Engine Went THUNK!

Obee · 08-30-2011, 08:35 PM

Well my 1987 Marathon just locked up. I think it broke a rod, won't turn either direction and is tight. I was coasting to a stop and was just about stopped when it went THUNK. Pulled the belt off the starter and tried to turn pulley on engine and no go.

How extensive is the damage usually when this happens? Is it worth taking apart and fixing? If I remember right it seems these engines are kinda hard to find. I didn't pay very much for it and was thinking maybe parting it out and looking for something else. Just thinking out loud for now and would appreciate your thought/suggestions.

Regards, Jeff

pachanga90 · 08-30-2011, 08:43 PM

You can pull the head and possibly find the carnage,The parts aren't terribly priced to rebuild(about $300-350 as long as the crank is ok),so I guess its' up to your finances,You might be able to find a donor-cart cheaper than the rebuild.We've bought quite a few carts for under $200 that ran great or just needed minor work to run.Hope this helps.

Wynelocked · 08-30-2011, 09:39 PM

Quote:

Originally Posted by pachanga90

We've bought quite a few carts for under $200 that ran great or just needed minor work to run.Hope this helps.

If you run short of funds for these....send them my way...hahahahaHA

ScooterMcTavish · 08-30-2011, 10:21 PM

Being unable to turn the crank leads me to think that you may have seized her up.

Are you running oil injection or premix?

Also, these old two-smokers are both cheap AND easy to fix - I'd think about fixing it first, especially if all it ends up needing is a new top end. If one thinks about how many more systems there are on a newer 4-stroke (valves, timing, etc.), these 2-strokes are excellently simple.

As Pachanga suggested - taking the head off and looking inside is a good place to start.

Obee · 08-30-2011, 10:41 PM

Running premix @ 128:1

Didn't know how expensive parts were so I had to ask. I will dig into it later this fall. Busy time of year coming for me so it will be a winter project. Wouldn't mind putting $400 or so into it. Questions to follow I'm sure.

Thanks Guys!

Regards, Jeff

ScooterMcTavish · 08-30-2011, 10:51 PM

No prob Jeff,

Good to hear premix - almost sounded like you ran out of oil through the injector. Possibly a ring broke or twisted up above the piston, or even plum wore out - if the cart has lots of hours on it, and has been run alot with the governor dialed up, these things can happen.

I did a top end rebuild on my cart, bought a stereo and lights (still to be added), repainted the cart, recovered the seats, and put in a new S/G belt and a new battery - counting the $200 I paid for the cart, I'm in for $800 total.

Think you can get a top end kit for $225ish - more in the $400 range if you also need the bottom end. My understanding is the cranks in these babies are pretty tough. However, Mr. Box suggests a good test - if you grab the clutch and try to pull it up and down and can get it to move, you'll likely need a bottom end too.

Can be a fun project though! Plus you get the satisfaction of bringing something back to life.

nck · 08-31-2011, 05:53 AM

i just got my top end from golfcartking com
best price i could find and the guys on this forum helped alot. good luck

Obee · 08-31-2011, 11:28 PM

Bought the cart used and it still had the auto oiler on it. Found this site and the pre-mix was the first mod I did.

I have been working on automotive stuff for years but have never been around or worked on the 2 timers. It will be a fun experience I'm sure. Like I said this is the busy time of year for me until late Oct-mid Nov. I am kinda anxious to tear into it but not until I can devote the time on it. I don't like working on something 5 mins here and there. Thanks again guys and I will be on here more when I get into it.

Regards, Jeff

crash12888 · 08-31-2011, 11:39 PM

If the crank will not turn I'd say it is still connected to the piston.
If the piston just stuck a top end will be your best bet for the money.
After the rebuild, double check RPMs and/or lean condition to prevent it again.

Obee · 09-13-2011, 10:42 PM

Well I took the engine out this weekend and took it apart tonight..................almost. Everything is off and apart except for the crank. It didn't break a rod but the crank won't turn at all. Anyone have this happen? Will I still be able to split the case with the crank being stuck? I am assuming the crank bearings seized to the crank? Like some feedback before it goes to the press. Thanks!

Regards, Jeff

08-30-2011, 08:35 PM	#1
Obee Getting Wild Join Date: Oct 2010 Location: KS Posts: 75	Engine Went THUNK! Well my 1987 Marathon just locked up. I think it broke a rod, won't turn either direction and is tight. I was coasting to a stop and was just about stopped when it went THUNK. Pulled the belt off the starter and tried to turn pulley on engine and no go. How extensive is the damage usually when this happens? Is it worth taking apart and fixing? If I remember right it seems these engines are kinda hard to find. I didn't pay very much for it and was thinking maybe parting it out and looking for something else. Just thinking out loud for now and would appreciate your thought/suggestions. Regards, Jeff

08-30-2011, 08:43 PM	#2
pachanga90 I Refuse To Get Stuck!!! Join Date: Jun 2010 Location: Hilton,NY Posts: 5,427	Re: Engine Went THUNK! You can pull the head and possibly find the carnage,The parts aren't terribly priced to rebuild(about $300-350 as long as the crank is ok),so I guess its' up to your finances,You might be able to find a donor-cart cheaper than the rebuild.We've bought quite a few carts for under $200 that ran great or just needed minor work to run.Hope this helps.

08-30-2011, 10:21 PM	#4
ScooterMcTavish Gone Wild Join Date: Oct 2009 Location: Manitoba, Canada Posts: 363	Re: Engine Went THUNK! Being unable to turn the crank leads me to think that you may have seized her up. Are you running oil injection or premix? Also, these old two-smokers are both cheap AND easy to fix - I'd think about fixing it first, especially if all it ends up needing is a new top end. If one thinks about how many more systems there are on a newer 4-stroke (valves, timing, etc.), these 2-strokes are excellently simple. As Pachanga suggested - taking the head off and looking inside is a good place to start.

08-30-2011, 10:41 PM	#5
Obee Getting Wild Join Date: Oct 2010 Location: KS Posts: 75	Re: Engine Went THUNK! Running premix @ 128:1 Didn't know how expensive parts were so I had to ask. I will dig into it later this fall. Busy time of year coming for me so it will be a winter project. Wouldn't mind putting $400 or so into it. Questions to follow I'm sure. Thanks Guys! Regards, Jeff

08-30-2011, 10:51 PM	#6
ScooterMcTavish Gone Wild Join Date: Oct 2009 Location: Manitoba, Canada Posts: 363	Re: Engine Went THUNK! No prob Jeff, Good to hear premix - almost sounded like you ran out of oil through the injector. Possibly a ring broke or twisted up above the piston, or even plum wore out - if the cart has lots of hours on it, and has been run alot with the governor dialed up, these things can happen. I did a top end rebuild on my cart, bought a stereo and lights (still to be added), repainted the cart, recovered the seats, and put in a new S/G belt and a new battery - counting the $200 I paid for the cart, I'm in for $800 total. Think you can get a top end kit for $225ish - more in the $400 range if you also need the bottom end. My understanding is the cranks in these babies are pretty tough. However, Mr. Box suggests a good test - if you grab the clutch and try to pull it up and down and can get it to move, you'll likely need a bottom end too. Can be a fun project though! Plus you get the satisfaction of bringing something back to life.

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08-31-2011, 05:53 AM	#7
nck Not Yet Wild Join Date: Aug 2011 Location: mo Posts: 18	Re: Engine Went THUNK! i just got my top end from golfcartking com best price i could find and the guys on this forum helped alot. good luck

08-31-2011, 11:28 PM	#8
Obee Getting Wild Join Date: Oct 2010 Location: KS Posts: 75	Re: Engine Went THUNK! Bought the cart used and it still had the auto oiler on it. Found this site and the pre-mix was the first mod I did. I have been working on automotive stuff for years but have never been around or worked on the 2 timers. It will be a fun experience I'm sure. Like I said this is the busy time of year for me until late Oct-mid Nov. I am kinda anxious to tear into it but not until I can devote the time on it. I don't like working on something 5 mins here and there. Thanks again guys and I will be on here more when I get into it. Regards, Jeff

08-31-2011, 11:39 PM	#9
crash12888 Gone Crazy Join Date: Jan 2007 Location: Chesterfield, Va Posts: 6,021	Re: Engine Went THUNK! If the crank will not turn I'd say it is still connected to the piston. If the piston just stuck a top end will be your best bet for the money. After the rebuild, double check RPMs and/or lean condition to prevent it again.

09-13-2011, 10:42 PM	#10
Obee Getting Wild Join Date: Oct 2010 Location: KS Posts: 75	Re: Engine Went THUNK! Well I took the engine out this weekend and took it apart tonight..................almost. Everything is off and apart except for the crank. It didn't break a rod but the crank won't turn at all. Anyone have this happen? Will I still be able to split the case with the crank being stuck? I am assuming the crank bearings seized to the crank? Like some feedback before it goes to the press. Thanks! Regards, Jeff

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