c.d.i. question

[grouper sandwich]

are you sure you do not have an exhaust leak under the cowling which causes loss of O2?
Once you pull cowling it gets all the air it needs.
Just a thought

No, not sure at all. How would I test for that?

[99yam40]

Good question, but I have no thoughts on that for right now.
Look for leaks maybe

[marinermikes]

I can't imagine that the CDI would cool that quick. If you are have an instantanious reaction to the hood removal, I would say it's an exhaust problem.
I've had it happen before on a Evirude 15. Some one took the lower apart and didn't get a baffle plate in right. It fell out and was laying in the bottom of the mid section blocking the hole below the megaphone(header).

If this is the case you are going to need to check the entire exhaust system for blockage.

[grouper sandwich]

I can't imagine that the CDI would cool that quick. If you are have an instantanious reaction to the hood removal, I would say it's an exhaust problem.
I've had it happen before on a Evirude 15. Some one took the lower apart and didn't get a baffle plate in right. It fell out and was laying in the bottom of the mid section blocking the hole below the megaphone(header).

If this is the case you are going to need to check the entire exhaust system for blockage.

I'm very confused now. When you say check the entire exhaust system, are you saying taking the powerhead off? How quickly should the CDI cool and correct itself if that were the problem. Oh, and thanks for all of the help and hints you guys have provided.

[marinermikes]

I'm not suggesting removing the power head but you may want to take off the lower and check the gasket where the exhaust tube connects to the lower. There should be a gasket there. If the gaskets bad the exhaust can leak out of it especialy at idle or low speed and with no where else to go travel up through the steering tube and such and get under the hood.

As far as the CDI, if it acts up from being warm it would take fif**** minutes or so to cool back down with the hood off.

[grouper sandwich]

It's not taking anywhere near 15 minutes with the hood off and idle speed to get going again. The two things that really make me suspect the CDI are that A) it only happens at 4900 rpm and above. Now it could be an overheat issue, but the alarm system appears to be working and it's not going off. And B) when the cowling is on it seems to want to bog when I push the throttle all the way home like it's starving for fuel or the timing is all of a sudden off. But when the cowling is off it operates through the entire throttle range as it should. If I run it at 4800 or below I can run it all day it seems without issue. But the top of the head never feels abnormally hot when the issue occurs. All that said, I'm not a mechanic nor did I sleep at a Holiday Inn Express last night.

I'm going to pull the exhaust covers and head and head cover and take a peak and make sure there are no blockages in there that could make it run warm. I guess while I'm at it I could pull the lower cowling and take a peak at the gaskets. But from just looking inside the thermostat housing it looks brand new in there. No rust, corrosion, build up or anything, just the blue paint that Yamaha uses on the inside.

[rodbolt17]

that engine requiers AIR to run.
14 parts air to 1 part fuel.
the AIR intake is in the HOOD.
if it runs ok with the hood off and not with it on either you have exhaust gasses leaking into the cowl area OR the air intake in the hood is restricted.

[grouper sandwich]

that engine requiers AIR to run.
14 parts air to 1 part fuel.
the AIR intake is in the HOOD.
if it runs ok with the hood off and not with it on either you have exhaust gasses leaking into the cowl area OR the air intake in the hood is restricted.

Is the air intake the open area in the back of the hood?

[99yam40]

Yep, that would be it

[grouper sandwich]

Maybe I should just take a 1 1/2" hole saw and make some new air intakes in the front of the cowling?

I kid, I kid...

[99yam40]

maybe just have a good look to see what you can find would be better

[grouper sandwich]

maybe just have a good look to see what you can find would be better

Yep, that's the plan. I already plan to pull the exhaust covers and head this fall when it cools off some to make sure all the passages are clear. It seems easy enough to pull the apron and inspect what I can inspect while I'm at it. I appreciate all of the tips and help everyone has given.

[99yam40]

So have you looked to see if air intake areas are clear and open.
Did someone modify cowling or change it out with a different one?

Is silencer opening still open and clear?

Has some one been working on this motor and did something to change fuel or air flow some how?

[grouper sandwich]

So have you looked to see if air intake areas are clear and open.
Did someone modify cowling or change it out with a different one?

Is silencer opening still open and clear?

Has some one been working on this motor and did something to change fuel or air flow some how?

I have not looked at the air intake to make sure it's clear, specifically, but the last time I had it off nothing jumped out at me. I will certainly double check though. Who knows, maybe a bird made a nest in it when it sat for a month after Debbie hit?

No modification to the cowling or changed out. I have owned the engine since new.

Can't answer about the silencer, but will certainly check.

I have taken the carbs off to clean them but made witness marks on the jets and carb body to make sure I got them back exactly as they were. That said, I pulled and cleaned carbs BECAUSE of this problem, so it pre-dates my handiwork.

Again, thanks for the tips, you've given at least something to hunt for.

Question. Would these issues only show up at high RPM's if it were an air flow or exhaust leak? I only have porblems when I get above 4800 RPM. If I stay below that I can run it all day without issue.

[rodbolt17]

double check your fuel system. double check the thermoswitch.
I doubt its the CDI.