WELL used 7900, where to start

[morewood]

I got a fairly good deal on a 7900, $300 to be exact. I knew it wouldn't be a prom queen, so no disappointment. It has approx 140 lb of compression. The plug was clean when received. Didn't fire right off so quit and moved to other stuff. I plan to pull the muffler and check the P/C. The muff. has 2 ports, I am guessing that is not factory. Whoever did the #2 didn't clearance the cover so that will be done. Wondering where to set the carb to start from and whatever else I should check. If it looks like more extensive work is needed, well, then maybe it should visit the doctor that massaged the clear/cream (steroid ref.) on my other saw. Oh yeah, that air filter is CRAZY small. Surprised me to say the least.

Shea

If your only contribution is to bash my new purchase......move along, nothing here to see

 

[nmurph]

With the compression at 140 (should be about 170), and the MM, I'm already betting you have a scored cylinder. Somebody dropped an extra hole in it and didn't know about the limited coil. If the cylinder is scored and can't be saved, spend the extra $60 and get the OEM P/C.
With the limiters off, and a non-MM muffler, the needles should be at 1&1. But those settings are moot with the spare hole in the muffler.

 

[IthacaMan]

opcorn:When you get a chance to take off the cylinder,post some pics.It may clean up ,and I think there is now a light weight OEM piston for these saws.:msp_thumbup:

 

[IthacaMan]

Oh ,and the stock air filters do seem small,but it takes me alot of cutting before it needs cleaned.

 

[Nemus Talea]

I rescued a 6401 from a HD rental fleet and among its other problems, the clutch side was a mess. Check the clutch springs, spring holes, drum, weights and needle bearing cage for wear and damage. All of the a fore mentioned was a wreck on mine. One weight was missing a chunk. No doubt heat from abuse and terrible maintenance caused this. If its been used hard, take a look. Not too expensive to replace new.
Tuning without the clutch working right will be problematic.

 

[bcorradi]

If your getting 140 psi...its not a for sure gig, but I bet your cylinder is salvageable at least. If so, buy a new OEM piston or a meteor one for it. I'm not a 100% sure if meteor makes one for a 7900. I myself mostly stick with that other german saw manufacturer

 

[Andyshine77]

A 140 pounds isn't all that bad, maybe just a warn out ring.

 

[WKEND LUMBERJAK]

A 140 pounds isn't all that bad, maybe just a warn out ring.

I will agree with Andy. It could be the compression release button. I've changed a coulpe of those on some older husky's 55's.

 

[morewood]

Tomorrow or Tuesday I should have a place on the work bench cleaned off and check it out more thoroughly. I noticed the comp. release felt 'soft', as if it didn't want to stay pressed in. Just another item to put on the check list. Thanks for the leads guys, if you can think of anything else don't be afraid to put it up.

Shea

 

[Andyshine77]

The decompression valve pops out when the engine fires. :msp_smile:

 

[Mastermind]

I like them 7900s Shea.

How's that OlyMac running for ya?

 

[ancy]

Just throwing it out there but my 6401 is picky on starting, choke on full untill pop and right off till start. If I giver one to two more pulls with choke on it's a hard go from there.

 

[Andyshine77]

Just throwing it out there but my 6401 is picky on starting, choke on full untill pop and right off till start. If I giver one to two more pulls with choke on it's a hard go from there.

Well pulling after the pop will flood the saw.:alien2:

 

[ancy]

Well pulling after the pop will flood the saw.:alien2:

Yep, but with the music jamming sometimes I miss that POP!

 

[Andyshine77]

Yep, but with the music jamming sometimes I miss that POP!

#### happens.:cool2:

 

[Mastermind]

#### happens.:cool2:

It is what it is......

 

[morewood]

The decompression valve pops out when the engine fires. :msp_smile:

I know, simply stating I noticed something different about it.

I like them 7900s Shea.

How's that OlyMac running for ya?

Funny you ask. I pulled the 24" bar off the 7900 (came with it), and the chain(so-so), had a big chunk of locust to test in. The wood was just wider than the bar. Mr. (that's what he asked to be called now) OlyMac rolled through it....with ease. Quite impressed. It wasn't the speed, but the ability to power through that is so impressive. After I get to look over the 7900 more if I see that it is above my pay grade it may visit the :msp_thumbup:'Mastermind Saw Spa and Gym Facility:msp_thumbup:' to learn how not to be a big bore sissy. You and Charles Atlas.....teaching people not to let bullies kick sand in their face at the wood-lot.

Shea

 

[Gologit]

Yep, but with the music jamming sometimes I miss that POP!

Music?

 

[ancy]

Music?

Yep!

 

[morewood]

Good day fellas! The saw runs....really rich. Started on the second pull, idled fine....just high. Revs come on very quick.....now. Pulled the muffler. The internals seem stock so only the second port was added. The exhaust port was clean, only a light color too it. Piston skirt..perfect, no scuffing. Piston top, looks great. Cylinder wall looks pretty good too. Pulled the clutch cover, looks good, just full of junk. Overall the saw is just very dirty, nothing some purple power and water won't fix. Now for the bad. A portion of the case is cracked. Where the forward/top screw for the recoil housing screws in, that 'ear' is cracked clean off, or so it seems. Hoping to JB it....if there are other choices let me know. Will get a pic tomorrow and let you guys look at it. Also, anybody got one of these or 6400 for parts? Would like to replace some small items. Thanks for the help.

Shea