Stihl 084 - Is it worth rebuilding?

[a. palmer jr.]

Thanks for all your replies so far. I've had some time to cool off and decided I'm not going to take a sludge hammer to the thing:bang:. That wouldn't be very economical either.
I'll try to pull the jug and get some pictures to see if you guys think it can be saved. If not still might try to rebuild or maybe have it done professionally? Unless I find someone with an 066 or ms660 in similar condition for trade. Really don't wan't sink too much more into it though. Looks like I'll need a long torx to pull the 4 bolts. So question so far is do I get this tool at the dealer and then how will I be able to pull the cylinder off the piston without doing any more damage, because it ceased up?
Oh and yeah what would new piston and jug cost?

Don't forget, if you do decide to rebuild, to fix the problem that caused the cylinder to go bad. Clean the carburetor, check the rest of the fuel system, use good oil and the right ratio, adjust the carb right, and make sure you have no air leaks, otherwise you will have this to do over again!

 

[BuzzKut]

Finally had a chance to pull the jug off and take a look. It came off easy almost seemed like the bolts were a bit loose. Many of the bolts on this saw were a bit loose and some missing (including a muffler mount screw which was re-tapped with larger bolt). I'll be sure to use some loctite when/if I put the saw back together. So I'm attaching some pictures of the jug and piston the exhaust side is scored up and has some aluminum stuck to it, I don't feel any deeper grooves but not sure what it will be like once I clean it up. So how should I get the aluminum off and does it look salvageable to you guys??

I hope so cause my dealer said new jug and piston would be $450 plus (if he can get it). Also how can I check for vaccum leak and if the bottom end is ok (crank bearings etc), how does the piston come off? Sorry for the rookie questions but hey never done it before and prolly better to ask then just wing it. I suspect the reason for it ceasing up was the carb because air filter was bad and there was sawdust around the carb when I bought it :dunno:. I know should have fixed carb first, next time will do !!

 

[Stihlofadeal64]

:

Probably not worth rebuilding. If you need 120cc's of cutting power, I have a deal for you. I have a bunch of 30cc Mini-MAC's here. I'll send you 120cc's worth of Mini-MAC IN RUNNING CONDITION, and you can send me that burned up 084. If you add the 14" bars up, you'll have 56" of bar too.

:greenchainsaw::greenchainsaw::greenchainsaw::greenchainsaw:

:hmm3grin2orange::hmm3grin2orange::hmm3grin2orange:

 

[Mastermind]

Heres your pics:

 

[Mastermind]

That cylinder should clean up, but you have to find out what caused it to lean out in the first place. I would say it was more than just a leaky air filter.

The search button near the top of the page is a great resource, use it to find threads about cleaning that cylinder. Search for vacuum testing too.

If you do get the jug cleaned up and a new piston in it, then proceed to fire it up with a vacuum leak it could fry again in as little as a minute.

I've spent many, many hours reading old threads on this site, the information available here as worth a fortune.

Post any questions you have and they will be answered, Good Luck

And BTW, welcome to Arborist Site.

 

[a. palmer jr.]

At the least I would try to find a new piston for it. That piston doesn't look usable. In answer to your question, On the side of the piston where the pin goes through, you'll see the little clips that need to be removed in order to get the pin out so the piston will come off the rod. Some pins are easy to push out and some aren't; just try not to damage anything while taking it out. The cylinder can probably be honed if you're not wanting to buy new jug. Other AS members might do it differently, as some are more perfectionists with their saws but some of us are on a budget also.

 

[mtngun]

Clean the cylinder bore with acid -- lots of threads on acid cleaning.

Assuming the jug cleans up, you'll either need an Espian piston from the guy in Greece, or the $140 OEM piston. I'd give the Espian a try. It's the same piston as for a 088 or 880.

If the crank spins smoothly and you can't feel up and down play in the rod big end bearing, then the bottom end may be good. Side to side play in the big end bearing is normal.

That jug looks like a lean seize, not sawdust poisoning. You need to find the source of the leak -- should have done that BEFORE pulling the jug, because the jug needs to be on for a leak test.

The 084 came with a thick paper gasket at the base of the cylinder. The paper gasket takes a set over time and lets the bolts loosen up. It can also lead to an air leak around the gasket -- which is why it would have been nice to leak test before pulling the jug.

Please keep us posted. If you get discouraged, you may want to ship it to me rather than continuing to throw money at it.

 

[Mastermind]

Please keep us posted. If you get discouraged, you may want to ship it to me rather than continuing to throw money at it.

Or me...just trying to be a nice guy, as always...

 

[Nitroman]

That jug'll clean up fine. Get your acid from a good hardware store or plumbing supply house, it is called "muriatic acid", which is just hydrochloric acid. Use a glove, apply and watch it eat the aluminum off the chrome.

 

[belgian]

You guys seem very confident that it will clean up nice...I am not so sure. That is a pretty bad scoring. I'll be looking forward to seeing the pics after the acid has done its work opcorn:.

 

[Gumnuts]

HI Roland.....yeh jug does look iffy.

 

[a. palmer jr.]

Sometimes you can't tell everything by looking at the picture, but from what I saw the cylinder didn't look that bad. I didn't notice any deep grooves in the cylinder walls, but if there is you may have to go a different route.

 

[BuzzKut]

Clean the cylinder bore with acid -- lots of threads on acid cleaning.

Assuming the jug cleans up, you'll either need an Espian piston from the guy in Greece, or the $140 OEM piston. I'd give the Espian a try. It's the same piston as for a 088 or 880.

If the crank spins smoothly and you can't feel up and down play in the rod big end bearing, then the bottom end may be good. Side to side play in the big end bearing is normal.

That jug looks like a lean seize, not sawdust poisoning. You need to find the source of the leak -- should have done that BEFORE pulling the jug, because the jug needs to be on for a leak test.

The 084 came with a thick paper gasket at the base of the cylinder. The paper gasket takes a set over time and lets the bolts loosen up. It can also lead to an air leak around the gasket -- which is why it would have been nice to leak test before pulling the jug.

Please keep us posted. If you get discouraged, you may want to ship it to me rather than continuing to throw money at it.

I'll check out how to clean it up with acid and honing. But will definately try to reuse the jug I'm on a budget here too! Think I'll get the espian piston (saw it on ebay) thanks. The rod bearing seems ok, and don't think I'll worry about the bottom end for now. Guess I'll have to test for vaccum leak when I put it back together, should I get a new cylinder gasket (thats not paper)?

I've seen your 084 project saw thread and I know my problems seem a bit minor to that saw your bringing back from the dead, but what can I say I'm a newbie at this rebuilding thing and so far it seems like fun, so think I'll keep it for now.

I want the big saw to do some milling:chainsawguy:...........and the guy offering up the mini macs hey I've already got a set of pruners that will do the same job.

 

[buzz sawyer]

Clean the cylinder bore with acid -- lots of threads on acid cleaning.

Assuming the jug cleans up, you'll either need an Espian piston from the guy in Greece, or the $140 OEM piston. I'd give the Espian a try. It's the same piston as for a 088 or 880.

If the crank spins smoothly and you can't feel up and down play in the rod big end bearing, then the bottom end may be good. Side to side play in the big end bearing is normal.

That jug looks like a lean seize, not sawdust poisoning. You need to find the source of the leak -- should have done that BEFORE pulling the jug, because the jug needs to be on for a leak test.

The 084 came with a thick paper gasket at the base of the cylinder. The paper gasket takes a set over time and lets the bolts loosen up. It can also lead to an air leak around the gasket -- which is why it would have been nice to leak test before pulling the jug.
Please keep us posted. If you get discouraged, you may want to ship it to me rather than continuing to throw money at it.

Lots of great input mtngun. I agree, leak test should have been done before the jug was pulled but can't it be reinstalled without the piston and checked? Maybe a little more work but at least that way he can find any possible un-repairable leaks (e.g. cracks in the crankcase) before spending any more money.

 

[Sprintcar]

You guys seem very confident that it will clean up nice...I am not so sure. That is a pretty bad scoring. I'll be looking forward to seeing the pics after the acid has done its work opcorn:.

+1. That cylinder appears to be too far gone. try to clean it up and repost some pictures. The price quoted on a new OEM piston of $140.00 is spot on.
Even if you end up needing a complete top end these great saws are worth it.
I finished mine thursday night.

She is a beast.

 

[teacherman]

That jug'll clean up fine. Get your acid from a good hardware store or plumbing supply house, it is called "muriatic acid", which is just hydrochloric acid. Use a glove, apply and watch it eat the aluminum off the chrome.

Use Q-tips and lots of patience. Maybe a gentle use of a brass, not steel scraper after softening up the aluminum. That seize happened way before you ever got that saw. May need crank seals. although it could be from the cyl. gasket loosening up, not sure. Jacob and someothers will know.

DO NOT let muriatic acid get on the margin between teh cyl. plating and the cylinder body, which is aluminum. The acid eats aluminum, which is why you are using it. Q-tips will come up green as long as aluminum is being removed. Use many qtips, and a lot of patience. Aluminum transfer such as that will take a couple hours to remove.

 

[mtngun]

should I get a new cylinder gasket (thats not paper)?

You'll definitely need a new base gasket, but as far as I know, the Stihl 084 gasket is going to be paper.

The squish on 084's is pretty sloppy, so you may want to make a custom gasket, anyhow, to set the squish. Smear or spray the gasket with a good fuel-resistant sealer -- like hylomar, the permatex copper spray, or even RTV. After break-in, retighten the cylinder bolts.

Paper gaskets are not the end of the world -- there are millions of them in use.

All I see on the jug is aluminum transfer, but you won't know for sure until it's cleaned up. Go easy on the honing.

 

[Mastermind]

I'm not seeing anything but aluminum transfer...the crosshatch pattern is still visible in this pic. Right at the top left handle point of the port does look rough, but it may still clean up. Forget all about using a hone on it though, that would surely ruin it.

Degrease it with starting fluid, make sure it's dry, heat it (the oven works well, not too hot around 250 seems to work great), take it outside, while wearing gloves and any other protection you may deem necessary, apply the muratic acid to the aluminum transfer. After waiting around ten minutes, wash it off good with water, sand only the aluminum transfer with 240-320 grit, reheat, apply again. The upmost patience is required here, if you're in a hurry buy a new one...if you can afford it.

I use a small jar to put a little acid at a time in, and use a q-tip to apply the acid. I try to prop it cylinder up in a manner that pools the acid in the affected area, and try not to get any in the ports, or on any bare aluminum.

I saved some like I thought were trash, but all I stood to lose was my time. I think you will be very surprised to see that under all that melted aluminum is a nice bore.

 

[BuzzKut]

Well crap!! Just spent the evening acid cleaning the cylinder and thought it was going great until I got down to just a couple spots of aluminum left on either side of the exhaust port. Then I noticed it was starting to pit the bore in these spots particularly the right side. Take a look at the photos and tell me if you think its worth spending any more time on. I haven't tried sanding it at all yet, only acid which was working well till this point.
Oh well if it can't be saved I did manage to find a guy who has a used OEM piston&jug in good condition for under $200 so may have to go that route I guess. What do you guys think about the pictures?

 

[blsnelling]

I'm afraid your right.