Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

[aussie_mike2]

Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Hi Guys , been searching the net for some information and come across this forum.

Would appreciate and input/help with a problem that has shown its ugly head.

My boat has a Yamaha 90A Petrol 6H1 Two stroke carbureted which is a 90Hp 3 cylinder motor.

Last trip out in Port Philip Bay I noticed the motor was down on power and using more fuel than what it usually would use on a similar trip out in the bay.

I noticed the motor is running rough and stalls , so back at home I started investigating and found that spark plug in cylinder number three is not firing. The plug is extremely wet with fuel. I replaced spark plug in cylinder number one with spark plug in cylinder number three and the problem still remained in cylinder number three. So it is not a spark plug problem.

I did a manual cylinder compression test and all three cylinders had 110PSI compression in them. So there is no mechanical problem in cylinder number three.

Then I swapped lead/coil number one with cylinder number three to see if it is a lead/coil problem , still the problem was in cylinder number three.

So now I have established its a ignition electrical fault of some sort.

I have no manual nor do I know how this electrical system works. Nor do I know what the electrical system consists of to run the ignition side of things on this Yamaha 90 Petrol 6H1 Two stroke.

I am very familiar how a automotive electrical system works on a breaker points system (Kettering Ignition) , mechanical electronics ignition system and ECU system but marine outboard motor ignition systems are not my strong point.

Q1. What generates a electrical pulse for each cylinder?

Q2. What controls the ignition timing on the motor?

Q3. Does anyone know of a manual for Yamaha 90 Petrol 6H1 Two stroke engine with ignition electrical details on the web. I have done a few searches but very limited information?

Q4. Where is a good source to purchase the parts for this Yamaha 90Hp motor overseas or Australia at a realistic prices once I have established what I need to purchase?

I have also done a search on this forum and found people with some form of no start issues with their engines and read the threads. Which I will be searching the archives in this forum in the meantime and doing some more reading.

Any help/input would be appreciated to solve my problem.

Cheers

 

[robert graham]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Same motor as mine. Sounds like a classic case of a bad fuel pump diaphragm causing raw fuel to be sucked directly into that cylinder. Pull your fuel pump off and check it, very easy fix, just a new diaphragm, entire new pump is only about $45. Good Luck!

 

[99yam40]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Hi Guys , been searching the net for some information and come across this forum.

Would appreciate and input/help with a problem that has shown its ugly head.

My boat has a Yamaha 90A Petrol 6H1 Two stroke carbureted which is a 90Hp 3 cylinder motor.

Last trip out in Port Philip Bay I noticed the motor was down on power and using more fuel than what it usually would use on a similar trip out in the bay.

I noticed the motor is running rough and stalls , so back at home I started investigating and found that spark plug in cylinder number three is not firing. The plug is extremely wet with fuel. I replaced spark plug in cylinder number one with spark plug in cylinder number three and the problem still remained in cylinder number three. So it is not a spark plug problem.

I did a manual cylinder compression test and all three cylinders had 110PSI compression in them. So there is no mechanical problem in cylinder number three.

Then I swapped lead/coil number one with cylinder number three to see if it is a lead/coil problem , still the problem was in cylinder number three.

So now I have established its a ignition electrical fault of some sort.

I have no manual nor do I know how this electrical system works. Nor do I know what the electrical system consists of to run the ignition side of things on this Yamaha 90 Petrol 6H1 Two stroke.

I am very familiar how a automotive electrical system works on a breaker points system (Kettering Ignition) , mechanical electronics ignition system and ECU system but marine outboard motor ignition systems are not my strong point.

Q1. What generates a electrical pulse for each cylinder?

Q2. What controls the ignition timing on the motor?

Q3. Does anyone know of a manual for Yamaha 90 Petrol 6H1 Two stroke engine with ignition electrical details on the web. I have done a few searches but very limited information?

Q4. Where is a good source to purchase the parts for this Yamaha 90Hp motor overseas or Australia at a realistic prices once I have established what I need to purchase?

I have also done a search on this forum and found people with some form of no start issues with their engines and read the threads. Which I will be searching the archives in this forum in the meantime and doing some more reading.

Any help/input would be appreciated to solve my problem.

Cheers

Have you checked to see if there is spark on #3 with a spark tester or are you just thinking it is not sparking because it is not firing that cylinder?

Like Robert said if the #3 cylinder is running too rich with fuel because it is sucking fuel from the pump, it will not fire even if it is getting good spark.

Q1. charge coil
Q2. CDI
Q3. Do not know where to find manuals for non US motors. Check with local Yamaha dealer for the part # of the manual you need and see if you can find a place to buy online.They are copyrighted so no freebies, but sometime you can find down loadable ones that are cheaper than the printed ones.
Q4. lots of parts can be bought on the web but shipping may be a killer. you just need to punch in the Yamaha part # you are looking for into a search engine and find the place you want to buy from.

 

[aussie_mike2]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Same motor as mine. Sounds like a classic case of a bad fuel pump diaphragm causing raw fuel to be sucked directly into that cylinder. Pull your fuel pump off and check it, very easy fix, just a new diaphragm, entire new pump is only about $45. Good Luck!

Hi robert graham...............Very good point , a VERY RICH AIR/FUEL RATIO will not ignite also ....... ok , but each cylinder has its own carburetor which should be fed fuel via a common fuel rail which is connected to a fuel pump.

Just be patient with me again I'm not familiar with this fuel system on my Yamaha 90.

The atmospheric pressure is forced thro a carburetor venture when the throttle butterflies are opened and fuel is mixed with the incoming air stream , if the float level is too high we would have a flooding situation of the needle and seat is stuck open for some reason we would have a very rich situation .

So my question is if the fuel diaphragm is causing this problem in cylinder only number 3 , why isn't it also flooding the other two cylinders the fuel pump?

or does this run a individual fuel pump for each cylinder ? The fuel pump pressure is shared with the other carburetors , how can a fuel pump, pump directly into the cylinder (s).

Sorry for the silly questioning as I'm not very familiar with this fuel system.

Does anyone have a electric diagram/drawing of the ignition system for this particular motor hand and willing to share?

Also some information on the fuel system diagram/drawing ?

Will have a closer look tonight with the air cleaner removed and study how the fuel system works,

Thanks guys for the feedback


Cheers

 

[robert graham]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

The fuel pump is operated off the bottom(#3)cylinder crank chamber's pressure/vacuum, so when the fuel pump diaphragm fails it floods just that cylinder. Look at the location of your fuel pump. Easy fix! Good Luck!

 

[cousinabe]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

when the fuel pump diaphragm tears, fuel is sucked in through the crankcase directly. usually settling in the lower cylinder #3.

The fuel pump works on pressure from the crankcase along with a diaphragm.

http://www.boats.net/parts/search/Yamaha/Outboard/1998/90TLRW/FUEL/parts.html

 

[aussie_mike2]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Hi robert graham ...... thank you for that explanation will have a look tonight

cousinabe ..... thankyou for that link, item number #13 part number 692-24411-00-00 DIAPHRAGM on that link cousinabe post is the actaul diaphragm you guys are reffering to. YES or NO ?

Link : http://www.boats.net/parts/search/Yamaha/Outboard/1998/90TLRW/FUEL/parts.html#

cheers

 

[aussie_mike2]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Sorry about the double post

 

[aussie_mike2]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Hi, so feedback on my adventures on fixing the issue, try and find someone ( marine shop ) that will just sell you a fuel pump overhaul kit for this Yamaha 90Hp 2 stroke is just not going to happen.

So in the end I had no option but bought a whole New fuel pump at a cost of $116 AUSD.

Amazingly ( my fault, cause i didn't open the box at the shop and check ) the new pump didn't come with a gasket that fits between the pump body to the number#3 cylinder intake runner. So this in tailed another few days wait which I was not a happy bloke.

You think the guy at the shop would of said gasket is separate to the initial purchase of the pump. Upon speaking to the guy at the shop over the telephone he said, "Use the old gasket , should do the job....". I cracked up laughing as their supposed to be experts in their field.

In the end I bought some correct thickness gasket paper from a automotive accessories shop and cut a new gasket.

The motor responded to the new pump but idle quality was not 100% so I played with the idle mixture screws which varied enormously between the three carburetors

number#1 cylinder carburetor mixture screw was out only 2 full turn.
number#2 cylinder carburetor mixture screw was out only 3 full turn.
number#3 cylinder carburetor mixture screw was out only 1/2 turn.

So hence why someone prier to me had screwed number#3 cylinder carburetor mixture screw to a leaner setting to compensate for the addition fuel that was seeping into this cylinder.

I end up screwing in totally the idle mixtures screws one at a time and them screwing them all the way out until the engine responded to the screw position changes. To determine a nice idle balancing point. In the end the idle mixture screws now are approximately 1-1/2 turns out in relations to each carburetor. Adjusted the base idle screw and now she idles perfectly. Just need to open up the throttle to see how the motor responds to load conciditions out on the water.

I dismantle the old fuel pump to see if the actual diaphragm was damaged and there was no evidence that it was. The two diaphragms still looked fine. The only thing that I could say is the three star screws that holds the pump together were very loose MAYBE the issue don't know.

WIll take the boat out and test it properly in the next coming days, hopefully we get some nice Melbourne weather, as it was very choppy and windy the day I replace the fuel pump and did some short runs in the bay. Fingers crossed the problem is fixed.

Just curious how do you guys synchronizer multiple carburetors on a outboard motor ? DO you use any specialized tools or just by ear.n.feel method?

Multiple Carburetor synchronizer tool for Honda : http://reviews.ebay.com/Multiple-Carburetor-synchronizer-tool-for-Honda_W0QQugidZ10000000015288599

DIY 6 column Manometer for carburettor tuning :
http://www.zcar.com/forums/read/1/1918017

Once again I would like to thank you guys for your assistance, greatly appreciated.

cheers

 

[99yam40]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Your service manual should give a Sync and link procedure for adjusting the linkages that control the timing ,butterflies, and the pilot screws. From what I have read the carbs are adjusted by ear and tach. There is not place to hook up the manometer to the different cylinders for checking, but that is just my opinion.

 

[aussie_mike2]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Hi 99yam40 , I don't have any manuals at this stage for my engine details, am chasing a set.

By chance do you know of any manuals on the internet for factory correct sequence to adjust the carburetors?

Will cnc machines venture adapters to fit on the end of the carburetors and make some manometers up to try and get 100% equal idle quality performance out of my engine.

At this stage what I have done by ear'n'feel with the boat dash tachometer i would say I'm right on the money. Just being anal about doing it with manometers.

cheers

 

[99yam40]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Here is a thread I started that might give you some info, but my C40TLRX is a totally different motor.

http://forums.iboats.com/showthread.php?t=366637


I looked at the links you put in your post and all the manometer is doing is giving a reference to adjust the different butterflies so they are opening the same amount. This is accomplished on the Yamahas with the linkage being adjusted so that they are all closed completely and then locking the linkage together at that point

There are lots of different manuals and places to get them.
Factory manuals are the ones that Yamaha techs usually recommend.

here are a few links for some sites that I think sell down loadable ones , but I have not tried them so I do not know if they are any good. It is ammasing what you can find on the web by just punching in outboard or marine manual

http://www.readmanual.com/outboard.motors/

http://imracingmanuals.com/

http://www.marinepartsman.com/Yamaha-outboard-service-manuals-index.html

 

[munjue]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

here is a good manual to use

the sync procedure is in this manual

motorka.org/doc/yam-remont-50-90.pdf

it is of a slightly latter model but seems to give me all the info that i need for my 91 yami

also number 3 plug always comes out wet looking compared to number 1 and 2,
mine always has and always will even after a FULL motor recon it still comes out wet looking,

i should also add, there is a model range at the front of the book being a factory YAMAHA manual, with procedures on different carburetor numbers listed.

Multiple models are shown in this manual
Model name 75CET 75CETO 75CEHTO 80AETO 90AEHD 90AED 90AET 90AETO

USA and
Canada nameC75TR 75TR P75TH ? ? ? C90TR90TRB90TR

Indication 75CET 75CETO 75CEHTO 80AETO 90AEHD 90AED 90AET 90AETO

 

[rodbolt]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

always remember, NOT ALL international motors use the same specs,carbs,water pumps and ign systems as US market motors.
it will bite ya in the buttocks if your not careful to identify WHICH fuel,ign and control systems your dealing with BEFORE testing.
in fact that advice works with variations in the same HP range of US market motors.

 

[munjue]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

umm

 

[megapom]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

Your service manual should give a Sync and link procedure for adjusting the linkages that control the timing ,butterflies, and the pilot screws. From what I have read the carbs are adjusted by ear and tach. There is not place to hook up the manometer to the different cylinders for checking, but that is just my opinion.

You could attach manometers to the oil injection hose-tails on the inlet manifolds but that would necessitate running the motor on pre-mix whilst carrying out the adjustments. If the carbs are out of sync with each other and you do need to adjust the throttle butterflies, be aware that the locking screws on the linkage arms have a left hand thread.
I have a similar donk (90 AETO) that was running great when opened up but ticked over like a dog. Found out that the bottom carby was out of sync, adjusted it by eye so that the gap between the carb barrel and OD of the butterfly flap on all 3 were the same and now she's 100% better. Lot of my symptoms were similar to what you were describing.
Hope you get it sorted.

 

[rodbolt]

Re: Yamaha 90 Petrol 6H1 Two stroke Runs but is missing on cylinder 3 and stalls

this thread is almost a year old and the above method to link and sync is not good.
to simple just to follow the correct procedure, faster too.
nothing in any of the US market motors manuals ever mentions a manometer to properly set them up.