Yamaha 115BTO V4 cdi unit measurement

[gbraen]

I have an -96 V4 115BTO with an misfire/stalling problem.

Did a full resistance check on all components, all in range. But the CDI Unit is all out of range, i guess all measurement is done with all wires diconnected? Anyone can confirm this before i order a new one?

[99yam40]

I would take peak voltage readings before buying new CDI, just do not trust ohm readings that much.
Might post your readings you have so others can see and maybe give advice

[gbraen]

In the workshop manual the resistance reading should be from 3.6 ohm to approx 260 ohm on different points.

I'm measuring aprrox 425 MOhm, that's a big difference.

What's the peak voltage readings, can't find it in the workshop manual?

[99yam40]

Yamaha service manual should give the peak reading specs for the inputs into CDI and out of CDI listed at minimum. Need a proper meter to take the reading or a DVA adapter and regular meter. That way you know for sure what is going in and out of CDI

[gbraen]

I have an DVA adapter for peak readings, i guess it should be min 100v.

[99yam40]

should be specs at idle, and different RPMs.
My guess would be higher than 100 at the higher RPMs
Need to find the specs in service manual

[gbraen]

Min 125 volt at cranking speed. Will check it out tomorrow. Thanks.

[gbraen]

Out from stator all good, well over min voltage. But little on the low side out from CDI unit to the coils, 110-115 volt. Compression test OK on engine.

It starts occasionlly, and runs quite OK, but then it stops abrupt. And it won't start again. Any suggestions? Anyone?

[rodbolt17]

as yours is an international market engine I don't think they gave the input and output specs for a CD77.
generally it cannot spark if CDI output is much less than 60v.
the CDI doesn't amplify anything.
typically I see a 10V drop from input to output.
your going to have to test it when its dead.
could be a CDI,keyswitch,stop switch or harness.

[gbraen]

It IS dead. And i have disconnected the white wire on cdi unit.

Still dead. Suddenly after long it shoots very loud out the exhaust with flames. No lower unit attached at the moment.

All seems ok, but wont start. Doesn't even try.

[rodbolt17]

test stator inputs and outputs while its dead, if the inputs are good and no output and the kill circuits are disconnected then you have a bad CDI.
running with the lower off you will get a lot of flame.

[gbraen]

Funny stuff...

Have both input and output on the CDI, but still won't start. Guess it's ok then, even if two of the outputs to coils are lower than the other two.

Last time engine runned, it misfired once and then wouldn't start again. And hasn't since.

Spark on all plugs.

Wet plugs.

Won't start or even try with start gas either.

I have gasoline with 1:100 mixture AND oil from tank at the same time, can this be a problem? Seems to be a lot of oil on the spark plugs.

[rodbolt17]

the C85 is a non oil injected motor.
are you sure its a C model powerhead?

[99yam40]

You might post the voltages you are getting, just so others will see and it may help them also in troubleshooting their motor later if they look up this thread. If the CDI puts out enough voltage to coils to make spark it does not mean the plugs are sparking. Need to test to make sure they are

If you have good compression, and get a good spark ( test with spark tester), and timing is in spec then I would be looking at the fuel condition and fuel/air mix being messed up. May just be needing to clean carbs and adjust properly

[99yam40]

the C85 is a non oil injected motor.
are you sure its a C model powerhead?

Rodbolt this thread is about a 115 BTO,
Think you were thinking about wrong thread