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husqvarna 350 spewing fuel out of intake when runniNG


cameroncrofter
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9 hours ago, cameroncrofter said:

Tried with h screw all the way in and slowly turning out 1/4 a turn at a time and still blowing back fuel 

Not being funny but if the H screw is all the way in, you have shut off the high speed check valve and the only other way of getting fuel in to the engine is through the low speed jets and these won't support combustion past 1/3rd throttle. Could the carb casting be cracked?

It is also possible you have two carbs with shot high speed check valves but it is extremely rare especially on a new carb. Can you try these carbs on another 350?

When you take the choke off, is the choke valve completely horizontal in the carb bore? I have seen some carbs get stuck with the choke in a half closed position causing this sort of issue.

One other thing on top of the air leak issues I have already mentioned...the rubber manifolds on these saws, as well as 346, 357 etc are often fitted badly and have a deformed or split impulse connector and will cause over revving. 

Have you popped the muffler off to check the state of the piston? If it has seized but the ring is free, it is possible the inlet skirt is shot and that is causing free porting.

BTW....I trust your comment above isn't being a bit glib....you have the benefit of the machine being in front of you!

 

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7 hours ago, spudulike said:

Not being funny but if the H screw is all the way in, you have shut off the high speed check valve and the only other way of getting fuel in to the engine is through the low speed jets and these won't support combustion past 1/3rd throttle. Could the carb casting be cracked?

It is also possible you have two carbs with shot high speed check valves but it is extremely rare especially on a new carb. Can you try these carbs on another 350?

When you take the choke off, is the choke valve completely horizontal in the carb bore? I have seen some carbs get stuck with the choke in a half closed position causing this sort of issue.

One other thing on top of the air leak issues I have already mentioned...the rubber manifolds on these saws, as well as 346, 357 etc are often fitted badly and have a deformed or split impulse connector and will cause over revving. 

Have you popped the muffler off to check the state of the piston? If it has seized but the ring is free, it is possible the inlet skirt is shot and that is causing free porting.

BTW....I trust your comment above isn't being a bit glib....you have the benefit of the machine being in front of you!

 

 

7 hours ago, spudulike said:

Not being funny but if the H screw is all the way in, you have shut off the high speed check valve and the only other way of getting fuel in to the engine is through the low speed jets and these won't support combustion past 1/3rd throttle. Could the carb casting be cracked?

It is also possible you have two carbs with shot high speed check valves but it is extremely rare especially on a new carb. Can you try these carbs on another 350?

When you take the choke off, is the choke valve completely horizontal in the carb bore? I have seen some carbs get stuck with the choke in a half closed position causing this sort of issue.

One other thing on top of the air leak issues I have already mentioned...the rubber manifolds on these saws, as well as 346, 357 etc are often fitted badly and have a deformed or split impulse connector and will cause over revving. 

Have you popped the muffler off to check the state of the piston? If it has seized but the ring is free, it is possible the inlet skirt is shot and that is causing free porting.

BTW....I trust your comment above isn't being a bit glib....you have the benefit of the machine being in front of you!

 

Just took it apart and think I’m going to just put a new piston and cylinder on it 

 

many advice on revoking old piston  are installing new one ? Thank you for or the help so far 🙏

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The piston has had a light seize that can be seen from the exhaust side. If the cylinder is an original Husqvarna one, I would rub the inner bore with a bit of 400 grit emery and fit a new quality piston but that may be an issue getting hold of one. The bore doesn't look too bad from what I can see.

Many of these cheap cylinder kits are a bit suspect Meteor and Hyway are about the best.

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I have looked at this again....

1) When you rotate the flywheel, there is a noticeable "clunk" every time you move it...any idea what this is?

2) You talk about "Dicking" around with the carb and "That is with the L screw turned anti clockwise been tweeting both screws but can’t get it to idle nice with out bogging "....you got the saw a bit closer but what did you do to get there? What were the settings?

If I took one of these saws in good order with a good carb, I could wind the H&L scews clockwise so they were lightly seated and then undo them 1 &1/4 turns and the saw would 100% run OK and all I would need to do is to adjust the idle. If you can't do this, something is wrong.

Going back to the saw, if you take the piston off, take the ring off and push it in to the bore so it sits in the first part of the bore in its normal position at the bottom of the stroke, can you get much movement on the piston when rocking  it from the exhaust side to the inlet side? You can just measure it with verniers across the skirts but am guessing you don't have any.

Personally, I would whip off the upper crankcase alloy casting, clean it and reseal with a LOT of liquid gasket as the lower plastic cases on these machines often leak on this join.

Have you inspected the inlet manifold for splits? These often get fitted badly (you must separate the rubber part from the clamp and fit to the cylinder correctly before fitting the clamp and THEN refiting the cylinder. Look for a deformed or split impulse connector as in my image below. The yellow line shows where they often split.

Air leaks will cause the racing top end and the bogging but not the over fuelling. The carb you are using looks OEM unless you have swapped the diaphragm cover out. Over fuelling would normally be caused by the H screw being too far out from seated, 2-3 turns or more, or a faulty high speed check valve but this is rare and the machine would tend to rev out OK but idle would be near impossible and it may do what you are getting. 

If your carb is OEM and BRAND NEW, the check valve is very unlikely to be faulty.

 

Manifold.jpg.9df888e56ae9b2abf8c27d678ec3c784.jpg

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