2007 90HP Yamaha 2 stroke Idle Problems

[muddfunk]

I'm having an issue with my idle. When I start the engine, it idles at 1400-1500 RPMs. After about 2-3 seconds it drops to 1200-1300 RPM's. Then it takes at least 45 seconds(I timed it a few times) it drops down to 800-900 RPM's. I can make a 20 minute run from one spot to another, shut the engine off and and start it up. And it will do the same exact thing. It doesn't seem to matter if the engine is warmed up or not. Can anyone please offer some advice?

[robert graham]

I'd check your throttle/carb linkages first.....then try turning your Primestart lever to each of it's 3 settings and start your motor at each setting to see if it may correlate to a Primestart issue....throwing your motor into gear at 1200 RPM's is not good for clutch dogs in lower unit...

[holmen78]

It is supposed to do that. It is programmed into the CDI. The CDI adjusts the ignition timing after each start up.

[muddfunk]

Ok, thanks for the advice. Is this an unusual or common issue?

[holmen78]

It’s not an issue, it is meant to behave like that. My 90 2-t does the same.

[robert graham]

My 1999 Yamaha C90 starts right up and I usually use the fast idle lever to keep it around 1500 RPM's for a minute or so....then the motor settles into about 750 RPM's at idle for the rest of the day.....your motor sounds like it has a problem to me...

[muddfunk]

Yes, I agree. It's definitely a problem. I just don't know exactly what. I had someone adjust the idle down today, but it didn't help. It didn't do that last season. It started doing it as soon as I put it back in last week. 45 seconds is a long time to wait for the engine to idle down. l really appreciate the input.

[99yam40]

My 1999 Yamaha C90 starts right up and I usually use the fast idle lever to keep it around 1500 RPM's for a minute or so....then the motor settles into about 750 RPM's at idle for the rest of the day.....your motor sounds like it has a problem to me...

since you say you idle your motor at 1500 for a minute or more, and his takes 45 seconds to drop down to normal idle , how can you say his has a problem?

I believe the CDi changes the timing at start up and depends on a temp switch to tell it when the motor is warmed up to go to normal timing
and the primestart has to warm up also to shut off the extra fuel.
how cool is the water where you are running

[TownsendsFJR1300]

since you say you idle your motor at 1500 for a minute or more, and his takes 45 seconds to drop down to normal idle , how can you say his has a problem?

I believe the CDi changes the timing at start up and depends on a temp switch to tell it when the motor is warmed up to go to normal timing

^^^^, if so, perhaps the temp switch should be inspected.

If it's sending wrong info to the ECU, telling it the engines COLD, when it isn't, That would likely raise the idle, keep it there (thinking it's NOT warming up-when it IS)..

Just a thought..

.

[holmen78]

Ok, one more try. Take a timing light and watch the timing at start up. The CDI advances the timing to about 10-12 degrees BTDC at startup if I remember the numbers right. The CDI retards the timing during the 40-45sec period after startup. After the 40-45 seconds the final timing should be 6 degrees ATDC if adjusted right. The change in timing makes your motor to rev up and stay running when cold. The CDI does not know if your motor is warm or not, that’s why it does it every time you fire it up no matter if you just run 20miles and had it shut down for a minute. The startup “sequence” on a warm motor is a little different because the prime start valve will be shut off on a warm motor. The only temperature measuring device is the thermo switch for your over temp alarm, an on/off switch. The thermo switch is not even wired through the CDI, the pink wire goes from the switch directly to your remote control alarm buzzer.

[99yam40]

^^^^, if so, perhaps the temp switch should be inspected.

If it's sending wrong info to the ECU, telling it the engines COLD, when it isn't, That would likely raise the idle, keep it there (thinking it's NOT warming up-when it IS)..

Just a thought..

.

my c40 has 2 switches on it ,one for over temp and the other for motor warmed up,
I would think all of the 3 cylinder motor would be similar.

[99yam40]

Ok, one more try. Take a timing light and watch the timing at start up. The CDI advances the timing to about 10-12 degrees BTDC at startup if I remember the numbers right. The CDI retards the timing during the 40-45sec period after startup. After the 40-45 seconds the final timing should be 6 degrees ATDC if adjusted right. The change in timing makes your motor to rev up and stay running when cold. The CDI does not know if your motor is warm or not, that’s why it does it every time you fire it up no matter if you just run 20miles and had it shut down for a minute. The startup “sequence” on a warm motor is a little different because the prime start valve will be shut off on a warm motor. The only temperature measuring device is the thermo switch for your over temp alarm, an on/off switch. The thermo switch is not even wired through the CDI, the pink wire goes from the switch directly to your remote control alarm buzzer.

The CDI does not retard the timing to make the idle RPM higher, it advances the timing.
If this 90 is like my C40 ,after the motor warms up ,one of the switches on the head tells the CDI it is time to drop back to its normal idle timing (which is ATDC, retarded) and the RPM drops to normal.

But I agree, use a timing light to watch what the timing is doing while motor is running in the driveway on muffs or sitting in the water at the dock.
turn the motor off after it warmed up, and start it back up right away to see what it does.
then turn back off and wait for some time and start it up again
see what it does

pull and check the stat to make sure it is not stuck open and also test it in a pot of water as you heat it up to see if it operates according to specs.
monitor the water temp and watch when the stat starts to open and when it gets to full open

you can also test the switches like that , but monitor the switch action with an ohm meter

[robert graham]

O.K., I stop to fish for an hour, then when I start my motor it doesn't run at high idle at all.....if it ran at 1500 RPM's on it's own, then I'd say that was not normal or desirable for my motor......what I'm supposed to do, sit there and weight for my motor to idle back down so I can put it in gear?...you've got some kinda problem...

[99yam40]

O.K., I stop to fish for an hour, then when I start my motor it doesn't run at high idle at all.....if it ran at 1500 RPM's on it's own, then I'd say that was not normal or desirable for my motor......what I'm supposed to do, sit there and weight for my motor to idle back down so I can put it in gear?...you've got some kinda problem...

but why do you open the fast Idle lever when you start it cold?
it should idle up all by itself and then go back to normal idle without your help, that is what the prime start is designed to do.

If your does not do that, then you may have a problem also.
it is not that he may not have a problem, but comparing his to yours when you have to raise the idle for cold start and he does not may mean more that one has a problem.
if he is boating in cold water it would make a difference.
My C40 always starts at high Idle without any use of the fast Idle lever, even warm, but if it has been running within the last few minutes of the restart it only lasts for a few seconds, if it has been an hour the it stays up for a little longer, but I am in warm water here on the Tx coast and I have no idea where he is located

[holmen78]

The CDI does not retard the timing to make the idle RPM higher, it advances the timing.
If this 90 is like my C40 ,after the motor warms up ,one of the switches on the head tells the CDI it is time to drop back to its normal idle timing (which is ATDC, retarded) and the RPM drops to normal.

But I agree, use a timing light to watch what the timing is doing while motor is running in the driveway on muffs or sitting in the water at the dock.
turn the motor off after it warmed up, and start it back up right away to see what it does.
then turn back off and wait for some time and start it up again
see what it does

pull and check the stat to make sure it is not stuck open and also test it in a pot of water as you heat it up to see if it operates according to specs.
monitor the water temp and watch when the stat starts to open and when it gets to full open

you can also test the switches like that , but monitor the switch action with an ohm meter

Advance the timing is what I wrote Could you send a picture of the switch that tells the CDI that the motor is warm? I am curious to see what it looks like.

To Robert Graham and mudfunk: Can you write here when you fix this problem and how you did it, I want to fix mine too.