spudulike

Sounds like lack of fuel, most likely cause is a blocked gauze filter in the carb, it may be a sticky or too low metering arm/needle valve as a second suggestion or beyond that, a dodgy solenoid but this usually lets the saw rev but will constantly die on idle.

The check valve is where the high speed fuel mix enters the carb throat. It is a valve that lets the venturi effect of the air ripping through the carb pull fuel through from the metering section but then seals in the opposite direction allowing the low speed circuit to control the mix at low revs when the throttle is closed. If this is stuck closed, you will fail to get high revs or power, if it is stuck open, idle will be non existent and the high speed will be very rich.

You can see the light bouncing off it in the last pic so it is definitely still in place.

If you have one turn out on the carb and it wont pull around 14krpm then something is tight, the engine is making very poor compression or the carb is over fuelling. The things that stop a two stroke revving are load, wear or fuel. It could be the check valve in the carb is stuck open. Have you checked the compression yet? I have had some very worn engines do the same as yours, not make top revs and lack any go. One other thought, someone hasn't swapped the original black coil for a limited one at 13Krpm...a 390XP at a guess?

Bloody hell Joe, top marks, top of the class and I never thought I would say that. Bang on my friend, the CAT is the limiting factor and it is still sat there with everything going through it.....and that is BAD!

Yup, think Stubbys been on the US sites!

Well it is bloody obvious to me, can't see why no one else has commented on it!

No, no, no, not the burning of ones kecks!

Sounds like we are getting there. Just need to learn about how to file which is pretty easy tbh, remember to take care with the depth gauges once the cutters start getting filed down significantly. All good and hope the thing is beginning to perform now. You could try a new chain and you will then see how a chain should cut although many will say they can file a chain to work better than that

Your "friend" is a very naughty boy. I have to climb a tree to test all the top handle saws I fix. Unfortunately, there are now no trees taller than 5 foot for a ten mile radius of my workshop because of this law. It is very annoying.

Ha, manuals are for girlies...we are men, and men don't need manuals

Lets see what JR comes back with on the chain tension, oiler efficiency issues and see where that ends up....hopefully after he has re adjusted his carb!

Word of mouth is probably the strongest marketing so you need to always go that extra mile to discuss the job, be pleasant and do what you say you will. Exceeding the customers expectations is always sound. Any reviews - Google, Forums etc are worth having. I guess Arbtalk is my website but it is worth having some sort of online content even if it is just a single webpage with a bit about you. Local papers are worth a punt.

Give the side of the muffler, just in front of the rib, a tap with a hammer, the front will come off revealing a couple of more screws either side of the exhaust port!

We may sort this before 2021....hopefully!

Firstly - TURN THE "H" SCREW 1&1/2 TURNS OUT.....failure to do this will seize the machine.........3/4s turn is with the limit "plastic" caps fitted. Sorry for shouting but I have seen MS880s seized like this and don't need the work! So, the machine runs better now and am not surprised with the carb being an extra turn out before. Check the oiler - just fire up the saw with the side cover and bar off, rev lightly and wait for a trickle of oil to make its way down the side of the saw. Check the oil hole in the bar is clear of chip - that's the little hole that is in line with the oiler channel in the bar mount on the saw. Once the bar is on etc, fire the saw up, point the end of the bar at something like a clean cut piece of wood, a piece of card etc, rev the saw and it should make a clear line of oil as it is thrown off the bar. Make sure you don't contact anything with the bar tip but this is a basic and best test for correct oiling. Finally, when you have tensioned the chain correctly, if you hold the shaft of a screwdriver behind one of the teeth and whizz the chain forward with it, should turn freely and carry on spinning for a short while (1-3 inches) and NOT stop absolutely dead. My tensioning technique is to put the side cover on, nip it up lightly so you can still move the bar up and down, tighten the chain until the bar tip starts to lift, hold the chain off the bar by resting your forearm on the chain brake lifting the chain between thumb and forefinger, aim for around 1cm gap between the chain and top of bar and tighten while still lifting. Once let go, the chain should be a light fit around the bar and the spin test above should work as described.

Air leaks from the clutch side crank seal and inlet manifold!

Nope!

Going back to my comments and the later comments about the bar and chain, one more thing to try, whip the bar and chain off, replace the clutch cover and then rev the saw and see if it sounds a lot more peaky and revs very much higher. The bar and chain do seem pretty tight, have you checked the oiler is throwing out decent amounts of oil? with no bar and chain on, it should dribble out of the bottom of the saw in good amounts if revved flat out for 5-10 secs.

If you want to learn about saws and have spare time, fill your boots. They are good enough machines but pretty heavy by todays standards. It looks like it needs a damn good clean.

There is one fundamental issue with this mod though, I will leave you to work it through!

The muffler bracket also supports it being a 50cc. There are only two types of bore, 42mm and 44.3mm, the rest are Chinese versions of the original. Best try to clean the bore, 346XPs tend to score a bit more than most but worth a try then if OK, stick a Meteor piston in it. These saws have a couple of issues worth checking on rebuild and take a little more care than some but other than that, plain sailing!

Interesting!

Right, two issues, the main one is that the saw just isn't hitting top revs as it should - I reckon about 6000rpm instead of around 13000rpm. This could be caused by: - 1) Throttle not opening the carb fully - On the bench - just get the top cover off, hold the throttle open and see if you can get to the side of the carb and try to open the carb more with the bit the throttle rod pushes in to. 2) Choke is partially on - take the air filter off and see if the choke is fully off - that is it is not covering the bore but is parallel to the carb bore for maximum air flow. 3) Check the air filter isn't blocked - you could try running the saw without it - nylon mesh air filters can look very clean and be completely plugged. 4) Carb settings - should be 1+1 turns out. You could try turning the H screw in to see if the saw top revs increase as they should. 5) It is possible the high speed check valve is faulty but this would kill the idle - your saw sounds like the H screw is 3 turns out hence the smoke and poor revs. 6) I have seen faulty coils do this but usually check everything else and change the coil as a last option as they are a bit £££££ Try not to go aftermarket as they are more fragile. The other issue is that your chain should be chipping better than that and looks pretty blunt - this isn't the main issue, not hitting the power band is the issue!

So to clarify, when run without the bar, you are getting oil coming out of the channel the saw uses to oil the bar and in good amounts? If this is so, and the oil hole is clear in the bar, it should oil. If it doesn't, check the bar oil hole lines up with the channel - sometimes it doesn't if the bar is the wrong one or the bar is at full extension due to a slack and worn chain. Other than that, the oil pump isn't producing enough pressure to push the oil through.