Husqvarna 455 Rancher

[TommyT315]

I’m at a loss, can anyone help?
I have a Husqvarna 455 Rancher that is dying after two or three minutes on medium to high throttle. 
I have done the following to it:
New piston & cylinder
New crankshaft seals
New bearings
New muffler
New carb diaphragms
New fuel lines
New tank vent
I also tried a brand new replacement carb. 
It was first run with a full tank of fuel at idle so the new piston wasn’t damaged. 
It will run all day on idle. It only dies after revving it for two or three minutes. Once it stops I found that if I open the fuel cap and then close it again it will run again for two or three minutes. 
Any advice will be much appreciated as this saw is driving me bonkers.

[Stubby]

11 minutes ago, TommyT315 said:

I’m at a loss, can anyone help?
I have a Husqvarna 455 Rancher that is dying after two or three minutes on medium to high throttle. 
I have done the following to it:
New piston & cylinder
New crankshaft seals
New bearings
New muffler
New carb diaphragms
New fuel lines
New tank vent
I also tried a brand new replacement carb. 
It was first run with a full tank of fuel at idle so the new piston wasn’t damaged. 
It will run all day on idle. It only dies after revving it for two or three minutes. Once it stops I found that if I open the fuel cap and then close it again it will run again for two or three minutes. 
Any advice will be much appreciated as this saw is driving me bonkers.

You say you have replaced the tank vent , but , it does sound like its pulling a vacuum . Is there any way you can remove the tank vent , half fill it and run it upright for a while just cross cutting and see if that cures it ?

[Dan Maynard]

You haven't listed spark plug but you must have changed it?

[TommyT315]

I think it has to be a vapor lock as it runs again as normal for 2-3 mins when undoing the fuel cap. 

Have tried changing the spark plug, and have also sprayed wd40 to see if the carb is leaking air but it’s not. 

Will half fill it and remove the tank vent as suggested and see if that is the issue. 

It is a brand new vent but I suppose that it could be a bad one from a bad batch. 

Thanks for any of the ideas to fix it. 

[spudulike]

Sounds like you have replaced most of the saw, costing ££££ when giving it to someone with the right skill-set may have given you an answer for less cost.

That being said, if the tank is venting and has been vacuum tested then I would suggest the impulse circuit is faulty, the pump section of the carb isn't working correctly or there is some sort of blockage from the fuel filter to the carb. 

It sounds like the saw is getting enough fuel to idle but anything more is an issue but isn't always easy to tell without seeing the issue.

 

[TommyT315]

I bought the saw as a non runner needing a new piston cylinder & muffler. 

Was wanting it as a keeper but have been chasing my rear end with this issue. 

Will try the tank vent first, then the impulse line after that as I’ve tried a brand new carb but still doing the exact same thing. 

[GilesO]

I had exactly the same and the problem baffled far greater minds than mine- it was the ignition coil in the end. I put a new one one and all was A1 straight away although the greater minds couldn't explain why as the old coil was still putting out a spark and all thought it was fuel/tank/ vents/ carbs etc as that was what all the symptoms pointed too.

[TommyT315]

Wow, I wouldn’t have thought that as mine has a great spark and actually starts superbly. 

Does anyone on this site know how to properly test a coil to see if it could be this without having to go and purchase a coil?

 

thanks for your reply Giles

[billpierce]

Wow, I wouldn’t have thought that as mine has a great spark and actually starts superbly. 
Does anyone on this site know how to properly test a coil to see if it could be this without having to go and purchase a coil?
 
thanks for your reply Giles

Ideally you could just borrow a known good one. I had a bother with a saw and the spark seemed good but just went weak sometimes. I guess you could wait til it stops working, pull the plug and check spark then.

[Stubby]

7 minutes ago, TommyT315 said:

Wow, I wouldn’t have thought that as mine has a great spark and actually starts superbly. 

Does anyone on this site know how to properly test a coil to see if it could be this without having to go and purchase a coil?

 

thanks for your reply Giles

Some times they appear to have a good spark  and will even spark under compression until it gets warm and then they fail .   Can you borrow a known good one from any one ?     Just piped me to it Bill !

Edited October 26, 2018 by Stubby