What's on your bench today?

[spudulike]

Hi Steve and Wisco

Managed to get back to the 435 again, as suggested, pulled it over on full choke 15 times without using the bulb and got fuel in both pumping and metering chambers. Fuel lines appear ok ( blow down the long one that goes to the bulb and fuel comes out of the carb fuel pipe and holds pressure if you do the same thing with your finger over the end. Seriously stuck now.......

 

In simple terms, a running engine needs Compression, spark and fuel. Life is never that simple but this has been a mantra I have used for many years.

 

When you changed the piston, did you clean ALL the transfer off the bore - have you got 145+ psi compression now?

 

Does the spark plug spark when you pull the saw over with the plug out and earthed on the cylinder - AWAY from the plug hole - the flames can be quite spectacular:001_rolleyes:

 

When you pulled over the saw on full choke, did the spark plug get wet?

 

Check the piston out as the other fella said.

 

You could try pulling off the carb and trying a bit of carb cleaner down the manifold to see if it fires!

 

It is possible the saw has flooded so pull the plug out, turn the saw upside down and pull the saw over a few times to clear the puddled fuel. If the fuel is getting through to the plug, try heating the plug up with a plumbers lamp and then pull the saw over with no choke and open the throttle fully - see if it fires.

[Eddy_t]

Rule number 1: never EVER lend saws out! Especially ported saws!

I have always been lucky until now, as far as repairs go, it has always been simple repairs, split hoses and fuel based seizes. Stupidly, work asked to borrow a big saw, so I lent my ported 385 out. Today I have received it back with the words 'it's broken, it was running and cut out' so I stripped the muffler to see if it had seized or caught a ring. The rings were perfect and the piston was clean, so I took the cylinder off and immediately found the problem. The big end has gone... Spat a bearing and killed the piston. Oddly the cylinder lives and is perfect, so I'm in the process of stripping the saw to rebuild. The reason is either poor mix or incorrect warming of the saw. To say I'm pissed off is an understatement!

[div_h]

Rule number 1: never EVER lend saws out! Especially ported saws!

I have always been lucky until now, as far as repairs go, it has always been simple repairs, split hoses and fuel based seizes. Stupidly, work asked to borrow a big saw, so I lent my ported 385 out. Today I have received it back with the words 'it's broken, it was running and cut out' so I stripped the muffler to see if it had seized or caught a ring. The rings were perfect and the piston was clean, so I took the cylinder off and immediately found the problem. The big end has gone... Spat a bearing and killed the piston. Oddly the cylinder lives and is perfect, so I'm in the process of stripping the saw to rebuild. The reason is either poor mix or incorrect warming of the saw. To say I'm pissed off is an understatement!

 

Not good I only let the old man borrow my saws, plenty have asked but they don't get them....

[wisecobandit]

Rule number 1: never EVER lend saws out! Especially ported saws!

I have always been lucky until now, as far as repairs go, it has always been simple repairs, split hoses and fuel based seizes. Stupidly, work asked to borrow a big saw, so I lent my ported 385 out. Today I have received it back with the words 'it's broken, it was running and cut out' so I stripped the muffler to see if it had seized or caught a ring. The rings were perfect and the piston was clean, so I took the cylinder off and immediately found the problem. The big end has gone... Spat a bearing and killed the piston. Oddly the cylinder lives and is perfect, so I'm in the process of stripping the saw to rebuild. The reason is either poor mix or incorrect warming of the saw. To say I'm pissed off is an understatement!

 

Eddy ive got a brand new crank here if you want to make me an offer? (got new oe seals and gasket kit to I believe)

 

Sounds more like its been over revving? Do you know what it was tached up at?

Edited October 1, 2014 by wisecobandit

[wisecobandit]

I had a good one tonight not a saw tho but basically the same!

Partner k650 disc cutter which I bought as "spares or repair" due to "overfuelling" issues.

 

So the carb was stripped and straight away my eyes popped out my head. Not only was the needle height set to the top of the carb which is about 2mm to high but also a loose welch plug that hadn't been swollen into place and to cap it off someone had actually fitted the fuel filter gauze fitted underneath it! (the welch plug)

[spudulike]

Just pulled a clean 395XP apart, it has been lightly seized so the bore has been cleaned up, piston on order and will investigate the reason for failure on rebuild.

 

Also started on a MS200T that has a poor pickup, compression is a healthy 180psi and suspect carb issues but am giving it a full strip, service and porting/muffler mod.

 

Will be good once done:thumbup:

[GardenKit]

The reason is either poor mix or incorrect warming of the saw.

 

Or, could it be that the extra bit of power and higher engine revs achieved by porting exceeded the design strength of the big end?

[Eddy_t]

Eddy ive got a brand new crank here if you want to make me an offer? (got new oe seals and gasket kit to I believe)

 

Sounds more like its been over revving? Do you know what it was tached up at?

 

 

13k rpm, this was done whilst the saw was running on aspen, I also checked it at a later time, and then before it was sent out.

 

My porting is quite conservative, especially as the cylinder is OEM.

 

You'll have to pm me a price for your crank, or I'll just offer £1! I have no idea on what to offer

[spudulike]

Or, could it be that the extra bit of power and higher engine revs achieved by porting exceeded the design strength of the big end?

 

Generally the bottom ends are the last thing to blow - most real old saws I have seen have intact bottom ends with nice tight bearings and it is the top ends that suffer.

 

I haven't seen any bottom end detonation on any of the saws I have ported and usually tune them to around 500rpm below max revs so it is probably just an unlucky fault.

 

Significantly advancing the ignition could cause issues with the ends - having heard a saw with the ignition too advanced - it sounds a little bit like a bomb ready to blow!

 

Was the ignition timing changed??

[Eddy_t]

No, no ignition advance, I learned that lesson on the 090!