Algee

[Algee]

Hi, I have a Mac cat839, about 20 years old but only done around 30 hours work. I can't get it to start.

I have rebuilt the Walbro carb with new diaphragms etc, but still won't start.

I can get it to run for a second or so by squirting easy start into the air intake and I have used neat petrol with no oil in.

When it starts I get clouds of smoke even though there is no oil in the fuel. Is it possible that chain oil is leaking into the 

crank case and preventing the fuel pump from working correctly, if so is it a big job to replace the seals or pump.

its in too good a condition to dump so any guidance would be appreciated.

I look forward to hearing from anyone with an idea.

thanks and best regards

Al

 

 

[bmp01]

Here's some back ground reading for you.

https://arbtalk.co.uk/forums/topic/65438-mac-cat-839/

 

You can also use the search feature on here.

 

A couple of points and a start...:

-If isn't garbage already,  it soon will be if you run it on neat petrol and not 2 stroke mix. Google why you need 2 stroke mix.

-The easy start shows the ignition system and engine compression are probably OK, not 100% guaranteed though. 

-Smoke from a running engine is just as likely from too much fuel (as it is from oil in the fuel).

-A crude compression test - pick the saw up by the pull start cord, if it unwinds the cord quick its knackered. If it unwinds the cord slowly with a series of  resistances over 15 seconds or more your in luck. Try this with the plug out, you'll see what no compression is like.

-If you want to see if bar oil is leaking into fuel tank,  empty fuel out,  leave oil in.  See if the empty fuel tank fills with oil. 

-I'd try this,  plug out - is it wet with fuel?  Continue with the plug out,  pull the engine over dozen times with choke off and throttle open - gives it a clear out. Dry the plug and if posible warm up the sparky end with blow torch/gas hob. Drop a couple of cc's of fuel mix down the plug hole, fit the hot plug in a hurry and see if it goes (without choke). You can do this over a few times if you want but if it won't run like this for a second or 2 it could be back to the hand saw time. 

 

Good luck.