Husqvarna 550xp pop up

[WoodsliverDan]

So, after doing some research and not finding much on making a pop up piston for the 550xp, I have decided to make one to try and post my results. After measuring the squish, (with gasket) and finding it to be .030" I have decided to turn .030" off the base of the cylinder and .020" off the piston. This should put me right at .020" squish with gasket. I hope to have more time this week to turn the base and possibly reassemble saw for a test drive this weekend.

Edit: a little more background, I have decided to do pop up vs squish band cut due to the fact these pistons are so heavy! Figured they could use the diet??! Any ways, I think dropping the cylinder with the pop up should give me pretty good timing numbers as well..

 

[ammoaddict]

Let us know how it turns out. Did you happen to make a before video for comparison?

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[WoodsliverDan]

No, I actually got 3 of these saws in a deal and none were runners. This one is the closest to running, just had a carbon stuck ring. I can make one to stock specs and do a side by side?

 

[ammoaddict]

No, I actually got 3 of these saws in a deal and none were runners. This one is the closest to running, just had a carbon stuck ring. I can make one to stock specs and do a side by side?

That might let you know if the pop up improves it or not. I love those 550xp's but never have been able to afford one. Always something coming up that takes my money. Maybe one day if the good Lord lets me live long enough, I will have one.

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[WoodsliverDan]

That might let you know if the pop up improves it or not. I love those 550xp's but never have been able to afford one. Always something coming up that takes my money. Maybe one day if the good Lord lets me live long enough, I will have one.

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Good chance I will have 1 or 2 for sale in the future! I just may make a stock one for comparison.

 

[ammoaddict]

Good chance I will have 1 or 2 for sale in the future! I just may make a stock one for comparison.

I would love to have one, but I'm on an extremely tight budget right now. Not letting me get any overtime at work.

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[ammoaddict]

Good chance I will have 1 or 2 for sale in the future! I just may make a stock one for comparison.

Keep me in mind if the Lord lays it on your heart to sell one cheap enough that I can afford.

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[WoodsliverDan]

Keep me in mind if the Lord lays it on your heart to sell one cheap enough that I can afford.

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Will do.

 

[WoodsliverDan]

So tonight at work I had a chance to turn the base on the cylinder. I took .030" off both the base and the cylinder skirt. I have a new piston ring and circlips ordered which should be here Friday. Stay tuned.

 

[ammoaddict]

Looks good

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[Poleman]

Dan, are you going to port this saw with the already mods you’ve done? With increased compression and porting it will be a real “Killer”!!!

 

[Termite]

I was going to say PM tlandrum on this subject. His recipe for 550 uses a pop up but you already have a plan. However, you may still want to correspond with him. I have a 2253 he did and it is very strong..

 

[WoodsliverDan]

Looks good

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Thank you!

 

[WoodsliverDan]

Dan, are you going to port this saw with the already mods you’ve done? With increased compression and porting it will be a real “Killer”!!!

I have been doing some research and bouncing ideas off a few folks. Correctly all I have in mind is taking the lower transfer bridge out. And smoothing the lower transfer area out. I haven't really seen much for exhaust and intake work. Seems they like to be right about where they are stock? They like the lower intake though I have heard. We'll see, she's not done yet

 

[WoodsliverDan]

I was going to say PM tlandrum on this subject. His recipe for 550 uses a pop up but you already have a plan. However, you may still want to correspond with him. I have a 2253 he did and it is very strong..

Maybe he will reply? I don't mind asking people for help, but don't like hounding people for their hard work findings. I like to try finding out things myself as well.

 

[blsnelling]

Be sure to bevel the outside of the cylinder skirt. I just put a 45° on it when I turn it.

 

[WoodsliverDan]

Be sure to bevel the outside of the cylinder skirt. I just put a 45° on it when I turn it.

Done.

 

[WoodsliverDan]

Suggestions on ignition timing advance?

 

[Ketchup]

Wait on the advance until you can time your cuts. You may want more porting first. Then try 2 degrees if all seems better. 1-2 more if you think it is working. Few saws need more than 8 degrees advance.
Doing everything at once creates too many variables in the recipe.
MM and timing can be sorted on the other two saws and then added to the port job once you know what works.

 

[WoodsliverDan]

Wait on the advance until you can time your cuts. You may want more porting first. Then try 2 degrees if all seems better. 1-2 more if you think it is working. Few saws need more than 8 degrees advance.
Doing everything at once creates too many variables in the recipe.
MM and timing can be sorted on the other two saws and then added to the port job once you know what works.

Yes, that's not really helpful. I'm asking if the 550xp likes timing advance or not. As in, have you tried it for this model saw?