30hp 2 stroke Carb/idle questions

[yamahaSS]

I have a 1989 Yamaha 30lf 2 stroke... 3cyl engine recently had some idle issues... had carbs removed and cleaned,, replaced plugs, all fuel lines did all the basics and verified good compression, been using ring free and went thru all the basics.. After the rebuild she now idles real good,, even in gear. Seems to be a hesitation off idle and then she runs great at full throttle. Tried all the basics..motor is low hours over all and well maintained even with regular decarbing

Noticed before the carbs were removed and cleaned" and the place "adjusted" them up the butterfly on the middle carb was slightly open at idle compared to the top and bottom carb.. they all are parallel now... is the middle butterfly supposed to be slightly open?

Secondly it seems the air/fuel mixture screw on each carb were a little tricky to adjust.. currently they are all approx 3 turns out and she seems to idle best.. when adjusting the air/fuel screw on the bottom carb nothing seems to really change..

Any help appreciated

[99yam40]

I would follow the link and syn steps in manual and adjusting everything. If the motor will not idle properly with it adjusted to specs the you probably need to try again and clean them better

[aambrose]

carb adjustments

hey its aambrose,sounds to me like you may have leaned out to much ,if memory searves you shoulnt be out 3 turns but more like 1 1/2 so i would check out specs on that before you run again.also check your float levels per specs.i like to use non ethanol fuel because ethanol can cause many problems in your fuel system through out.might need to run a quality fuel system cleaner but because its a two stroke stick strickly to instructions. i use lucas fuel system cleaner.sync adjustments are necessary on butterflies and linkages per specs.happy teching

[yamahaSS]

thanx guys but now more issues

Spent some hours on the lake today with my 30lf 2 stroke.. She ran great all morning idles great, top end and midrange was great... just a bit boggy or sloppy off idle as I throttle up...say between idle and maybe 1800 or so RPM... the prop is of the correct size.. etc so I am content.. later in the day idle was still perfect but now she does not want to accelerate beyond 2000 rpm or so.. I verified fuel going to the carbs. primer bulb good etc.. even changed out plugs. I've been chasing down an intermittand problem for a while,, first it was hard to restart..now it restarts fine just doesn't accelerate... after all the work I have done I am strongly thinking it may be a problem with the cdi/ ignition box. What are the symptoms of a bad ignition box?

[yamahaSS]

last day on the lake today with my 30lf 2 stroke.. starts right up and idled well once again... just would not throttle up.. everything seems to be intact.. put her back on the trailer and drove 150 miles home... started it up on the driveway with the muffs on and now shes accelerating fine... it was tilted in the shallow water position on the way home and 150 miles of road... perhaps a float was sticking? other than a slight off idle bog which may be normal she runs great... idles soooo smooth and low for a 2 stroke.. this is a rope start motor and fires up in half a pull..

[Doug Cane]

Hi guys
iv got a 2004 yamaha cv30 two stroke, single carb outboard.
its been oiling up the plugs and running rough. If i clean the plugs its ok for abit but never 100%. I gave it a compression test... 100psi in each pot. I striped the carby and completly cleaned everything with carby cleaner, ensured the jets/valves were clear and clean and re-assembled. I noticed the mixture screw was three full turns out at the begining. After assembly i set the mixture screw at 1 and 3/4 full turns out to begin with. Installed two new spark plugs. Cleaned all fuel lines and fuel filter. Filled the tank with new 100-1 fuel mix and ran the motor up in a drum of fresh water. After the engine had warmed up alittle i began to try mixture adjustment + and - . The engine ran best in nuetral with the mixture screw 1/2 a turn out. While it was running i screwed the mixture screw completly home, which i presumed would kill the engine but it continued to run smoothly enough. Does this not indicate the carby is accessing fuel from a secondary source? Im thinking eventualy these plugs will oil up and ill have the same problem. Can anyone shed any light on my mixture/ carby problem. Apreciate any advice

[boscoe99]

The carb setting agrees with the service manual.

If your only problem is plugs fouling, and you are using Yamalube, I would switch to a 100% synthetic TC-W3 rated two stroke oil. Pennzoil for instance.

The carburetor continuing to run with the idle mixture screw completely closed does not seen abnormal.

[robert graham]

Pennzoil quit making the 100% synthetic 2 stroke oil about a year ago….so I ‘ve been running the Lucas 100% synthetic 2 stroke oil and it seems to smoke/ foul plugs less and it’s also cheaper by the gallon ($30)……

[99yam40]

The carb setting agrees with the service manual.

If your only problem is plugs fouling, and you are using Yamalube, I would switch to a 100% synthetic TC-W3 rated two stroke oil. Pennzoil for instance.

The carburetor continuing to run with the idle mixture screw completely closed does not seen abnormal.

I would think the throttle plate would have to be cracked open a little more than usual to allow the off idle ports to help if the pilot screws are completely closed off

[Doug Cane]

Cheers guys,
i have now mixed new fuel with tcw3 oil and cleaned out the old fuel completly. Advice appreciated
im at the stage now i have re-stripped the carby and sonic cleaned it first with electronic cleaner solution and then again with a ulp petrol solution. Then blown out all apartures with high pressure air. Re-assembled carb and refitted to motor. Attempted to start the outboard but no luck. Iv ordered a carby kit from over east and expect to wait awhile( covid), for it to arive...considering it atleast ran before, im alittle lost. Might remove the reed valve assy while waiting for the carby kit.
i appreciate the comments and will post again once iv progressed

[Doug Cane]

Sorry also the throttle plate is naturally cracked open slightly at minimium.

[99yam40]

does this carb have a choke or prime start system?
what was your starting procedure?
where did you have the carb screws set this time?

[Doug Cane]

Yeh, single carby, two cylinder, two stroke. Manual choke. Idle mixture screw set at 13/4 turns out.

its frustrating

this morning i downloaded a service manual and followed the proceedure to adjust the control linkages and throttle cables. At the end of the proceedure the control linkage marks are way out. Iv returned them back to the original settings for now
if the motor would run i could put a timing light on it but thats not the case yet so ....mmm

[TownsendsFJR1300]

When you cleaned the carb, did you spray carb cleaner or brake cleaner thru all the orifices?
I know you blew air but sometimes a blockage won't show with just air.

Also, you might use (if you hadn't) a carb jet cleaner, the very, very fine, different sized needles that clear out all the small holes..