bmp01

+ 1 Never had a defective plug ..... until the first time and now my default is new plug every time. It was visually fine, would show a spark just like normal outside of the engine but swapping back and forth between new and old plug proved beyond doubt the old one was knackered. When i cut it up it turned out the ceramic was cracked and it had been arcing inside the plug. Rare case but it does happen.

Do you mean the drive sprocket (or the nose sprocket on the bar) ? You say everything is fine with a half used chain - doesn't that rule out the new bar as the problem? Edit : but new chain on the old bar was fine too which says chain is fine. ... lol ! Is the drive sprocket in good condition, ie no deep wear marks? Could be the drive link on the chain be riding up onto the unworn surface of the sprocket? Otherwise, have a look at the drive links on the chain, any damage or burrs on the edges of the drive links that might catch on sprocket or entry to bar rails? 9 I've had that before and it does make a click noise. Put a pen mark on the chain and see if it's the same place on the chain every time .... Let us know how you get on. bmp01

Yep, can pump the primer bulb as much you like. ...still the same. ...just didn't feel right. Inflates by itself and not slowly, if anything a bit quicker than you'd expect. I started with a part full tank but quickly brimmed it - to rule out air through the filter. Lines all look good. Thanks for replies - it isn't right is it. ... Here's an update: After much head scratching I've established that the air (that's all the air) is being pulled into the fuel circuit via the jets in the carb. Specifically, through the low speed circuit. And I confirmed this by temporarily blocking the low speed circuit with bluetack (a 8ugger to clean afterwards !). It's worth noting, the primer bulb sucks from the metering chamber - so you can see how it will suck air through the jets if there is nothing to stop thIs back flow. Still surprised you can suck so much air through the tiny dia 0.4mm jet though. Further, I have a spare (high mileage) carb from a MS171 and in this one there is a one way valve in the low speed circuit (as well as the more obvious main jet /one way valve for the high speed circuit). Now, the MS171 doesn't have a primer circuit which makes me wonder why they bother with the one way valve in the low speed circuit - I can't see it serves any purpose....and pretty sure most carbs for chainsaws don't have it. Parts consistency I suppose. So, given the main jet/one way valve was fubarred (see post one) and now it seems the low speed circuit one way valve has gone the same way, I'd be tempted to say the carb has been 'cleaned' with an air compressor or maybe the engine has been 'popping' back through the inlet (due to the engine seizure).... who knows? Looks like new carb time or just live with it. bmp01

Steady. .... expected some authoritive put down not an apology The thing is, there is much to learn from those that have 'been there, done that'. Unfortunately, i have the age bit but not the other .....

Spec Saver moment there mate Beechhunter has matching bar and chain it's just the sprocket he's worried about. Presumably if the sprocket was a spur sprocket that wouldn't work, unless it was practically new, as any wear would try to guide the new chain in a bad way? But as it's a rim sprocket it will shift itself to centralise on the chain run. Think I'd run a new rim in any case for the money involved, keep the rims matched to the specific chain gauge.....

Hello all, I'm after some opinions and experience please. I've got this MS211C that I'm sorting out - its been seized so has had a replacement engine (genuine parts). I'm VERY keen to avoid a repeat engine seizure, so have been trolling through the fuel system just incase, although i suspect crap fuel was the root cause of the problem. That said i did find the main jet one way valve was fubarred so thats been replaced. Here's the thing, when i use the fuel purge bulb to suck fuel through the carb i get a surprising amount of air coming through with the fuel, was worse before the main jet one way valve was replaced. So the question, what's the usual fraction of fuel and air drawn through with the purge bulb on an MS211C? I recon I get 50:50. FYI, I've looked in the carb and can't see any sign of one way valves on the low speed fuel circuit - i think it's impossible to get 100% fuel and 0% air. In the past I thought strimmer engines etc pulled through pretty much neat fuel. BMP01

Good result, thanks for the update. I bet you're glad you persevered with it

There is a tiny reservoir of fuel in the carb so if it really is instantaneous then I'd be looking in the carb for the problem. I think a pinched fuel line or pick up issue would take a few seconds to show as an issue. It could be the metering lever is not operating quite correctly and in need of a tweek - its the only thing i can think of that gravity might affect in an otherwise sound carb. .... but that said the spring should pay the major role in controlling lever position. bmp01

I'm not sure there is much to conclude from the damaged band - with that much change to its geometry its going to adopt a different shape to a new one, plus it's bound to have got blinkin hot so it might be distorted too. I'd be a bit worried about the wear to the inside of the cover (3rd picture) - it says to me things are not aligned the way they should be, could be the cover or the machined face on the engine case. It's got to go back for repair / investigation. I'd be asking for a replacement cover as well as the brake band, hoping that fixes any alignment issue. If that doesnt fix it, then it's replacement saw time. BMP01

There was a 480 advertised on gumtree earlier in the week, think it was advertised in Corby, 29 quid, missing chain. Probably just a coincidence. bmp01

Thoroughly agree. The clever bit is establishing what value to assign to 's'.... not got there yet though

I asked the question badly. ... think i should have said 10 "drive links" not "rivets" 0.325 pitch per drive link ------> 3.25" for 10 drive links (thats over 11 rivets if you count the first one ) 3/8 = 0.375 pitch --------> 3.75" for 10 drive links (or 3.375" over 9 links, 10 rivets - most likely). My guess is it's a 3/8 pitch chain with a bit of stretch. ... can you confirm, incase someone wants it? bmp01

Hello, I'm interested in this, postage necessary though. ... Could you measure the distance over 10 rivits and tell us the number please? (in mm or inches....) thanks, bmp01

Have a look at this thread, might not be exactly the same but nevertheless worth understanding some of the worn carb issues . http://arbtalk.co.uk/forum/chainsaws/107694-200t.html?highlight=ms200 Also, +1 on checking the fuel tank vent. One way to diagnose if it's this - run the saw until it gives trouble, undo fuel cap to allow air in (ie get rid of vacuum), refit cap and see if saw runs fine for a bit - until vacuum builds again. How old is saw? What's the service history like? bmp01

So, obviously you've checked the throttle linkage isn't tight sitting level... Back to the idea that it's fuel related, seems i had it arse about face in my previous post, so does it immediately idle slower when hung up or does it progressively get slower and finally stall? If it were rich at idle (I'm assuming it might well be from that plug) and then made richer it would get slower (and possibly slower and slower until it stalls). What's the orientation of the carb? I'm wondering if the metering lever and valve are working (but only just) when the saw is level, and not operating when the saw is hung (i know the spring on the metering lever ought to cope with this but if the valves not sealing, who knows). Solution in this case would be: check the valve, set the metering lever correctly, make sure the metering diaphragm is up the right way and also that the gasket is between the carb and the diaphragm etc. If that's good you could try squashing the metering lever down a 1/4 mm in the name of experimentation ... Also is the metering chamber vented to atmosphere or is there a compensation for filter blocking? bmp01

Top result, well done ! You'll be out scouting for more "fixer-uppers" next :lol: bmp01

Nice set of options for WoodED to choose from Just looking at the thickness of the bridge (on the bar) and the amount of slack in the chain, if the heel of bar is ground out and the bar moved forward to tension the chain - its got to be touch and go whether the bar will be located by the "screw" that WoodED refers to. Add in a little wear and further adjustment .... Also what's the situation with adjuster travel? WoodED take the screw out temporarily, so you can see where the bar needs to sit - that'll answer the question. You could also work out where the bar would sit with a 1 link shorter chain, ie moving the bar inboard by 3/8". Rob - what's the "known" set up that others have used successfully on this saw? That's probably the best guidance. bmp01

Knock off 2 more on the opposite side then, that'll fix it. ..

You can not remove that screw, it's the only thing that keeps the bar aligned and stops it rotating around the single clamping stud. Have a look at the wear pattern on the screw where it contacts the bar that tells you it's doing a job. If it were a cheap old bar you might consider cutting the slot right out the end (like the Stihl).... bmp01.

Thanks for the thought. It's a long reach HL135 hedge trimmer with the usual rod bearing failure due to a lack of maintenance. I should probably just bin it really. ... bmp01

Wow, how is she not dead ? ? ? So here's the thing, how do stupid people get away with stuff like this? Anyone with half a brain would be so tentative it would have gone wrong .... Is there some sort of higher power looking out for stupid people or something?

I was looking at Farmertec gears for Stihl hedge cutter gearbox. Number one requirement has to be material quality and correct heat treatment. So thats another good plan down the drain then. ... bmp01

Thats never a good sign - fuel screen missing. When you spray through the low speed adjuster hole you should see the spray coming out of the tiny jet holes in the carb port - 2 or 3 jets up stream of the throttle plate. Make sure each hole is flowing. Spraying through the high speed adjuster hole, spray will come out of the main jet (brass cylinder protruding into the carb post). Some folk like to use compressed air to blow through the passageways but Id be cautious of that. Sometimes the main jet has a rubber disc in it which needs to stay put, fuel screens can be dislodged, even the welch plugs .... HTH. bmp01

Spuds the man. I hadnt even considered you might have left the screws in place ! Worth gently winding the screws in first and noting number of turns it takes, sometimes gives a clue when you know where you are relative to the factory start point, (the 1 - 1 1/4 turns out). Just winding screws in and back out is sometimes enough to reset the clearances but if you have the time do it right.

Have you touched the low and high speed mixture screws at all? Take a note of screw positions before you start. I'd turn the low speed screw out a 1/4 turn anti-clockwise (= richer) and see what that does. You might get away with less. It might also need the engine speed screw winding in slightly (to increase speed) at the same time just to keep the speed the same. When its up to temperature do the low speed carb adjustment properly. And high speed if you know what you are doing. bmp01