crankcase weep + magneto base moving

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forestcreature
Posts: 10
Joined: Tue Jul 17, 2018 12:40 pm
Location: London

crankcase weep + magneto base moving

Postby forestcreature » Tue Jul 17, 2018 8:32 pm

Hi all,

new seagull person. I have a 40 that looks to have been kept clean and tidy, and which seems to start and run well.

I get a slow oil weep from the crankcase, looks like from the seam between the two halves, and maybe again at the bottom of the crankcase where the driveshaft leg bolts on. It's not cataclysmic, just noticeable. Is there supposed to be a gasket anywhere there?

The other thing that I'm unsure about is that the plate under the magneto (holding the coil) has a few degrees of play on its main axis, so it jiggles around when running. The retaining screw is absolutely fast in the plate, and the slot looks like it's seen a bit of torque at some point! I was wondering whether there is something on the shaft that the screw goes into, or whether it just screws against the tube that it's mounted on. I'll see what's what when I free it up, but forewarned &c.

RickUK
Posts: 452
Joined: Wed Mar 08, 2006 12:58 pm
Location: Huntingdon

Re: crankcase weep + magneto base moving

Postby RickUK » Tue Jul 17, 2018 9:44 pm

You might want to just live with the crankcase weep unless it gets too bad - there is no gasket, so the cure is to split the crankcases - i.e. a total strip, where the recommended procedure is to manually lap the crankcase halves on a flat surface, e.g. a piece of plate glass - using an abrasive compound such as a valve lapping compound (do they still sell this stuff?) - and reassemble with a smear of sealant - crankcases were originally just 'dry' assembled.

The lower weep might be two stroke mix finding its way out of the bottom crankcase bearing, but you shouldn't see this at the joint you mention - see if you can nip up to two nuts a little. Again, no gasket at this point.

The magneto baseplate should not move - the locking screw should engage with a dimple in the crankcase 'nose'. The screw may be seized - see it you can get it moving, and you may be lucky in tightening it a little more in order to lock it. You might need to take the flywheel and baseplate off to understand where the dimple is in order to line up the screw.

The was a mod. covered in the old Seagull workshop manuals to compensate for a worn dimple, but too complicated to explain!

forestcreature
Posts: 10
Joined: Tue Jul 17, 2018 12:40 pm
Location: London

Re: crankcase weep + magneto base moving

Postby forestcreature » Wed Jul 18, 2018 12:32 am

I think lapping compound is still around! Okay thanks, that makes sense now.

I'll get that screw unstuck haha. Reading this, and other advice, makes me think that there's a finite set of possible failures with these motors---all of which are known. Maybe they could be compiled into a list with codes like for early microprocessor systems: "Error 707: worn dimple".

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Nudge
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Location: Auckland, New Zealand

Re: crankcase weep + magneto base moving

Postby Nudge » Wed Jul 18, 2018 9:36 am

The was a mod. covered in the old Seagull workshop manuals to compensate for a worn dimple, but too complicated to explain!


Have you got a copy of that text? I havent seen that before.
"THE KING OF BLING"!
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forestcreature
Posts: 10
Joined: Tue Jul 17, 2018 12:40 pm
Location: London

Re: crankcase weep + magneto base moving

Postby forestcreature » Wed Jul 18, 2018 8:46 pm

[...]
If the flywheel plate is loose when the screw is tight it will require a little work!

Drill out the recess with a 11/32” drill bit and install a 3BA washer this will securely lock the plate into place and can be removed in the future.


<- https://www.classicseagulls.co.uk/index ... &cat_id=14

Bit of an economical description, but is that what you meant?

andrew
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Joined: Wed May 24, 2017 5:37 pm
Location: Greenwich, USA

Re: crankcase weep + magneto base moving

Postby andrew » Thu Jul 19, 2018 2:13 am

Workshop manual service sheet #5. Happy to send a copy if you send me PM with your email.

RickUK
Posts: 452
Joined: Wed Mar 08, 2006 12:58 pm
Location: Huntingdon

Re: crankcase weep + magneto base moving

Postby RickUK » Thu Jul 19, 2018 12:36 pm

HI Nudge - sorry I couldn't find it (passed a lot of my Seagull paperwork on), but Andrew has covered it as I remember it.

RickUK
Posts: 452
Joined: Wed Mar 08, 2006 12:58 pm
Location: Huntingdon

Re: crankcase weep + magneto base moving

Postby RickUK » Thu Jul 19, 2018 12:43 pm

Forest creature - this what I meant - unless it tells you, I have to imagine that you drill the dimple slightly deeper with the aforesaid drill, and then somehow locate the washer within the dimple (or stick it there with some grease)

I have no idea what diameter a 3BA washer is - I assume it is the 11/32" of the drill?

Grease the locking screw before re-insertion - good insurance for the future!

forestcreature
Posts: 10
Joined: Tue Jul 17, 2018 12:40 pm
Location: London

Re: crankcase weep + magneto base moving

Postby forestcreature » Wed Aug 01, 2018 4:29 pm

I finally got the flywheel off and it looks like somebody had partially threaded the dimple, but the screw wasn't going in far enough to engage with the threads. If it was supposed to have a tapered end to sit in the dimple then somebody's cut it off flat. I ended up drilling out the magneto base thread, as it was stopping the screw from engaging with the (now-)threaded dimple. It seems to have done the job and the base is much less wobbly. I don't think it's even remotely ideal and I'll keep a skeptical eye on it when it runs!

I'll retap and fit something more appropriate and permanent over the winter.


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