Problem on Husqvarna 460 rancher

[Dimitrije Jovic]

Husqvarna 460 rancher when it is cold starts well but when it warms up it is very hard to start. The mechanic is going to change the carburetor and says the carburetor is the problem. The compression has not been measured, but I think it is around 6-7 bars (87-101psi). Is the problem compression or carburetor or crankshaft seals or something else??

 

[coffeebrk]

Hopefully the mechanic will look at piston and cylinder before doing anything else

 

[Dimitrije Jovic]

Hopefully the mechanic will look at piston and cylinder before doing anything else

how to check crankshaft seals. I can close the exhaust duct with a tire, but how should I close the intake part on the carburetor and what should I connect the pump to in order to create pressure in the engine?

 

[Tomos770]

how to check crankshaft seals. I can...

Jaooo Dimitrijeee...

 

[muddy42]

I would check the air filter and fuel delivery first - clean out fuel tank, check tank breather, change fuel filter etc.

But yes next as per your mechanic, I would try cleaning out the carburetor with carb cleaner and carefully reassembling with a carb kit.

If that didn't cure it I would move on to a leak test. To do this you need to remove as much casing as possible, starter rope, handle and muffler. Now you need to seal both ends of the crankcase. Generally I put the carb back on with an extra piece of rubber to block the intake area and use the muffler bolts and bits of wood to press another piece of rubber on the exhaust port. Then I pump air into the spark plug hole using a bung into an adapted/butchered spark plug. Pump up to 7 psi and look for leaks, rotate the crank. However leaks are often hard to find so I often resort to dunking the whole saw in water and looking for bubbles.

Let us know what you find.

 

[a. palmer jr.]

100 psi. is not very good compression for a piston ported engine. Works okay for a Lawn Boy, not so good for a 460 Rancher.

 

[Wood Doctor]

100 psi. is not very good compression for a piston ported engine. Works okay for a Lawn Boy, not so good for a 460 Rancher.

Agreed. at 100 psi, the top end has about had it and needs a rebuild. I'm surprised it runs at all.

 

[singinwoodwackr]

Husqvarna 460 rancher when it is cold starts well but when it warms up it is very hard to start. The mechanic is going to change the carburetor and says the carburetor is the problem. The compression has not been measured, but I think it is around 6-7 bars (87-101psi). Is the problem compression or carburetor or crankshaft seals or something else??

That is way too low for compression.

 

[a. palmer jr.]

Pro saws are a bit easier to rebuild but the 460 is do-able. I've done a few, just make sure you get it sealed up good..

 

[muddy42]

To be fair even if the compression is low, I'd still do a vac/leak test first. You need to know what you are dealing with and whether to decide with a repair - are the crankshaft seals leaking (this makes the task and tools required much harder) or was there something else that could have caused a lean?

 

[a. palmer jr.]

To be fair even if the compression is low, I'd still do a vac/leak test first. You need to know what you are dealing with and whether to decide with a repair - are the crankshaft seals leaking (this makes the task and tools required much harder) or was there something else that could have caused a lean?

When I rebuild those type of saws I always replace all the seals, it's kind of a must on homeowner type saws and since you have it all apart anyway..

 

[muddy42]

When I rebuild those type of saws I always replace all the seals, it's kind of a must on homeowner type saws and since you have it all apart anyway..

Im not yet very good at replacing seals, so if a cheap saw demonstrates a crank seal leak I sell it on for parts, being honest about what the issue is.

 

[a. palmer jr.]

Im not yet very good at replacing seals, so if a cheap saw demonstrates a crank seal leak I sell it on for parts, being honest about what the issue is.

I doubt if that's the problem, those saws have pretty good crank seals. Besides that, those crank seals are easy to install. If I had one of those engines apart I would replace the crank seals with new ones whether the old ones leaked or not.