Mastermind
Work Saw Specialist
Don't feel bad Glenn........I was born confused. And it's slowly and steadily gotten worse.
OEM Dolmar 7900 Kits?
- Thread starter shorthunter
- Start date
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mp5n
ArboristSite Operative
If I understand Short Hunter correctly you need raise the cylinder to set the squish with a 460 piston. This means the compression height on the 460 piston is taller than the stock 7900 slug. If this is the case it would be a perfect candidate for a pop up to adjust the squish, and get a little more compression to boot.
I just happen to have a 7900 with a scored piston. I'll have to look into it to see what may work.
I just happen to have a 7900 with a scored piston. I'll have to look into it to see what may work.
slovcan
ArboristSite Member
Thanks, I think. Now I'm REALLY confused. I don't know if that's something to look forward to or not...
The 7900 is on the right.
7910 exhaust port is about an 3/16 taller and 1/16 wider than a 7900. 7910 port doesnt match up to a 7900 muffler perfect but it can easily be port matched if you want. looks like all the extra that would need ground out of the muffler is just sheet metal and not the thicker bracing inside. even if you dont grind the muffler to port match it i dont think it would hurt much if at all on a stock saw. the entrance to the muffler has a nice rounded edge. i traced the gasket onto the muffler to show just how much of a difference there really was. 7910 gasket on the left and 7900 on the right. sorry for the blurry pics. cheap camera and shaky hands
On a stock saw that won't hurt anything.
You do lose most of the support bracket to port match. Making a gasket is the only way to keep one.
doesnt look like much has to be taken out. sad thing is i just did one a few weeks ago and cant remember. i found my picture if it helps. here is that reinforcement plate from inside the 7910 muffler after removing the slr chamber and removing a bit more material.
shorthunter
ArboristSite Guru
I would skip the popup. Your timing numbers will be better with a spacer
ncfarmboy
Addicted to ArboristSite
I have heard from a reliable source the "Greek" has a real nice AM 7900PC. That's where I'm going if I need one.
Shep
Shep
slovcan
ArboristSite Member
Well, that settles it then. I WAS confused! I ASSUMED (I know, never assume) the used cylinder was the 7900 and due to be replaced by the new 7910 cylinder.
The stated price is not from a Dolmar dealer.
It is from a small engines repair shop that claims to repair and stock all saw brand types - as such it might be they just want to get rid of the cylinder/piston kit.
They do claim it is an OEM part , but I'd have to double check not to end up with an over-payed AM kit.
They also have an piston kit listed , supposedly OEM , it costs as much as half the price of the P&C kit , thus the P&C kit looks more attractive.
My guess is that ALL the power loss of he PS-7910 compared to the PS-7900 is due to that awful CAT muffler as most of the other engine parts apparently stayed the same.
Loosing 0.5 HP (6.2 down to 5.7 HP) and 0.5 Nm torque (5.2 down to 4.7 Nm) is not a small thing.
They also reduced WOT rpm's from 13.500 to 12.800 , that will most likely reflect on rpm's under load reducing chain speed (the PS-7900 has 20.83 m/s declared , can't find info on the chain speed of the PS-7910).
Interestingly the PS-7310 lost less power compared to the PS-7300 , 0.2 HP and 0.3 Nm.
Those are nicely priced!
Shame that shipping and customs/VAT would eat up all the price differential.
That 7300 is no slouch!!! I have a 7900, 7900 84cc BB from watsoner on a 7300, and they are all pretty close. The 7300 is very good on gas and very zippy, the 7900 is strong and zippy, the BB is more low end torque with out the zip, kinda like an 051. The BB and the 7900 suck the gas+++
watsonr
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That BB Kit is still the best aftermarket kit... not one failure, direct bolt on and a reasonable price!!
I would like some expert opinion regarding these pictures , does it look like a genuine PS-7900 P&C to You guys?
I know the pictures are not perfect , especially the one from the piston , but that is all I got on my info request for a PS-7900 P&C kit I keep eyeballing.
I have been quoted ~175USD (without shipping) for this supposedly OEM Dolmar PS-7900 P&C kit.
I don't need it , but I'd like to have one as a spare IF needed in the future.
And what is that circled screw for , it can't be a DECO valve plug or could it?
Opinions are appreciated!
I know the pictures are not perfect , especially the one from the piston , but that is all I got on my info request for a PS-7900 P&C kit I keep eyeballing.
I have been quoted ~175USD (without shipping) for this supposedly OEM Dolmar PS-7900 P&C kit.
I don't need it , but I'd like to have one as a spare IF needed in the future.
And what is that circled screw for , it can't be a DECO valve plug or could it?
Opinions are appreciated!
Adirondackstihl
Flyz, Fuel & Fotos
MAHLE is OEM for Dolmar.
And yes, that looks to be a Husqvarna decomp plug
And yes, that looks to be a Husqvarna decomp plug
