Author Topic: Thin Metal Base Gasket?  (Read 2470 times)

fl3501985

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Thin Metal Base Gasket?
« on: September 27, 2013, 06:35:29 PM »
Five years ago I bought a fl350 with a blown piston.  I installed a piston that came with it.  I was told that I could reuse the base gasket if I just put high temp sealant on it.  This gasket was just a piece of metal.  I coated both sides and reused it.  Compression was good.  I couldn't do a leakdown test, as one of the bolts for the exhaust was stripped so it wouldn't tighten enough to seal(I think I have this fixed now).  The odyssey never ran well(only ridden a half hour) and was always out of oil.  I am wondering if the base gasket was leaking and sucking the oil out through the exhaust?  There was always black oil running down the frame from the exhaust, is this normal?  I am new to two strokes.  It was always really smokey.  Is there any logic to this?  Since then I have had two kids and am just getting around to looking at it again.

I ordered a honda gasket to put the head back on, but what is the purpose of the thin metal gasket?  Should it be left out or does it serve a purpose?  Above or below the fibre gasket?  I don't see it in the manual.  Also, think I should I separate the cases and replace all the seals or put it back together and do a leak down test?  If replacing the seals, should I bite the bullet and do the bearings?  I really don't know the history of the machine.

Any advice is greatly appreciated.  Thanks.

shoubadaba

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Re: Thin Metal Base Gasket?
« Reply #1 on: September 27, 2013, 08:36:07 PM »
The metal gasket you speak of is the stock honda base gasket it usually comes with a coat of sealant on one side.  Only 1 base gasket should be used. That gasket is discontinued and an aftermarket one will be needed. The oil and smoke you describe sounds like your carb jetting is too rich. As far as resealing your lowerend If you split the cases you will need to replace the bearings as well. It only make sence if you have it apart to go ahead and replace all seals and bearings
« Last Edit: September 29, 2013, 05:21:03 PM by shoubadaba »

fl3501985

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Re: Thin Metal Base Gasket?
« Reply #2 on: September 28, 2013, 05:50:02 PM »
Not sure I understand.  The metal honda gasket was used with another gasket?  So, I need a new metal gasket as well as the gasket that I already have?  When I bought the gasket that I have, I never saw any metal gaskets???  Does it come in the complete gasket set?

Also, I haven't split the case yet.  Are you saying that I should split and replace everything or only replace if it has been split already?

Thanks.

LiveWire

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Re: Thin Metal Base Gasket?
« Reply #3 on: September 28, 2013, 06:56:09 PM »
Your carb likely has the stock 52 slow jet. I suggest dropping it to a 45. Also run a good synthetic or semi-synthetic two stroke oil at 32:1. The smoke will be reduced and reduce if not eliminate the oil running out the exhaust.

What fiber gasket are you talking about? For the head? You seemed to have shifted modes and were talking about the head. So I assume you mean head gasket. A fiber head gasket is a piece of crap Cometic. It's proper location is the nearest trash bin. Only metal head gaskets should be used: Honda, Athena or Veserah.

You can replace the case seals without splitting the case. They are pressed in from the outside anyway. The old ones can be removed by driving screws into them and pulling out. You'll need a clutch puller, flywheel puller and a ultra deep socket for the nut that holds the counter balancer gear on. If the cases are split, the bearings should be replaced.

Am I to understand the piston was damaged and was replaced with another of the same size or was it bored? What does good compression mean? If you mean by how hard the rope is to pull, it will seem hard well below what I would consider bad compression at 130 PSI.

An FL350R will last a long time between rebuilds if care is taken to follow certain steps. They will last an amazingly short period of time otherwise.

http://www.aftershockmotorsports.com/technical-articles/FL350-Rebuild-Tips

fl3501985

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Re: Thin Metal Base Gasket?
« Reply #4 on: September 30, 2013, 12:22:26 PM »
Also, I forgot to mention, this is my first two stroke.  It isn't the stock carb.  I think it is a 34 or 38mm Keihn(if that makes sense), but the machine isn't here to check.  I ran 25:1 as I was leery about going 32:1 on a fresh piston.

I am still talking about the gasket between the jug and the crank case.  After rereading shoubadaba's post, I see that there is only one gasket, but the new ones are different.  The thin metal one is all that came on it stock?  It just doesn't seem like it could seal.

Yes, the piston was replaced with the same size.  It came with the machine.  It was a Wiseco, but I can't remember the size.  I measured the jug and it seemed ok.  I can't remember the measurements or method(probably not accurate enough).  Not sure about compression either.  Although, I did measure it, it wasn't by feel.  What would you consider good?  My brother ripped it apart, before I checked it again.  The machine would run, just not consistently and very smokey.  The exhaust bridge had been relieved and the piston had the holes drilled in it.

I guess what I am asking is a leaking base gasket going to cause the same problems as leaking crank seals?  I am hoping that someone will say that if I slap it back together with a new base gasket my problems may be solved, but in reality a complete teardown, bore and rebuild is required.  Just seams like a waste to throw out a piston that is pretty much new, although, one of the rings is stuck - I might be able to get it loose, I haven't tried yet.  I might just bolt it all together, do a leak down and compression test and then get back to you guys.

What about the oil in the balancer disappearing?  After pulling the head, there was quite a bit of oil on the crank side.  Is this getting sucked through the seal because of a leak, or is the seal between the two halves shot as well?  Or is it from running rich/wrong mixture?

Where is the best place to get clutch puller(or what size bolt will fit the threads to use the oil method), flywheel puller and case splitter?  Approximate cost?  Or, am I better off just taking it in?  How much should I expect to pay for labour/parts on a complete rebuild?

Thanks for all the info.

DMoneyAllstar

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Re: Thin Metal Base Gasket?
« Reply #5 on: October 04, 2013, 06:49:20 AM »
Balancer oil disappearing....
1. Crank seal leak
2. Oil is getting tossed into the starter.
Replace the crank seals.

Leaky base gasket will cause an air leak, an extreme lean condition, and will destroy your engine.

Pull your starter and look for excess oil.  It can fry your starter, too.  If the brushes look worn, there are starter rebuild kits on eBay for like $20 and they're very simple to so.

Special tools that are must haves...
- Clutch puller on eBay
- Flywheel puller (get one and you'll have it forever, plus it fits a ton of other 2-strokes)
- Motion Pro also makes an extension for your socket torque wrench to get the one jug nut tightened.
- If you're doing a full tear-down, you'll want a set of bearing pullers (Harbor Freight, or borrow from Autozone).
- To check piston/wall clearance...
    - Set of Vernier calipers, or a 3-4" micrometer for measuring piston OD
    - Bore gage for checking bore ID
- Leakdown tester...one can be assembled for under $30.
- Compression tester (under $20 from a few places).
'85 FL350R Odyssey
'88 LT500R Quadzilla

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