spudulike

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 -

Most chainsaws have two carb settings, a High and Low speed as most saws generally spend their running life at idle or flat out or "WOT", wide open throttle! The standard adjustment is to wind in the L screw until the saw races and then bring it out past the max revs and then set the saw to within 1,000 rpm of the max factory setting. This suits most owners who want to release the fastest cutting speed from their saw - no point in getting a 346XP capable of over 14,000rpm to tune it to 10,000rpm:confused1: The exception to this is if the saw is to be used for milling - when I would make sure the top end mix is richened for when it is flat out for longer periods than used for ringing up! This will keep it cooler and better lubricated on long cuts. Your problem has probably been caused by the stringent laws in the USA known as EPA laws, two strokes are dirty engines, much of the fuel mix is pumped out unburnt and the US laws are clamping down on this - I see the 125cc class of GP racer is being stopped from 2012 being replaced by 250cc four strokes - environmental laws! Large manufactures have to demonstrate they are doing all they can to uphold the EPA laws so they make all our saws run lean as they possibly can, I see the latest Stihls are using two choke carbs and the US MS200Ts have a power valve on the carb to keep it lean plus all their saws have catalytic convertors - poor sods! Also see the comments about the new 201 bogging down off idle - WEAK MIX:thumbdown: Your saw - my theory is that it was tuned correctly for fast running from the factory but at mid revs, due to the factory setting the low rev mix so lean to meet EPA laws, the saw leaned out and seized. If I was to set up a saw for carving, I would fatten up the L setting - perhaps 1/4 - 1/2 turns out on top of standard and 1/4 turn out on the H screw - it may smoke a tad more when cold but it wouldn't seize! Just got an MS200T in for the same reason -carving, went bang - seizure! Let your service technician know if you are carving and get the saw set up accordingly, if he looks at you blankly - change your technician!!

Latest news on the 880 - new piston fitted, in the process of cleaning the carb - noted the H screw was at 1/4 turn NOT 1/2 as per spec so probably the route cause of the seizure. Pressure check was 100% fine: -

You may have heard it wailing a mile away around 5.00pm on Sunday today! Seems OK now and idles/revs out fine - you will have to see what you think of it now!

I work for a non Arb related German company and their advertising borders on the unbelievable at times! What works in GmbH doesn't in the US and UK markets - this is one weird ad:confused1:

Yes - with your saws, I need all the help I can get:biggrin:

I know, I know but this one has a nice case and and ... Actually I thought the taps for cleaning up mucky threads may be useful!! Your carb - I have stripped out the throttle valve rod and now rebuilt with another spacer washer and a good dollop of copper slip grease. I am not 100% sure if this is the reason for the poor idle but have a good way of testing for leaks in this area and will test tomorrow and run it up again, the bottom end and inlet boot are 100% perfect, no leakage and this is the only area I have found to be leaking. If this doesn't work then it is new carb time and they are around £100 - the saw has good compression......on all three gauges:001_rolleyes: 160psi so the rest of the saw is sound - you may hear it sometime tomorrow:thumbup: