Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Dolmar Makita => Topic started by: KilliansRedLeo on June 11, 2014, 08:12:18 am

Title: 7900 Piston Recommendations?
Post by: KilliansRedLeo on June 11, 2014, 08:12:18 am
Looking for a recommendation on an AM piston set for a Dolmar 7900. This is a red o older saw and uses the windowed piston but could also use the slab side piston from a later model.
Title: Re: 7900 Piston Recommendations?
Post by: 660magnum on June 11, 2014, 09:11:17 am
http://www.hlsproparts.com/Makita-Dolmar-chainsaw-piston-assembly-52mm-p/h31790.htm

http://www.hlsproparts.com/Caber-piston-rings-set-52mm-x-1-2mm-p/cr5212.htm
Title: Re: 7900 Piston Recommendations?
Post by: KilliansRedLeo on June 11, 2014, 09:33:59 am
Jim, got one of those the other day, pure junk. So poorly made it was a crime, wrong ring supplied with piston, circlips break when trying to install. Then with new correct ring and good clips, saw would only make 90psi with oil in the bore. Threw the thing in the trash metal bin, and when it hit the skirt broke off.

Now you know why I am looking.
Title: Re: 7900 Piston Recommendations?
Post by: Nathaniel Vansickle on June 11, 2014, 10:00:02 am
haven't seen any quality AM ones but I will surely stock them when I find them. OEM is pricey
Title: Re: 7900 Piston Recommendations?
Post by: 660magnum on June 11, 2014, 11:16:44 am
That one that HLS sells is the only after market one I know of.
Title: Re: 7900 Piston Recommendations?
Post by: aclarke on June 11, 2014, 12:03:55 pm
That Greek dude (kafar?) on eBay sells a decent AM cylinder and piston w/Caber ring. 52mm  EPISAN brand piston
Title: Re: 7900 Piston Recommendations?
Post by: KilliansRedLeo on June 12, 2014, 02:47:22 pm
Thanks Adam, found the guy (Dandrikop) also had an AM moly-coated piston for 29$ so bought that. The original jug cleaned up real well. He has the C/P on sale for $91.
Title: Re: 7900 Piston Recommendations?
Post by: aclarke on June 12, 2014, 05:13:59 pm
Tim, he's the guy!!!  Have a 52mm p/c coming from him too.  friend ordered a kit from him a while back and the quality was nice.  Piston was nicely cast, not the portly Chinese piston I was used to seeing
Title: Re: 7900 Piston Recommendations?
Post by: KilliansRedLeo on June 12, 2014, 09:07:36 pm
Thanks Adam, was toying with putting an 038 Stihl piston in it but not into all the screwing around.

Did you get the RD-400 crank in yet? Is it in good enough shape to be useful after rebuild?
Title: Re: 7900 Piston Recommendations?
Post by: aclarke on June 12, 2014, 09:29:20 pm
I know what you mean about messing with odd compression heights on piston swaps!!

I got the rd400 crank and it's in surprisingly good shape! Was a little nervous as the eBay pics were real dark.   I'm sourcing some oem Rods, bearings, etc then I'll send it For a rebuild and true.  There's a veteran two stroke engine builder (Scott Clough Racing) south of me and his pricing Is quite reasonable.  I'll keep everyone posted.
Title: Re: 7900 Piston Recommendations?
Post by: farmboy on June 12, 2014, 10:04:10 pm
That Greek dude (kafar?) on eBay sells a decent AM cylinder and piston w/Caber ring. 52mm  EPISAN brand piston
Kafar sold out real nice lady Janie Williams a while back.  Knows her stuff.  Stocking Meteor pistons now.  I have a business acct with her my cost on Meteor is $28.00 + ship.  Ship cost is very reasonale too.
Shep
Title: Re: 7900 Piston Recommendations?
Post by: aclarke on June 12, 2014, 11:10:02 pm
Good to know.  Thanks Shep
Title: Re: 7900 Piston Recommendations?
Post by: KilliansRedLeo on June 13, 2014, 10:19:57 am
Quote
I got the rd400 crank and it's in surprisingly good shape! Was a little nervous as the eBay pics were real dark. I'm sourcing some oem Rods, bearings, etc then I'll send it For a rebuild and true. There's a veteran two stroke engine builder (Scott Clough Racing) south of me and his pricing Is quite reasonable. I'll keep everyone posted.

Adam, I know what you mean about the dark pictures, I don't know how you could tell it was a '1A1' crank!

I'll have a look at the BBK for the 64/73/7900 saws. I have had a lot of them come through my shop in the last month, three to be exact which is a lot for my location in NY. Only a couple of dealers in upstate NY so don't see a lot of them. Have one on the way from Vermont that a guy wants restored.
Title: Re: 7900 Piston Recommendations?
Post by: aclarke on June 13, 2014, 02:16:44 pm
Seller responded quick with the p/n on the crank.  We used the 7900 and 681's for a few years at work and found they were pretty reliable, clutch/bearing issues till we started using the revised clutch drum. Only other complaint was the lousy air filter and the case/plastic is way more brittle than Stihls formula. Great Saw for an individual owner who cares for their equipment but I found the Stihls hold up better to employee use who will never care for your equipment like it should be!!
Title: Re: 7900 Piston Recommendations?
Post by: farmboy on June 13, 2014, 03:55:12 pm
I have an NWP 7900BBK that I would part with.  It will keep me from buying another 6400 LOL.
Shep
Title: Re: 7900 Piston Recommendations?
Post by: Chainsawr on June 20, 2014, 07:14:42 am
We have these windowed pistons made for us with a 1.5mm ring instead of 1.2: http://store.chainsawr.com/products/dolmar-ps-7900-chainsaw-52mm-piston-kit-038-132-002-new

Seem to build a bit more compression and wear better in our customers saws.