Husqvarna 435 Idle Problem

[JCarter]

Hi,

I have a Husqvarna 435 that has had a lot of use. I am having an issue with the idle and wondering if anyone has any advice. Here's the basics:
- Idle seems erratic. Sometimes takes a long time to go down to idle speed where the chain stops moving.
- It's common for the motor to cut out after a little while once it has finally gotten down to the low idle.
- Motor cutting out seems to be more common if I am moving or tilting the chainsaw when it is idling.
- I have replaced the carburetor, pipe inlet, air filter, spark plug, fuel filter and made the most precise mixture of 50:1 gas that I've ever done.
- When I try to tune up the carburetor I feel like I'm losing my mind. Although this is the first chainsaw I've ever tried to tune, I'm starting with the default carb settings, but in the process of tuning the parameters seem to keep changing and it seems like the gas/air amounts have a mind of their own. I am able to tune it to a point that basically replicates the condition it was in before swapping out the parts.
- The idle adjustment doesn't help because in order for it to not cut out the idle speed has to be high enough that the chain is moving fast during idle.
- Engine seems good when cutting and I'm still able to use the chainsaw if I have a lot of patience to basically wait for it to idle down after a cut, and restart it about 30% of the time between cuts (no fun).
- I am about to poke around the fuel tank and check the valve and fuel lines - but like all of this I'm not exactly sure what I'm doing.

Any thoughts or guidance would be appreciated.

 

[Vintage Engine Repairs]

Hey mate, It’s lean, it is likely an air leak (probably the crank seals). Don’t run the saw until you’ve fixed it or you can damage the saw.

Don’t replace any more parts until you have done a pressure and vacuum test, found the leak and fixed it. If you don’t have a tester, buy one, because unlike the parts you’ve replaced already this is worth doing!

You can buy one on eBay pretty cheap, just ensure it does both pressure and vacuum. Watch a few videos on how to do it and you’ll be there before you know it!

Edit to update: Your post should be made a sticky, because it lists about every possible symptom of a lean saw and could be good for others to check theirs against

Warm regards, Tom

 

[cuinrearview]

Classic air leak symptoms.

 

[cranman1951]

Harbor Freight has the Minivac pressure tester for about 35 dollars, or a cheaper Pittsburg one for mid twenties. I made a pressure tester from the Minivac and took an old compression tester and modified it to be able to pressurize from the spark plug.

 

[JCarter]

Thanks all for the input so far - I will explore this route. I'm a little confused with my options in buying a cheap pressure/vacuum tool. The cheapest one that I could find was the Mityvac MV8255 for around $50 - it's hard for me to figure out if cheaper options will work for both pressure and vacuum. If anyone has any suggestions or opinions on something other (and preferably cheaper) than the MV8255 it'd be great to hear.

Also with my chainsaw's condition I'm wondering if the change in idle speed caused by the orientation of the saw points to anything more specific? I was trying to tune it again today (couldn't resist) and when I put the saw vertical it instantly changed the RPMs.

 

[Vintage Engine Repairs]

Thanks all for the input so far - I will explore this route. I'm a little confused with my options in buying a cheap pressure/vacuum tool. The cheapest one that I could find was the Mityvac MV8255 for around $50 - it's hard for me to figure out if cheaper options will work for both pressure and vacuum. If anyone has any suggestions or opinions on something other (and preferably cheaper) than the MV8255 it'd be great to hear.

Also with my chainsaw's condition I'm wondering if the change in idle speed caused by the orientation of the saw points to anything more specific? I was trying to tune it again today (couldn't resist) and when I put the saw vertical it instantly changed the RPMs.

A saw even without any leaks can dip or raise in revs with a change in orientation. It could be as simple as some fuel pooling and being released. Honestly don’t start it until it’s fixed, you are asking for a scored piston and cylinder and many hundreds of dollars fixing it, not to mention time.

https://www.ebay.com.au/itm/Hand-He...41c083b1299d89026bea|ampid:PL_CLK|clp:2334524

 

[JCarter]

I assembled the tools and did a pressure check today and found air passing with no problem through the clutch seal. I ordered a new one (as well as a new flywheel seal) but have a question in advance on reassembling.

Should I apply gasket maker to any areas when I put it back together? The gasket on the piston cylinder looks good and there's no evidence of a gasket anywhere else by the crankshaft. Should the new seals be enough or should I reinforce with some gasket maker?