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Labyrinth seals, how much play is too much?

J

Jaybey

Contributing Member
Hey again guys,

1969 Merc 1000ss serial 2685637.

I've got the powerhead completely disassembled, and I'm at the stage of servicing the reed cages. I know they aren't supposed to be an airtight seal on the crankshaft, but I can wiggle them side to side about 1 to 2 millimeters... is that acceptable?

The reeds and stoppers all look good, some were just stuck with old fuel mixture gum. They've since cleaned up nice however. I'm really hoping to not have to invest (track down) replacement cages here..
 
" Wiggle side to side " means very little to me.-----Bad bearings would wear out those seals.-------Use a product that a mechanic would use to check bearing clearance.-------Something called ----PLASTIGAUGE-----To get a meaning full number.
 
Just how is someone to check bearing clearance in a 2 stroke like that with Plasigage?

Replace the seal(s). The lips have to be tight against the shaft.

Jeff
 
Sorry, I guess that was indeed a bit vague..

To elaborate: while on the crankshaft, with a thumb on one side of the cage and fingers on the other I can twist the cage a bit. Meaning, with the crankshaft laying flat on my bench, the top of the cage moves a bit towards the bottom of the crankshaft and the bottom of the cage moves toward the top of the crankshaft and vice versa... wiggles a bit I guess.

My top bearing is making noise when spinning, so going to replace that. The bottom one is starting a bit too, might just go replace them both. I've yet to remove the two center bearings for inspection, but I'll look into that tool you've mentioned (thank you). Is it used for the outer or inner bearings or both?
 
Unbolt the halves and inspect the crank for ridges (there should be none) and the cages for "mushing" and, sharp edges on the grooves, - which they should have.
 
The crank journals have visible lines where the labyrinth seals were sitting, but can't feel any discernable bumps or ridges. The ID of the cage halves have some "mushy-ness" but are still sharp-ish.. I wonder if someone tried to smooth any ridges on the journals with emery cloth and maybe took it a little too far. The original issue and reason for the tear down was cylinder 1 not getting any fuel at all. I had spotted a crankcase cover fuel leak on further inspection (which seems quite wide spread now that it's apart), but now I'm wondering if I'm looking at a poor seal between cylinders 1 and 2 because of this.
 
racerone said:
Run to a machine shop and have these parts measured.
Click to expand...

Thanks racerone. I have digital calipers and a micrometer in my garage, I'll take some measurements first and depending on what I find I will definitely take that advice.

Kinda puts a stop to what I'm doing though haha.. oh well, it is what it is I guess
 
Time to evaluate the whole project.----Perhaps search for good used parts.------Find what other models use the same reed blocks / cages I guess.
 
Yes, I have a parts engine in hand. Going to pull the powerhead over the weekend and hope it's alright inside. The cylinder bores on the water jacket side have cracks in them where each bore meets the nex, but it still turns over by hand.

Fingers crossed!
 
There is about .020 play on the seal to crank edges. As long as the seal edges are sharp, still look aluminum and not brassy they are good.
 
faztbullet said:
There is about .020 play on the seal to crank edges. As long as the seal edges are sharp, still look aluminum and not brassy they are good.
Click to expand...

Ok, that's the tolerance spec I was looking for.. I'm going to take pics of each half on all 3 and post here, I think they're ok but there's no substitute for a trained eye ��
 
Crud, 0.002 seems like it'd be a lot tighter than what I've got here...

I need to get some time in the shop for some accurate measuring, I've got three kids aged 5 and under, time is at a premium here haha..
 
Ha! Indeed..

Can you tell me, because I'm really not all that familiar with the standards.. In what format should my digital caliper be in for my measurements? Inches or millimeters?
 
Inches.-----Not sure if a caliper is the correct tool for this inspection.--------But it depends on skill level.------Was at a job interview years ago.-----Was asked if I knew what measuring tools were on display.-----I said " yes " I know how to use them.-----Was asked to demonstrate.------After measuring one dimension I asked if the interviewer wanted some more dimensions done.-----His reply was----" No that is good "------Got the job.
 
Haha... nice to have the skill set. I'm using the caliper because it's what I have on hand, just going to compare the diameter of the journals to the ID of the cages. To the best of my ability anyway...

What other means were you thinking of for a more accurate result?
 
Compared to some I've seen on this board and others, mine don't look too bad. Being the vintage they are, I can't find pics of a new one to compare with however
 
Thanks faztbullet, the petals themselves are original as well. The have some visible wear, but I can't seem to source any replacements, any suggestions on that front? They still feel quite solid mind you, so not sure if I need to replace them or leave well enough alone
 
Put a piece of newspaper ( 1" square ) on the crankshaft.----Install the reed block.----Does it tighten up ?----Will reed block still turn easy ?
 
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