EVINRUDE FASTWIN 18 hp 1968 IDLE NOISE

[bolk]

Hi !

I'm new to this forum : first post.
I live in France and I have just re-built an old 1968 FASTWIN 18hp which was blocked.

New pistons, new rings, new motorhead, new coils, new caps, new points.

The motor start at first pull.
Oil ratio for break-in period is 24:1.

But I listen a clunk noise at Idle, coming from the top end of the motor, near the flywheel.
https://youtu.be/y4qPICItaF8
Disapearing at higher RPM.
listening noise when neutral or in gear.

So I open it again to check something wrong : nothing really bad...
A very very little movement when pushing the top piston through
I removed the piston and assembled it again. ROD bearing seems OK.

The noise is not continous : I can hear a cycle it each 7 turns...

I also checked if something was worn or moving in the flywheel : nothing.
The coils are well aligned and centered.
Flywheel is set at torque.

Could it be :
- main needle bearings ? seems OK when turning it.
- reed valves ??
- low unit ?

thanks for your help !

 

[Joe Reeves]

You say the coils are well aligned but you do not say exactly how you aligned them. They may not be perfect which allows the flywheel magnets to touch them occasionally.

Where the metal portion of the coils sit on the aluminum armature plate, there is a slight bevel. The vertical metal portion of the coil(s) should be aligned so that the vertical portion is aligned with the inside top edge of that bevel... check it.

 

[bolk]

Hi Joe, thanks for your quick answer.
Yes, having coils aligned is not that simple. I know there's a ring tool, but I don't have it.

One of the two coils has one side out of the top edge of the bevel... but it's a nail thick...
Could be this ??

I had to sand the inner bottom of the plastic coils to fit the plate...
If not, impossible to align.
I should sand it again to allow this little gap to disapear.

In your opinion, should not be a crank/bearing/piston/rod noise ?

 

[racerone]

I believe it is the crankshaft moving up and down.----Perhaps normal or you could shim the thrust washer to reduce end play.

 

[Joe Reeves]

A very little movement when pushing the top piston? There should be no movement Up/Down UNLESS you're speaking of a extremely rocking movement due to piston/cylinder wall clearance. Pertaining to a flawed bearing or anything out of normal with your rebuild work... you'll need to be the judge of that.

You need to sand the coil to fit the armature plate??? IN my 30+ years experience, I've never heard of or encountered this scenario. Can you explain why this is needed?

There were originally two different OMC magneto coils, 580416 and 580197... the metal lamination portion of the 580197 coil is thicker in height than the 580416 coil and they are not to be interchanged.

Your 1968 18hp model calls for the 580416 coil... However both the 580416 and the 580197 coil supersede up to coil #584477.

Bottom line... If you are using a original 580416 coil or the superseded 584477, that's okay. If you are using the original 580197 coil, that's NOT okay....... Yes, the finger nail thickness misalignment should be corrected.

Many older engines suffer a wear of the brass and aluminum support rings holding the armature plate... a rocking motion. A couple thousands of rocking is normal..... a 1/8" or more is not! If excessive, this can be corrected as follows.
********************
(Magneto Armature Plate)
(J. Reeves)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically (as well as other problems) as the armature plate turns.

The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make a slight indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.

You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.
********************
Let us know what you find.

 

[bolk]

I have checked and made again the coils alignments.
Difficult to do better.
I had to use a Dremel to sand the coils inner edges to fit the armature plate. Low quality exotic coils ?

Last time it ran, I tried to stabilize the coil plate as it was a little bit moving. No change with the noise I heard.


Before closing everything and testing again, do you have other ideas ?

Thanks.

 

[Joe Reeves]

Nope... Out of ideas, sorry.

 

[bolk]

Thanks Joe and Racerone !

Joe Reeves
The side to side wrist pin movement was existing, but the up and down : no.
The rod needle bearing looks good. Pins OK...
Pistons and powerhead are brand new : so it could not be piston slap ?

The coils I bought were 584477 replacement.
https://www.ebay.co.uk/itm/173514534353
The glossy sealant part is so big that it doesn't fit. That's here that I used my Dremel in order to align everything.
Weird.

Yes the armature plate has a loose fit.
The 4 screws part is in the right position (plan facing up) but even if thightened, it moves.
So I guess I have to follow your advice and use my hammer.

racerone
When I first tried to remove the flywheel, I slowly tried to pry the flywheel against the powerhead while knocking gently on the crank. Nothing happened... for sure.
So I made my own tool with the 3 screws made for this on the flywheel. It worked great.
But when I gently pry the flywheel, I noticed a little movement up and down of the flyhwheel i.e. the crank.
I didn't notice any movement while the motor was turning.

Good idea to shim the washer. Is it ref 304732 here #82 ?
It doesn't look like this in reality : it'more like saturn

 

[racerone]

I know what that washer looks like.

 

[bolk]

I guess yes
It was mostly to be sure that I understood your advice. Thanks.

 

[bolk]

OK. I have checked the crank for play.
And there's (again) a little clic and very small play when whaking left and right (exhaust <--> fuel pump direction).
No play when shaking carbs <--> spark plugs
Is it something tolerable or absolutely not ?
Does it mean bad bearing ? Or is this clearance acceptable ?

Also one question : when I've installed the 3 main crankshaft bearings, I've aligned the big hole with the pin on the powerhead.
Is that correct ?