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Old 11-28-2008, 05:39 PM   #1
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Default Engine tear down

A few questions..

Without any "Special" tools.. how do you go about tearing down an engine for cleaning , sleeve, bearing removal etc..

I am having trouble removing the sleeve atm without having any special tools at my disposal. Once it is removed, how do I remove the bearings.. (Or should I) ...

I'm sending in the sleeve/piston for pinching and want to clean it all up for the when it returns.
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Old 11-28-2008, 06:39 PM   #2
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Karnage,

breaking an engine down isn't all that difficult. & it isn't a bad idea to make notes of the order you take things apart the first couple times.

here is the basic order for tearing an engine down.
1. remove the carb
2. pull the head and shims
3. pull the back plate and gasket
4. slip the con-rod off the crank (if it doesn't come easy you can do this after you've pulled the sleeve)
5. pull the sleeve and piston
6. remove the bearings

Some times the sleeve can get stuck in the block. Above all you want to protect the ports and inside of the sleeve from nicks and scratches. A simple trick I use is to use a popcicle stick that's been split length-wise.
-after you have pulled the head, run the piston to BDC (bottom dead center) and insert the stick all the way into the exhaust port. turn the crank by hand, as the piston is driven up it will pinch the stick against the top of the ex-port and lift the sleeve w/o damage.

Removing the bearings is also a pretty simple task. The only trick is heating the block & bearings evenly at one time. Once the block is stripped down and all that remains are the bearings and crank; pre-heat your oven to 400-degrees and toss the assembly in for 10 minutes. After heating the bearings will fall out or slide out with little effert. The bearings are held in the block by an interfearance fit. Since the block is aluminum the bearings are steel; the aluminum block will expand more than the steel @ 400-degrees. (I also use the over to heat everything before re-assembly so I can get the bearings properly seated).

This will make the oven stink so get the wife's permission if you value your marriage!

any other questions, just post and I'll keep answering.

chunk
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Old 11-30-2008, 09:44 AM   #3
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If you are only doing some simple cleaning you do not have to remove the bearings. I don't like to reuse them after you remove them from the case so plan on buying new ones if remove them.
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Old 11-30-2008, 10:46 AM   #4
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Quote:
Originally Posted by chunk t View Post
Karnage,

breaking an engine down isn't all that difficult. & it isn't a bad idea to make notes of the order you take things apart the first couple times.

here is the basic order for tearing an engine down.
1. remove the carb
2. pull the head and shims
3. pull the back plate and gasket
4. slip the con-rod off the crank (if it doesn't come easy you can do this after you've pulled the sleeve)
5. pull the sleeve and piston
6. remove the bearings

Some times the sleeve can get stuck in the block. Above all you want to protect the ports and inside of the sleeve from nicks and scratches. A simple trick I use is to use a popcicle stick that's been split length-wise.
-after you have pulled the head, run the piston to BDC (bottom dead center) and insert the stick all the way into the exhaust port. turn the crank by hand, as the piston is driven up it will pinch the stick against the top of the ex-port and lift the sleeve w/o damage.

Removing the bearings is also a pretty simple task. The only trick is heating the block & bearings evenly at one time. Once the block is stripped down and all that remains are the bearings and crank; pre-heat your oven to 400-degrees and toss the assembly in for 10 minutes. After heating the bearings will fall out or slide out with little effert. The bearings are held in the block by an interfearance fit. Since the block is aluminum the bearings are steel; the aluminum block will expand more than the steel @ 400-degrees. (I also use the over to heat everything before re-assembly so I can get the bearings properly seated).

This will make the oven stink so get the wife's permission if you value your marriage!

any other questions, just post and I'll keep answering.

chunk





pull the butt plate , head and shims , sleeve (use a cutoff toothbrush from the under side to push on the sleeve , never use anything metal !!!!), piston/rod , crank . carb is not always necessary to remove (especially if you know there is no air leak) .
and if you are sending it in to get resized , use rayaracing.com , replace rod, check tolerances on crank journal and more than likely replace bearings
if you value your engine as many do , these things are best left to the engine guys who have no doubt how to do all these things and more
happy motorin',
Monty


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Old 11-30-2008, 10:49 AM   #5
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Since we are on the topic of engine tear down I just have one question about replacing bearings. Lets say you need just the front bearings replaced, is it necessary to also replace the rear bearings?
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Old 11-30-2008, 10:58 AM   #6
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Since we are on the topic of engine tear down I just have one question about replacing bearings. Lets say you need just the front bearings replaced, is it necessary to also replace the rear bearings?
no , but it is usually the seal that needs replaced . just use your heat gun to heat the front bearing area , pop it out and pop the new one in , make sure you gently work the new bearing in or else you will scar up the outer area where the bearing seats .
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Old 11-30-2008, 05:16 PM   #7
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Omar,

I agree, never re-use... replace both bearings, they work as a set to share the work load. And if one is "bad" you can be sure the other bearing is closing in on the end of its life. Anyway bearings are cheep and fresh bearings mean fresh seals. An erratic running engine isn't exclusively caused by air leaks in the fule line... It can also be caused by an air leak through the bearings. & I've had new engins with leaky bearing seals. (This is why I pull the carb; it's the only way to pressure test the block, P&S.) But I only pressure test when I am building an engine (new or rebuilding a used one).

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Old 11-30-2008, 05:45 PM   #8
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i use a folded ziptie to pop the sleeve.
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Old 11-30-2008, 05:54 PM   #9
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How much fuel have you run through your motor? Are you having tuning/flameout issues with it? Is it down on compression? If it still holds good tune with good power and no flameouts, then all i'd do is replace the rod as preventative maintenance, check the bearings (replace if too much play) clean it all up and reassemble. If it's having tuning and flameout problems then it could need a pinch, but only if it's down on compression. Otherwise it's an air leak or carb issue.

The point i'm trying to make is you didn't say why you want to pull it down? If it's still running fine, then it ain't broke.... "If it ain't broke, Don't fix it!"
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Old 11-30-2008, 08:15 PM   #10
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what do you mean by pinch an engine?
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Old 11-30-2008, 08:44 PM   #11
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Originally Posted by lowey79 View Post
How much fuel have you run through your motor? Are you having tuning/flameout issues with it? Is it down on compression? If it still holds good tune with good power and no flameouts, then all i'd do is replace the rod as preventative maintenance, check the bearings (replace if too much play) clean it all up and reassemble. If it's having tuning and flameout problems then it could need a pinch, but only if it's down on compression. Otherwise it's an air leak or carb issue.

The point i'm trying to make is you didn't say why you want to pull it down? If it's still running fine, then it ain't broke.... "If it ain't broke, Don't fix it!"
Well, It's had a few HARD ran gallons through it. I noticed the last few times I was running it that it didn't run aswell once it heated to temp. (loss of compression)...
I've decided to send it in for a mild pinch.. and wanted to get it all cleaned up for next season. The bearings seem fine, no oil leaks or anything that I have noticed. all in all it seems fine other that the piston moves almost all the way to the top of the sleeve if "warm" much less at operating temp.

But in general, Was just asking for options on tear downs.. and thanks to you all for your replies.
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Old 11-30-2008, 09:01 PM   #12
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Originally Posted by omarwashington View Post
what do you mean by pinch an engine?
It refers to the sleeve inside the engine inwhich it is pinched to create (re-create) a tighter tolerance with the piston so it has better (or again, re-establishes) the compression ...

I.E. brings an engine back to life a bit you could say
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Old 11-30-2008, 09:51 PM   #13
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When ever you replace bearings make sure to insert the crank to align the new bearings before the block cools. If you cant get the crank through easily dont force it one of the bearings are cocked. If the block cools like that & you force the crank through & call it good you may very well crack the block. You can gently tap the bearings in to seat them with the correct size socket if you like but gently tap is not the same as beat in. There should be no "FORCE" required for install or something is not right.
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Old 12-01-2008, 05:35 AM   #14
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FYI... the piston/sleeve fit will loosen up when the engine comes up to temp. All of the heat is at the top end of the sleeve, this is why the sleeves are milled with a slight taper, so they are tight at TDC. Once the sleeve heats it will expand and the piston will move freely.

I, on the other hand, do not subscribe to "Pinching" sleeves. I ring the piston.

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Old 12-01-2008, 05:23 PM   #15
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Great information from everyone so far.
Anyways I’m looking at front engine bearings they don’t cost too much, between 15$ to 20$, but rear engine bearings cost twice as much. That seems a lot to me. I know that the rear bearings are bigger but it really doesn’t explain the price difference.
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