spudulike

That second fault may be a split inlet manifold - it is obviously getting a big slug of air from somewhere OR the choke isn't closing properly. Check the manifold, typically the underside splits!

I have done more of these little feckers than I have had hot dinners and that is what I have found, no need to elaborate, it is what it is......just had one with a welch plug made out a bit of aluminium beer can.....seen it all now:001_rolleyes:

The first one is almost definitely the orange throttle lever, it has a little stop on the end of it which often breaks. The second sounds like some sort of fuel issue so check the carb out, pumping diaphragm, gauze filter etc, if these look OK then possible accelerator pump or air leak!

The important thing is you have learnt a fair bit in doing this repair and that is worth the outlay:thumbup:

I sort of....know where you are coming from but I have found so many issues when doing pressure & vacuum testing that I think they are VERY valid checks and have probably saved many machines. The thing with air leaks is that if you have a slight one and the carb is set a little rich and the fuel oil mix is good, the engine may run fine for a long long time with no perceivable running issues. The issue is if the carb is set a tad lean or the fuel is a few weeks old AND you have an air leak then POP, the machine is far more likely to fail. Not sure about others but I have had a number of saws in, predominantly Stihls that still have their limit screws in place and have been serviced and on taching, have had to pull the H cap as the saw is over revving on the Stihl Max revs Spec. I guess Stihl set saws a little lean and as they bed in, they run higher and higher revs! I think that if one of these saws running close to more than max spec revs then gets a bit of an air leak or has a bit of suspect fuel then it is much more likely to fail. The other thing is a small air leak is a sign of a potential big one happening in the near future. I know you can get hung up on this sort of stuff, heck some people run their saws with small air leaks without noticing that it has one so GK is sort of right with some guys getting hung up on leaks but I have found on some MS200s, if you push the crank around, you can make it leak down to zero in two seconds but left as is, it will take a minute and pass the 20 second rule. The point is that it will only leak once running and with a bit of chain pressure on the crank shaft. The last repair I did potentially saved a 3120 from smoking it's new P&C kit, a seal was actually rotating in its seat and it had a real BAD leak. So.......don't always grasp at the worst case but my opinion - passed pressure and vac tests give solid foundations that the issues on an engine are elsewhere. Sorry GK - just my opinion but do look at general condition and age of the saw as well:blushing:

45 mins - longer if the transfer is really thick!

Just going through this on PMs......

Been porting a local guys 395XP, nice saw! Husqvarna did a good job in port width, not a great load to do in this area but you can make improvements by shaping the inlet and exhaust ports, lots to be done on the lower transfers and the uppers. The ignition is advanced, the base gasket dropped and increases the compression by at least 20psi and then the muffler mod. This one looks pretty nice IMO, just needs a run up and tach tune now:thumbup:

Another pic of that piston: -

Been on Husqvarnas "Big Lump" 3120XP, came in with zero compression and could see that it looked seized. On taking it apart, I found that both rings had broken and pretty much destroyed the cylinder and piston. I fitted a new OEM kit, a pressure check showed a BIG leak, traced this down to the clutch side seal that was actually rotating in its seat and had worn it to the point that air was pissing past it. I put a new seal in but it dropped through the pump casing so cleaned it and smeared a little JB weld around the seal and seat then refitted and let it go off, refitted the pump and all good. On this model there is a rather weird valve in the crankshaft that puts a little fuel air vapour through the crankshaft and in to the clutch needle bearing. This causes the saw to leak under pressure but seal under vacuum and is accommodated for in the carbs jetting so is quite normal. The piston photos show that the exhaust top edge of the piston has almost carbonised and granulated. All I can put this down to is the heat from the air leak. Not seen it before and almost looks like detonation but there are no signs on the piston crown. The saw is now sorted, clean and fires up well.

Most saw mufflers deflect and re-direct exhaust gasses as this is how you dissipate loud noises. The 560XP (not seen the 550XP one) has a baffle plate directly in the entrance of the muffler and a small hole in it and that will retain heat.

Husqvarna 254XPs are a good bet as are the Stihl 026, worthwhile saws to refurb.

Do you mean the exhaust Andy as the port looks OK, there is a very typical XTorq outlet angle which assists scavenging, it is very steep as it is on most XTork machines. The muffler has that plate with a hole in the muffler inlet and can imagine that this retains a lot of heat in the cylinder rather than letting it deplete in the muffler. Easy to find out, run a saw with a standard muffler and take a cylinder temperature reading and then do the same on a saw with a muffler mod! Interesting point, probably better to have the restriction further in to the muffler.

Nope, I detest working on MS390/039 etc, just drill the muffler and leave it at that!

It probably involves reregistering your company with the taxman (HMRC) and may involve the Government Gateway - that is where I would start first!

You did ask, firstly you need to find a suitable area where it is possible to mark one of the fin tips on the flywheel and see around and inch either side of the mark from the top side. You need to fabricate a plate that will fit above the flywheel and allow the flywheel to spin freely. You then get a timing wheel, put a stop in the plug hole and rotate the timing wheel clockwise and anti clockwise so the readings are the same so you can get TDC. Once the readings are the same both clockwise and anticlockwise with "0" in the middle, the stop can be taken out, TDC set and a flywheel fin can be marked as well as a mark adjacent on the plate, you then move the flywheel clockwise in 5 degree increments marking the plate. do this for 35 degrees. You can then stick a strobe on the sparkplug and see what the machine ignition is doing. These modern machines will generally have a big retardation at low starting revs, building to around 15-20 degrees at 3000-5000rpm, at around 10000rpm you will be at circa 27 degrees and this will then fall to 15-20 degrees flat out and peak revs. Probably simpler to mark a flywheel fin you can see at TDC and then make sure the mark advances as you rev the machine and compare to another machine...........I have done the above to set the ignition on a machine I fitted a non standard coil to and had to take the flywheel key out to set the timing - I don't advise playing like this unless you really have to and know your onions!

Saw this, liked the simplicity of design: -

I'm interested, tell us more:001_tongue:

I run a BG85........sorry, I run a ported BG85:sneaky2:

What he is trying to say is that if it is the round stub then the 365 top end will fit and if it is the other, the 365 top end will still fit but the inlet manifold will need changing......sorry Andrew:001_tt2: I did exactly this to a 2172 Jonsered.....I can't be 100% sure the 2065 is exactly the same but guess it is.

There is a system where you pay the duty before shipment and that way, you don't get done with import duties when it arrives in the UK as this and the handling charge is usually 20% plus £10 handling. Just purchased something from the US and have used this system, not landed yet but expect it to work. I had similar with a Fiskars X27 I purchased through Amazon form the US, paid all duties up front and 3 days later, it arrived and no further costs.

A well running engine will make the plug go a tan colour, black means too rich or oil and grey means overheating and white means very lean and seizure is imminent

Now you tell us:001_rolleyes: glad it is sorted now:thumbup: Wasn't that difficult was it?

Possible the baffle has collapsed and is partially blocking the exhaust gasses leaving the first part of the exhaust thus retaining too much heat. If a valve had failed, the engine would be pretty sluggish and wouldn't raise the temperature.

25" on a MS390, sounds like it may be a bit lethargic to me:lol: