spudulike

Well - what happened to it then, we all like a happy ending:thumbup: Hope it is out there making lots of noise and smoke:lol:

Good pics - The bore/ports look ok from what I can see, the deep impact on the combustion chamber worries me as this will have transferred it's energy directly in to the con rod and big/small end bearings. If you are lucky, all will have survived but reckon the rod may well be bent and is impossible to tell visually. The piston may well have survived, just need to be sure the impact marks havent cracked the crown of the piston - have seen this before with use of piston stops. Personally I would remove, smooth the top and inspect the end bearing for damage and piston for cracks. To remove the lower clam you will need to take the crank shaft out and to do this you normally need to remove both the flywheel, the clutch and any ancillaries like the oil pump etc, all saws are a little different and I haven't had a 390 apart but am suspecting it is similar to the Stihl 180, and Husky 345/ Jonsered 2149....etc that I have had apart. The clam sometimes needs a light tap from underneath with a drift and mallet to shift it. When you come to reassemble (I would certainly make 100% sure the rod is ok) then the seal between the clam and the bottom of the cylinder is critical, a small bead of sealer is required and any technician worth his money will pressure check the engine, I appreciate you probably can't do this but that is your choice - if you were local - I would do it for you. Two strokes use the crankcase to pull fuel in to it and then disperses the fuel in to the combustion area by way of transfer ports, it is critical the only air that gets in to the engine comes in via the carb otherwise you will be dogged with erratic idle, poor pick up and run the risk of seizure - the saw, not you:laugh1: Hope this all helps but guess you are probably understanding why many just send their kit to me and get it back running with the satisfaction I have done the works on their saws! Keep us posted

He is probably concerned, he will correct me if I am wrong, that you will need to clean both mating surfaces of the crank case and add a suitable sealent between the two before joining them. Failure to get a good seal will seize the engine. He will also be concerned that you havent truely found out if the con rod is bent, if this is bent, it will wear the piston and bore very quickly. I thought the saw was a vertically split crankcase but know the 390 is a clam type crank case, just missed it this time. It is difficult to know what damage has been done to the bore without seeing the damage. The test for a bent rod is pretty much valid but would suggest taking out the motor as in Megatrons pic and assembling without rings and seeing if the crank can be turned over without much effort, if you can't turn the crankshaft round by twisting the crank shaft NOT the flywheel or clutch, you probably have a bent rod. The lower clam part of the engine should always be removed so it can be cleaned and sealed properly - any split crankcase should be pressure tested on re-assembly. re-assembly is easier if you have the whole engine out of the saw, the bore should be oiled and the rings eased up the bore - I use a small blunt screwdriver and patience, some use ring compressors - just depends on what you find works - Husky single rings are easier than Stihl two but be patient with it. Sometimes the old sealent looks like an O ring gasket, it isn't and should be cleaned off and fresh sealent used - much easier with the bottom clam removed - these engines are much harder to work on when doing top end work as the whole unit needs removing and generally the flywheel and clutch being removed to get it out! The top part of the crankcase is formed out of the lower part of the cylinder! Appologies for missing the fact it is a clam engine - don't do quite so many of this type.....fortunately! Doing a 023 Stihl soon and will show pictures of it's rebuild!

Anything is worth what another will pay for it - ebay price would be £300 but on there, there is a cost of sale - 10% of sale value and 4% paypal so how about offering £300 - 14% = £258 - that is what I often do for non ebay sales! Strike a deal for cash:thumbup:

Yup - I never lend out saws - it won't come back in better condition and the friend may lose a limb. I would offer to help out - last one ended up with free wood, a fry up and a drive home in a foot of snow - interesting day:thumbup:

If the saw is clean, decent bar and chain, 2 years old, £300 sounds fine but if it is a bit used and battered then £250, make sure the thing idles well and revs out of idle well.

Bugger - forgot the 390 was clam type crankcase, see your point - been too long on pro Huskys and Stihls - he can't have been able to tell if the rod was bent or not. Looks like you will have to reassemble the engine as in the pictire and make sure it turns over very freely with the plug removed - a picture tells a thousand stories - give us a look up the bore at the damage so we can give a better assesment. Having seen the type of engine it is, are you sure the rod is straight? Personally I would get the saw running and have a few tanks of fuel through it before tuning it - the clam will need resealling and pressure testing before running it - not quite as simple as it could be. Should have known, got one on the shelf:001_rolleyes:

Did the operator then drive home with his handbrake on:001_rolleyes:

Gives pretty much the same result - easier to do on large bars then holding the chain - glad we got there in the end - I just learnt by trial and error as I did on many of the techniques I use with saws and engineering. I have noticed that many need to be told and have no abillity to develop these skills by themselves but am a firm believer that everyone has their own skill set allbeit service, climbing, felling, carving or knitting:001_tt2: or any other job, skill or hobby around!

Taupotreeman was saying he thought one of his workers was being a bit limp wristed when doing the bar nuts up and had instances of them coming undone and would this cause the issue. I was saying that if this happened and the side cover came a bit loose, all the vertical movement would be on the bar studs but the horizontal movement and torque of the saw would be transmited in to the tension adjuster and using a nice big drive and socket plus a bit of training on correctly tensioning chains may resolve his issue! Many operators can be a bit green and some kids don't even know what a spanner is for:lol: Just read what I have written again and what I think you mean - if you tension a chain on a bar so it is round about right and take the end of the bar and pull it upwards, more often or not, the chain becomes loose - what I am saying is to tension the chain with the bar in this lifted position is advantageous as if the bar gets a knock and moves as a reasonable size bar will, you won't lose tension in the chain. The bar is clamped but goes through a bit of abuse and there is always play on bar to stud fixing! Sorry - I know what I mean and am guessing some others do as well?

Yes - send it to me:thumbup: If the piston has been removed, make sure you get the direction correct and the circlips in correctly - it is very easy to get this wrong, removing the handle gives you extra space to work in, oil the bore before reassembly, make sure th eopen ends of th erings are central to the piston lacation pins, make sure no chips or crud has fallen in to the crank, lube the big end, small end and crank bearings, ease the cylinder over the piston, make sure the closed part is located in the cylinder held at a slight angle to the piston, ease the ends of the ring in to the bore carefully - leave the mallet in the box:lol: When fitted, do up the bolts in a diagonal cross pattern and at even pressure same as any cylinder head, turn the engine over slowly when thehead is slightly loose and check for catching and then crank it down. Make sure all boots and carb mating surfaces are holding presure - I always pressure check and compression check at this stage as it is important for me to know the health of he rebuilt top end but many are less festidious. I than tach the rebuilt engine but hope that you will get away without doing it. Hope it all goes well - be careful not to break a ring - I never have but.....

That sounds like a good explaination, the bar would move and the adjuster would be the only mechanical fixing stopping the bar moving in and out - very likely. Not sure what your guys are using to tighten the bar, personally, I always pull the chain off the top of he bar with it loose and do the nuts up with a socket and drive bar - this stops the chain loosing tension when the bar moves upward on a large cut. Perhaps a little training session and a new tightening technique - the Scwrenches are good but you can tighten better with a conventional drive and socket and difficult to overtighten on pro saws! I think you have hit the nail on the head:thumbup:

The 880 will be a pussycat to start compared to my 298XP - no decomp and a small pulley - thought it was seized when it came in:thumbup: The art is in making sure the saw is in fine tune and will start on the two choke pulls and one fast idle otherwise hope you are a big bloke - being 6'2" and 15 stone helps:thumbup:

Look at it possibly being a worn sprocket - both drive and bar nose, bent crank, sprocket bearing, stretched chain. Just make sure the chain rotates freely??

Very difficult to judge the damage - put some decent pictures up on this thread. I would think that the con rod may well be bent - the way I would check this is to pop off the piston rings (with the piston still on the rod) insert the piston in to the cylinder and bolt it down so it is held in position but you can still lift it 5mm upwards, spin the motor over with the pull start and watch out for the cylinder rocking from side to side - apply the lightest of pressure whilst doing this - you should be able to spin the motor over slowly or with around 1/2 starting speed without the head moving or rocking. Areas of other damage to look out for are around the transfers, inlet and outlet port, gouges in the plating and debris in the crank bearings. Make sure the piston crown isn't cracked!

Apologies - think my typing was going faster than my synapses:001_rolleyes: This is what I meant: - To clarify - I was talking about the L screw, if you have adjusted carbs before, you will know that if you screw the L screw in, the saw goes from normal idle, to a racing idle and then dies as the screw shuts off all the fuel. The max revs I am talking about is the FAST IDLE speed caused by the weakness of the idle mixture - the same effect you get when you are about to run out of fuel. Standard procedure for a rough cut tune to the idle mix is to turn the screw in until the idle races and a bit beyond to the point the saw dies and then undo the screw past the fast idle stage and about 1/4 turn past it and then adjust the idle with the idle speed adjustment screw. This would be followed by either a tune to the H screw by ear or by tach if you have one. If you don't understand the effect of fourstroking on the max revs of a chainsaw or have experience of doing this adjustment - leave it to the experts! If milling or carving, making both adjustments rich would be benificial to the saws life. Hope this clarifies - any questions - just ask! Thanks for pointing out the error - I put the blame on beer:thumbup:

Got the Octavia estate with 2.0TDI engine - MPG average 56, best I have ever got driving like an old woman 74mpg, pretty rapid if you push it, three figures faster than you may imagine - under the Skoda badge, you are buying VW design and reliabillity!

Just picked up the new muffler for the MS200T I have on the bench - job list includes carb clean and tune, pressure check and fit the new exhaust. Stripped it down as it makes pressure testing far easier - pretty dirty state....it isn't now:001_rolleyes: Compression check is a healthy 150psi, I have had the recoil apart as it had a nasty creaking noise - all good now. Cleaned all the grot off - passed the pressure check, just need to reassemble and clean the carb then a final tach. One important point all the MS200Ts I get in have NO chain catchers - please replace these if you have a saw without one, if the chain comes off or snaps, it may save you a trip to A&E plus they only cost a couple of quid:001_rolleyes: This saw will be fitted with a new one before it goes out!

Not sure - didn't take note and it is back on the saw now, the IPL says HT12E and it looks about right to the one fitted. One big carb compared to the MS200T one I am doing at the moment.

Nice job - think I can see how the esaw seized now - you must have shifted one heck of alot of wood to make that - puts the normal owls and mushrooms in to the shade! Good job and think we have come to the conclusion that running a richer carb setting will reduce the risk of premature detonation of the saws top end!

OK - the YPVS powervalve wasn't the one I was on about - brought back some good memories though:thumbup: Some of the MS200Ts in the states have a small valve that pumps fuel in to the inlet when you open the throttle from idle, this appears to be highly problematic with the usual fix to be blocking it up with suitable sealent and retuning the L screw. Just another issue caused by overly stringent US environmentalists - well thats what the US guys say!!

Open the picture using Microsoft Office Picture Manager and resize it to around 45% and it should upload then. If you don't have it, use "Paint" and resize - just right click on the image and select "open with". Oh - I fix PCs as well:thumbup:

So the 880 is running, needs a tune, MattyF 357XP has been run up for 30 mins and tached at a conserative 13,500 and it idles fine and revs very swiftly. Time will tell if I have cracked this saws problems! All I know is tat it has good compression, is 100% airtight and the carb is definitely the problem if the idle goes again! Got a Husky 136 on the bench now - needs a new sprocket and tune.

OEM piston - no, used aftermarket after consulting the customer and going through the prices - tested the old piston for steel inserts and found no steel present - wouldn't Stihl just increase the aluminium thickness to increase strength and the aluminium would conduct heat more efficiently? Limiter caps are off - the saw seized so it is important that I know where the tune is, once I have reset the mix, they will be replaced. The saw was set at 3/4 on the idle and 1/4 on the H screw with caps removed, the rear filter cover says H=1/2 L=1/4 Having very roughly got the saw started, the L is at 3/4 and the H at 1 turn, I will do a tune before the saw goes back to use. The carb is a tillotson of a considerable size:thumbup: The damage on the saw was almost definitely caused by the H setting being too lean, possibly by removal of the caps and setting to the settings on the cover - I will leave this on the rich setting to give the piston a chance to run in especially baring in mind the sort of work it will do but will rely on my tach to do the final tune. Happy so far:thumbup:

I have two 357XP EPA saws - both have decomps that push the fumes back in to the crankcase - the decomp valves cost £30, it is over engineered and they go wrong leaving you with a fried piston. My thinking is that without the US EPA laws, the saw would have a standard decomp valve and few problems. Been on Arboristsite - the US one and there are many posts on there about the cats in their saws - just going on what they say - I don't mean spark arrestors. The point I am making is that if you carve with your saw, running a little rich at the low and high end will protect the saw from this sort of problem and manufactures tune their saws on the lean side to meet emissions laws so using a new saw to carve with may not be a good idea - no points scoring just good advice:thumbup: Oh .......Power valve -