Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Husqvarna => Topic started by: KilliansRedLeo on May 05, 2014, 05:28:21 pm

Title: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 05, 2014, 05:28:21 pm
There was a thread up here somewhere where Spike60 made mention of a potential difference in deck height between a set of 372XP carankcase and an 372XT crankcase. Well I cannot find it. What Spike60 mentioned was that you could put an XP top end on the XT cases but not the opposite. Inferring that the XT case had a higher deck than the XP crankcase. Does anyone know if there actually is a difference.

Here is the reason I ask. Weimedog and I are toying around with using a 272XP piston in a 372BB kit. The 272 piston is shorter overall but quite a bit taller in compression height than the stock 372XP piston. Talking to Weimedog we were thinking that we might be able to use a 272XP piston in the BB kit and get two advantages out of the piston. Increased compression because of the increase in Compression Height and a change in intake timing because of the shorter overall height. The only problem with this train of thought is that because of the difference in compression height you would have to use two or more base gaskets.

However if the deck height of the 372XT is truely higher than the 372XP them perhaps one could get away with a single base gasket or no base gasket. If anyone knows the answer to this let me know. I have 372XP cases floating around and already know you cannot put the 272XP piston in the saw using a pair of XP cases without using three standard base gaskets. However I do not have a set of XT cases to try, so am asking the questions to avoid buying a set of XT cases.

Here are the specs from Meteor on the stock 372XP piston

Brand HUSQVARNA
Motor Chainsaw mod. 371 - 372 XP
Piston 1725
Diam 50.00
Compression 22.50
Head P
Length 42.50
Pin 12 X 36 X 8

Here are the specs from Meteor on the stock 272XP piston

Brand HUSQVARNA
Piston 2061
Diam 52.00
Compression 24.00
Head P
Length 40.50
Pin 12 X 33 X 8
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 05, 2014, 05:45:29 pm
From looking at IPLs it appears that at one time there MAY have been a different case used on the 372XT. The earliest IPL I could find lists a different CC part number for the XT than the XP. See below, the first entry is from the earliest IPL for the XT the second and third parts are for the later XT and the XP, which show the same part number.

Husqvarna 503626808 (replaces 503626876) RP CRANKCASE

Husqvarna 503626808 CRANKCASE ASSY

Husqvarna 503626808 CRANKCASE ASSY

It also appears that the XT C/P kit has changed part numbers, see below perhaps indicating a change

 Husqvarna 575255702 (replaces 575255701) RP CYLINDER ASSY

Husqvarna 575255702 CYLINDER ASSY

I cannot find an IPL for the 365XT so perhaps the earliest IPL was actually for the 365XT!
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: 660magnum on May 05, 2014, 08:08:21 pm
Troll brought up the fact a while back, that  IPL's, replacement OEM, & "as built" may not match?

I was messing with a 111 Dolmar and if you've seen several different years of these, you have noticed differences. You can see this on the IPL's if you have the real examples to help you out. You certainly can not go by what the sellers on Ebay say!

The 371 cylinder and clutch bell are different from the the 372. Either part will fit either saw but they are different.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: Reddog on May 05, 2014, 10:48:39 pm
Here was the info.

I've never had the need to mess with one of those impulse pipes myself. But you'd think that there would be instances where someone might need to order that as a spare part.

One thing to add here regarding cases is that there is a difference between the originals vs the new X-torq models. The skirt on the bottom of the XT cylinders is deeper than the originals, so the corresponding cut in the XT cases is also deeper. If putting an original jug on an XT case, you will have no problem. But you cannot put an XT cylinder on the original case. (unless you do some grinding) As far as deck height, I really can't say.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 06, 2014, 06:03:05 am
Thank you Reddog! What I was thinking was that if the deck height was higher in the XT case that might allow the use of the 272 piston without the need for a stack of base gaskets. Oh well, perhaps a spacer out of copper shim stock.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: SawTroll on May 06, 2014, 09:04:24 am
Here was the info.

I've never had the need to mess with one of those impulse pipes myself. But you'd think that there would be instances where someone might need to order that as a spare part.

One thing to add here regarding cases is that there is a difference between the originals vs the new X-torq models. The skirt on the bottom of the XT cylinders is deeper than the originals, so the corresponding cut in the XT cases is also deeper. If putting an original jug on an XT case, you will have no problem. But you cannot put an XT cylinder on the original case. (unless you do some grinding) As far as deck height, I really can't say.

That isn't about deck height, as I read it, but about the cutouts for the cylinder "skirt" (going below deck height).
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: farmboy on May 06, 2014, 09:10:22 am

I cannot find an IPL for the 365XT so perhaps the earliest IPL was actually for the 365XT!
I couldn't find one either.  Although I haven't looked on HVA manuals.  I use the 372XT IPL.  The starter cover decal and the transfer covers are the only difference.
Here was the info.

I've never had the need to mess with one of those impulse pipes myself. But you'd think that there would be instances where someone might need to order that as a spare part.

One thing to add here regarding cases is that there is a difference between the originals vs the new X-torq models. The skirt on the bottom of the XT cylinders is deeper than the originals, so the corresponding cut in the XT cases is also deeper. If putting an original jug on an XT case, you will have no problem. But you cannot put an XT cylinder on the original case. (unless you do some grinding) As far as deck height, I really can't say.

That isn't about deck height, as I read it, but about the cutouts for the cylinder "skirt" (going below deck height).
That is the difference.  Cylinder skirts are longer on XT cyl.  I use a reg 372XP CC for case matching.
Shep
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 06, 2014, 09:18:30 am
Spike does mention deck height, that is what I remembered but he says that he doesn't know about differences between XP & XT crankcases. What I was thinking was that if the deck height was higher in the XT case that might allow the use of the 272 piston without the need for a stack of base gaskets. Oh well, perhaps a spacer out of copper shim stock. The 272XP piston is just too tall to use in the Hyway BB kits for a 372 without a bunch of base gaskets.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 06, 2014, 01:14:36 pm
I just put a mako 272 and Jinhua piston together with the wrist pin. was approx. .052 difference in crown height. If the cylinder is like the last one..... big if....  with no base gasket it was .032 squish. So one base gasket would get me to that .052!  A .040 gasket/shim is needed to get that 272 piston to .020 squish.. So there is hope. On the other end there is approx. .115 in difference in skirt height. that translates between 5 and 6 degrees difference on intake timing. Take a gasket moving the cylinder up .040 or loosing a couple of degrees and we are in the ball park. 76- 2 (gaskets)= 74 degrees...then with the .115 in shorter skirt, approx. 6 degrees... that a net 80 degrees btdc. So net net net the other cylinder & piston & .020 stock gasket had .052 squish & approx. 75 degrees btdc....  With the 272 Mako piston & .040 gasket/shim? looks like it might end up close to 80 degrees btdc intake timing and .020 squish.  Of course the other differences would be the windowed piston & change in exhaust & transfer timing, but no change to its large 27 degree blow down ... maybe cutting some material at the base of the transfers,( the cylinder wall away). Might make a mess but also might be an interesting build.

Also did the same thing with a Stihl (Meteor am) 064 piston with interesting results! Only .010 more distance to the crown but the piston skirt was actually longer than the Jinhua piston.....buy .010 Real interesting.. Maybe those Jinhua Farmertec folks know what they are doing? Going by the "old Jinhua (Huztl saw) cylinder, that .010 would in fact get me to .020 squish and it would be easy to grind the intake port lower to get the intake closer to where we want... I think an easier path to an interesting AM build. And the Stihl (Meteor) is also a windowed piston. Also have a X-torq carb, those things along with a muffler with a 3/4 inch pipe should run well. And Loud!

Am I way off???

But back to the 350 build. (modified transfers (hogged out dividers on the vertical section & matched the lower to look like a 346xp both on bearing cap& cylinder), muffler mod, intake lowered, 357xp carb & intake tract. )

Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 06, 2014, 02:45:32 pm
Well, the reasoning on using the 064 piston in a 52mm  BB kit was nearly the same I had for using the 064 piston on the first one I did. I could have lowered the intake but I was after, 'no grinding required'. That is also why the 272 piston is still on my mind. The 'IF' you mention is a really big one, I've seen as much as 0.015 difference in squish between two cylinders from the same vendor, on the same saw! I do mean 'the same saw' put one jug on, measure squish, then put a different one on and measure again!

Post pictures and results on the 350 when it i done. Your 372 chain brake parts go out in tomorrow AM mail.

Cheers!
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 06, 2014, 03:16:41 pm
Question is if its harder to build a .040 shim or lower the intake? AND what happens to the transfer & exhaust timing by raising the cylinder .040? Not certain at that point in rotation of the crank & location of the piston how much difference the .040 lift will make. I also think there is ground to be tilled because of the windowed piston, both on the 064 and the 272 piston designed for those older two transfer port designed cylinders. But that too would require grinding the 372 cylinder some to open up the bottom of the transfers. Of course trimming the skirt on the Stihl piston is an option,just I hate doing that for a whole variety of reasons.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 06, 2014, 04:59:52 pm
In my old age, my eyesight is not what it used to be, so making a shim is easier for me than detail grinding in the cylinder because I made a jig out of a trashed (white death) pair of 372 cases. I have a very small router that I use with a spiral carbide cutter (it is used for inlay cutting in furniture making) that has a bottom bearing that will follow the case without damaging the case and cut out the shim. I have used it on copper shim stock up to 0.060 and aluminum up to 0.080.  The port timing is difficult to measure, I have thought more that once about cutting the top off a cylinder to try to make it easier to make those kinds of measurements but have never gotten around to it.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 06, 2014, 05:28:38 pm
Can rough measure with a wire through the exhaust port. Measure the wire first of course! Then adjust what you get with the wire by the number of degree's it takes to rotate the piston that distance of the wire thickness. Not perfect but can ball park the numbers. Easier to get good numbers on the intake side as you can see it on the 372's. (Have just the cylinder on the cases)


I'm game to try either build concept. I can approx. the .040 with 2 base gaskets and measure the port timing. But would rather use a shim & 1194 for a real running trial.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: sharkey on May 06, 2014, 06:57:52 pm
If you dont have a lathe, you guys may want to try fashioning a cylinder base cutter out of a piece of plexiglass or thin hardwood.  Something that has a flat surface.  Trace around the base of the cylinder spigot onto your flat material.  The spigot is the metal guide that sticks out of the cylinder base and fits down into the crankcase.  Cut out the hole making sure the spigot just fits and there is enough room for the ears of the cylinder.  Fix a piece of good quality sandpaper to the flat with some spray adhesive.  Cut out the sandpaper from the opposite side using a razor blade.  Fit the cylinder spigot into the hole of your flat over the paper and give it a couple twists.  It takes maybe 10 minutes to cut .015 inch off the base of your cylinder with good paper.  Check your spigot as it may also need trimmed but you can do this with a file.  You can now set your squish a little closer and still use a thin gasket.     
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 06, 2014, 07:39:13 pm
Good idea! Will give it a try in another situation. Right now we are dealing with a piston that is too tall for the jug by 1.5mm so we need to add not subtract from the jug.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 06, 2014, 09:17:44 pm

Post pictures and results on the 350 when it i done. Your 372 chain brake parts go out in tomorrow AM mail.

Cheers!

Roughed out the 350... no paint on the muffler, no polishing on the die grinder work. Just wanted to see if things would go together and work......they do. Will run it then go back and make things pretty if it runs WELL enough to be interesting....uploading a video of its guts and is first minute of run time. It needs a chain and air filter..... the air filter might be interesting... If it shows promise, then we can go back and tweakm& clean things up and make it right .. pretty as well. But for now... just proof of concept saw. I'll stick the video on youtube where my stuff usually resides on my afleetcommand channel  Its the "fugly Husqvarna 350...."
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 10, 2014, 01:22:15 pm
OK, I put together the Hyway BB piston from a 372 BB Kit and a stock Meteor 272XP piston 52mm. In the attached prictures you can see that the 272 piston is noticably taller in compression height, it is however noticably shorter in overall height 2.0mm. The BB kit piston has clipped corners on the skirt where the 272 does not. The BB piston is a semi 'full circle' design and is only 31mm at its narrowest point the 272 being a full 5mm wider. OH height of the BB kit piston is +2.0mm taller than the 272XP piston.

So what do you think? My thoughts are that we should pick up some in the intake timing and also come compression due to the taller CH. However we now have to deal with the impact of the 272 piston being a windowed design and the BB kit piston not. Howeve this is mitigated by the fact that the Stihl 064 Piston is windowed and runs fine in many of theses saws I have built.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 10, 2014, 02:35:04 pm
Test assembled the saw with no base gasket and 272 piston, runs hits cylinder top. Tried again with AM base gasket, same results. With 2 gaskets clears cylinder top but don't know by how much. 2 base gaskets are nominally 0.0343 uncompressed. So if 1 gasket is half that 0.0171 perhaps a copper shim and a single gasket. Got to take it apart and measure squish with two gaskets.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 16, 2014, 02:11:26 pm
There is some manufacturing tolerances between individual pairs of XP cases (don't have any XT cases to try). Same cylinder, same piston, same gaskets, first pair of XP cases, squish measured 0.0112. Substituted another pair of XP cases all else remained the same, squish measured 0.0153. In both cases cylinder was mounted and torqued to factory specs 10NM. Substituted a stack of gaskets from Northwoods saw squish now measures 0.025-0.028. Good enough to put the saw together and see what it does!
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: sharkey on May 16, 2014, 06:36:22 pm
Maybe a piece of soft flashing between two thin gaskets would give you the squish your looking for?  Had you posted that you had a small router that you used on the copper shims?
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 16, 2014, 09:30:01 pm
Sharkey, yes I have a small bottom bearing spiral bit used to do inlay work on furniture that will cut up to 1/8 inch soft non-ferrous metal, like brass, copper or aluminum. You can get it from www.woodcraft.com (http://www.woodcraft.com) or www.rockler.com (http://www.rockler.com). Got to get the one with the eight inch spindle so you can use it in your Dremel.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 17, 2014, 06:16:30 am
There is some manufacturing tolerances between individual pairs of XP cases (don't have any XT cases to try). Same cylinder, same piston, same gaskets, first pair of XP cases, squish measured 0.0112. Substituted another pair of XP cases all else remained the same, squish measured 0.0153. In both cases cylinder was mounted and torqued to factory specs 10NM. Substituted a stack of gaskets from Northwoods saw squish now measures 0.025-0.028. Good enough to put the saw together and see what it does!

And???

Have "critical" mass to build a compete build with the meteor 064 piston & Huztl (Looks like hyway =Jinhua FarmerTech too BTW) Got a Huztl handle today, its much upgraded from the prior one! Has the right AV spring and the throttle cable is upgraded. Better looking plastic too. Hope to build it next rainy day this coming week.

Plan to use 365 cases, plastic & intake. A 3/4 tube muffler mod. Tweak the intake timing about 2 degrees...assuming the Cylinder is the same as the last. Bring it from 76 to 78 (about .030 including the correction for the .010 longer Stihl 046 piston skirt. Also its getting s X-torq carb & Huztl "black" ignition. Should be fun.

HOPING to get my stock 365 back from a friend to build it with an OEM BB along with the same Muffler mod & intake mods. Real curios to see how that runs relative to the Jinhua / Stihl blend
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 17, 2014, 08:20:42 am
Quote
And???

Well the second set of 372 cases had a slightly higher deck height, using three gaskets I am right at 0.024 (0.023 left 0.025 right). The 272XP piston works fine with no modifications. New bearings and seals in the case, all buttoned up ready for pressure/vac test today. Have both the stock 12B and XT intake, going to start with the 12B and use the low filter and top because it is what I have. Have several mufflers already done with 0.800 ID pipe. Best you can do on the muffler mods is 7th pulse third would be better but due to the interior dimensions of the muffler 7 is the best you can do. If you reduce the depth of the muffler be 0.500 you might get to fourth order harmonic but who knows. My bet is that the 0.800 pipe is a waste but will try it and see. Guess is that 0.374-0.500 will be better.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 17, 2014, 05:14:55 pm
I'll call in a bit, winding through a bunch of stuff today. Interesting that the Huztl / Jinhua FarmerTech Muffler comes with no baffles and a .5in dia And for 13 bucks delivered..... its a great place to start. How do you figure opening size?
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 17, 2014, 05:25:07 pm
Bob (Spike 60 ) is coming up tomorrow to help with the logging work. It's a 3.25 hr drive for him! We might do some video time. I got that "Fugly 350" running a bit better. Changed out the carburetor flange, rubber "boot" inside all the intake manifold & stuff. And put a new "steel clamp" on it as well. Didn't finish the cylinder yet but it running really strong right as it is making me reluctant to fix what's not really broken, BUT wanting to complete the experiment. I sort of talked it down on the video...mainly to tease Bob as it will eat up any 350 variant I've run to this point in time. He has a 346xp top end on a Jonsered 2150 that's a favorite work saw when he comes up to break down tops. My goal is/was to have the Chinese fugly 350 match that saw. Pretty certain I accomplished that goal without going any further. I've put two days of work time on the saw dropping & topping trees, and it's a solid build...
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: KilliansRedLeo on May 23, 2014, 08:54:06 am
Walter, are you going to use the Stihl 046 piston? Was that a typo because the 046 is only 39.5mm tall, it is the 064 is 43mm tall.
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: weimedog on May 25, 2014, 01:25:18 pm
typo...:)
Title: Re: Deck Height Difference in XT Cases Versus XP Cases
Post by: Cut4fun . on November 06, 2017, 08:18:39 am
Re reading some XT XP OE NE info. TTT for those that never noticed