NE 346XP - Affects of Cat Muffler & Muffler Mod - Porting & Popup To Come

[bjorn773]

107 is quite low on the exhaust. If you raise it, I wouldn't go any higher than 100. If you do so, I would raise the transfers about the same, to keep close to 25 of blowdown. 77 isn't bad on the intake. I assume this was measured after lowering the cylinder?

Now, if you just widen the ports, you will see good gains. Have you ported a saw before? If not, maybe do this in steps, and start just by widening the ports. First time through, don't touch the transfers. Eventually, you'll have to widen them towards the intake to hold the RPMs in the cut. With the single ring, you can go really wide on them.

I've been working on the ports. I'm at 102 on the exh and 125 on the trans. I left the intake alone at 77. Do you ever take into account the gasket when calculating the numbers. I notice you tend to use pretty thin gaskets. Mine is .021, so won't I gain a degree or two. Should I take that into account?

 

[blsnelling]

I've been working on the ports. I'm at 102 on the exh and 125 on the trans. I left the intake alone at 77. Do you ever take into account the gasket when calculating the numbers. I notice you tend to use pretty thin gaskets. Mine is .021, so won't I gain a degree or two. Should I take that into account?

Definately. If you were to remove the gasket entirely, you'd be about 79° on the intake. Make sure you check your squish though.

 

[TRI955]

So does that mean I have to mod the tank vent on my 346 Brad and if so how is that done?And that saw in the last vid looks alot like mine

Sorry to keep you waiting Woodyman. I've been in bed all day. I don't know if that was your saw in that vid or not. Remove the tank vent and use a drill to open up the hole in the plastic parts. I'm not sure if you need to drill down into the tank or not. If so, that'll require removing the tank. I actually left the hose off on my 372 because of vent issues.

What I did was remove the vent and drill a VERY small hole in to the tank just behind the vent filter, all has been well every since. I would not remove all the guts, it will leak fuel when turned on it's side. From what I understand, when Husky/Jonsered molds these tanks, the vent hole in the tank is very small, almost non-existant. When the saw is ported, the fuel demand goes up and the factory vent hole in the tank cannot keep up. I had no problems from the saw until after it was ported, muffler mod did not have any affect on the vent issue.


Mike

 

[blsnelling]

What I did was remove the vent and drill a VERY small hole in to the tank just behind the vent filter, all has been well every since. I would not remove all the guts, it will leak fuel when turned on it's side. From what I understand, when Husky/Jonsered molds these tanks, the vent hole in the tank is very small, almost non-existant. When the saw is ported, the fuel demand goes up and the factory vent hole in the tank cannot keep up. I had no problems from the saw until after it was ported, muffler mod did not have any affect on the vent issue.


Mike

Thanks Mike. Believe it or not, I still need to do this to my own saw

 

[TRI955]

Thanks Mike. Believe it or not, I still need to do this to my own saw

Make sure when doing this, pay attention to the angle of the drill bit, not to drill through the outside of the tank.


Mike

 

[bjorn773]

Definately. If you were to remove the gasket entirely, you'd be about 79° on the intake. Make sure you check your squish though.

My intake reading is 77 without a gasket . So with it installed I'll be around 75, correct? I can't eliminate it because I milled the cylinder with the gasket figured in to the equation. The .016" squish includes the .021 gasket. I should have milled less and used a thinner gasket. With no gasket, my piston would slam into the cylinder. Anyway, since assembled I'll be 75 on intake, should I lower it to achieve 80? Is my math correct in the exh and trans increasing with the gasket, going to 100 and 123 respectively?

 

[blsnelling]

My intake reading is 77 without a gasket . So with it installed I'll be around 75, correct? I can't eliminate it because I milled the cylinder with the gasket figured in to the equation. The .016" squish includes the .021 gasket. I should have milled less and used a thinner gasket. With no gasket, my piston would slam into the cylinder. Anyway, since assembled I'll be 75 on intake, should I lower it to achieve 80? Is my math correct in the exh and trans increasing with the gasket, going to 100 and 123 respectively?

I think you've got it right on all accounts. I would go ahead and lower the intake to 80 if it were mine. Did you widen the transfers towards the intake? That makes a big difference. You've got lots of room to play since it's a single ring piston.

 

[blsnelling]

Make sure when doing this, pay attention to the angle of the drill bit, not to drill through the outside of the tank.


Mike

That would certainly make for a bad day

 

[bjorn773]

I think you've got it right on all accounts. I would go ahead and lower the intake to 80 if it were mine. Did you widen the transfers towards the intake? That makes a big difference. You've got lots of room to play since it's a single ring piston.

Yes, the transfers have been widened toward the intake. Thanks.

 

[bjorn773]

I did some porting over lunch. My intake is at 80, exh at 100 and trans at 123. These are with the base gasket installed. A bit of bevelling and I'll be ready to assemble. Would you recommend the vent mod while the saw is apart, or wait to see if it's an issue?

 

[blsnelling]

I did some porting over lunch. My intake is at 80, exh at 100 and trans at 123. These are with the base gasket installed. A bit of bevelling and I'll be ready to assemble. Would you recommend the vent mod while the saw is apart, or wait to see if it's an issue?

Should be a screamin demon. Yes, I'd do the tank vent mod now.

 

[bjorn773]

What I did was remove the vent and drill a VERY small hole in to the tank just behind the vent filter, all has been well every since. I would not remove all the guts, it will leak fuel when turned on it's side. From what I understand, when Husky/Jonsered molds these tanks, the vent hole in the tank is very small, almost non-existant. When the saw is ported, the fuel demand goes up and the factory vent hole in the tank cannot keep up. I had no problems from the saw until after it was ported, muffler mod did not have any affect on the vent issue.


Mike

So you've just made the existing tank vent hole larger, then replaced the vent filter. The external parts are not modified, just the hole in the tank. I assume there must be at least a tiny hole there from the factory, right?

 

[blsnelling]

So you've just made the existing tank vent hole larger, then replaced the vent filter. The external parts are not modified, just the hole in the tank. I assume there must be at least a tiny hole there from the factory, right?

I understood that he drills an additional hole into the tank, underneath the vent cap/insert, but still inside the recess it covers.

 

[bjorn773]

I understood that he drills an additional hole into the tank, underneath the vent cap/insert, but still inside the recess it covers.

Is this normally an issue on the 372? I ported my 365BB last fall and haven't experienced any issues with fueling. However, I've only run a couple tanks through it. Just wondering if I should do the same to it.

 

[blsnelling]

Is this normally an issue on the 372? I ported my 365BB last fall and haven't experienced any issues with fueling. However, I've only run a couple tanks through it. Just wondering if I should do the same to it.

I nearly burnt up my 372 due to tank venting issues. I removed the tube on it and all seems well. I didn't see a blockage, but it worked.

 

[TRI955]

So you've just made the existing tank vent hole larger, then replaced the vent filter. The external parts are not modified, just the hole in the tank. I assume there must be at least a tiny hole there from the factory, right?

I understood that he drills an additional hole into the tank, underneath the vent cap/insert, but still inside the recess it covers.

Yes, you are both correct. I did nothing to the external parts.

There should be a tiny hole from the factory, but, some are too small and can't keep up with the fuel demand of a ported saw, it creates a vaccum in the tank and it cannot draw anymore fuel. If the saw was not ported, it wouldn't have ever been an issue.


Mike

 

[bjorn773]

Here is my tank with the vent plugs removed. The hole is about two inches down the narrow passage in the middle. I don't have a drill bit that will reach much less when chucked into a drill. Can I drill the aux. hole inside the outer diameter so only the outer screen covers it?

 

[TRI955]

Yes, just get down in there as far as the bit will allow, make sure to go down into the tank at an angle. Use the smallest bit possible,1/32 or so.


Mike

 

[bjorn773]

I have three drill bit sets and none go down to 1/32. Do you think 1/16 would be to big? Otherwise I can head to the hardware store.

 

[TRI955]

1/16 is kinda big IMO....


Mike