395 xp big bore porting

[stuh]

Hi guys, new here. Im wanting to port a 395xp with a big bore kit. The saw needed a freshen up so thought I'd do a bit of port work. I've done smaller saws but not this size before.

Wondering if anyone has some numbers that will make a good work saw? Will be doing a muffler mod too

Thanks,
Stu from New Zealand

 

[farminkarman]

Hi guys, new here. Im wanting to port a 395xp with a big bore kit. The saw needed a freshen up so thought I'd do a bit of port work. I've done smaller saws but not this size before.

Wondering if anyone has some numbers that will make a good work saw? Will be doing a muffler mod too

Thanks,
Stu from New Zealand

Just curious, is the 395xp a Husqvarna saw or a clone?

 

[stuh]

It's a Husqvarna

 

[farminkarman]

It's a Husqvarna

Ok, was the OEM cylinder still good?

 

[stuh]

Yes the cylinder is still good, would it be better to use that rather than the bb cylinder

 

[farminkarman]

Yes the cylinder is still good, would it be better to use that rather than the bb cylinder

If you want to just get some practice on the BB cylinder, that would make sense. But then I would go and port the OEM cylinder if you want it to run well. Some generic numbers for a 395xp would be EX: 100, TR: 120; IN: 80. They like some timing advance too. If you want the saw to be more of a stump puller, then keep the exhaust & transfers a couple degrees lower. If you want it faster, then raise the exhaust & transfers a couple degrees. The lower transfers are pretty small on a 395 and need to be opened up a bit as well.

 

[stuh]

Awesome thankyou, I've just been looking at the differences between the bb and OEM cylinders. The big bore has very small transfers compared to the OEM. Makes me think the bb will just be for practice

 

[farminkarman]

Awesome thankyou, I've just been looking at the differences between the bb and OEM cylinders. The big bore has very small transfers compared to the OEM. Makes me think the bb will just be for practice

In order to make room for the bigger bore, they have to infringe on the transfer tunnels. Kinda defeats the point of having more swept volume.

 

[stuh]

Yeah wondered if that was why. Will it do any harm to widen the lowers a bit and extend down towards the base? I don't have a 90* tool to play with the upper transfers yet

 

[farminkarman]

Yeah wondered if that was why. Will it do any harm to widen the lowers a bit and extend down towards the base? I don't have a 90* tool to play with the upper transfers yet

I widen the lowers and thin the divider.

 

[stuh]

Cool. I'll get some stock numbers after work and see what you think of them

 

[Powerstroke Cowboy]

A little more blowdown will raise case compression and help get the air through the transfers of the BB. More like a dolkita 7900. Their transfers are a little smaller and they have more blowdown.

If the BB is just for testing try this and see what you think.

 

[stuh]

Here's the numbers for the bb no base gasket

Intake 102* abdc open for 152*
Exhaust 118* atdc open for 140*
Transfers 129 atdc
Squish 40 thou

OEM ,no base gasket

Intake 102 abdc duration 152
Exhaust 103 atdc duration 150
Transfers. 123 atdc
Squish 30 thou

A little more blowdown will raise case compression and help get the air through the transfers of the BB. More like a dolkita 7900. Their transfers are a little smaller and they have more blowdown.

If the BB is just for testing try this and see what you think.

 

[stuh]

I made a mistake there intake on both is 79* btdc and exhaust on bb is 108* atdc not 118

 

[farminkarman]

108 exhaust will suck on a 395…speaking from personal experience. But if you raise it up to 100, and don’t have a way to raise the transfers, you will have too much blowdown. It might cut fast in a small log I suppose, but probably wouldn’t be good for long bar work.

 

[stuh]

What would be ideal for blowdown? Around 25? I'll try to find a tool to do the job. Would like to do it properly and hopefully have a strong saw with a big bar

 

[farminkarman]

What would be ideal for blowdown? Around 25? I'll try to find a tool to do the job. Would like to do it properly and hopefully have a strong saw with a big bar

Somewhere in the 18-20 range.

 

[300whisper]

Following this thread because

 

[stuh]

Ok cool. If I take the transfers up to get a 20 blowdown will the longer duration matter?

 

[stuh]

Just wondering, to save some grinding on the cylinder upper transfers, could I grind a bit off the top piston edges to make transfers open sooner?