Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Dolmar Makita => Topic started by: Cut4fun . on May 07, 2011, 09:18:00 am
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Have any of you guys tried putting a stihl 064 meteor or stihl 038 mag piston with pop up in 7900? Just curious, been seeing 7900 and 7901 with small spacers under base and pop up pistons in them.
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or maybe even a Wiseco 52mm piston with 1mm rings or stihl ms460.
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what would be the advantage? compression?
What was your initial feeling , buying a used saw with shims under a wrong piston?
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Never owned one and never will. I have only seen them Jeff. They were strong as get out torque wise.
Look on youtube and you will see more of them being built here and in Calif. ;)
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Guess I better clarify this. I owned a 7900 - 7901 in 07-08 that had a stock oem dolmar piston and off center pop up with finger ports DN Dave Neiger had put in. I was talking about the new stuff people are putting out there with non dolmar pistons.
For me now days Jeff I dont even want pop ups since I cant make one quickly to replace in a firewood saw.
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I looked at a lot of pistons, including the ones you mentioned. None of those made the list I kept for one reason or another. Foran OEM 7900 jug, I came up with a 272 piston which should require about a .174" spacer under the cylinder. If a 13mm wrist pin could be used, a 281 could be used with only a .095" spacer.
For the 7900BB, I only found the 288 piston, which has a 13mm wrist pin and would require a .095" spacer.
I don't recall if my calculations took into account for a popup or not. The main thing I was looking for was increased skirt width. I've not tried any of these combinations yet though.
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Guess I better clarify this. I owned a 7900 - 7901 in 07-08 that had a stock oem dolmar piston and off center pop up with finger ports DN Dave Neiger had put in. I was talking about the new stuff people are putting out there with non dolmar pistons.
For me now days Jeff I dont even want pop ups since I cant make one quickly to replace in a firewood saw.
If it's a work saw why would anybody even consider one, unless the builder is close by or your a machinist.
Now here's a something to ponder, how much better "flow" or how much more of a port is exposed so you can go lower or higher to get "gains" or how much "better" is 200lb compression vs. 160 or 180.
Percent wise I'm talking.
If you had a saw that cut 10 seconds in a given stick, what time would be the final time with all those "upgrades"?
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I just noticed this topic.
I've got a Makita 6401 that I'm putting a OEM 79cc top end on and will be porting.
And I'll be playing around with a couple different pistons, seeing which one works best
I've got a 272, 281, 046, and 064 pistions I'm just going to see dimensions if any will work.
Since the skirts are so narrow on the OEM Dolmar piston.
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The current 7900 OEM piston has no windows
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New 510-5100-5105 piston doesn't have windows either. Looks just like the "upgraded" 7900 piston. The area around the pin boss is too thin to put windows in.
Shep
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I thought the 7900 used a windowed piston for the whole time. I remember cutting scott posting about a new updated one a couple months back. I remember romeo used the 272 piston in the 7900. I haven't researched it in a long time since I sold the 2 I had.
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The one I have is a new top end and no windows in this piston, I'll post pictures tomorrow if I get a chance.
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I found the thread over there. The new updated piston has no windows.
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Anybody else heard of the Wiseco 52mm pistons being put in the hot woods ported 7900's out there. Anyone else using them?
I had heard about them being made for the 5ci builds in 52mm bore racesaws in 372xp with 2mm stroked cranks. But this is the first I have heard of a wiseco going into the 7900's.
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in 1 month I will have wide skirt pistons , skirt width of 1.66 inch in 12mm pin size but will need a spacer as they were based off of the 272 piston and with the wider skirt its easier to fit the piston into the crankcase when with a lower pin location
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Cut I pit a picture of the wide skirt 52mm piston on my site , picture is to big to post here
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Cool. Is it OK to leach your pic there and post here for other signed in members to see? I will embed it so guest cant see it. ;)
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sure go a head
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Thanks Ed. I'll let you give the info and weights etc.
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piston on left is a 7900 used piston, with ring it weighs 85.4 grams , skirt width of 32mm/ 1.260 inch
middle is the wide skirt wiseco piston, with ring it weighs 79.7 grams and has a skirt width of 1.670 /42,5mm
right piston is a stock 272 piston weight was 82.9 grams with ring , skirt width is 35.83mm/1.414 inch,
so race piston is wider and lighter and will fit the 7900/272/460 stihl , I built this piston maining for a race piston and to be run on alcohol/nitro, as you can see its coated everywhere , I also have pistons made in 60mm, 62mm, and 66mm
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Those wide skirt 52mm will go real nice in the stroked and bored 372 5 cube builds.
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8 of them have already left and I know 2 went to be in 372's for racesaws ,
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How many pistons does Wiseco require for initial order. I had been told 12 in the past and I was wondering if it might be 24 now?
How many do you order at a time to keep up with demand?
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the amount depends on what you want in a piston , my first order was 24 pistons per size but you always end up with more than you ordered , this order I got anywhere from 10 pistons to 20 pistons per size but 12 pistons is the lowest amount they want to make but if you are doing 2 different mm sizes but use the same mold they will do a 20 piston order ,
I never really tried to sell my pistons before so an order latest me quite a long time but this time I'm selling pistons of other people and they are selling very fast
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the 52mm pistons are to be used on a nikasil bore, not chrome bore as Wiseco does not make a 52mm ring to run on chrome bore , you also have to use the pin from the stihl 460 as that is the pin I had the c-clip groove set at
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Ed I havent seen a chrome bore for awhile. I thought even the oem stuff is nikasil now.
Of course most people will be taking that new 52mm race piston and having Millennium plate and fit piston to specs for stock appearing racesaws..
So how do you think they will work in a so called gtg woods ported 7900 681 race saw ;) .
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what stock OEM bores like the 460 stihl and 7900 are what I call chrome bore , they are for sure not nikasil , nikasil bore is way harder to grind on and the ring is meant to run on this type of material, you put this ring in a stock bore and about 30 seconds later you will not have a bore left , I'm keeping a 52mm just to put in a 7900 , the first alcohol dolmar I built ran pretty good for a stock piston with those very narrow skirts , and I know for myself I like the nikasil bore better than the stock chrome bore for a racesaw , the piston wear is less on the intake skirt as the nikasil bore seems to cause less wear
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as of right now I only got a couple 52mm left , they sold very fast , I only got a couple pistons left in all bore sizes . I got 1 left in 62mm
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1-62mm , 2-66mm left , that is it boys and girls , the rest are spoken for . If I get enough request I will place another order of pistons so if you want any let me know plus if you want to see any other bore size made , let me know as well thanks Ed
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Of course most people will be taking that new 52mm race piston and having Millennium plate and fit piston to specs for stock appearing racesaws..
So how do you think they will work in a so called gtg woods ported 7900 681 race saw ;) .
Kevin could explain, plate and fit to me?
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when you get a jug replated you can ask for whatever clearance between the piston and bore you want , On my 52mm jugs I had replated I went with 52.01 mm bore size so that gives me .0025 of a inch clearance and that is not counting on the coating so they are a touch tighter than that , once you get up to say .004 that is getting pretty loose and 99.9% of the time you are loose material on the intake skirt so you have to watch you donot get to much clearance and drop that skirt off your piston cause when that happens , lets just say its not a good thing ;D
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when you get a jug replated you can ask for whatever clearance between the piston and bore you want ,
Thanks Ed.
I know one guy that tried to make his 5cu build so tight he kept scuffing brand new pistons. Couldnt have happened to a :-X :-X :-X :-X :-X :-X guy ;D
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Okay plate the jug... I thought he meant plate the piston... I didnt understand that...the piston already has a heat resistant "slippery" coating and now you want to plate it... brain fart on my behalf sorry
Kevin those WORK saws will flat out fly if ported to the pistons potential, might get a little hot in the wood pile though ;D ;D
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Quick everybody, you've got 2 weeks to Webster.... :D :D
One will be there for sure....
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I'm not sure how many will be at Webster but figure a couple should be there but I know 1 that will not be and that is me , I need to get the foot infection taken care of first , I figure keeping my foot is a little more important than a contest
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Kevin, I'm not sure what he had for clearance but my first 60mm were at .0015 and had no problem but found that a touch more clearance you got full power alot faster instead of waiting until the piston loosen up abit , now those were on alcohol but the very first piston that went into a racesaw was in Chopwoods 3120 and I first took that piston and put it in a stock 3120 and took the saw to the wood pile and ran it as hard as I could for 3 or 4 hours just to make sure no problems , I honestly think that turned out the best way to do a saw
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pretty sure we are sold out of pistons at this moment , if everyone comes threw with the coin we are sold out thanks Ed
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I just seen a guy showing off his alky 7900 with a wide skirt piston he called it. I just had to laugh to myself because all it looked like inside the exhaust port was a 1.5mm ring 272 piston.
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some guys are putting the stock 272 piston in these but the race piston would gain alot more wide the far wider skirt and being coated the heat does not seek to bother the piston , I have put a couple of the 60mm race pistons in gas racesaw and so far no problem
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I just seen a guy showing off his alky 7900 with a wide skirt piston he called it. I just had to laugh to myself because all it looked like inside the exhaust port was a 1.5mm ring 272 piston.
You could tell just by taking a muffler off and peering inside it was a 272 1.5 mm ring piston? dayuuuuum!!!
Btw my 7900 ,vintage about 2005, is the 272 piston. Its works fine...
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The Wiseco pistons are different enough that you can tell what they are.
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you can tell if its got a 272 piston quite easy , first the saw will have a spacer under the jug as the pin hole is lower on the 272 piston and as far as there being a wiseco wide skirt piston out there I would say no cause they had to make the mold to build mine . may have been a narrow skirt piston but not a wide skirt and I had a hell of a time getting them to build the piston the way I wanted as they kept wanting to narrow the skirt on the bottom and I told them that that would not work
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anybody got a picture of the new 7900 piston , I just want to see if its any wider on the skirt than the old 7900 piston
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All I have read is the skirts were pretty much the same. Just the new piston was half a ounce lighter.
Last pic is new 7900 p compared to 6400 p.
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Ok I thought someone told me they were full skirt but that for sure is not the case ;D
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The new piston is about 2mm wider.
Shep
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The new piston is about 2mm wider.
Shep
Good news on 5100 piston it's about 2mm wider.
Shep
The 7900 is 2mm wider too or are you talking about the 5100 piston?
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every little bit helps on a 7900 , they cannot make the skirt to wide unless they change either the crankcase or pin location in the piston , a wider skirt hits before ever getting to BDC
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What is the old 7900 skirts and new lighter replacement 7900 skirt widths? Top of pin hole to crown height?
Found your spec info Ed.
7900 piston with ring it weighs 85.4 grams , skirt width of 32mm/ 1.260 inch
52mm wide skirt wiseco piston, with ring it weighs 79.7 grams and has a skirt width of 1.670 /42.5mm
stock 272 piston weight was 82.9 grams with ring , skirt width is 35.83mm/1.414 inch,
Just trying to compare to a 52mm mahle piston I pulled out of another saw.
272 comparing too.
Height 40.5mm
Pin 12mm x 33mm x 8mm
Pin hole top to top of Piston 18mm
BB7900 specs
Height 40mm
Pin 12mm x 7mm x 32mm
Pin hole top to top of Piston 13.25mm
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the 272 piston pin is set lower in the piston than a 7900 piston so this raises the piston once its on the rod , that is why you put a spacer under the cylinder but also because the bottom of the piston skirt sits higher on a 272 piston than a 7900 the piston can have alot wider skirt cause it will clear the top of the crankcase when the piston is at BDC
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The 52mm oem open windowed I have here I know is around 16.75mm top of pin hole to crown and 12mm pin. I will have to get the rest tomorrow if I get time.
Oh I aint looking for a piston for a dolmar either. Pretty much staying away from them now days.
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Man if I measured this OEM 52mm piston right (my digital calibers was giving me fits). It is a very nice stock piston ;D.
Correction made on ext and int today with new battery
top of pin hole to crown 16.75mm
ext int skirt 35.20mm 35.15
height 42.65mm
pin 12mm
(http://i59.photobucket.com/albums/g289/doemaster789/415/52mm001.jpg)
(http://i59.photobucket.com/albums/g289/doemaster789/415/52mm002.jpg)
(http://i59.photobucket.com/albums/g289/doemaster789/415/52mm003.jpg)
(http://i59.photobucket.com/albums/g289/doemaster789/415/52mm004.jpg)
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PP475 piston ?
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PP475 piston ?
Yes
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CORRECTION:
New battery put in and checked skirts again. The first measurement is WRONG they are NOT 40mm they are only 35.20 ext and 35.15 int. Sorry, but like I said the digital calibers were acting up first time.
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Anyone know the skirt width on the meteor 064 piston? I know the meteor was wider then the oem piston. Used to have a BB372 with a meteor 064 piston in it.
Stihl 064, MS 640 Meteor
Height 43mm
Pin 12mm x 33mm x 8mm
Pin hole top to top of Piston 17mm
BB372
Bore 52mm
Height 42.5mm
Piston Pin 12mm x 8mm x 36mm
Pin to top of Piston 16.75mm
2 different makers of 046 pistons
Stihl 046, MS 460
Replaces Part Number 1128 030 2009
Bore 51.96mm
Height 39.25mm
Head Type Flat
Piston Pin 12mm x 35mm x 7mm
Ring 52mm x 1.2mm (Caber F-Cast GH.F)
Compression/Pin Top to top of Piston 15.5mm
Compression/Pin Center to top of Piston 21.5mm
Stihl 046, MS 460
Replaces Part Number 1128 030 2009
Bore 52mm
Height 39.25mm
Head Type Flat
Piston Pin 12mm x 7mm x 35mm
Rings 52mm x 1.2mm Ductile Split Groove
Circlips 12mm
Compression/Pin to top of Piston 15.5mm
Compression/Pin Center to top of Piston 21.5mm
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Here's a well broken in 7900, with I believe is a stock piston in dry hard sugar maple, its as tough as it gets in my area. 16 x 18 inch material
http://youtu.be/aQbfh9klJGo (http://youtu.be/aQbfh9klJGo)
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Your link is corrupted
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how does that happen, link runs fine on Eds site
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It works now. I don't know what the problem was?
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1st time I tried to watch and it works for me.
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Is that the ole red top you were trying to sale for awhile on Ed's? Thought it finally went to a new owner.
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whew
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yup, same saw..no new owner.. and as it ran today ,what in gods name will I buy for the 450 I offered it for?
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Up there nothing.
You going to post that NE346 EHP video?
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you be spying... ;D even more are downloading ..you can post it, I wasn't sure where
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Up there nothing.
You going to post that NE346 EHP video?
what in gods name could you offer me for 450 that would beat that..its one of those saws that cant fit me ergonomically...but it starts, and just lugs through big wood tank after tank with absolutely zero maintainance
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Not saying beat it up there but we have ported saws down here by the groves in that price range. Just a few of mine I let go.
I sold my ported like brand new not much time on 7901 $400. 2 ported 372 $400 ported 066 $600 ported 066 $500 and so on. Just saying you can find good deals on ported saws down here.
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please advertise them, I'm all ears and have logging types loving deals.
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please advertise them, I'm all ears and have logging types loving deals.
All sold very quickly. No need to advertise down here or even here. Word of mouth was good.
The little ported saws like 3ci size I advertised here and there to sale. All gone too. Everyone in their brother has a 50cc around here.
Matter of fact dont even own a ported saw anymore.
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Bump for good read on EHP 52mm wiseco pistons
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In an earlier post in this thread someone said
For an OEM 7900 jug, I came up with a 272 piston which should require about a .174" spacer under the cylinder. If a 13mm wrist pin could be used, a 281 could be used with only a .095" spacer.
For the 7900BB, I only found the 288 piston, which has a 13mm wrist pin and would require a .095" spacer.
Since I had an older red top 7900 on my bench for a rebuild, I thought I would test that, I used a stock 7900 jug a 272 & 038 magnum pistons. I cut out a spacer out of 0.305 material, thinking 0.305 should get me the required space for an 038 Magnum piston since the CH of the 038 is 22.5mm and the 272 is 24mm or about 0.059055 taller than the 038 Magnum. So if you take the spacer 0.305 add to it 0.059 you come up with 0.364 as how much room you would have. Subtract the 0.174 from the 0.364 leaves you with 0.019 no base gasket needed......COOL, thought I!
Wrongo! The 038 Magnum piston runs smack into the head with 0 squish, so that blows that number all to hell. Be back in a bit with the 272 numbers.
OK, with the degree wheel on the saw the 272 piston hits the top of the cylinder about 2.5 degrees before the 038 hit which stands to reason because the 272 piston is 1.5mm taller than the 038 Magnum e.g. 0.018-0.019 = 1°.
So my feeling is that the quoted set of numbers must be for a pop-up.
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(http://chainsawrepair.createaforum.com/index.php?action=dlattach;topic=273.0;attach=12537;image)
@jacob j. Think the pics and info specs start on page 2 by EHP on wide skirt 52mm wiseco made pistons.