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8rcob 1985 8 hp electrical problem

ba_50

Regular Contributor
When trying to start it backfires through the exhaust and is almost impossible to start. It i is difficult to fire with with carb cleaner. It will buck up and down some, smooth out ok then quit, not in that order. The compression test was about 135.


The flywheel key is like new. It has new plugs.

We got this motor new.

What ground should I check? Which is more likey to be bad the charge coil or power pack? These are original parts.
Thanks
 
You didn't say you have checked the spark.

Too much fuel can make it backfire out the exhaust. So can intermittent or out of time spark.
 
Electrical pertains to the electric starter system, charging system, lights, etc...... You are speaking of a possible "Ignition" problem. There is a difference,

First step is to actually check the spark by using a tester (available at most auto part stores) whereas you can set an adjustable air gap... set the gap to 7/16"... Note that the gap is important.

You can make a multi spark tester as follows (below)... and some members have designed various testers that would put mine to shame (they may jump in here)... BUT... you can build mine quickly with a "hammer". :)

Remove the spark plugs (all of them) first in order to obtain the fastest cracking rpm. The spark should jump that 7/16" gap with a strong blue lightning like flame... a real SNAP! If this is the case, you do not have a ignition problem.

Let us know what you find.

********************
(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

This can obviously be modified to a 6 or 8 cylinder setup tester.

********************
 
I cleaned the coil and p pack grounds. It was a little awkward trying to use the rope/ flywheel pull but it looked like the spark jump went about 1/2". One was blue and the othe r more orange.
Twice there wasn't any spark so I tried it several times.

I put it in a barrel but no luck.
 
Did it fail over a storage period, or while it was running. Power packs generally fail, at least from my experience, while the motor is stored.....especially this vintage. Boobie may be correct, looks like improper spark.......did you build a Joe Reeves tester? I did......works great......always have it on top of my tool box. Diagnosed motors 100's of times with it.....gonna try to post a picture sometime to give Joe a good laugh.
 
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I cleaned the coil and p pack grounds. It was a little awkward trying to use the rope/ flywheel pull but it looked like the spark jump went about 1/2". One was blue and the othe r more orange.
Twice there wasn't any spark
so I tried it several times.

I put it in a barrel but no luck.

Seems that you do have an ignition system fault

Systematic testing is the way forward, unless you go down the route of replacing parts one at a time until you cure it and spend all your beer tokens on bits you did not really need in the process.

You may find the CDI Electronics troubleshooting guide useful, although you will need a DVA adapter for your multimeter

http://www.cdielectronics.com/wp-content/uploads/2013/02/CDI Troubleshooting Guide - 2012.pdf
 
You are correct, Vic. In this case, if in fact it does really still have the original power pack, that would be my first suspect. I have a very low hours 15 (1982) Johnson up at camp. That lost spark on one cylinder while stored in the motor shed. Turned out it was the pack. Had a used one in a box....the camp is remote, and we needed the motor because it was the last longshaft that wasn't up till now needed. Got it running great with that used pack. Next trip, however, I brought with me a new pack. Have you noticed that sometimes while looking through the gel....if its semi- opaque...you can see rust, discoloration, or the like? I think that as they age....like anything else, they become potentially problematic.....I gain suspicion.
 
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I made a spark block with 2 clips on 12 volt wire thinking it would be more accurate.
This time blue spark from both coils

Does that mean the ignition system is ok?
 
One last thing is I like to check spark in ALL throttle positions, which means temporarily over riding the recoil start safety gizmo. If it checks out then put some new spark plugs in and give it a try, brother.
 
Right, brother.....what Joe says is "golden". However......the spark has to be consistent, and not missing a cycle, and a blue / blue-white color spark as well. A yellow, orange, or gold color is not desirable.
 
I soaked the carb 2 days and nights in cleaner. The needle was opened 1.5 turns but alwas took 2 or more to start before.
It has new plugs. The cam roller is lined up with the mark when the throttle plate starts to open. The key was good.

It still pops through the exhaust 3 out of 5 pulls. E
Ven with carb cleaner in plug holes it won't start.

What else could it be but electrical?
 
As per and comparing port #5 and post #9.... I'd guess that none of us have any idea what kind of spark you're obtaining with thew tester.

Start from scratch............. The ignition... check it again as follows.

Spark plugs removed.

Have a tester set up what has a air gap set to 7/16"

Have someone helping you so that you don't have to crank the engine over and try to see exactly what the spark is doing all by yourself.

Have the someone else do the cranking while you observe the spark.

Explain the results in detail.... no generalities. We need it to be crystal clear.
 
My ex- mechanic friend says both plugs have a good blue spark set for 7/16" gap. 6 pulls on each one.

I was wrong about thr roller setting it is about 1/4 to 1/2" past the mark when the throttle plate starts to open. Do I adjust the roller screw or the cam screw?
 
The roller adjustment screw is all the way in and goes past the msrk about 1/8" whe n throotle stsrts too move. The linkage rod has wear eough to make that much differece. It must be timing?
 
From what my two mechanics say and from what I have read, the motor has to be running for awhile because an electrical problem could be intermittant. The power pack may not malfunction until it heats up and so forth.
When it was running sometimes it would just quit and wouldn't start. It usually took 30 pulls to get it going.

Just because there is a spark doesn't mean the pressure/vacuum in the crankcase could be the problem due to a bad seal another possibility but not likely.

A new fuel line didn't help by the way.
 
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And how would a powerpack heat up ??-------Run with a timing light to see how spark acts up.----How did you check flywheel key ?
 
I don't know. Are you saying it could't be an intermittant problem for some reason'
? It has been awhile but it would start again after say 15 minutes.
It won't start or I would.

Not too long ago the key looked perfect but with all of the backfiring maybe it should be checked again.

The key was gone and didn't do the flywheel any good. I don't have any spares either.
 
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Lap the flywheel and crankshaft with some grinding compound .-----Install a new factory key.------Torque the nut properly.-----Test run this fine machine.
 
Where do I get gringing compound? Fine machine?
I haven't given up hope but after so long it makes me wonder!
 
Any automotive supply store has valve grinding compound.------These are wonderful motors.----But folks invent new ways to damage them every day !!
 
Intermittent spark on this motor is usually power pack, unless somebody's been "playing around" under the flywheel......and granted that coils have been passed as okay. I have changed many upper crank seals on these too, they do fail, not sure why but I really hate to blame ethanol all the time.
 
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The seal costs 10 bucks, easy to change....is it leaking? There will be oil under the stator plate, under the flywheel. They are a problematic seal.....at least here where we are in Northern MN. Many people are unaware of the effects of ethanol on some style of crankshaft seals, but it seems that the upper seal on these is the one affected, not the lower....so I really can't blame ethanol for certain. It might be the seal quality from the factory. I order a higher quality seal from the bearing/seal supply wholesaler here in town.
 
I have one of those Lisle seal pullers so that simplifies any leak problems. I've had the head off to chisel all the salt out of the water passages.
 
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