Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: qigley on October 27, 2016, 10:37:16 am

Title: 028S - worn piston
Post by: qigley on October 27, 2016, 10:37:16 am
Hi everyone..
Im a bit of a noob when it comes to repairing saws.

I have a 028S with a scored piston, low compression, and blowback,  so its engine reco time. Do you  rebore the cylinder and use oversize pistons, or get a complete new cylinder and pistons assembly? Both can be got off Ebay   for $50 and $120 respectively.
Also are there any tests I should do on the machine before pulling down, such as the crank seals, etc.

Thanks
Title: Re: 028S - worn piston
Post by: Cut4fun . on October 27, 2016, 12:23:18 pm
No reboring as the cylinders are plated. Just find out why yours scored and then rebuild.  If you cant clean your cylinder up (most you can), you buy used or new cylinder. Piston kit too.
Title: Re: 028S - worn piston
Post by: jmester on October 27, 2016, 07:30:29 pm
Check your hotmail. Sent you a service manual. Hope it helps.
Title: Re: 028S - worn piston
Post by: Al Smith on October 28, 2016, 05:02:51 am
It depends on weather the piston is scored or scuffed .Scored most likely  is caused by a lean run condition and will transfer aluminum to the cylinder and the damage will be on the exhaust side .Scuffed is slight damage on the intake side and could be nothing but a faulty air cleaner ,Usually no transfer .

On a scuffed intake side unless it's real bad all it might take is a set of piston rings .Fact I have several that all it took was a little clean up with a 3M pad,rings and good to go .You can't tell them from a brand new one .Some it took a new piston .
Title: Re: 028S - worn piston
Post by: qigley on October 28, 2016, 03:20:38 pm
Check your hotmail. Sent you a service manual. Hope it helps.
thanks that would be handy but I never received it.   

Thanks to other for their replies. I'll attempt to pull it down and see whats what.
Title: Re: 028S - worn piston
Post by: Cut4fun . on October 28, 2016, 07:00:22 pm
Check your hotmail. Sent you a service manual. Hope it helps.
thanks that would be handy but I never received it.   

Thanks to other for their replies. I'll attempt to pull it down and see whats what.

Check your spam folder for SM.  Still using the hotmail?
Title: Re: 028S - worn piston
Post by: qigley on October 28, 2016, 07:27:06 pm
Check your spam folder for SM.  Still using the hotmail?
yeah still using it, I checked all folders, nothing. I changed it to a gmail address, can you send it there, pls? Thanks
Title: Re: 028S - worn piston
Post by: oldpro on November 12, 2016, 10:20:38 pm
How badly is the piston damaged, is it obviously melted and scraped up or the there just some small scuffing in a small area? A couple photos would help. Is the damage to the piston on the exhaust or intake side? Also find out and determine if the cylinder is really damaged,often the cylinder can be repaired saving you a lot of money. A new piston assembly(Or piston and cylinder assembly) is available from several makers.
Title: Re: 028S - worn piston
Post by: qigley on November 12, 2016, 11:16:49 pm
How badly is the piston damaged, is it obviously melted and scraped up or the there just some small scuffing in a small area? A couple photos would help. Is the damage to the piston on the exhaust or intake side? Also find out and determine if the cylinder is really damaged,often the cylinder can be repaired saving you a lot of money. A new piston assembly(Or piston and cylinder assembly) is available from several makers.
Ive just looked at the piston thru the exhaust port. doesnt look good to me.  Motor starts ok, but there is a fair bit of blow by back out the carb.. Im going to pull this apart soon.
Title: Re: 028S - worn piston
Post by: jmester on November 13, 2016, 06:24:41 am
I can send you the manual to your gmail as long as you updated your profile page here. Also based on the pic looks like you have a 029 super. A clamshell engine design.
Title: Re: 028S - worn piston
Post by: jmester on November 13, 2016, 07:17:57 am
Check your gmail. I don't have one for the 029. The one that I sent is for the MS 290-390. It will work just fine. There is only some minor differences from the 0 model to the ms model 029-290. Hope it helps, don't hesitate to ask questions as that is why we all come together to help each other. Looks like it had a lean running condition based off the scoring on the exhaust side of the piston. Could be caused from many things lean carb setting,crankcase air leak are some of the more common ones.
Title: Re: 028S - worn piston
Post by: qigley on November 13, 2016, 10:15:43 pm
I can send you the manual to your gmail as long as you updated your profile page here. Also based on the pic looks like you have a 029 super. A clamshell engine design.
Thanks I got it. And is an 028 Super, as per the decals attached to it.

The one that I sent is for the MS 290-390. It will work just fine. There is only some minor differences from the 0 model to the ms model 029-290. Hope it helps, don't hesitate to ask questions as that is why we all come together to help each other. Looks like it had a lean running condition based off the scoring on the exhaust side of the piston. Could be caused from many things lean carb setting,crankcase air leak are some of the more common ones.
Thanks. Does the fact it is an 028 super change anything in the statement you made about its relevance to that service manual?
Title: Re: 028S - worn piston
Post by: Cut4fun . on November 14, 2016, 12:03:01 pm
This saw in pic isnt a 028 super. 

Like jmester said. Looks like 029 or 029 super

(http://chainsawrepair.createaforum.com/index.php?action=dlattach;topic=6152.0;attach=19477;image)
Title: Re: 028S - worn piston
Post by: Cut4fun . on November 14, 2016, 12:08:06 pm
Here is what a 028 super looks like. http://chainsawrepair.createaforum.com/stihl/stihl-028-super/

@qigley
Title: Re: 028S - worn piston
Post by: oldpro on November 14, 2016, 03:11:12 pm
From the photo the piston is fried,the cyl. won't look too good either,but you can try to save it if you want..
Title: Re: 028S - worn piston
Post by: qigley on November 14, 2016, 07:38:33 pm
This saw in pic isnt a 028 super.  Like jmester said. Looks like 029 or 029 super
Yep, you guys are right, that wasnt my saw in the pic I put up on Pg 1.  I downloaded that pic off the net some time ago, and forgot, and now wrongly assumed  that it was a pic I took of my problem.

My saw is definitely a 28S, and of course looks exactly like it does in the link I was given.I tried to take a pic of the piston, but my camera cant focus properly.  What I see thru the exhaust port is some hard scuffing just below the rings for 1/5 of an inch or so, then the remainder of the skirt is clean and shiny below that and not scuffed at all.

Anyways I was wondering more than the fault itself, whether there were other diagnostic checks I should do, such as crank seals, etc?  Since the 28 is not a clamshell motor, it is  a simple service  to just pull off the cylinder. So Im thinking of just doing that, replace the cyl + piston if needs be, and re use and go from there and see whether its useable as is.  The carb has been rebuilt, so if the cyl/piston rebuild doesnt make it run good, then all I have left to do is get in to the crank area.

False strategy or not?
Title: Re: 028S - worn piston
Post by: jmester on November 14, 2016, 09:45:57 pm
Maybe just carbon smear or the beginning of a lean run condition. Before you tear it down any more I would check the crankcase for air leaks. This is done by a pressure and vacuum test. Then go from there. I will send the 028 service manual to your gmail. I will send you a Stihl engine fault manual as well maybe there is a pic in the manual that looks like what you have going on then I can better help.
Title: Re: 028S - worn piston
Post by: jmester on November 14, 2016, 09:57:55 pm
Manuals and IPL should be in your gmail. Hope it helps.
Title: Re: 028S - worn piston
Post by: qigley on November 14, 2016, 10:55:39 pm
Yep I got all all thanks a lot for that, that will help a noob like me heaps. Much appreciated.
Title: Re: 028S - worn piston
Post by: oldpro on November 23, 2016, 10:54:26 pm
That piston is cooked! but being an older saw it probably has chrome plating,which means there is a chance to save the cyl.