloved 18 HP the 30 is not smooth at idle/fast idle speed, probably that's the nature of that beast.

Happy Boating

I think you're correct.

 

[TwoRivers]

So I cleaned the carb again paying extraordinary attention to the small air ports in the top of the carb. Took it out on the lake and it ran like a dream. I was elated because it's never run so smooth at trolling speed before. So I start patting myself on the back thinking that I finally figured this carb cleaning operation out. After a few hours of fishing I remembered that I topped of my 6 gallon tank with 2 gallons of new fuel before launching.
The station was really busy so I decided to mix the oil in when I got to the lake.
You guessed it, I never put the oil in the tank. First day of Walleye season will do that to you. I'd blame it on getting older but my teenage son is worse than me.
So I figured I was running about 75:1.
Once I figured it out I stopped running at WOT for the rest of the day but the motor ran beautifully.
I filled up my tank since and I'm back to 50:1. Haven't been back out on the water but I expect it to be back to rough low speed operation.
Any thoughts?
Rob

 

[Sea Rider]

TR,

By air ports do you mean the air/fuel mixture screw passage or the upper round plugs ? If running rough at idle, fast idle probably needs more fuel/air ratio, turn mixture screw CCW a bit untill engine starts running more even. Has to be completely warmed up before adjusting.

Have you tried running premium fuel as opposed to the lowest octane available. Buy fresh fuel whenever possible, try to consume it all on that outing so to refill fresh fuel on top leftovers for next outing..

Happy Boating

 

[TwoRivers]

TR,

By air ports do you mean the air/fuel mixture screw passage or the upper round plugs ? If running rough at idle, fast idle probably needs more fuel/air ratio, turn mixture screw CCW a bit untill engine starts running more even. Has to be completely warmed up before adjusting.

Have you tried running premium fuel as opposed to the lowest octane available. Buy fresh fuel whenever possible, try to consume it all on that outing so to refill fresh fuel on top leftovers for next outing..

Happy Boating

Just came off the lake and the rough idle/low speed operation is back. Not too bad though.
I didn't feel like playing with the motor today while on the lake.
Too many fisherman and pleasure boaters putting in for the first time this year.
My plan is to play with the air/fuel setting a bit and if that doesn't smooth it out: I take along a three gallon tank with a 75:1 mixture and use it for trolling. I'll switch to the 50:1 tank when running in and out.
I had a Suzuki that ran on 100:1 and the Evinrude / Johnson VROs cut the mixture way down at slow speed.
Anyways that's my plan till I come up with a better one.
rob

 

[LukeFishWalker]

Two Rivers, I know this might sound odd. But, when I cleaned my older Evinrude carb,
I removed the lead shots and drilled holes in the plugs to allow cleaning.
I used a #10 - 32 tap and simply made threads.
I replaced them with a #10 - 32 Stainless screw.
Of course, I ran the screw in a couple times (To Clean The Threads), soaked the carb, then blew it out good.

This allows the unaccessible ports to be cleaned at anytime in the future.
And used some teflon tape to wrap the threads as a sealant.

I know it's an unorthodox method, but it worked for me.