Heavy Oil Saw

I’ve had a look at the rubber inlet manifold, and there’s no sign of damage, but I’ll try and leak test it. Use the carb on the plastic carb mount (has the two threaded bars) and slide in a slither of rubber between the carb and manifold, then tighten all down, and see if it works. I keep forgetting to put the metal washer in when I assembly it though.

We’ve got three kids in the house, so I got distracted, and came back later and found no drop in pressure, I wouldn’t choose to stand there and watch the gauge, unless it was a decreed law by the manufacturer. Not doing it for a living, and having never built a 2 stroke, with the inherent dangers of lean running from air leaks, I’m glad I’m taking my time, and proving my work as I go.

Got it pressure tested. Held a 7psi pressure for over 10 minutes, and vacuum of 10inHg vac. Here’s some pics

Here it is installed. Those washers cover up the butchery behind them. Talking of butchery, where’s that old spark plug? That’s my 1 year old daughter in the background plodding about, hoping she takes a liking to “mechanics”.

Thought I’d knock up a couple of plates and “gaskets”, while I wait for a seal kit for my Mityvac (put it to bed full of fuel and it’s perished the seals/age as well). As you can see, they certainly aren’t aerospace quality, but nothing I do is, but hasn’t ever failed me. This could be a first [emoji33]. Used in-hex bolts on the exhaust side as I cut them down to allow clearance off the cylinder. The large washers are for comedic affect. Had the chipped cylinder/inlet manifold/old exhaust gasket as templates, and cut the best I could using a dremel, old Ikea kids table and vise-grips (I don’t have a vice at home). All mounted, it looks feasible, and I’ll indeed spray them with leak detector as well to ensure my leak isn’t self induced. They’ll all get cleaned before installing on the saw, so no nasty pixie dust is ingested. Here’s some pics.

Started again, after checking the play in crank and piston. Ensured the arrow on the piston was pointing towards the exhaust. Moved from island to table as the kids are doing their art lesson today. Now just waiting on parts. Hoses mainly, and an air filter, lets see when they’ll arrive. Gotta build something to pressure test the crank seals, I have rubber sheet to seal things up, need some plate to screw it all down. Can you pressure test through the spark plug opening? As I could cobble an old spark plug in to an adapter and block cylinder inlet and outlet. Keep the cylinder at BDC(?) and let the pressure build, 7psi I believe

@spudulike Spot on, glad you understood my terminology. All seems fine then, no rotational movement in the crank at the bearing ends, no movement up or down in the piston (all new parts), or the the crank big end. There is movement as you suggest in the crank. Thank you for replying so fast. I’ve lathered the internals with 2 smoke oil, to preserve it while it’s open, and give maximum lubrication on dry pulling and eventually start up. Found the fuel tank breather blocked/failed, so that’s on order as well. Trying to cut down potential on problems when fault finding a non starter. Pretty much only the carb is left unopened, but passed a pressure test. Gotta pressure test the cylinder as well. Has anyone deleted the base/cylinder gasket to any detrimental affect. I’ve read early 261s had too little squish for this, but later ones are looser in tolerance, and can accept it better. Any opinions?

Pulled the jug off, again, anyone got a good idea about “free play” in the piston and crank. Got no vertical play, but some horizontal play in piston and crank. I believe this is acceptable, but in what measurement?

On the damaged M-Tronic case, it’s that part that’s been modified, so I followed Stihl’s way of doing it. Didn’t want to mess with the coil.

@Ratman Only thing that’s worrying me is clutch side crank bearing, I’m sure it did something when I reheated the case half and fitted the crank. It isn’t interfering with the bottom end or the oil pump. I’ll let you know when it drops it’s guts on start up (if it starts up).

Sat in bed, watching the news, and thought to myself, those pipes will cause you nothing but problems once you get the Aspen in, best run down, strip it back, order the hoses and wait. The carb can wait, that’s easy to get at. Upgraded the solenoid to the white one, and the orange mesh filter though, just as a precaution. Edit:- Yes that is a tea spoon, great tool for hoses and leverage, no sharp edges and thin.

Kitchen island, I’ll have you know [emoji1787]. It’s closer to the kettle in there, and my work oven.

In the lock down situation the country is experiencing at the moment, thought I’d get the project moving, and here it is, pretty cack handed and bodged together, but looking OK. The book said 10Nm for crankcase bolts, but the kit instructions said 3Nm and 90 degree turn, so I went with the kit destructions. It’s a 261 carb case, and I have an M-Tronic get up, so came across this problem The M-Tronic coil was hitting this guide, which in turn allowed the flywheel to foul the pick-ups. Soooo, in great heavy handed fashion....... Almost there And finally pulling 150ish PSI, I was slow getting the camera, and my tester must leak. Oh, and there’s spark as well. Thank you to people who’ve answered my questions, and to the forum in whole for info, been lurking about reading about tapping the ends of the crank and helpful tips like that. Honed the cylinder with 1000 grit and 2 smoke oil as lube, worked a treat. Most of the parts are 2nd hand, cleaned in works parts washer and cobbled together by me. Hats off to you small engine guys, it’s fiddly as ****, and big hammers won’t achieve the desired effect as on heavy plant. Last final part is getting the clutch and chain lube side sorted and then run it up.

I’m ready for it, carb kits/primers for the saw and strimmer, and new fuel lines and filters all round. I like tinkering, so I’m happy it’ll perish all the lot. There’s another post floating around about Aspen, and it was mentioned about this occurring, as I researching using Aspen, as it keeps for so long (conditions prevailing).

Saving an ex grounds maintenance HRX537, none runner, used 4 stroke Stihl Motomix in 1l, and had it running within the day. Spark plug was defunct and magnet and coil pick ups rusted bad. Could not get it to tune at all though (back firing, hunting, unable to hold idle), went through the bottle and went and bought Aspen 4 in 5l. Topped up and began tuning, and had it tuned within 30mins (yes I’m slow, paid by the hour though [emoji23]). Cuts like a champ now. At the same time got a bottle of 2 stroke Stihl Motomix for the strimmer, FS70, primed off bulb and started on choke second pull. It ran amazingly well and had more response on the throttle than on pump fuel mix. Didn’t stink either, and lasts up to five years if stored correctly, no brainer for me really. So I had a “bad” experience with the Stihl 4 stroke (there could of been other factors involved), but not the Aspen 4 or Stihl 2 stroke mix. Who knows, but I’m sticking with the Aspen 4 for the foreseeable future, and going to test some other 2 stroke pre mixes out in the strimmer and saw (MS171). Edit:- Both strimmer and mower used pump fuel all their live (in their respective requirements). Both items are 2nd hand, repaired by myself for personal use.

How’s that exhaust blowing? I’m looking to mod mine, and unsure where to go with the cuts.

Probably runs better than on its suggested mix of 25:1, and less issues.

They use 30W SAE oil to mix, not Stihl Synth or the like. China doesn’t need to conform to environmental laws (I know 50:1 was introduced before laws, but now it’s a factor), end user in China ain’t worrying about ratio or even oil they use. They are cheap due to exchange rate and subsidised postal system. Plenty of threads/vidyas of them running 40/50:1. A janky saw, is still a janky saw, no matter the mix.

This is how I’d feel running an old saw. Everyone says it’s true, but you don’t want to find out it isn’t.

From what I’ve gleaned from old saw restoration vidyas and the likes, modern 2SO alleviates the need for ratios in old saws. So a 25:1 mix old saw will run 50:1 on modern mix (Stihl Motomix, Aspen 2). I didn’t believe it at first, but heard/read from many sources, so I believe it true. If you don’t think it’ll work, run Aspen 4 stroke and mix to ratio as mentioned above. I was contemplating this method for a run in period of 40:1 for a saw I’m building (use the 4 for your mower as well).

@spudulike Any recommendations on after market cranks? I’m think of building a second MS261, with a standard carb, will need a crank though and OEM really don’t justify the price for my needs. All I keep finding is Chinese or smaller saw 171, 181 or big saws 362, 661. Seems like mid range saws aren’t popular.

When the odometer/speedo was changed it was logged in the documents distance at change. Odometer changed at 32,000 due to failure, new odometer reads 000000, something like that. So probably a genuine 32k, not bad for such an age vehicle.

They were serviced according to time, not mileage, so the wagon had done 24km since the last oil change, it was still changed, along with air filter and all that went with it. Grease on the props, hinges and that would still be clean. Could of done with being driven more. Crazy really.

I drove them, pretty good. Solid engines, easy to maintain. Inner hub seals always leaked. Simple electrics. Spacious cab. Look after it and it won’t go far wrong. There was a box body attachment for signals and electronic repairs, think metal smiths had a version (had a lathe in the back). The CVR(T) used the same engine, so plenty of power from the unit as they shifted. DAFs accelerated fast unladen. You pull off in 2nd no problem, 1st was the power gear and short in duration unless in low ratio.

I bit the bullet and bought the Stihl splitter, next month for the flywheel side one. As you can see, works a treat.