Well found my 2 stroke power problem

[TLB Nut]

My new to me 79 Marathon 2 stroke, has been way under powered. So after fresh plug, belt, filter and some wire repair didn't help I borrowed a compression tester. Well bingo I only have 45 psi in forward and 50 in reverse. Guess I need to do a top end refresh.

So should I just bite the bullet and get the jug too? I think I should get the kit with the gaskets, piston, rings and the jug and just be done with it.

Another question should I pull the engine to do it or can it be done in cart after muffler is removed.?

Thanks friends

Sent from my Nexus 6 using Tapatalk

[cart around]

The head is part of the mount. It has to come out.

I always say take it apart, measure what you have, and then order parts accordingly.

Don't guess.

[Dabble Inn]

Normally I would say oversize piston/rings wrist pin bearing and bore the jug, And while it's on the bench definitely replace crankshaft seals especially with a new top end.......

However;
Since recently having to completely tear down my 85 Marathon as the crankshaft bearings were shot I realized how inexpensive the parts are. So I went ahead and ordered a complete short block kit, Even though mine still had great compression at 115lbs. The little bit of extra cost was a no brainer...

It's on backorder till the 24th but it'll be worth the wait in the long run, everything brand new from the crankshaft up. Only reusing the case and head

[TLB Nut]

Well my trouble continue... I tear down the top end, to find a broken motor mount bracket, No, i repeat NO gasket between the head and the jug, the lower gasket was nearly disintegrated, piston scored, jug was scored and the upper piston ring only had half of it. Know wonder it had such low compression. Guess I got taken on the purchase. Oh well now to fix it.

Crank shaft seal replacement hard? Is taking the flywheel assembly off hard? I will order a jug and piston kit in the morning.

[TLB Nut]

Ok, correction there was a top gasket it was just baked on to the jug and hard as a rock I missed it originally. However this being a 79 I noticed my flywheel is different and will take some thought on removing it. I guess from reading other posts I have to get 2 m5? bolts and thread them in then bend them so I can you a standard steering wheel puller? I also took the clutch cover off and it was full of rust dust like brake dust. Does a 79 model require a different bolt to remove?

[Dabble Inn]

Well ya know how one thing leads to another with engine repair, And I don't mean to keep harping on a complete rebuild with a short block kit. But....

Consider how old the buggy is? If ya just do the top end you'll still have a 38 year old bottom end, Sure you might be able to get away with it for awhile. But remember, There's 4 bearings on the crank including the lower rod bearing. Any wear/slop on the 3 main bearings will take out the new seals in a short time and you'll have to start over.

Since you're this far into it and so close to splitting the case why not keep going? Compare the cost of a top end kit to a complete short block kit, Might only be $100ish diff. And you'll get a brand new crank with 4 brand new bearings and seals.....

I can't help ya on what clutch puller to use as mine was an aftermarket clutch and I had to modify the puller it calls for.

On the flywheel I had to buy two bolts (sorry don't remember the size) but my steering wheel puller worked just fine, Here's the link to the thread on my rebuild. Like I said above I'm still waiting on the short block kit so I'm at a stand still dang it, Good luck!

http://www.buggiesgonewild.com/gas-e...e-rebuild.html



EDIT; I just realized your buggy is a 79 and the kit I'm talking about is for an 80 to 88, I'm not sure of the differences but Sorry bout that.

[TLB Nut]

yeah I bought the top end kit and crankshaft seal already. I am worried that they are listed for 1980 -88, other then the flywheel I hope nothing else is different and I can use that that kit.

[Spicyunicorn]

Those short block kits are nice until they keep pushing the back order date back because it's coming on a boat from China and takes forever to get here (speaking from experience)

[cart around]

I know that the internal starter has a different size bearing on one end of the crankshaft.

There's a good chance the seal is different too. I don't know that for sure, but there's probably a good reason it's only listed from 80 to 88.

EDIT: I just found the fan side seal for you. The clutch side is the same as all other later 2 strokes. I will send you the link in a PM because he is not a sponsor.

[Dabble Inn]

Originally Posted by Spicyunicorn

Those short block kits are nice until they keep pushing the back order date back because it's coming on a boat from China and takes forever to get here (speaking from experience)

You are soooo right about that, I ordered it in early May and have heard a new arrival date 4 times now.... But still nothing

I called another place yesterday that said they would match the price I got and to call back on Friday as they think they'll have it by then, I'm definitely tired of waiting and about to order just the bearings and seals to get back on the road