JLO L300L Engine. Rebuild?

[Duck89]

Has anybody on here messed with tearing down one of these single cylinder JLO motors? I am considering doing this with the one out of my ST/300/D, but may not do it if it is too much of a pain. For being as old as it is, it could probably use a good cleaning and probably some new gaskets/seals.

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[Duck89]

I did a compression test today and it read about 85. Should this be about right for its age/visible condition? Would doing a re-gasket instead of a complete rebuild be anything I should do instead?

[jpswift1]

Martin, in my 440 twin after a rebuild the compression was around 130 something in each cylinder. I really don't know what it should be for a single cylinder though. Maybe in the service manual it will say. Here's a link for you:

http://www.6x6world.com/forums/conte...e-engines.html

[Bazooo guy]

Gaskets and seals and maybe hone the cylinder and install new rings.
Check the wrist pin bearings and replace them if they are worn.
When you replace the crank seals check the bearings....they are usually ok to re-use but at that point not too difficult to replace.

[hydromike]

I did a compression test today and it read about 85. Should this be about right for its age/visible condition? Would doing a re-gasket instead of a complete rebuild be anything I should do instead?

Hey Martin,

A good compression number on your JLO would be closer to 185. Your low 85psi could be a result of a stuck compression ring, a leaking head gasket, or from just being worn out. Try squirting some WD-40 down the spark plug hole (or right in the intake/exhaust since it's out of the machine) and recheck. Parts for the common JLO singles are just that; "common". You can get pistons, rings, jugs, heads, seals, gaskets and just about anything else pretty cheap. I have more than one pile of JLO single parts if it turns out you need a part or two. I still have that L300 gasket set that I offered a while back. It's yours if you want it.... (I don't think it has crank seals, though....)

How does your cylinder bore look when you peek into the exhaust/intake ports? You should be able to get a real good look at things without removing the head. If the engine is going to sit around a bit, spray the bore down really well with WD-40 or a more sticky oil (Castle's "Endura" is a great product.... my Dad has sworn by it for years and puts a couple squirts in his tea everyday... just look how well it works for him!)

[Duck89]

Thanks for the replies, everyone. It's a good thing I decided to look at this thread today...for some reason, I never received email notification for replies to it. (odd)

Mike- I'll let you know if I end up needing anything. I have a local powersports place in town trying to find a gasket kit for me. Ill also have to get a better look at the cylinder bore tomorrow and see, but if I recall correctly, it didn't look too bad the one time I did look at it. Ill hit it with a little WD-40 too and see if that has any effect on a compression reading.

[jpswift1]

Martin,

There are a few on ebay and also through mfg supply.

all JLO/Cuyuna Engine L297 Snowmobile Parts | MFG Supply

[Duck89]

Thanks for the link Jeff. I took the head off yesterday and I thought everything looked pretty good from what I could tell (aside from all the carbon build up).

[Bazooo guy]

Looks like the gasket was leaking to me.

[Duck89]

What makes you say that? Just all the gunk built up on the top of the jug or is there some sort of sign on the mounting surface that would lead you to think that? I have a little bit of knowledge on engines, but this is my first actual overhaul.