spudulike

Determining if an air filter is effective is simple, tach a saw running with a brand new air filter to pre determined RPM, put on a soiled filter and register the RPM, replace with the aftermarket one and measure again. if the revs drop when the air filter is fitted, it is restrictive. I actually tached a MS460 with and without its HD2 filter as the owner wanted to fit a Maxiflow and the result was that the cleaned used HD2 filter had very little restriction on the airflow compared to no air filter being fitted. You can tell from this that the HD2 air filter is working pretty well.

I don't do milling but a pair of tights makes a good sock that will keep your filter clean and have the advantage of making the saw run a little more rich thus stopping it overheating in the longer cuts. BTW.....You don't wear the stockings, you put a piece of tights around the air filter!! I know the Monty Python song....no smoke......... just saying!

A bit harsh, he was only asking about his hedge

If you are using 25:1 mix with an oil specified to be mixed 50:1 it will smoke, cover the engine internals with more carbon and the oil will deposit inside the exhaust and will generally foul the engine/plug unless it is worked at full heat and revs but even then, at best you will just produce more carbon. The comment you use "running lean" is generally used in relation to the AIR and FUEL (Fuel =petrol + oil) entering the engine. If you mix lots of oil in with your petrol, your FUEL to AIR mixture will stay the same (assuming the viscosity of the fuel isn't significantly affected) but you will be burning more oil and less petrol so is this technically running lean?......not really because in two strokes, "running lean" is normally used in conjunction with the engine over revving and thus overheating and seizing as the piston overheats and melts on the exhaust (hot) side. If you use too much oil, the engine will not seize, over rev or overheat but it will carbon up, foul the muffler/plug with unburnt oil and in extreme cases, will stop the engine revving out as it should. A mix of 50:1 or perhaps 45:1 if using modified kit is sufficient. 25:1 dates back to a time where the oils were not as advanced as they are now. The only time I have known machines to back fire is either on starting - mostly the 372XPT saw and assume that the coil has a very retarded start circuit and the other time are ignition issues and more often or not, it is a sign the flywheel key has failed and the ignition timing is that retarded, the ignition happens far too late causing the fuel in the muffler to ignite and backfire. Yours starts and runs for a period so it is very unlikely that this has failed. The fact it runs for a period, back fires and then starts again when colder leads me to believe that the coil heats up as coils do when you put a charge through them and this is making it fail - your coil may have a separate spark unit as explained earlier, it is possible that either this is failing under the heat of use or the connections are faulty. With ignition issues it is always worth changing the plug for a new one as people drop them causing unseen damage and it is always worth checking the HT lead and spur connector in the cap with a multimeter for continuity but beyond the "easy to do" options, the issues will be ignition linked. But ADW and I may be wrong!

The mix is dictated by the quality of the oil and not the machine. When the machine was manufactured, most oils had to use a 25:1 mix as the oil was of a lesser specification than the oils of today where most oil manufacturers now stipulate a 50:1 mix. Look at the oil you are using and see what the manufacturer recommends. Stihl and Husqvarna recommend 50:1 and some like Almsoil recommend 100:1. Your oil from your local garage is probably pretty low spec! It is very unlikely that this is the issue!

I think ADW is correct. The backfire would appear to be the ignition unit sparking too late and causing a backfire similar to when the flywheel key has failed but seeing this runs for a period, it won't be the key. I would close the coil to flywheel gap - you usually set to 0.3mm but try setting it with a piece of printer paper or similar so the gap is much closer. If this doesn't do it then it looks like the coil is failing when it gets hot and is showing up as the ignition timing going wrong. I had a MS460 once fail after 20 mins running and found this gap was too big, once adjusted....no issues. He is also correct about the spark unit and the connections - it may need a new one if it has one (it probably does - but make sure the connections are clean and good - a bit of a going through may save £££ in parts you don't actually need. The spark unit looks like this - the little metal box on the end of the wire....the big lump is the coil. The box needs earthing : -

How did he accelerate past the van with his hand off the throttle whilst doing the hand signal? Do they still teach hand signals for bike tests? Been nearly 40 years since passing mine!

Not being funny but once the location pin is in one of the holes on the semi circular plate, the head is locked solid and nothing will move that more than a degree or two unless the plastic handle is pulled back to retract the location pin. Is the cutter head loose on the part that connects to the pole shaft? It is possible the main screw that runs through both parts has failed or has been replaced and not tensioned correctly.

No problem, glad it worked out, always good when it saves time and expense. Just pass on a helping hand to others when you can as a "thank you". Thanks for letting us know.

Pull the plug, turn it upside down and pull it over hard to clear the fuel in the bottom of the crankcase. Ensure the ignition is off!!! I would suspect that you are getting the piston locking due to fuel entering the engine top end. If there is no fuel in the engine, the compression will be down to fuel in the cylinder drying leaving old oil in it making for excessive compression. This can be cleared by taking the plug out and using WD40 in the cylinder, pulling it over a few times then clearing it by pulling the engine over hard when upside down. It will be one of the two!!

I have had similar in giving a diagnosis to a saw issue over the phone. They piss off in to the distance and have left me with parts on the shelf before now after promising to send it in...bloody frustrating!!

Yes but I get called by you arb types at all sort of times even bank holidays, late at night and Sundays so it isn't just your general public types!!!

Thanks, glad I am not losing it. I did have a 550 like this once. The bit of the cover that houses the latch was just not close enough to the guard not meshing well and couldn't work out if the cover had somehow bent which seemed unlikely. I sorted the issue by removing a little metal from the top of the covers mount area thus moving the top part of the cover closer to mesh with the guard latch which it did and operated correctly after I did this. A strange one but what I did, however unorthodox, worked.

I thought the 560 chain brake wasn't the quadrant type as found on the 346, 357 and many of the 3 series saws. The ones I have seen have had a stainless latch on the chain brake guard that slides in to the brake cover...a completely different mechanism!

And where do you work My old company was always 3-6 months behind on their new releases...not uncommon!!

I have a Stovax Riva. It is lined with firebricks so can't see the steel walls. We replaced the secondary baffle as it rusted after a pile of soot rested on it we didn't find and it overheated a tad - circa 10 years use. I made a replacement and it has rusted but has lasted for a fair few years. The primary baffle went through after some 15 years and fitted a new stainless one which looks and works well. These items do rust, logs will contain a little water and when you burn logs, that and a bit of water will corrode steel parts, same as your car exhaust rots through. I guess a lot depends on the thickness of those fire parts that are rusting. If they are say 3mm+thick, I wouldn't worry but if they are much thinner then more concern should be shown and would expect fire bricks to line the firebox if the walls are thin gauge. There are a few fitters on this site who should be able to help further than us mere end users

All done and back with the customer. Annoyingly, the previous owner had put a screwdriver through the inlet manifold and that is an expensive part with aftermarket parts being pretty crap so a new OEM part fitted and a new crankshaft seal as the original was leaking. All should be good now but always sort out any annoying issues in a reasonable way if the first pass didn't sort them and show up again with a bit of running.

Looks like light surface rust. Steel and Iron does that, just the surface oxidizing. Don't worry about it, it will do that but not an issue.

No, Front Side Bus....computing term and of major importance to overclockers!!

As above but the wider kerf being cut with the 1.5 chain will sap more power from the 450 than the 1.3 so expect the performance to be slower. A full chisel will take more power than a semi. If you have the B&C, try the 450 on the 346 cutting gear and see what it is like. All the B&Cs should be 0.325" pitch.

You could try a standard "Treasure Hunters" metal detector. There are older ones on eBay for around £30 and they will go down to a good depth if it is a decent brand like C Scope, Garret etc 6" - 8" detecting depth is quite possible on a nail, especially after it has been in wood a long time as the nail rusts, putting salts in to the area around the nail making a better target.

Yes, thanks for the info. Bit baffled as to why a carb should stop working when the engine got hot but as long as it is sorted, all is good.

I can't see any reason why bare metal isn't OK on the inside of the crankcase. As long as there is no loose paint then it should be OK in my opinion.

If it still plays up, check the tappets and also the gauze strainer, just done two more of these. One seemed to have low compression and the tappets were a bit tight. Backing them off restored the compression. The gauze strainers were also a bit grotty - remember to flush the tank out if you find chip in the strainer. Hope it is sorted though!

Bugger all I would say