Ms 440 air leak

[Lumberwolf]

So I pulled an old 440 out the shed the other day and put new crank seals in it. I didn't think this would solve the problem and it hasn't. It's racing on and then dying after revving. I haven't checked the manifold and impulse line yet but should that be my next port of call. Oh, cylinder head bearings are tight.

[peatff]

What are cylinder head bearings please ?

[Lumberwolf]

Haha oops. Sorry. Kids were talking to me at the same time. Bolts!! I meant bolts. 😳

[spudulike]

Make sure the crank seals havent deformed around thier sealing rim against the crank - easy to do when fitting - need to wiggle a little over the ridges!

 

Other than that - impulse line, split inlet manifold, L screw running lean or the throttle rod is being held open somehow - perhaps catching on the petrol line!

 

Also check both internal sleeve and outer sleeve are on the manifold where it seals against the carb.

 

DO NOT RUN at speed as it is - if alll else fails, get it pressure and vac checked - also check the decomp valve is closing OK!

[Lumberwolf]

Thanks spud. Definitely not the decomp valve and the seals went in nicely. It was much easier to take the old ones out and put new ones in than I thought it was going to be. I'll go for a new impulse line and manifold next. They're old and will probably need replaced anyway. Aye the good guy at the local fixers said he'll pressure and vac test it for me if I'm still having problems.

[wisecobandit]

And don't forget to check the fuel line. They tend to go first off.

[spudulike]

Thanks spud. Definitely not the decomp valve and the seals went in nicely. It was much easier to take the old ones out and put new ones in than I thought it was going to be. I'll go for a new impulse line and manifold next. They're old and will probably need replaced anyway. Aye the good guy at the local fixers said he'll pressure and vac test it for me if I'm still having problems.

 

Those two tests have saved me hours of work on many saws and have saved many saws from early demise by finding many seals on the edge of a bad leak.

 

Goodluck

[Lumberwolf]

Thanks chaps. I appreciate it 👍