What's on your bench today?

[spudulike]

Ok mike. I will try but neither am I really.

 

The old piston looked ok. There was the usuall heavy soot on the top but lean intake. The exhaust had a bit of crud around it but nothing major.

 

I will investigate the piston more when I next get to workshop, will need to inspect the rings very closely. I'm suspecting at this stage the rings being scored. But they look ok.

 

If they are scored it would have meant the crank case leaking through them and going straight out exhaust rather than into transfer ports and piston. This gap would seal when full throttle applied and fuel would fill the gaps.

 

Hense the problems with running seemed like an exhaust issue.

 

There is no doubt the bearings and crank seals had gone when the saw turned up, and by this I'm alo suspect that the piston was able to move about in pot and either catch a ring on a port and damage it or allow the piston to scrape the pot and loose some alli on it.

 

Thinking out load here but will get a really close look at old piston and go from there. Need a magnifying glass.

 

P.S worked on one of them David browns in college. Complete engine rebuild. Don't think it was the Same one but it had fixed sleeves. Had to have a re bore for new pistons and rings. But the one I had to work on was no where near as clean as yours when it turned up. It has used for the dairy poo scraping tractor.

 

Rich - get the verniers on the piston and measure across it and also in line with the inlet and exhaust port. Also measure the thickness of the skirt - middle and outer bottom.

 

Measure the top ring thickness middle and ends - that is the depth that goesa in to the ring groove!

 

Must be something there! Possible that transfer damaged the rings or just wore them unevenly!

[Rich2484]

Rich - get the verniers on the piston and measure across it and also in line with the inlet and exhaust port. Also measure the thickness of the skirt - middle and outer bottom.

 

Measure the top ring thickness middle and ends - that is the depth that goesa in to the ring groove!

 

Must be something there! Possible that transfer damaged the rings or just wore them unevenly!

 

Cheers spud. Will take a look at it when I get time. If it hasn't already made it to the scrap pile.

 

Going to order a couple of 200t pistons as they seem to be the most popular saw going over the bench at the moment.

[Rich2484]

Had to laugh about this one.

[Mull]

I,ve rebuilt the engine on this David Brown 1412 and it runs so well that i thought i,d tighten the steering up with new axle pivot bushes and a trackrod end.

 

 

Was looking for some axle stands, did you get them from screwfix?

[mikerecike]

Was looking for some axle stands, did you get them from screwfix?

 

No they're part of the Draper 'Rustic' range I think

[Rich2484]

Well. A Honda mower turned up today. Wash backfiring from carb and exhaust. Check valve clearence and flywheel/coil for timing. But all was good.

 

New plug and away it went. (Thanks gardenkit for that one )

 

Husky went back today. Owner very happy. Next saw should be a 026 arriving any time soon.

[spudulike]

Got a Stihl backpack blower on the bench, recoil spring busted, needs a damn good clean but the compression is good, as far as the spring let me test it.

 

Got a Stihl hedge trimmer up next, will take a look at that and get an order in for parts.

 

A siezed Jonnie 2171 is also on its way.....all go as usual!

[Rich2484]

Oh. Completely forgot about the rings on the 200t piston.

 

Did a check on them today.

 

The top rings was 1.67mm on the "open" end. And 1.53mm on the back side or exhaust side. It's something I should have known to check and have been taught to check and measure but just didn't as the piston looked fine. Not sure what the measurement should be but the taken measurements tell a monkey that the rings where worn out.

[GardenKit]

I have recently had a Mtox saw in for service. Now, I sold this one a couple of years ago to a local log merchant. He needed a large saw quickly, to replace a totally shot Stihl, but at the time did not want to spend too much.

Neither of us really expected too much from this 60cc 20" saw, for £269, but he has now got through 4 chains and is chuffed to bits with it. It always starts well, cuts well, and has been 100% reliable ( well, except for a sticky recoil)

 

I just serviced it and was amazed by its condition. An unworn clutch, no broken plastics and best of all, not one loose screw or bolt.

 

Chinese?, yes. Rubbish? certainly not.

 

 

[GardenKit]

This horrible mess came in today in a Mountfield mower.

 

The carb had a long hot bath in the US cleaner, the tank was flushed and all is now OK.

 

It could have been avoided by good fuel management, ..........or by using.........(who can finish this sentence?)