Dolmar 7900 chain tensioner

I kind of have a saw habit, and in reading what most folks have said about the Dolmar 7900 I went out a couple of days ago and bought new one of the bubble saws to try it out for myself.

(I'll admit up front that I am a really fussy guy when it comes to my equipment.)

The chain tensioner on my new 7900 is terrible and after reading posts from over a year ago about this problem, I figured that Dolmar must have fixed it by now. The manufacturing date on my new saw is about 14 months ago (even though my dealer had to order the saw for me) and here's the question in my post:

** Anyone know if Dolmar has come out with a update to that sticky chain tensioning mechanism during the last year? I would love to replace it if so.

I examined it at length and think the engineering is poor in regard to the gear and spline for that application. I think the right engineer could improve it in a heartbeat. Maybe even just a finer toothing.

I've got a number of hours using and fiddling with the saw and for what it's worth here's my impression so far for anyone interested:

Cons:
* The design under the sproket cover doesn't clear the long shavings (noodles, as Sam Madsen calls them) well. Worse than any of my other saws in that regard. I'll spare the detail why. Works fine for normal crosscutting, which it has been optimized for..
* The chain tensioner is funky and Dolmar engineers should be ashamed. Sticks and awkward. Took it apart and greased it several times to no avail. With the right fiddling and wiggling the bar it will eventually tighten, but not ready for prime time.
* I run REALLY sharp chains, so I don't sharpen on the saw (I bring a bag of chains to the site). So I swap chains pretty often and I find the 7900 tensioner design very akward with the tensioner's bar locating pin on the cover instead of the saw body. Nothing to hold the bar and chain in place once the cover is off and more difficult to see where to adjust the tensioner when putting on a chain of a different length. Most folks sharpen on the saw, so that is not a problem for them.
* So far it smokes a bit more than any other of my saws using the same mix (50:1 Stihl). It is not running rich, and I am hoping it miraculously clears up over time. Suggestions?
* Cheesy chaincatcher compared to Huksy or Stihl of this size, but no biggie.

Pros:
*Great weight for it's size. Feels about the same as my 371 in the hand. Decent balance.
*Much smoother than my 066 although not as quite as smooth as my 395. But acceptable to me and I am a fanatic regarding saw smoothness because of the kind of cutting I do. So I say pretty good here.
*Starts great.
**Heres the kicker: This is a really fun motor to run. Peppy, great throttle response, strong and even power. I can see why people like them. I usually have about 4 saws out at a time, and I keep wanting to pick the bubblesaw up. Just plain satisfying, just like certain motorcycles that for some reason just kind of make you feel good.

The airfilter looks too small, but at least now when it's clean it seems to be making plenty of power. For the kind of cutting I do I'm still not decided on whether I would buy it again, but for the normal crosscutting the bubblesaw with a squareground chisel chain is pretty impressive. But even in the Seattle area it was like pulling teeth to find a dealer to buy one from.

Chain tensioner design isn't the best. It does get a bit better with use, though. I have not found it to be a problem in real-world use, even when tensioning a 28" bar.

The air filter works fine, doesn't accumulate too much junk, and shouldn't be a problem. It just looks small.

As for the smoking, I agree with that assessment. The one tank I put through it of non-synthetic oil when I first got it did smoke a bit more than I expected. Hasn't been a problem since then, though, running 40:1 semi- or full-synthetic oil.

Ok, good feeback, I guess

I have a three year old Makita 6401 that I made into a 7900. It has hundreds of hours on it with nothing funny or goofy with chain tensioner. If you have a bad gear in the adjuster, you might need a new gear set. No biggie. I have replaced more than one gear setup on Stihls.

Smoking? that isn't from 50:1. that is from a saw that is not tuned correctly. IT is set way to rich if it is smoking constantly, or it needs rings.

BTW, I know a local dolmar guy that makes differant chain catchers that aliviate the long noodle clogup problem. He charges about 5 bucks for them and they are worth it if you are doing any cross cutting noodle type cuts.

I believe that I read here long a whlie back that Dolmar did upgrade the tensioner/worm gear assembly. If I am correct the updated unit has all black plastic.

I have several 7900's. While it doesn't seem to let you tighten the change as much as........say...........a 372, you can get it tight enough!!!

The 7900 I had was one of the cleanest running, smoke free saws I have ever ran. I also ran it at 32:1 exsclusivly. I never had much problem with the chain adjuster on mine, but for some reason replacing chains is a little funky compared to a Husky which has the same basic design. The stihl chain adjuster is better than either Husky or Dolmars IMO.
I would check to see what your carbs set at if your getting smoke. be careful as the saw has a rev limiter.

I ran a few more tanks through the saw today and it seems to be running pretty clean now. The dealer had actually done a good job setting up the saw, but of course I checked that as well being a new toy. It was not smoking badly before, just more than my other saws. Now it seems to have settled down for some reason.

In terms of the tensioner being the same as huksy, it is not like any of my huskies. It is my only saw that has a side adjust tensioner that uses a pin that moves the bar mounted in the cover rather than on the case side. I run square ground chains and swap out chains pretty often, and am used to being able to change the chain pretty quickly. With the 7900 I find it a little more awkward because nothing holds the bar and chain in place until I actually have the pin in the cover adjusted close enough to put the cover over the studs. And then once the cover is on the tensioner is really sticky, often refusing to turn even with the nuts loose. And pulling up on the bar to give slack can actually move the tensioner backward a little, which is not true on my other saws and kind of frustrating. I am sure I will get better at it, but I can swap chains on my other saws in a flash and I think my 7900 could/should be smoother. When I turn the screw to tighten the chain on my other saws they tighten evenly and predictably.

The 7900 is a great runner, though ,and in cutting up some pretty big blocks today I got better at keeping the side cover clear with the noodle shavings as each saw is different in this way. I think I'll keep it, although I still seem to have an itch to get my hands on a 441 for it's purported smoothness and a 390xp because I really like my 395 except for the weight. I've talked to someone that has had their hands on the 390xp and they say it is only a touch heavier than the 385 and stronger. And I've heard even a touch smoother than both saws as well.

The probs you are having are NOT NORMAL your adjuster assy is definitely bad. Have a new one installed under warranty we were still seeing one like you describe every now and then last winter and this spring but none as of late. A new assembly will eliminate your issues.

Scott

Is that mechanism something I can order online and save me the trips? The only dealer in my area is most of an hour a way and has only started carrying Dolmar 3 months ago. He had never even seen a 7900 before I had him order mine.

Two trips to him and possibly having to leave a saw part for his rep isn't worth the 25 bucks or so the part should cost. It would be great to have that adjuster working right, as it is a pretty sweet saw to run.

Funny how Dolmars are still so hard to find even in a high populated area like greater Seattle WA.

Since I dealer I bought from only ordered this one from his rep a week ago, I sort of assumed it would be a fairly fresh copy. WHen I got home I noticed that the saw was made 14 months ago.

Any other changes or tweaks made to the Dolmar in the last 14 months?

Just wondering.

B_Turner said:

Since I dealer I bought from only ordered this one from his rep a week ago, I sort of assumed it would be a fairly fresh copy. WHen I got home I noticed that the saw was made 14 months ago.

Any other changes or tweaks made to the Dolmar in the last 14 months?

Just wondering.

Click to expand...

Have your dealer order Part# 957213022 Tensioner and have them send it to you. It's about a 5-10 minute fix.

There has been no changes since the "black hood" saws came out in 8/05

Steve

In terms of the tensioner being the same as huksy, it is not like any of my huskies. It is my only saw that has a side adjust tensioner that uses a pin that moves the bar mounted in the cover rather than on the case side.

Click to expand...

The Dolmar design is nearly identical to the Husky 372. For some reason the 372 is easier to use.

The longer bars make it hareder to keep everything in line on the 7900/372 style tensioner. I wind the tensioner in all the way and then tighten the bar nuts finger tight then wind the chain tension up. Sometimes you need to spin the chain in order for everything to seat ( for lack of a better word ).

My brother the arborist and lots of arborist friends and woodturner friends have a 372 and I have run them numerous times. But I have never owned one or changed a chain. I knew they adjusted from the side but I never realized that the tensioning mechanism was on the cover like the Dolmar. Duh. I am still using my old 371 which is the old style behind the bar tensioner as is my 395. My stihls of course all the standard stihl side adjuster. The all work fine for me, except the stihl a little easier for eyes that now need bifocals.

Funny how I realize now I've never had a 372 cover off...

I'll order the Dolmar tensioning mechanism and and start practicing the new dance. Thanks.

For roughly the same weight the 7900 seems a fair bit stronger than my 371, although that 371 has been a fine saw and cut alot of wood and still runs great.

I'v owned two 7900, never had any problems with the chain tensioner.

I own an older 7900 and also had a problem with the chain tensioner, but only after a lot of use. Ordered a replacement and it is much stronger and smoother.
Mine was the same smoke wise, a bit at first then cleared up to nothing at all. 40/1
I do the same as you and usually swap out ground chains. For me the fastest and easiest way to change is with the saw on its left side handle bar and the bar tip on the ground. The longer the bar the easier it is. Put the chain on the sprocket [but not in the bar rails yet] Put theside cover on, then flip the saw upright and spin the chain on the bar and retension. I change chains like this on all my saws and its easier for me than the standard upright method, moreso with the 7900 because of the tension pin being in the side cover.
I too think its a great saw. Not perfect, but then none of them are.

Thanks for that detailed description of the method. Makes sense and I'll give it a try.

I am hopeful now that my tensioning mechanism is just a bad copy. When I tried it out a bit at the dealer when I bought it, I noticed even with no bar on it at all the tensioner seemed pretty locked up. That didn't seem right, but I hoped somehow it would be better with a bar. It wasn't and taking apart and regreasing it didn't help either.

So I'll order a new mechanism and should be back in the pink.

I would be curious to try the next size Dolmar but it weighs 4 lbs more and thus wouldn't benefit me over my 066 or 395. But that would be a different thread.

166 said:

Have your dealer order Part# 957213022 Tensioner and have them send it to you. It's about a 5-10 minute fix.

There has been no changes since the "black hood" saws came out in 8/05

Steve

Click to expand...

Looking at the Dolmar online parts list, it looked like the part (whole tensioner assembly) was listed as 957213021. Is the 957213022 the better number?

B_Turner said:

Looking at the Dolmar online parts list, it looked like the part (whole tensioner assembly) was listed as 957213021. Is the 957213022 the better number?

Click to expand...

The 957213022 part number supersedes the 957213020 & 957213021 numbers.

Steve

THanks much, Steve for the good number.