What's on your bench today?

[spudulike]

Had an MS200T back in after refurbing and porting it. Symptoms were down on power and a strange flubbing noise when running. A different carb hadn't resolved the issue but was not convinced it wasn't a fuel issue.

 

When I was cleaning the carb, I thought I would check the plug colour, I hadn't changed it as it was near new and looking at the central electrode, it looked a bit......long:confused1:

 

I went to adjust it and the electrode dropped.......the damn thing was loose so the plug was replaced with a nice NGK one - the original was a cheapo Rockwood Chinese one - Crap!

 

Carb was rebuilt and bingo, full power again:thumbup:

[wisecobandit]

Ive been quiet as been a bit hectic.

Lots of strimmers tho and literally everyone a carb issue.

An ms250 with bad impulse line

Started to build up a new ms660 all from new spare parts. Almost done!

 

Interestingly Ive had 2 engines to rebuild side by side. One a 2006 and one a 2011 fs55 engine. The later being the 2-mix. (the same as used in the fs/km 56)

Now I expected the difference in pot and piston on the strato 2-mix engine but nothings the same. The conrods on the crank are different lengths, the bore diameters are the same but obviously ported much differently, 2-mix uses 1 piston ring (thinner) earlier uses 2 thicker rings. The flywheels use the same part number yet coils are different also and altho fitment is the same the timing isnt.

[Dinosaw]

Hi Chaps

I have a chum's 435 in which I have replaced a scored piston. Pressure and vac checks ok, it starts after priming the bulb but won't run. Have fitted new carb kit from Hugo without improvement. Fuel inlet clear when carb dismantled but if I pressurise it after assembly there is no drop in pressure if I pull the saw over. Impulse is not blocked. Any suggestions? This could get you a splined screwdriver for Christmas, Spud!

[wisecobandit]

Hi Chaps

I have a chum's 435 in which I have replaced a scored piston. Pressure and vac checks ok, it starts after priming the bulb but won't run. Have fitted new carb kit from Hugo without improvement. Fuel inlet clear when carb dismantled but if I pressurise it after assembly there is no drop in pressure if I pull the saw over. Impulse is not blocked. Any suggestions? This could get you a splined screwdriver for Christmas, Spud!

 

Sounds carb related.

Did you remove, clean and renew welch plugs or was it just the diaphragms you replaced?

After its started and stalled pull the plug to see if its dry to give the game away.

The other obvious assumption but best to ask the l and h screws have been reset to factory positions?

[Dinosaw]

Definitely carb related. Plug dry. Changed diaphragms and needle valve but did not replace welch plugs. Internal filter clean. Carb cleaner coming out of all the right holes. H and L screws set to the rather strange factory settings of 2 and 2and1/2 turns. Just behaving as if no fuel is getting in. Hoses checked no leaks. Checked all diaphragms in correctly??

[spudulike]

Worth checking the orientation of the soccer between the diaphragm and carb body and also the pumping diaphragm and spacer gasket. The thin polyester pumping gasket should be next to the carb body.

 

Also worth checking the carb holds pressure when lumped against the fuel inlet.

Good luck

[wisecobandit]

Definitely carb related. Plug dry. Changed diaphragms and needle valve but did not replace welch plugs. Internal filter clean. Carb cleaner coming out of all the right holes. H and L screws set to the rather strange factory settings of 2 and 2and1/2 turns. Just behaving as if no fuel is getting in. Hoses checked no leaks. Checked all diaphragms in correctly??

 

Yeah that's the same settings as I have for that saw.

Sometimes you can get a build up of crud under the welch plug but it is quite rare.

How does the pressure feel in the primer bulb once the saw has run? Does it feel that it needs pumping back up again as it has air in there? Certainly in some stihl carbs they have a check valve (small 1 way valve) which when they fail they will allow air back into the system which give symptoms similar to what you have but husqvarnas don't normally suffer as its normally zama carbs. Do you know what carb it has fitted which is normally somewhere on the carb housing?

Also last but not least you have got the primer hoses fitted right as the primer bulb is also basically a one way valve.

[Dinosaw]

Hi You Two! Don't know if Spud's been on the cizzer but I don't know what a soccer or lumped means! The ipl I looked at shows the thick gasket between the pumping diaphragm and the carb body. Primer hoses are the right way round and no problem with the bulb ( tested with finger over inlet and outlet). Carb is Zama EL41A O2A. Thanks for helping out!

[Dinosaw]

Oh Spud, If Lumped means pumped, yes it holds lots of pressure but it doesn't reduce when the engine is pulled over which it should ( I think) when the impulse pressure is working.

[spudulike]

Hi You Two! Don't know if Spud's been on the cizzer but I don't know what a soccer or lumped means! The ipl I looked at shows the thick gasket between the pumping diaphragm and the carb body. Primer hoses are the right way round and no problem with the bulb ( tested with finger over inlet and outlet). Carb is Zama EL41A O2A. Thanks for helping out!

 

 

Soccer is spacer, lumped is pumped, bloody predictive text is not very predictive