'92 70hp problems ... the continuing saga!!

[Mr. Ed]

Looked for my old post on this one, but it looks like there are a week or two of posts missing.

Anyway I'll try and recap the best I can:

Out fishing one evening, ran to my spot ... no issues. On return motor bogged down and stalled. Restarted right away, bogged down when given throttle. It will start and idle fine. Drop it into gear and no issues. Give it a little more throttle and it will bogg down and eventually stall. If I 'play' with the throttle and bump it up a small bit, let the motor recuperate (from bogging down) ... bump it again, and repeat 4-5 times, I can get it to WOT about 60% of the time. Took it out today (to check timing) and was running 37mph across lake ... slow down, give throttle again ... boggs down.

1) rebuilt carbs late winter/early spring. This was preventive (had not been having any issues) and motor ran great afterwards on several trips this spring.

2) Replaced fuel pump (was going to do that over winter also ... but).

3) No change when running off auxillary tank vs built in tank.

4) Replaced fuel lines from conector to carbs

5) By-passed built in fuel filter (though may be it was sucking air).

6) Pulled carbs back off ... checked floats and jets.

7) Ohms for Pulser coil, crank sensor, charge coil, and ingnition coils all w/in range per Yamaha manual. Coils and coil grounds are tight also.

8) Checked timing (once I got my light to work) Retard timing 7 ATDC and Advance 22 BTDC.

9) Spark looks good on all 3 cylinders.

10) Also checked Ohm readings for CDI, per manual, and did have some that were slightly out of range. Now that I'm typing, I can't find where I wrote them. I will recheck tonight and post later.

Any other things to look at or check?? Can the CDI be checked in any other way, off the motor?? (I live 2 hours from the nearest Yamaha dealer). Right now I'm thinking the CDI is the issue ... but that is a lot of $$ if I am not sure!! Anyone have a good used one laying around??

[Hamfisted]

Still sounds fuel related. Like fuel is flooding into the motor when you open the throttle plates up. Hard to tell without looking at the carbs. Was there an O-ring seal on the ends of the main jets? I know on the bigger motors if that O-ring seal is cracked or torn gas will get around the jet and free flow into the carb throat when the throttle is opened. Your symptoms sound a lot like that. Do you have the factory manual for it or are you using a Clymer?


Mike

[Mr. Ed]

Mike -

I have the manual from Yamaha.

No o-rings on the main jets or the secondary jets (I guess they'd be a mid range jet). The only O-rings I recall were on each needle seat for the float.

[Wally]

Could it be getting a gulp of water from the water separator when you suddenly open the throttle? You didn't mention if you have drained it recently.

[Bazooka Joe]

You've covered the fuel issue well enough to have it covered, IMO.

I think you have an electrical issue. Fuel is too predictable and consistent to be the cause of your problems.

Try this- Connect your timing light to the engine and go for a cruise. Get the engine to bog, and then observe the timing light. If it's still flashing while the engine is bogging & stalling, then it's fuel, but I'd bet you'll see a dead timing light.

Good luck with it.

[Mr. Ed]

Well, I couldn't find the Ohm numbers that I wrote down for the CDI box ... so I pulled it and checked it more carefully on the bench.
Here are a couple of abnormal readings I got followed by the Yamaha spec:

Charge coil:
+ lead on brown, - lead on black ... reading of 12.8 kohms ... range should be 2.5-6.7 kohms

Pulser coil:
+ lead on white/red, - lead on black reading of 160 kohms ... range should be 2.7-7.0 kohms

Crank Position sensor:
+ lead on blue/red, - lead on blue/white reading of 140 kohms ... should be infinite resistance.

+ lead on blue/red, - lead on black reading of 0 ohms ... should be 8.9-20 kohms


Wally - no water in the filter/seperator.

Bazooka - I did make an attempt at that yesterday. However, I had my 10 year old driving (for the first time, LOL). She was VERY nervous at anything over idle. However, I was able to get the timing set/checked on the top end. I also think the timing was jumping around quite a bit while it was bogging. But again I had half my attention on my daughter and trying to convince her that she was doing fine.

Hamfisted - With out o-rings on the jets of this model, what would you suggest ... new jets and needles? Main jets or 'Pilot' jets?

I should also mention that once it is at higher rpms, it will run there all day ... or until I need to slow down. Then trying to get back up to RPMs ... same issue. Oh, also, warm compression check is as follows 118, 121, 118.

[Wally]

Ed, If you really think about it, it sounds like for some reason the engine isn't getting enough fuel when you open the throttle. Kind of like the fuel pump isn't giving enough output pressure for throttle up.

If it runs fine once you get to high rpms it doesn't seem like it would be a spark/electrical issue. Have you tried running the problem past a Yamaha mechanic for ideas? Try calling a couple dealers and asking for the mechanic. The worst they can say is "bring it in".

[Mr. Ed]

Thought the same as you originally, fuel issue. And that is where I started the troubleshooting, etc. Is there a way to test the fuel pump out put pressure, on this type of a pump?? I guess I could look at putting a 'T' in the line with a gauge coming off of that. Now that I think about it, I was pumping an already hard primer bulb when it was bogging yesterday ... so wouldn't that eliminate fuel delivery up to the carbs??

Hamfisted may be correct with the jet issue he mentioned ... but why would it have started like a switch was turned on.

The reason I am thinking CDI, is that on this model, that is where the timing is controled. There is no advance control under the fly wheel like most units I'm familiar with. On this one (probably your 90 also) the linkage to change the timing goes from the throttle to the CDI box (in a round about way). This in turn moves a rheostat (or something similar) inside the CDI unit itself. I did find those 4 or so ohm readings out of spec ... don't know if they are too far out or not.

I do know one thing ... they are catching limits of walleyes on the other side of the state and I'm sitting here with my thumb stuck somewhere, LOL.

[Hamfisted]

Ed have you run it on the water with the hood and air box off, so you could look into the carb throats while your doing this? If it's a fuel flooding issue you'd be able to see raw fuel squirting up into the carb throats.
With the CDI timing control issue, have you tested it running on a garden hose and watch with a timing light (pointed at the timing marks...) while someone else manually moves the timing lever on the CDI? Like disconnect the motor linkage off the CDI arm and just move the arm by hand to change timing momentarily and see that the marks on the flywheel reflect this movement?
Or maybe you can do it by yourself, I don't know your setup.
Does it bog in neutral, or just in gear?
You can pump the primer ball up firm I guess? The gasket on the back of the fuel pump is new as well as the fuel pump itself? If that gasket leaks air you'll lose most of your fuel pump ability. It still sounds fuel related to me, but I'm stubborn.


Mike

[Mr. Ed]

Mike -

Yes I have ran it with the hood and air box off. I can see small fuel drops coming from the needle tube for the main jet. Should no fuel be visable with the naked eye?? I would not call it squirting ... but definate small droplets coming out of the tube.

I think that I tried manually moving the timing lever yesterday ... but honestly do not recall the results now. I will try that again on Friday when I am off.

Starts and runs in neutral fine. Can put it into gear with a slight bit of throttle with no issues (up to about 5mph on gps ... tach is not reading correctly). Any more throttle and that is where the issues begin.

Correct fuel pump is new. Dealer did not have the gasket and said they'd have to order it from Japan, as there were none in the distribution centers (I found that hard to believe). The old one was intact and stayed in place on the motor. I put a slight bit of permetex on the matching fuel pump surface when I installed it (very careful not to get it into the hole). HOWEVER, the issue began BEFORE I changed out the fuel pump. When it is bogging down I can give the primer maybe 1/4 pump until it is solid, and keeping pressure on it does not change the bogging down.

Just another thought while typing this. If the bogging is from too much/poorly atomized fuel, I should be able to pull plugs and check for a soaked plug ... correct?? Although, wouldn't stalling from a timing issue would show a wet plug also? I guess if I find a wet plug it would rule out a lack of fuel issue (and the fuel pump).

Too bad you all are in Fla and Texas & the like ... I'd have you all over for a beer and we'd get it running right!!

Ed

[Wally]

I know nothing about the sensors that are on Yamaha engines but it is beginning to sound like a sensor is providing bad info to the fuel feed or timing somewhere. Isn't there a troubleshooting analysis computer connection somewhere on these engines? If so, maybe you could get the dealer to do a diagnosis. I still think trying to talk to a Yamaha tech is your best bet to narrow it down.

[Hamfisted]

Ed are you seeing "droplets" in all the carbs? It should be a spray if you see anything. Droplets are unmetered fuel. Finding the cause of the droplets is the challenge. Do you think maybe you set the floats a little too high and now with the summer heat the bowls are overflowing?


Wally, no there weren't too many sensors on '92 motors other than the overheat sensors. There is a crank position sensor but Ed said he tested that already and it tested good.

Too bad you don't have another set of carbs to try.


Mike

[Mr. Ed]

I think the fuel coming out of all the carbs was pretty much looking the same. I would classify it as HEAVY spray, or small droplets. I did not pay that much attention to it though (knowing it was running good after the carb tear down). I will put her back into the water on Friday and watch the fuel a little closer and check the timing advance a little closer also.

The floats were all w/in spec. I double checked that after I started having issues. And looked at jets etc to malke sure I didn't get some crap in there after the carb kit install. Now ... the measurement MAY have been to one side of the spec or the other. If I remember correctly those floats are all plastic, even the tab that the needle attaches to. Maybe I'll pick some up and some jets as well.

Correct, not too much for sensors on this one. Crank sensor and I guess I would consider the pulser coil a sensor also ... but they were both good.

Too bad I don't have another set of carbs ... AND ... another CDI box!! LOL.

As far as techs/dealers ... the one nearest to me I do not have a good fealing for, period. The next nearest is a couple hours away ... I suppose I could call though. However, from the posts I've seen on this sight there are some pretty good wrenches here as well.

I'll post back on Friday, after I get a chance to dig a little deeper.

Ed

[Mr. Ed]

Well here is today's update as promised ... I'm sure you were all on the edge of your seats in suspence waiting for it.

Put the CDI back in this morning and headed to the lake. Looking at the spray from the main needle jets ... it is even in all 3 carbs. In mid range it is very visable, at WOT it is a little harder to see. I do see an ever so slight bit of fuel pooled on the bottom of the carb bores. All 3 carbs looked to be operating pretty much the same.

As for the advance, it looks like it is working as well. I unhooked the linkage and checked it quickly while at idle, like mike suggested. It advanced until the pointer got to the 'advance timing mark' on the CDI (this is a mark that is used for initial set up of the timing). Once I past the mark ... the timing dropped off. Not sure if that is abnormal, but it kind of seemed odd.

What ever the issue is ... it was quite a bit better today. The motor ran the best it has run since I started having the issue. What was diff today? Temp was hottest of the year so far, 90*. Same tank of fuel (actually finished off the tank and filled it up on the way home). Today it came up in rpms without bogging down ... it did hesitate just a little bit when given throttle, but came up in rpms. I would like to be able to have the timing light on the engine when it is the middle of bogging down. If the potentiameter (sp?) in the CDI for the timing advance has an intermittent ... it would show up when the motor is bogging down.

I have new floats and jets coming, along with new gaskets for the prime start pump (trying to rule out anywhere I could be sucking air). I also found a new CDI box for almost 1/2 price! It is coming also. If it is not the issue, I should be able to get my $$ out of it if I sell it. However, I did have those 3 or 4 bad ohm readings on the one I have ... so even if it is working, it might be just a matter of time until it does fail.

Hamfisted - Anything else on the carbs you'd be looking at for replacement, to rule out your fuel theory? Already has new float needles and seats.

I will get this thing running correctly!! I know I probably should have just taken it in .... but like Hamfisted, I'm stubborn too!!

Ed

[Ken]

Ed,
Thanks for the update [img]smile.gif[/img] .
Persistance pays off when it comes to something like this, but, boy, it sure can get frustrating !
At this point, I'm gonna bet it is the timing inside the CDI - the mechanical/electrical conversion, the potentiometer thingy. Shame you can't replace just it.
Keep us posted [img]smile.gif[/img] ,
Ken K