spudulike

Would you believe 45mm or 46mm:001_rolleyes: If you measure the piston with your verniers, it will come up at something like 44.95mm or 45.95mm which would equate to 45 and 46mm, the cylinder would be around 0.03mm larger (Gnats cock in the trade) but for measurement purposes, just measure across the crown of the piston -just above the gudgeon pin as the sides will generally not wear as much as the front and rear - it should be pretty obvious which one you have. I could probably find out from your info but easier just to measure the component.

TBH I haven't seen wear like this ever but would suspect that either the saw has been seized but continued to run - if the bore is clean then this doesn't really support this. The other theory is that the piston skirt has worn badly, possibly down to ingress of fine wood chip and this gave the saw piston skirt wear, producing something called "piston slap" where the lower piston is that worn that it slaps the lower cylinder at the bottom of the stroke - more common on longer stroke machines and have had 024/026 & 038s with this. Are you sure that the piston has come in to contact with the con rod - the skirt may have just got thin and shattered! Guess that is what the knocking noise was! Sealent - I have used Blue Hylomar and blue loctite in the past but any heat resistant liquid gasket material will do, Stihl do their own that you can purchase. Hylomar is specified by Honda on horizontally split motorcycle crankcases and that is where I first used it. Good luck - glad to help!

No Worries, had hoped you were local or at least on one of my beaten tracks but you are well away from that! Your problem is a bit baffling - the pump you are using looks like a vacuum pump to me, does it also pump air out to pressure check as well as sucking air out to produce vacuum? does the saw leak vacuum at the same rate as pressure - usually air leaks around boots or splits show less under vacuum as it pulls leaking joints togther! Good luck with it - shame I cant get to look at the little tinker:lol:

It may help if I posted this:001_rolleyes:

Blimey.....big bucks, don't remember ever being paid them:confused1:!!! The compensator is the cover that fits over the diaphragm, in the later ones, it has an O ring round a fitting that pushes in to the air filter - I have only seen them on 026s and 260s but are fitted on later models. Non compensator models have a flat plate cover held in place with four screws. All carbs will leak air around the throttle valve shaft, I would expect the air to leak down over a number of seconds and not to stop you getting any pressure in to the crankcase - I use a bicycle pump so you get a fair bit of air in each pump but you should see a reading on the gauge and the needle slowly descending to zero as air escapes. It would be very strange for a new carb to have this issue if it is a new Walbro one - the Chinese ones can be a bit hit and miss. I thought the carb was an old one and now you have said it is new have confused me some more:confused1: I think we are missing something here, I can't see air coming out of the NEW throttle valve shaft that fast that you can't get a reading at all??? Where are you in the country - wheres that phone box - I look good with my underpants on the outside of my trousers and wearing a cape! I am coming to the end of what I can do - the carb test you explain will show any leaks in the carb but have no figure to work on as to what is right. Bugger - think I have an idea - your impulse line isn't sited correctly, it has a flange on it - look at the pic below - the red vertical lines are the back plate of your air box, the bit to the LEFT of the vertical lines, sticks out in to the air box, the far left lines are where the impulse line plugs in - have you got it the wrong way round or not pushed in correctly - if it is too long, it will hold the carb off the rubber inlet boot:001_rolleyes: Hope this helps - try it!

There is a chunk of piston missing so would flush the crankcase out with white spirit or fuel - spin the crank round with fluid in the crankcase void until the fluid comes out as clean as it went in. On the cylinder, look for damage or chips to the inlet and exhaust port plus check the transfers for any damage as well as the plating. As far as pistons go, go on ebay and purchase one of the Meteor or Episan ones from Leo Dandikrop or Max Moto - both good traders and about one weeks delivery - there appear to be two types so make sure you get the right one. Both types are good quality with decent rings - I usually opt for Meteor first. Working on the 029 is a sod so personally I would fit a quality piston and end up with a nice saw with original power than a Chinese one that may be a bit loose in the bore with brittle rings - choice is yours:001_rolleyes:

To get zero pressure when pressure testing you would need a serious air leak, you have taken the crankshaft seals, inlet boot and impulse line out of the eqation as well as the crankcase gasket and cylinder base. Personally I don't see how you can have an air leak between the carb and the boot from what you have said - I have part WT110 listed for a Stihl 024 without the later diaphragm casing compensator! the WT195 for an 026 and not sure if your carb is correct or not:confused1: The £15 I mentioned was for a second user part and not new - £45 is a good price for a new part! Have you tried removing the steel ring around the inlet boot and the steel inner ring and try the pressure test again with the carb in place, there has to be something stopping the carb mating with the inlet boot from what you have said. The only thing left is to make up a spacer gasket to fit between the carb and the inlet boot but really don't understand why the seal isn't being made without a non standard part??? Are you sure the carb is free to move up to the inlet boot and compress against it?? Weired?

As per Morten said, probably the wrong thread but for the record, the 365 will never set the world alight for speed but it will ring up all day with a decent amount or torque and power so a solid reliable working saw but no racer!

Think this may be the longest post in history:lol: If the saw is getting you down that much - bung it on ebay:lol: Having read your post, it sounds like you have a good seal between the carb and the inlet manifold, the hole the manifoldgoes through being slightly oval is probably not an issue. I would say that you have a bad leak around the throttle valve shaft that is letting in air and letting out air on your pressure and vac tests - this would cause issues with idle speed fluctuating. It isn't an easy one to test but on your pressure test with the carb in place, I would expect leakage from 10psi down to zero over 20-30 seconds and not well under. There are a few carbs for this model on ebay that I have seen, for around £15 it may be a simple way of getting the saw working right - the latter carbs have a different diaphragm cover that plugs in to the air filter and the 026 carbs are a mm or so larger in the bore but it will work OK once the diaphragm cover is swapped over. No need to get depressed over it, just dig in and not get beaten by the saw. The throttle shaft is where my money is - not an easy one to check either. To check the carb needle valve is good, stick your pressure gauge on the fuel inlet connection and pump the carb up to 7psi - you should get no leakage at all. It is unlikely you will damage the carb in this way as there is a "pop off" pressure on the valve. Good luck - let us know how you get on, you are not alone:thumbup:

Suppose it is better than the Krankies:lol:

Just buy parts off ebay, some are still available but many are EOL! I have one in the workshop that I picked up, supposed to be a runner - PM me a sensible offer and it is yours - what parts are you after? Please don't insult if you do make me an offer:001_rolleyes:

Sounds like worn rings/piston, engines loose compression when hot so it may have 135psi when cold and will run but when hot it will fall to 115-120psi and cause starting/running issues - worth fitting a new piston and rings if they are worn. The ring ends will be thinner than the centre of the ring when laid flat on a table viewed from the top - I don't mean the thickness of the ring in the up and down direction -hope that makes sense:confused1:

I usually use turps substitute/white spirit in mine but make sure the fluid doesn't get too warm as it may ignite:thumbdown: The accelerator pump is internal to the carb and can't be got to easily.

The news about the ends is good, one more thing to check is up and down play in the crankshaft bearings by waggling the crankshaft up and down both ends. From what you have said, by money is on the clutch but inspection under both the clutch drum and recoil cover would be good - sounds like the 034 I got - pics on htis thread....somewhere - getting rather long:thumbup: If Gardenkit and I are a double act, I am the tall good looking one:lol:

Think there is an Echo on this site and not the Japanese type, we either both know what we are talking about or are both equally stupid:lol:

Sorry for missing the cry for help, the easy bit first - I would use the 0.325 bar mainly because the saw will not be a power house and 0.325 will be less power hungry than the 3/8 and probably smoother in operation IMO. The rattling - does the saw run? Has it run and expired? My thinking on the rattle - could be a clutch spring that has expired and the clutch shoe is now loose - take the clutch drum off and take a look - the clutch centre/boss may have split in two - just had a 034 I purchased with this. If this is OK then it may be more serious - the big end can expire - serious and will cause low compression - you can usually tell by turning the flywheel back and forth and the piston will stay in place with much to and forth movement of the flywheel. The small end bearing may have expired - possibly serious and you will get similar symptoms as the above. I have only had one big end failure and no small end fails, the big end one is still in a box awaiting some time:thumbdown: My thoughts are that the clutch has busted but use this as a guide. Also check the flywheel isn't clouting the coil on rotation. To get rid of the carbon, get the piston to cover the port, scrape the carbon off without damaging the piston, turn the saw over so the port faces downward and blast a bit of WD40 or similar in the port to wash it out. raise the piston a little to make sure as much of the crap has been washed out as possible. Use a cotton bud to clean any further crap out. Compression - may be time for a gauge - you can generally tell by pulling the engine over slowly, lots of spongey feeling as the engine pulls over TDC is good, if it pulls over TDC with ease than you have issues. Good luck, let us know how you get on.

You need to get the piston at TDC on the compression stroke and check the valve clearances - if someone has done up the rocker nuts, the valves may well be leaking when they should be closed. Take the exhaust off to see if the piston is in good shape or look down the plug hole if you can see the exhaust port from there!

Is it still making compression when it is hot? If the compression is enough for the engine to fire and run until warm, perhaps the normal drop in compression when hot is enough to make it die! Other than that, is the exhaust clear of heavy carbon or oily crap, sometimes they can get blocked. The mix sounds right judging by the plug colour:confused1:

Got a Stihl MS650 in with a bad seize, cleaned the bore up, it looks worse than it really is, bit scored above and to the side of the exhaust port but would rather refit this cylinder with a new OEM piston (No decent aftermarket ones available) than risk Chinese parts. It feels smooth and the owner wants a light tune done to it so reckon a thinner base gasket will help the compression - anything over 150psi is good and reckon it will make that!

No worries, glad you fixed it, it is what the forum is all about and if members get really stuck, I can usually give it a going over that gets the saw back to earning money for a decent cost. Good luck with it:thumbup:

Yup. main reason for a chain to get tight in use is lack of oil - worth sorting out!

It is always unsatisfactory when you don't know if you have hit target with advice or you are just trumpeting away and having to open the window because of the fug:lol: Just hoping for a breather fix and one hat to be consumed....Helmans - nice thought - you could try a little sweet chilli!

Mmm Life is full of unanswered questions!!!

Thats what I started on...look at me now:lol: On the Aspen front, the plug looked like new, no colour on it at all, like it was out of the box - if that is an old plug then I am impressed - no good for the ported saws though as I use the plug colour as one indicator to correct running! I will look at the piston crown before it goes back - no time to strip it down for inspection - got an MS650 and a 048 to fix - it never stops:lol:

Please meet my sales assistant....yup, thats the fix and it won't go wrong again:thumbup: