Various adjustments on messed up F80

[akis-yamaha]

Hello

Could someone please tell me how to adjust the idle air mixture on the 4 carbs on the F80? Do I need any special tools to help? How will I know if the mixture is too lean or too rich?

Also, how do I adjust the remote control's throttle and gear cable linkage? Is there a proper procedure for this?

I have the tool and know how to sync the carbs. But the F80 has hard time maintaining idle, drops to 500 rpms, often backfires and many times cuts out. The mechanic thinks it is always carb #1 that backfires and needs adjustment. Another issue is the throttle and gear cable linkage: I cannot engage forward or reverse smoothly, there is a "clunk" noise and a **** if I do it fast, and if I do it slowly the engine will cut out. The mechanic messed with the two cables adjustment screws (throttle and gear) and I believe they are now out of sync.

many thanks

[rodbolt17]

it takes a 4 channel manometer to properly sync the carbs.
its designed to go clunk when shifted, its supposed to.
DO NOT baby it into gear.
two reasons.
1 is it wipes out the clutch dogs.
2 it can hold the shift cut switch in the on position and make the already poor running engine stall.

a backfire through the intake is almost always a lean A/F mix in the intake runner.

[akis-yamaha]

Once I sync up the carbs I will then have to adjust the idle air mix. Will there be a perceptible difference while adjusting the air/fuel mix? Will the vacuum gauges increase/decrease or will the engine rev up or down? And how do I tell when the fuel mix is at the correct setting ?

If I engage forward/reverse quickly the boat either ****s or goes too fast. I need to be able to move smoothly and slowly, for example when entering and leaving port.

[99yam40]

when putting in gear he was meaning to move the shifter into gear not move it so far that you increase the throttle

[akis-yamaha]

when putting in gear he was meaning to move the shifter into gear not move it so far that you increase the throttle

Unless of course the shifter linkage is so much out of adjustment that the throttle increases before the gear gets engaged.

So it seems to me that the engine should be on idle, and should remain on idle even when forward is engaged, and only then should the revs increase as you move the lever upwards more?

[boscoe99]

There is very little that can be done to adjust a Yamaha control box itself. The terminals on the ends of the throttle and shift cables can be varied somewhat, but not a lot.

The general procedure is have the throttle/shift control in the neutral position. Handle straight up. At the engine end have the lower unit in neutral. The throttles should be at the bottom end of their travel due to the return springs on the throttle valves.

Adjust the terminals (in or out) at the end of the throttle and shift cable to find the position at which they just slip onto the throttle and shift pins. Make sure that the terminal is threaded onto the cable by at least 8mm. If you don't have this amount of threads to work with go to the throttle and make a similar adjust at that end.

The first X number of degrees of throttle handle movement is only for the shift function. Beyond that number of degrees the throttles themselves will start to open. The plan is to shift quickly and firmly so as to go into gear only. If the gears grind you are not shifting quickly enough. If the throttle advances you have pushed the throttle handle too far. Practice, practice, practice.

With respect to the idle mixture screws, they should be screwed in until they lightly seat. Don't force them. Then, turn them back out 2.5 turns, plus or minus a half turn. Start at 2.5 and then increase or decrease the idle mixture as needed.

There is a procedure in the service manual that describes how to set up and synchronize the carburetors. As noted, a manometer is needed. A vacuumMate device is really nice to have if you can borrow one. It makes the job so much easier. But, it is pricey. The desired goal is to have all four carburetors pulling the same amount of vacuum (unless the SM calls for different values amongst the carburetors) when the motor is set to the desired idle RPM.

Desired idle speed in neutral is 850 RPM, plus or minus 50 RPM. In gear, the idle RPM should be 750 RPM, plus or minus 50 RPM.

[akis-yamaha]

In the absence of other tools, how do I go about adjusting the mixture? For example I tried today with the engine idling at 900 rpms. It is not smooth, it does not sneeze, but at the same time, it is not smooth, there is a lot of vibration. I turned the mixture screw on carb #1 two whole turns in, back out, and then two whole turns out, and it made no difference to anything. By "whole turns" I mean 360 degree rotation.

[boscoe99]

Turn all of the idle mixture screws out 2.5 360 degree turns from being lightly seated.

Adjust the RPM to specs.

Without a VacuumMate or similar device I don't know how you will ever get the motor to run correctly. It can make all of the difference in the world.

[akis-yamaha]

Turn all of the idle mixture screws out 2.5 360 degree turns from being lightly seated.

Adjust the RPM to specs.

Without a VacuumMate or similar device I don't know how you will ever get the motor to run correctly. It can make all of the difference in the world.

I have a Sealey carburetor synchroniser which I have used to sync the 4 carbs. We used the 3 throttle screws at 1100 rpm. But I do not know how to adjust the idle mixture. Do I also have to use the Sealey balancer for that as well?

[boscoe99]

Just set the idle mixture at 2.5 turns. If you feel it is too rich, turn the screws inward, up to half a turn. If you feel it is to lean, turn the screws outward, up to half a turn. Do them all the same.

To answer your initial question, you won't ever know exactly what the idle mixture is. There is no provision for adding an O2 sensor to the motors to determine the air/fuel ratio nor is there any O2 specification to set them to.

Are you in the United States? We here are not supposed to be tampering with the idle mixture screws. Whatever they are set to at the factory is supposed to be the setting they are returned to following a carburetor cleaning.

[TownsendsFJR1300]

Re the idle air screws. Set them as noted above and run the motor and let it idle some. After it cools down, pull the spark plugs and examine them. If their black and wet looking, the carbs are set too rich, lean them out a tad and re-run/re-check.

Note, after opening the below pic, click on it again to enlarge it...

[akis-yamaha]

Re the idle air screws. Set them as noted above and run the motor and let it idle some. After it cools down, pull the spark plugs and examine them. If their black and wet looking, the carbs are set too rich, lean them out a tad and re-run/re-check.

Note, after opening the below pic, click on it again to enlarge it...

Would it be worth investing in a Gunson's Colortune to help assist in setting the idle mixture?

By the way thanks for all the replies, and I am currently in Greece. I do not think the carbs ever had a brass cover over the idle mixture adjustment screws.

[TownsendsFJR1300]

Would it be worth investing in a Gunson's Colortune to help assist in setting the idle mixture?

By the way thanks for all the replies, and I am currently in Greece. I do not think the carbs ever had a brass cover over the idle mixture adjustment screws.

I'm not familiar with the tool so I can't comment. On one of my past motorcycles, (with a carb), it had a bad hesitation right off idle (its set very lean for emisions here in the states). The idle air screw (same as yours) was covered by a plug. Once the plug was removed, as I recall, .5 a turn out(richening up the mixture) was all it needed. No more hesitation, ran great, spark plug a nice tan color.

IMHO, at least for the idle air adjustment, a spark plug color check is a basic, simple and very accurate way to check your settings.

I'm not familiar with your linkages BETWEEN the carbs. Usually a manometer is used to set the FI, or in your case the butterflys (being its carberated) to pull thesame vacuum. This is imperative.

I stongly suggest investing in a semi professional one (about $100 US). I personally own a "Carbtune" unit which I've used on up to 4 cylinder bikes to my F150 OB www.carbtune.com. No liquids, extremly well made, very accurate markings on the sides as well. For my current 4 cylinder motorcycle, Yamaha allows up to 10mm's variance. I was able to get them set within 3mm's with some fine tuning. Its paid for itself many times over working on other bikes..

I have to assume (unless you can post some pictures of the carb linkages) that once its synced, idle set, the linkages should be adjusted to slide on WITHOUT moving the throttle plates at that point..

Just for S&G's, if you have drain screws on the float bowls, try setting a small container under them and drain each bowl. Closely examine for ANY DEBRIS coming out. Should you find some, IMHO, I'd be pulling carbs and cleaning them.

Good luck..

[boscoe99]

Re the idle air screws. Set them as noted above and run the motor and let it idle some. After it cools down, pull the spark plugs and examine them. If their black and wet looking, the carbs are set too rich, lean them out a tad and re-run/re-check.

Note, after opening the below pic, click on it again to enlarge it...

Good point.

[akis-yamaha]

I know , a very old thread. Thanks to all the previous replies.

Boat and motor were idle for almost two years.

Was then serviced through and through and ran perfectly, achieving 5400rpm (for the very little while I was brave enough to try).

It however had developed an electrical fault, showing large voltages on the instruments and measured directly on the battery poles. Please see my other thread for what's happened this year.