# 90 Yamaha 2 stroke issue with extremely high idle at start up



## Poontangler (Jul 13, 2017)

Hello helpful brains! 
(1996 90 TLRU 2 stroke)
I have been having an issue with cold start ups that has only started at the first real cold snaps of the year, but have continued since and never done this before. It has no issue starting up as some say these old 2s do. But it actually starts up so well and holds a very high idle and pisses like a madman! Now normally I know the prime start fuel enrichment system gives at a little juice to get it going and up to operating temps of some sort, 2-3 mins and then drops down. Mine is now holding that for 20 mins more or less, then all of a sudden spudders down to normal, and then never does it for the rest of the day! The next day though it will do the same thing. I have checked the carbs to make sure they are closing and properly synching with cables, but not super in depth. I was thinking something with thermostat, I have changed it within two years is all I can remember, but wondering if I should pull that and check for it working? Was also told to possibly start the engine at cold, and let it run for a few mins just like a normal start up, then switch the fuel enrichment system valve to the off position and see if that immediately brings it down, then that would point to prime start system problem, have not got to that yet. Was also thinking some sort of vacuum leak? The problem is now consistent and not intermittent. But wondering if anyone has had this issue or other things to check? All I have found online is problems with engine having lean sneezes and dying at start, which seems mine is kind of the opposite. 
Thanks for looking!


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## jmrodandgun (Sep 20, 2013)

I've seen bad thermostats and worn water pumps cause fast idle in cold weather.

Edit. Never mind. I didn't read the entire post. My bad.


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## Poontangler (Jul 13, 2017)

The water pump lower housing definitely looked old and pitted, but then again I have not seen a new one to compare, I have always changed impeller and everything else looked good recently, the old impeller I changed last time almost showed no signs of use, might have to look into that housing more and then check the thermostat. Thank you!


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## BK922 (Jan 24, 2016)

Have you had issues getting on plane in this scenario? I had a very similar problem, cold weather, high idle, non firing 2nd cylinder wouldn’t spark for 15-20 minutes then be fine rest of day. Checked and traces every possible Avenue and ended up being cdi replacement


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## Poontangler (Jul 13, 2017)

Well I’m not sure that I have heard the possible dropping of a cylinder, I’m guessing you would be able to tell, but it seems to run great. My boat has also takin a bit to get on plane unless I’m tabbed down pretty good, but nothing out of the norm. Is there a tell tale sign of this happening? I know that I shifted into gear once or twice to get it off trailer, and that was a bad decision before the idle came down, and would not come out of gear and had to pull kill switch, I know not to do that again, and like I said as soon as it goes does, it’s business as usual.


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## BK922 (Jan 24, 2016)

Sounds similar but different. Here is a link to my issues/troubleshooting process. B90TLRX, anything but the CDI? - Yamaha Outboard Parts Forum


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## 60hertz (Oct 31, 2008)

I had a 2006 Yamaha 90 hp TRLR model (i think???) 2 stroke, seemed like there was an electric choke.

The choke circuit would be made up if the temp was low enough.

if this engine has an electric choke, I’d start there.


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## mwolaver (Feb 6, 2014)

Those engines have an "electro-magnetic" choke solenoid system. (think that's what they call it). The motor essentially is in a choked state while not running. Once the engine starts and current is introduced to that solenoid, it begins to retract. It fully retracts in something like 10 or 15 seconds and the engine will "idle down" to normal. There is also an "L" shaped, red lever alongside the air box on the front of the power head. Remove the cowling to see it. This is a manual choke. It has off-choked-normal positions, if I remember correctly. Memory says, fully clockwise for choke and middle position for normal run. It's been a few years. Made sure the manual choke didn't get moved somehow. 

Apologize to the OP....I have not experience exactly this circumstance. Guess: if the electro-choke solenoid is sticking, it would stay choked too long. Get your manual and find that solenoid. You can remove it, connect it to a 12vdc source and watch/time the pilot retract. The spec is in your manual. 

Good Luck! Mark


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## nicholas karolewicz (Jan 15, 2020)

Its the Thermoswitch (that choke solenoid you guys are referring to) sticking.


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## Poontangler (Jul 13, 2017)

I definitely know it has the electro thermal valve and prime start system, so no traditional choke. I am going to mess with the different settings tomorrow when I get to start. From there will let you know what it does, then decide whether to pull it and break it open, see if the diaphragm is damaged or if the needle is the culprit. I will then have to figure out how to test it which I’m sure one of you can tell me how to.


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## Smackdaddy53 (Dec 31, 2012)

Yamaha 2 strokes high idle immediately after shutting off then starting again but it should settle down to set idle in less than five or ten seconds. The PrimeStart system is easy to rebuild. Only use Yamaha parts.


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## BK922 (Jan 24, 2016)

I have the service manual at home that tells the exact specs for testing the electro thermal valve. I’m out of town until tomorrow but will try and remember to send it to you


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## Poontangler (Jul 13, 2017)

So I tested the fuel enrichment valve on the motor at cold start, it has been in the normal position forever, the motor acted pretty nice today running off muffs. Did not stay at high idle. It is very warm out today and seemed the problem started when it was very cold. So I switched it to open, and would bog the motor out and kill it. Switch it to closed and no effects. So after putting it back to normal, and throttling up, it seems to bog and run rough now, if I throttle up slowly it can handle it but sound rough, if I throttle fast it wants to bog down and kill the motor. It has never done that before I messed with this valve. I also disconnected the throttle linkage and noticed the top two would go forward and spring back, but the bottom throttle would stay stuck down and not spring home, with them linked together the spring pressure of the other two sends it back home, but I’m guessing that is another issue. Anyone know if that would be causing this and how to unstick that spring? Does the actions of the fuel valve point towards something going on with the prime start system? Funny how it did not do it today when I’m trying to diagnose it, and I found a new throttle problem haha.


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## Poontangler (Jul 13, 2017)

I also did put new plugs in a week ago, and maybe fouled them by playing with that enrichment valve? And need to add new ones again and see if it’s back to normal? Or does it sound like a possible carb issue now?


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## Smackdaddy53 (Dec 31, 2012)

If you ever have to fool with that red switch to get it to run decent you probably have a carb issue. Clean and rebuild carbs with Yamaha kits. I have worked on these a lot and own four.


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## DuckNut (Apr 3, 2009)

Send @Cut Runner a message - he is a Yamaha mechanic.


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## Poontangler (Jul 13, 2017)

Digged into this hard, and cleaned carbs, changed out filters and fuel pumps, waterpump, checked everything I could, and of course found lots of new things to replace in the near future. But when all done, it definitely runs really nice now! But messing with things like that fuel valve actually made it worse and created a snowball effect I believe. Possibly blocking up carbs and making it run different fuel/air/oil type things, and made it bog out completely and do crazy things. So it feels good to have gotten it back to good or running better now. But unfortunately the original posting issue, having a high idle and long warm up periods of 20 mins, is still occurring at first start of day, and very annoying, but I am just gonna let it ride. Plus mechanics around here and weeks to months out from even looking at it, and I just have to do things myself now, and I’m no real mechanic that’s for sure. But I thank all of you for your help and suggestions, and if you think of anything else I would to hear it!


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## Smackdaddy53 (Dec 31, 2012)

Poontangler said:


> Digged into this hard, and cleaned carbs, changed out filters and fuel pumps, waterpump, checked everything I could, and of course found lots of new things to replace in the near future. But when all done, it definitely runs really nice now! But messing with things like that fuel valve actually made it worse and created a snowball effect I believe. Possibly blocking up carbs and making it run different fuel/air/oil type things, and made it bog out completely and do crazy things. So it feels good to have gotten it back to good or running better now. But unfortunately the original posting issue, having a high idle and long warm up periods of 20 mins, is still occurring at first start of day, and very annoying, but I am just gonna let it ride. Plus mechanics around here and weeks to months out from even looking at it, and I just have to do things myself now, and I’m no real mechanic that’s for sure. But I thank all of you for your help and suggestions, and if you think of anything else I would to hear it!


Did you check the PrimeStart needle valve that moves in and out with temperature?


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## Poontangler (Jul 13, 2017)

I did not, I did not want to take all that apart and possibly dirty that up, although it is really easy to, I did open it and make sure the diaphragm was in good shape and it was, I was thinking of doing it later on, and checking the check valves and all that in there, and the needle. I am was unsure of checking the needle temp and still don’t know how. I think I can do it later without taking the carbs off again just from the side there, and looks very simple. Plus I really just wanted to open the carbs and get them done. I did briefly watch the Danger video where he goes in depth on the Prime start system. My mechanic says it’s super rare to fail but not out of question.


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## Smackdaddy53 (Dec 31, 2012)

Poontangler said:


> I did not, I did not want to take all that apart and possibly dirty that up, although it is really easy to, I did open it and make sure the diaphragm was in good shape and it was, I was thinking of doing it later on, and checking the check valves and all that in there, and the needle. I am was unsure of checking the needle temp and still don’t know how. I think I can do it later without taking the carbs off again just from the side there, and looks very simple. Plus I really just wanted to open the carbs and get them done. I did briefly watch the Danger video where he goes in depth on the Prime start system. My mechanic says it’s super rare to fail but not out of question.


The needle valve (part of the PrimeStart system on the carb) can be checked by removing it and hooking it up to 12v power. It has two wires. You hook it up and lay the valve flat with the needle lined up next to a stationary object and give it a few minutes and see if it is protruding any further than at the beginning of the test.
I saw this on Dangar Marine, the Aussie is one hell of a good mechanic. I did this on one of my Yamaha 70 2 strokes.


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## Poontangler (Jul 13, 2017)

I’ll rewatch that video, and see how he does it and how long it takes to move and all that. The only power source I have I think is one of those power probes, will that work or maybe some other type of rigged hot wire from the battery?


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## Poontangler (Jul 13, 2017)

Also was your needle bad on that 70 of yours?


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## Smackdaddy53 (Dec 31, 2012)

Poontangler said:


> Also was your needle bad on that 70 of yours?


No, just needed carbs rebuilt and I rebuilt PrimeStart while I was at it. I tested the primestart needle while I was in there and it was fine. Pretty good for 20 years old...


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## finbully (Jan 26, 2013)

Fuel pump diaphragm and/or diaphragm spring are common causes for this.


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## Poontangler (Jul 13, 2017)

I did just change the fuel pump at the same time just to mark that off the list. I’ll be taking it out again all week and see if it’s still doing it everyone, most likely will but not as worried, seeing as I fixed a bunch of other stuff, I still do think it’s possibly the prime start needle possible doing weird stuff, but won’t be able to get to it til the weather sucks again.


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## finbully (Jan 26, 2013)

Is it working better now?


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## Poontangler (Jul 13, 2017)

Yeah running awesome and feels tuned up, but the original problem of the high idle and 20 minute warm up period is still going on. I do think it has to do with the prime start system and maybe the needle, but this winter has been absolutely on fire and I have been fishing everyday possible, so haven’t had time to pull that apart and check it. I guess I’m waiting for the next bad front to come thru to test it. I will definetly update when I do, cause I’m sure other people out there might run into this.


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## Ed M (Sep 19, 2019)

I have had to replace the Diaphragm in the prime start circuit due to failure, causes fuel to bypass the thermo valve going directly to the intake. Caused the motor to idle high initially then failed on a fishing trip causing it to flood out and wouldn't run at idle, on the 70 it is on the front face of the middle carb. 3 screws in the cover needs to be removed to get to the diaphragm.










The diaphragm between the 2 gaskets under the cover will start to crack causing it to act like the thermo valve is stuck open.


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## Ed M (Sep 19, 2019)

Here is the info from the service manual


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## Poontangler (Jul 13, 2017)

I did just remove and test the needle for movement, it did move when connected to power. I did check the resistance and got in the 3.8-4.0 range which is a little high. But maybe I did it wrong, I haven’t really figured out multimeters for some reason, I feel like they always give me different readings than I want. I also think I was supposed to hookup the DVA adapter for the multimeter which I didn’t. I have checked the diaphragm as well when I pulled the carbs and it looked good. The issue has also went away now that it has been warm for a few weeks. It seems to only happen when it’s cold now. Signs may be pointing towards CDI problem when it’s cold maybe? As another poster had described their issue was similar and led them to replacing that. But it’s something I can deal with now as it only happens on cold days, still would like to figure it out tho or before it leads to other issues.


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## ChrisfromDelray (11 mo ago)

Reaching out to BK 922. I have the exact same motor as you do b90 tlrx and am experiencing the exact issue you described here and elsewhere....no spark to #2 cylinder until run out of gear at 5000 rpm for 10-15 minutes and completely warm. Then runs perfect.

Can you tell me how you were able to resolve? I cannot determine from posts whether it was CPS or CDI. I've replaced coil and cps but for obvious reasons don't want to replace cdi unless I know it's the issue

can you please clarify for me/us?

id be very grateful for your help in ending this issue for me

thank you.


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## BK922 (Jan 24, 2016)

To make a long story short. Had to replace cdi.

I thought replacing cps fixed it but it must have been just warm enough that day to make the issue go away, for that moment.
The guy who bought my boat, had a Yamaha dealer look at it and couldn’t/ wouldn’t spend the time to isolate the issue. He went ahead and replaced the cdi and problem solved. Interestingly I have had quite a few people reach out to me with this issue I’m the last few months so I wonder if that year class of engines/cdi are just finally hitting there useful lifespan. But hey if you don’t mind warming up for 15 minutes on the cold days then it doesn’t need replacing!


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## ChrisfromDelray (11 mo ago)

Man I cant believe how fast a reply I received. I am VERY THANKFUL.

I hear you about leaving well enough alone, but I guess having gotten up at 300am to get Flamingo in time to get to the gulf to chase the poons, to have to sit there at the ramp running my outboard at 5k for 15 minutes just p---es me off too much.

Very interesting thesis about number of others having this similar issue at this time. Japanese mechanical and electronic engineering and build quality is always very high, but it does seem as though things do eventually fail in a very similar way. 

But until I can find a 90 hp outboard that weighs less than the 270 lb 2 stroke yami, I'm gonna have to find a way to keep the thing going.

I think it was you that said in your post that asking a buddy with the same engine to borrow his CDI to see if it works is a bridge too far...so since ive run down every other thing, I think I'm going to bite the bullet and put a new one in.

Ill message after I open my eyes and uncross my fingers to see if it works!

Thank again so much

Chrisfromdelray


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## BK922 (Jan 24, 2016)

Ha yeah had some impatient and nerve wracking cool mornings on the chickees in the early season wishing that thing would go! I never found one to switch out and test unfortunately but the new owner replacing it and going to perfect kinda sealed the deal.


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## ChrisfromDelray (11 mo ago)

For the record...OK... so after biting the $600 plus bullet for a new CDI...yes that was the issue. Once i got the new one wired right, i sea trialed it and had all three cylinders firing out of the gate. 

Good news is all the other things i did running it down make it run better than it has in years.

Thanks again very much for the guidance.


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