Darkslider

Can't beat the locking DMM vault IMO, it's handy being able to lock it when you know you're going to be scrambling round in some conifer and you don't want to be clipping yourself into branches every 2 minutes.

8 hours ago, doobin said:

Facebook marketplace is full of fairly fresh diggers. For sale 'due to change in business direction'

 

It'll accelerate greatly after Christmas when the shit really hits the fan.

 

I bought a 1.5 tonner earlier in the year, one thing I discovered is a good proportion of the newer machines advertised at sensible prices on Facebook are scams, Impossible to view and the seller is only interested in taking a small deposit to hold it for you and can't answer any other questions or actually arrange a viewing. Not to say your observation isn't also true that's just what I found back in the summer time

54 minutes ago, Stubby said:

Hard to see in the pics but is the piston ring pin missing ? ( the pin that stops the ring rotating ) If it is could it be jamming something up ? 

I see what you mean looking at the photos but nope both rings have their pins, gudgeon pin and circlips there, crank feels nice and smooth when rotated I really am at a loss 🤣

Did a bit more tinkering with this today.

Removed spark plug and replaced with a mityvac bung I can hold in with my thumb while pulling over. Still locks up every 2 pulls but if I keep pressure on the cord and let my thumb off the bung it pops out with a bang and the starter cord comes out the rest of the way with it. Tried this with the coil, carb and exhaust all off to rule them all out as causes.

Thinking this definitely points to over compression now I try the Gunson tester on it with the 10mm adapter from the Sealey one. It's got a nice light spring on the Schrader valve and has given me reliable results on all my other saws, 5 or 10 pulls including a few that lock up and it's reading 160 psi. About what I'd expect from a 4 year old saw and I think I can trust this result now, however doesn't help with my problem.

Decide to strip it all the way down next, but that doesn't reveal anything untoward. Bit of carbon build up on top of the piston crown but everything else looks in good nick. Conrod looks nice and straight and no signs of scoring or gouging where the piston might have been nipping up or canting or anything. 

I think this one might be going to the dealer for them to try. I had a good play around with the recoil mechanism too couldn't get it to stick or jam or anything.

Last two replies are helpful and just the sort of thinking I lack sometimes. The saw is a 2018 model and came to me damaged and pretty neglected so anything could have happened to it, I think a wrong diameter piston being fitted is unlikely but not impossible

And remember it pulls over dead easily forever with no plug in, the problems only there when it's got the plug in and building compression which makes me think it's gotta be something in the cylinder causing it, just can't for the love of me think what

17 minutes ago, pleasant said:

Banana conrod?

Hope not, it's a possibility though! Think I'll get a 100% confirmed compression reading from somewhere first then take it to bits if it agrees with my tester

2 hours ago, pleasant said:

Incorrect plug length? Flooding due to low compression and hydraulic lock? Is the plug wet through when you remove it? That's where I would start.

 

 

Plug is the correct one for the saw as I replaced it when the saw came to me, it exhibits the same behaviour with a compression tester fitted in place of the plug too. 

The carb leaking fuel into the cylinder raising the compression was also one of my thoughts but the plug isn't sopping when I remove it, it's the same when pulled over with the throttle wide open too. I tried filling the cylinder with contact cleaner and giving it a few pulls to clean it out but no change there.

[quote]

Bit confused where you state 'and even after 30 hard pulls (10 of which were of the seized type) the best I could get was 90 psi' It's either 'seized' or you can pull it over...if it's seized, then it's seized...if you can pull it over albeit with increasing difficulty, then it's not seized...which is it?

[/quote]

This is exactly the confusion, you get two normal pulls then the third locks up solid, let the cord retract a little and give it a monster tug and it pulls through and then you get another 2 pulls and so on. So it's obviously not seized, but every 3rd or 4th pull it's behaving like it is.

I think my next step is to try it with the fuel line disconnected from the carb just to rule that out, then it might have to go to the dealer for a known good compression test to confirm my testers result is accurate 

Work colleague has just picked up one of these last week and seems to like it. I like the power to weight of it and the fact it's simpler than the 50cc class from Stihl/husky which seems to me like more of a tech race.

Just like all Echos though I think the high power and low weight comes at a slight reduction in durability, they seem a bit flimsier with thinner handles etc.

I've got two top handles that both have the same problem, an Echo CS350tes and a Husky T525. Bought them both second hand and they've both done this since I got them, I'm focusing on the Husky at the mo as that's the one I want to use more often.

Starter frequently (i.e every 3 pulls) locks up absolutely solid, making life very difficult up a tree. I've rebuilt a 200t that has 200 psi compression and have a 372 with no decompressor and this is harder to start than both of them so it's not just a case of MTFU.

Piston looks good exhaust is clear as is the flywheel to coil gap. With the plug removed it pulls over lovely and freely no sign of any nipping up or seizing, and once running it's perfect with stable idle and loads of power. But refit the plug and it's back to locking up solid again.

Immediate thought is it feels like it has stupid high compression, maybe been run oily or with a blocked filter and coked up the cylinder/piston crown. However I tried my motorcycle compression tester on it (Sealey MS100, only one I have which has a 10mm plug adapter) and even after 30 hard pulls (10 of which were of the seized type) the best I could get was 90 psi.

If my compression tester is to be trusted which I think it is as it should be designed for 50cc 2 stroke scooters,  then this isn't making much sense. The only thing I can think of causing this issue is a coked up cylinder ramping the compression up, but the reading on the gauge suggests it's knackered and needs a new pot and piston. 

Any suggestions gratefully received!

55mk2 is a cracking saw, had no problems with mine and I've kicked it's head in every day. 

5 hours ago, doobin said:

I run a 36" on my MS462. Knocked the oiler pin in and wound it to the max and it's fine for the felling cuts and ringing up the first few metres of big butts, which is all it gets used for.

Is this oil pump mod something that can be done on most oil pumps or just the ms462? I've got a little Husky T525 top handle that doesn't supply enough oil even with the adjuster wound up, I've cleaned out both the lines and it is oiling but a pathetic amount and the chain overheats easily especially around the narrow tip of the bar which is a solid nose carving type 

Just looked on L&S and while they list the right code of carb it's showing OOS at the mo, I heard Stihl are having parts issues due to lots of their suppliers being Ukraine based. 

On 31/03/2022 at 17:03, bmp01 said:

No worries, pleased to be able to help 

How do you go about diagnosing an accelerator pump problem? I've had a few saws where everything else has checked out but it still bogs when revving so as a last resort I've fitted a new carb which has cured the problem, however it's always felt like a lucky guess so far I'd like to know for sure how to pinpoint an internal carb/pump fault?

Still 550 xp money too which is what I went for. 4kg is light though, maybe it's the better tool for all day clearance and coppicing.

Have you tried putting the carb settings back to standard after fixing the inlet boot? Most owner's reaction to big air leaks is to wind out the mixture screws to get it sort of working again for another few months 🙄

Good compression tester is probably the first tool you should have when fixing saws, the basic Gunson one is ideal and quite cheap, you could end up on a wild goose chase looking for more complicated faults when actually you've got a nipped up piston with 75 psi compression 

7 hours ago, spudulike said:

The stihl vents are one way and only let air in so high pressure on the tank through heat may cause the metering needle to leak if the spring is weak. Not sure if the vents on Makitas are similar, don't do enough!

I think my Echo CS350 tes does something similar, I'm assuming a pressure test on the carb would reveal a problem though? 

Also got a spare 200t carb that wouldn't hold pressure I bought a rebuild kit for, I don't know if the spring comes in the kit but after reading this thread I think I'll have to replace it as well to be sure.

Love my 550 XP, mines the MK2 though which has had a fair few issues resolved apparently. The MS 261 CM is a nice saw and noticeably lighter in the hand, but was coming in at nearly £100 more than the husky when I looked which made my mind up. Echo CS501SX is between the two price wise, lighter than both but makes a little less power.

On 10/10/2021 at 22:24, spudulike said:

A compression gauge for small engines will typically have an extremely light gauge schrader valve mounted in the part you screw in to the engine. The valve type is chosen because you can only spin the engine over for a few revolutions unlike a car engine that you can hold on the starter for a few seconds.

The valve being close to the engine stops the tube acting as part of the volume of the combustion chamber and lowering the compression.

Car type compression gauges can have bicycle type schrader valves in them and will give lower readings than small engine gauges.

The Gunson "HiGauge" is one that works although I modified mine to take Presta valves as I was destroying the schrader ones with modified engines making 200psi+

The rings.....put them in the cylinder, make sure they are nice and square, measure the gap and it should be 7-15 thou, much more and the compression will suffer badly.

The light part of the cylinder ADW mentions may well be the Nikasil plating worn through - try scratching with a craft knife and if it scratches on the light part, it is through to the aluminium.

If you have another of these machines, just pull them over slowly and compare them. 75 or even 105 psi is pretty low. An engine in good condition will make 170psi.

This is my Gunson comp tester, would you say this should be pretty accurate on smaller saws?

8 hours ago, spudulike said:

Sorry, missed this. You are good to go, the rubber is just tighter on the shaft and is gripping it a bit - more noticeable on a small engine but is fine - you have end float so just reassemble it.

Spot on cheers, I'll carry on with the rebuild and hopefully the pressure/vac test reveals no issues!

13 hours ago, Mike the builder said:

Thx, great advice. I’ve a gauge to measure compression but surely 75psi is 75psi regardless of whether it’s a car or bike or anything. 
 

Spud wasn't disputing that 75psi is low, but saying that a vehicular compression tester designed for being pressurised with thousands of CC in a short cranking cycle might not be as accurate with a 40cc cylinder being pulled over by hand. I've got a motorbike/small engine compression test kit I use, I've had a few in the past that under read by miles which could lead you down the wrong path, hence the questioning of the starter cord behaviour.

So I've got this assembled but the crankshaft is noticeably stiffer to rotate with fingers than it was with no seals fitted. I think I might have knocked them in a bit far but I've still got some side to side float in the crank so does that mean I'm good to go or should I get them out and try again?

9 minutes ago, spudulike said:

The bakelite seal has a flexible material part and that is the other part you show.

I use nitrile coated metal seals as they are far easier to fit than the Stihl ones but you have no issues there.

Just make sure the bearing plastic needle retainer is intact before you fit the seal and do the pressure and vac tests on assembly.

I thought that was the case just wanted to double check from someone in the know first! Much obliged, I'll carry on with the rebuild tomorrow in that case. 

Crankshaft and bearings all look and feel good but I've spent a small fortune on bits, replacing all the serviceable items and perishables plus a new genuine carb and pot/piston. Will double check it holds pressure/vacuum once it's all together, should have tested it before taking it apart really but I was too excited to get it to bits 🤣

Replacing the original bakelite seals on my 200t with the updated rubber type, but on removing them I found another flat seal/guard on the crankshaft bearing side that doesn't show in any parts diagrams and I can't find. Attached picture shows old seal on the left, new on the right and the part in question in the middle. 

Best guess is that it's part of the bakelite seal that has become detached but don't want to reassemble without checking first.

Thanks in advance

Manitoba Maple according to Plantnet, don't know if anyone else could confirm but looks like it to me.