So this Mac436 chainsaw I bought back from 'the chateau' is being very unhelpful. It seems to have a good spark now I've cleaned and set the flywheel air gap and treated it to a new plug cap. It won't start unless primed repeatedly and will usually only run for 10 seconds or so. Once or twice it has run for longer and will respond to the throttle, but then when left to idle will suddenly pick up in revs before dying, then refuse to start again. Got to be shit in the carb or fuel line right? I'll give it the ultrasonic cleaner treatment if I can get the little barsteward off but I can't immediately see quite how to accomplish that with some prospect of getting it back together again without a manual. Probably better to just junk it and get a pikey Chinese one off Ebay TBH. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
Could be one of the fuel valve/pump thingies? Flappy bits of gasket accomplishes that iirc. What about the fuel cap? Unlike with bikes, I have deffo had a problem with the fuel cap - started and ran for a while, then stopped. Wouldn't start again until left for a while. Turned out someone had replaced the fuel cap with one from a petrol can. The carbs are usually pretty simple so you'd see anything obvious if you took it apart. I also found mine pretty sensitive to getting the mixture screws in the right place for it to run reliably. Noooooooooooooo. I bought a pikey chinese strimmer and it was sooooooo bad. I sent it back and bought a second hand Stihl. No regrets.
Mebbe, but thanks for reminding me why I bought an electric chainsaw! So much more civilised when you don't have to wander too far into the wilderness.
McC used to be a decent brand. I owned one for years, gave it to WUN. Given the name McChuckaway by professional users since production went to Taiwan.
Still got the original cap, though the plastic thread on it is a bit knackered and needs exactly the right starting position and some force to get it to tighten properly. Good idea, must check the air vent. Could be blocked with, well, sawdust. Looks crude in the extreme. I had a preliminary go at getting it off but there's a sort of fine wire springy connection bit that I can't see what it does. I can get the carb loose so I'll pull off the fuel line and hope the choke lever thingy just pulls up out of a slot OK. My Stihl strimmer is the most reliable of my small engines at 'the chateau'. The Briggs and Strattons in the three-wheeler brushcutter and ride on mower have played up, but haven't defeated me so far, though I had to get a new air intake moulding for the mower because the lad bust it by over enthusiastic use of the throttle (the cable is attached to it). The new one came with a primer bulb which is actually better at persuading it in to life in the spring than the complicated choke arrangement of springs and stuff. TBF I suppose operating in a cloud of sawdust at sub-zero temperatures is a pretty challenging environment for any engine. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
Hah, I could use an electric one for the main log for the log-burner cutting work, but it would have to have a cable of epic length to do some of the tree lopping. -- +-----------------------------------------------------------------+ | Pete Fisher at Home: | | Visit my *NEW* Home Page : http://www.flarefox.com/Joomla | | "Do not adjust your mind - there is a fault in the reality" | +-----------------------------------------------------------------+
Could be the high and low running screw settings. On my saw they set fuel flow rather than air flow and if out of adjustment I get poor starting/low running with occasional good behaviour at high revs. Try opening the slow running screw a bit - otherwise set the screws back to factory settings and try tuning from there.
Fisher <> saying something like: It won't start unless primed repeatedly and will usually only run for 10 seconds or so. Once or twice it has run for longer and will respond to the throttle, but then when left to idle will suddenly pick up in revs before dying, then refuse to start again. Bought a used leaf blower-It had the same symptoms 1 of the screws holding the carb had vibrated loose tightened it back up cured it
Well I've never fiddled with them. TBH I don't even know where they are. I'm going to have another look tomorrow but I'm having trouble finding any kind of repair manual for it. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
Exploded diagrams of the saw are here; http://www.4mcculloch.co.uk/cgi-bin...Type 2)&model_ref=552082&brand_ref=1282&shop= No luck finding the manual.
I've used them for years in RC helicopters and they're a cun until yu get the starting/running technique sorted. One thing to try is pull the choke lever (even when the fucker is hot), pull the starter and it'll fire, but not run. Now close the choke, pull the starter and let it rip. We had a bloke cutting a concrete section of our works yard with a petrol disc cutter and he couldn't get the thing to run either, so I offered him the same advice and within 10 seconds, he was cutting a swathe like a pro. Engines need to be reliable in RC heli's btw, VERY reliable and I've not lost one yet.
Still very useful though, many thanks. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
I have the ex-wessie and ex-WUN Mac 320. I've managed to find the user's manual for it, which covers "Power Mac 310, 320, 330, 340 chainsaws". Would a copy of that be of any use, do you think? Or I'll type and email the carburettor section out for you if you want. I had it fettled by my tame goblin, who looks after all such things for me. Mad Metal Mickey, the Mower Maniac is a sort of deformed idiot savant who lacks any shred of social skills, along with hair, most of his teeth and half an ear. He's genius at fettling POS little motors, though, and has a loft full of parts he's salvaged as people just give him stuff to get rid of him. He replaced plug, valve and piston in mine for the princely sum of 20 quid and four pints of Eagle Smooth. You could UR the thing here, and I'll chuck it at Mickey, of course.
It lives on here, engine rebuilt and chain fettled. It works well and seems quite happy to tolerate my occasional abuses.
glad to hear it is still alive. It must be around 30 years old now, being owned by my dad then me when he died in 1988.
Too late, my mechanical curiosity got the better of me. The carb is off and various bits dismantled and stewing in the ultrasonic cleaner. It was all fairly easy once I sussed that it was possible, nay impossible otherwise, to lift the carb out while still attached to the throttle cable. Couldn't see how to get the business end of that off without removing the choke butterfly and withdrawing the spindle though. Whether my short term memory, arthritic fingers and dim old eyes will enable me to get it all back together properly remains to be seen. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
<Note to self - when dismantling a complex mechanism without the benefit of a manual take notes or photos at each stage> Talk about a jigsaw puzzle. The gunk 'green'/water mix in the Chinese ultrasonic bath at 50 C and 30 minutes went encouragingly turbid and the wee carb came out shining like a new pin. Some atmospheric bluing ensued as I tried to figure out how the choke spindle and butterfly went back on so as to interact with the throttle properly. Then the base for the diaphragm could go back two ways - a look at the parts list sorted that. Realised that the throttle cable that was so difficult to disentangle shouldn't have been and this might, just might be a clue as to the problem. Putting it all back was like one of those assembly puzzles on that TV show for putative genii (can't remember what it was called). A manual may have made it clear just exactly the correct order of fiddling to get the fuel lines on, the throttle cable connected and the choke hooked up. Even with my Foster Grants on and good illumination this was a bit tricky. 'Tis done, but 'twere not done quickly. Too knackered to try to start it now, but I have a feeling in my water that it still won't play and that Grimly has the right of it and that a crankcase seal is duff. I haven't had a tiny two stroke apart down to its nether regions since I helpfully took my old Dad's Suffolk Colt mower engine apart when I was the lad's age and after amazingly getting it back together rather spoilt things by experimenting with running it on paraffin (start it on a float chamber full of petrol first is the trick). Still, a minor victory was also won, when while the bits were being jiggled about in the cleaning bath, I discovered that my theory that a sleeve of plastic waste pipe would allow 35mm Morini 350 Tomaselli headlamp brackets to fit on 32mm 250 fork legs, was indeed well founded. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
The carbs on little 2strokes are strange beasties which are a combined fuel pump and carb. 4 or 5 layers of diaphrams and metal plates to get mixed up. First take a look in the fuel tank, there are 2 pipes to the carb, pickup and return. The pickup pipe should have a little filter on the end which easily gets clogged with oil if left unused. Get a proper carb overhaul kit, they come with a full set of diaphrams, the old ones are most likely shot. Disassemble CAREFULLY laying each part out in a line in order, fit the replacements and reassemble. If in doubt GAMI.
Just one diaphragm (that I can see at least) in the case of this Walbro carb. At least 20 quid for a kit - ICBA. At XX quid an hour? Not worth it for a saw that can be replaced with one to do the same job for under a ton. Anyway, treated it to newly mixed fuel at exactly the right ratio. Started first pull ! Then stopped after 15 seconds. There is a spark good enough to give my finger a noticeable jolt when I wasn't careful where I was holding it when pulling on the rip cord with the cap off. The plug is a new NGK item which shows a good strong spark. The plug is getting as wet as a weekend in Wales. In fact it now exhibits symptoms similar to a gassed-upped crankcase. If it had a drain plug I would use it. Got the spark plug out and silencer off to give it a really good airing. If that doesn't go next time it's going to be Ebayed out in parts proven to work, if not all at the same time IYSWIM. -- +-------------------------------------------------------------------+ | Pete Fisher at Home: | | Aprilia Shiver Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" | | Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" | +-------------------------------------------------------------------+
