Oily residue, smoke and constant bog

[xerxes]

Hello, I have a Husky 450 that developed an intermittent problem with what seemed to be a carb issue so I replaced the carb. After the replacement, it started easily and I cut a good size log for testing and the only issue was that the idle was scary high with chain buzzing around. After making that adjustment I put the saw away for the day. The next day it started easily but the motor would not accelerate and all I can manage to get it to do is idle. When throttling up it just delivers a constant bog and the RPMs never increase. Oily residue and smoke coming from muffler. New gas filter and new gas, checked for kinked and or lines with holes or tears and not found any (maybe I missed a line problem?) to be an issue.

 

[Justin Taylor]

Muffler screen might be clogged

 

[motorhead99999]

I would say exhaust screen or air filter if you haven’t changed it. Or just extreme high levels of oil in you mixture.

 

[xerxes]

The screen is clear. I removed the muffler to check the exhaust system and that is all good. Ran with a new air filter and without any filter and as I stated, new gas mixture which I have running perfectly well in an identical saw.

 

[Brent Nowell]

Metering lever could be stuck. One that is allowing fuel to pass due to a weak spring or a blockage in the needle oriface allowing constant fuel to go through will cause this.

 

[xerxes]

I know what you are talking about. I will investigate that. Thanks

 

[Brent Nowell]

Check your primer bulb too inwhich the check is sealing for only one way operation

 

[alexcagle]

Impulse hose split or disconnected?

 

[xerxes]

good info, thanks

 

[Brushwacker]

Could your bar and chain oil be seeping in the gas somehow. I know it happens on some model saws more easily then others sometimes leaking through an oil pump diaphragm or from oil tank to the crank case. Was your old carb oily inside should of it got in your fuel tank ? Your spark plug might look oil fouled or wet oily if its entering the crankcase from the oil tank.

 

[xerxes]

I am pretty sure that bar oil is not seeping in as the color of the fuel would change and other other ways to rule that out. The plug does get fouled if I give it gas but that would be expected due to the way the carb is operating. I have replaced and un-foul them repeatedly in the process of diagnosis.

 

[Huskitoter]

Could you have adjusted the low mixture screw instead of the idle screw when adjusting the idle? It would be an easy mistake to make since going richer on the low would have dropped the idle rpm's.

 

[TBS]

It's a clamshell engine so bar oil can't get into the crankcase and the gas tank is in the handle.

 

[xerxes]

There seems to be little to no effect by adjusting H & L from stop to stop. Idle adjustment works.

 

[Huskitoter]

Pull the muffler and check for scoring? Did you tune it and adjust the idle before the test cut and then it went lean?

 

[xerxes]

I did tune it prior to testing and only adjusted idle after. There is no "impulse hose" on this model but a hard line from the carb into the motor. All fuel lines seem good.

 

[user 122190]

What is your oil/gas mixture? I was running 44:1 on all my saws, and only the ms290 was having problems. It once ran fine, but the problems, similar to yours, grew steadily worse and were finally fixed when I switch to 50:1. I suspect it will run at 44:1 again, after a gallon of 50:1 is used in it.

 

[TBS]

I did tune it prior to testing and only adjusted idle after. There is no "impulse hose" on this model but a hard line from the carb into the motor. All fuel lines seem good.

I'd recheck the intake, make sure everything is tight on the cylinder, the air valve mount, and the carburetor mount.

 

[Brent Adams]

Older saws with impulse driven oiler systems would sometimes burn bar oil when a pump diaphragm or check valve went bad, but your saw has a mechanical pump if I'm not mistaken.
That limots your issue to a fuel system problem. Saw would run lean if a crank seal or other air leak had developed, so that rules out the crank seals, clamshell seal surface(if this is a clamshell saw, I dont own one), and impulse passageway. You have stated that you checked exhaust screen. Make sure the muffler isnt clogged or a baffle came loose. Once that is done, you have to go back to the carb. Check the tank vent to make sure it is functioning correctly. Should let air into tank, but not out. When you remove the cap, you shouldnt hear air suck in or vent out if its cold. Warm saw or hot outside, you could hear pressure escaping sometimes.
You,said you installed a new carb. Was it an OEM carb or a Chinese replacement? Some cheap chinese replacement carbs have quality issues.
I think I would pull tje metering chamber cover off and see if there is something holding the needle open. Maybe you got a piece of something between the needle and seat. I have a Mcculloch Pro Mac 700 that started flooding gas out yesterday when I tried usimg it. That is probably my issue. Check the needle and seat. You can use a low pressure guage with a small pump and a line hooked to the fuel inlet to see if the needle is holding pressure. Not sure what pressure that one is supposed to pop off at, but someone on here knows.

 

[xerxes]

This saw is no more than 6 years old and that may seem old but there are not a bunch of hours on it. It was a cheapo Amazon chineseum replacement. I ordered another carb and should have it today. There are no obstructions in the exhaust and there is plenty of smoke to go along with the poor performance. Does the tank vent back into the carb?