Yamaha 200ETXN Surging Idle

[Jprevat]

Hey fellas, I hope yall are having a great fall so far. This is the first time I have actually run this engine in the water after it sat for quite some time.

When at idle I am hearing audible spikes in rpm and its not running at full potential. If I mat it then it falls on its face and did stall once. If I ease into the throttle it planes easily, but doesn't want to accelerate past 40mph. The old 140 OMC would push it 38mph all day so I think 60 hp should net more than 2mph.

I just had the carbs rebuilt and two coils were replaced. The ones he used don't match my stocks so I don't know if that's an issue.

I pulled the plugs and all but one were dark and they all are wet. I'm assuming that coil is dead (fingers crossed). There is no carbon tracing on the plugs either.

Is there any other reason a single cylinder wouldn't fire? I'll attach a link to a short idle video and some pics of the coils and plugs.

Thanks ahead of time guys.Idle Vid

 

[flyingscott]

2 strk/4strk , fuel injected/ carb motor?

 

[Jprevat]

It's a 1984 two stroke with three 2 barrel carbs.

 

[flyingscott]

You need to do a compression and spark test . If that is good go back to the carbs also verify the oil injection is working

 

[Jprevat]

You need to do a compression and spark test . If that is good go back to the carbs also verify the oil injection is working

Compression across all six cylinders is about 105 on my gauge plus or minus 2 psi. The oil injection has been disabled and unhooked. I'll run a spark test and get back to you.

 

[Jprevat]

Spark test done. I am seeing no spark from the top or middle cylinders on the port side. Getting out the multi meter and clamps to see if I have any current going into the coils. I would much rather replace coils than a cdi.

Edit: I was wrong about no spark. I do get intermittent spark on those cylinders. Input voltage seems to be equivalent to operating coils. I'll swap a couple around and see what I find.

 

[flyingscott]

You need a factory manual for the motor so you have the correct specs. You also need a DVA adaptor.

 

[Jprevat]

I'll go pick up a dva adapter tomorrow after work.

I'm not sure if I'm on the right track, but I tested spark using an induction timing light. On every trigger wire I was seeing a pulse however I was not getting a pulse on the plug wire for the two problem coils.

I guess testing with the dva will tell me more since I'm not sure what the threshold for the light is.

 

[flyingscott]

You need an open air spark tester also. Spark needs to jump a minimum of 7/16". Without a manual to tell you what the specs are your DVA test may be useless.

 

[Jprevat]

I'll go ahead and order a manual as well just to add to the library.

One odd thing I'm seeing is that the two problem coils are CM61-30 and the other four that are working are CM61-26. It looks like the guy before me replaced two dead coils with some from a 50 to 70 horse Yamaha. They are very easily 25% smaller even though they bolt up to the same mounts.

 

[flyingscott]

That could be the updated version. Get the factory manual

 

[Jprevat]

I cross-referenced the part numbers through yamaha parts diagrams and those cm61-30 coils are indeed wrong for this engine. I'm going to get a new multimeter and adapter tomorrow while I wait on a manual.

 

[Jprevat]

Just an update while I wait on the adapter and manual.

I swapped two good coils just to be sure that was not the problem and I am still getting no spark on the output side. Checked and cleaned common grounds on back of block and at the coils with no change.

 

[99yam40]

need to find out what sends signals to coils on this motor,
if cdi YOU CAN TEST INPUTS AND OUTPUTS, IF SOMETHING ELSE, YOU TEST THOSE.
Sorry for the caps, but i am not retyping

 

[Jprevat]

need to find out what sends signals to coils on this motor,
if cdi YOU CAN TEST INPUTS AND OUTPUTS, IF SOMETHING ELSE, YOU TEST THOSE.
Sorry for the caps, but i am not retyping

Hahaha all good. CDI was my next stop.

 

[99yam40]

if it is a CDI on that motor, you need to test the inputs that tell the CDI to fire those plugs.
if the inputs are not in spec find out why
if the inputs are good but the out put is bad, then maybe the CDI is bad

 

[Jprevat]

I have a spare cdi that the last guy thought was bad and changed but I'm thinking that the cdi was probably fine and the input source is going to be where I find the issue.

Thank you for the direction.