spudulike

You are using a ring compressor to get it in to the cylinder bore aren't you? If all else fails, remove the piston and try to insert it, with the ring fitted, in to the cylinder and see if that does it. It will get a tight fit, that is how it works. Use a bit of oil to ease it....you could measure the piston ring groove depth so you know it will work. Have you carried out many rebuilds?

Try putting the ring in the bore to make sure it fits OK and the gap being around 7-12 thou. Not being a dick but you are aware that there is a ring location peg in the groove? You can measure the thickness of both rings with verniers but, unless you have the wrong ring, it should fit and as Stubby said, clean the groove with a piece of busted ring as carbon can build up in the groove. Have you tried pushing the ring edge in to the groove, not as it would normally be fitted but the outer edge of the ring in to the piston ring groove?

As above and running in...lots of flat out but SHORT periods so excessive heat isn't built up so small rings/ cuts but always use the saw flat out and avoid long drawn out cuts for the first couple of hours use.

Good. The piston can wear like that but the bore, being much harder, will often be fine and a new piston and ring will restore the compression and decent running. The black bit on the piston looks like a bit of blow by down to piston wear but use semi or fully synthetic oil on these strato engines, the main bearings will thank you for it. BTW, when you remove the cylinder, you should always blast the chip and oil away from near the cylinder base to stop it entering the engine. Always the best policy.

The issue with measuring the compression is the small plug adaptor which can lose around 30 psi on the large plug type and also using a car type compression gauge which will top out on a small engine at 75psi. In short, use a Gunson HiGauge or something similar to get a correct compression reading. 150psi and higher is decent on a cold engine after 5-7 pulls. As Mark and ADW have said, these machines need a piston ring in decent order and if worn, the idle suffers. If you hadn't said the impulse line was connected, on Mk1 machines, this was one of the most common issues and have seen them come off or even the brass insert on the cylinder come out, the symptoms are stalling. The carb - worth checking the gauze strainer is clean. The pump and metering diaphragm, especially the metering diaphragm, can get a bit baggy causing running issues. On the CST test your dealer did, if you have the printout, the carb H&L settings can often be revealing.

The Mtronic version will not have holes for carb adjustment.....unless someone has swapped it out.

Not sure what the "rebore" means but you typically start with trying a helicoil. This is best done with a lead in tap but make sure you start the tap off well as you want the receiving thread to be cut dead square with the surround of the plug hole. BTW - use a decent quality tap, the really cheap ones are...well....cheap and the resulting thread form will NOT be cheerful. V Coil do some decent kits and good quality. If this method fails then you can use a reamer to open the hole up, a tap to retap the hole and then an insert that can be put in with Loctite. Personally speaking and having used both methods, a helicoil provides a strong and relatively simple repair. I usually stuff the cylinder with paper cloth (still fitted to the machine), form a cavity just under the plug hole and grease the tap liberally when using it. If you put the bar in a vice and get the plug hole as horizontal as you can, it helps.

Get your parts from L&S engineering and if they don't ship direct to Bulgaria, get them to ship to family/friend etc in the UK and get them to ship to Bulgaria.

Tillotson couldn't keep up with demand and Walbro and Zama took the lion-share of the business. Another recommendation for Rowena carbs...a very decent outfit, lots of knowledge from Hugo...the bloke I always deal with. They hold a lot of stock and have helped me out with some pretty difficult parts in the past.

Sometimes I received old saws in for repair with the serials missing, if they had been hot, it would have been ten years or so ago and finding the original owner would be near impossible. I just informed the owner, stated it on the invoice and did what the owner needed doing as there was little else that could be done and the owners were usually trusted customers not some dodgy lowlife with no trading history. As long as you are happy with the guy you purchased it from and a little digging gets no where then crack on, it is just a little of what life chucks at us - probably someone has produced what antique dealers call a "marriage"....hope it turns out OK for you.

I have done a few. Most fail due to the white alloy top support breaking or the long screw that goes through both halves of the gearbox breaking....it is held in place with a very small lock screw so never force it. I have found the internals to be relatively robust, I never did like those fiddly con rods in the early units, the hardened con rods are better in my opinion as the rollers have the habit of coming out and even rotating lengthways in their runner causing wear. As I said before...grease the things regularly. A couple of squeezes from a grease gun per 2 days heavy use will keep it fresh. As before...a re-grease every 25 hrs is the spec and not doing this makes the things fail in the main.

I would be very careful when purchasing secondhand trimmer gearboxes as they are relatively complex, not many can rebuild them correctly and replacement parts are very expensive. The main issue is that owners ignore the "grease every 25 hrs" spec and replace it with..."grease it when it makes strange noises or the head becomes slow". The normal components to fail are: - 1) The con rods shedding their very small rollers, 2) The pinion bearing in the bottom housing failing 3) The input bearings failing 4) The gears and/or inner bearing failing If you have the unit on your bench, you can get a good feel of how decent the gearbox is by pushing a suitable flat head screwdriver in to the square drive union and then move it slowly clockwise and anti clockwise to feel the amount of backlash in the gearbox. This is a bit subjective but suited me to carry out for a very quick health check on these heads. Unless the owner has checked all the above, I would treat the purchase with extreme caution.

Your life makes mine seem pretty boring, hope the old bill is nothing serious. On the music front, stick to Zeppelin and don't get in to Linkin Park...I like the music but it is pretty depressing.

024, 026, MS240, MS260.pdf 024 026.pdf

What is the compression if you keep pulling it over as 130 is a bit low. 150+ is normal on these machines with 175 being pretty good. Have you popped off the muffler front and taken a look at the piston? When a machine dies like this, electrical or seizure are the common issues.