How do you know when the clutch is bad?

My Dolkita 7900 has about 4 tanks of gas through it, but since the P&C I've noticed it bog more easily than I think it should. If I lean into a cut too much the chain stops and the engine bogs. This has happened with both a 20" & 28" bar. Normally the thing just eats through wood, but every now and then the chain will just stop when starting a cut if I'm not super careful about putting the saw gently into wood. So is it time to replace? It was a HD rental, so it may have had a hard previous life.

 

Replace !!!!!

 

There are a lot of folks here who have put more hours on saws than I have, but it does sound like your clutch may need replacing. When the symptoms you're describing start to show I usually feel the clutch shoes as well as the inside of the drum to see if I can feel wear. If the clutch shoes are no longer a true flat surface (more rounded, or grooved) that's a solid indicator of excessive wear and also if you can feel a 'lip' inside the drum where the shoes are wearing it down you have your answer as well (of course in that case it would be the drum that needs replaced).

 

I'm clearly no expert, but if the engine bogs isn't the clutch doing its job connecting the motor to the chain?

 

I thought the same thing.

 

I meant replace the whole saw !! LOL

 

I'm certainly not saying what's happening to him is absolutely a clutch issue, but I think it could be, and would be worth checking out.

You fellas bring up an interesting point though. Let's think about that? For starters, I always assume "bogging" is a description of lowered RPM. The way I looked at it was that when a clutch starts slipping the chain will likely cease to move. In that case I would imagine the saw will lose RPM while the clutch is slipping inside the drum (much like trying to run a saw with the chain brake on). Will a saw maintain full RPM when the clutch is slipping and not bog down?

I'm not saying I disagree with you guys, I'm just trying to think through your comments.

 

Could have something to do with the engine work ? Maybe a combo of things as well.

 

Definitely. Not knowing what make/quality of P&C he used (as well as rings) it might be on the low side of compression and have less power than he's used to.

 

Run a compression test with a tester with a schraeder valve. Report back.

 

If the clutch is bad it will either slip or be slow to disengage. Does the drum have any drag on the shoes?

 

could be clutch , it get real hot & start smoking when using hard ?

Have had
Rakers, to short
Drive sprocket worn bad cause similar problems.

Good oil to the bar ?

 

I thought the same thing, that the engine should rev more easily when the clutch slips. Because when it bogs, it does make a similar sound to if the chain brake was on. The same thing happened before I put on the new P&C, but I know that there was an issue with the throttle linkage then so that saw never ran past 3/4 throttle so it never made full power. I haven't run a compression test since the swap, but I used a new OEM P&C. Saw was at 180 psi stock, and it sure it noticeable more difficult to pull over now.

It's oiling fine, and this has happened with both brand new chains, as well as one's I've sharpened so I'm pretty sure it's not the rakers.

I'll check the compression tonight, as well as take a look at the chain brake. I guess there could be something wrong with that.

If it happens to be the clutch, are those universal like rim sprockets, or will I have to go to a Dolmar dealer to get one?

 

I dont know if it makes sense for the Makita.... But my old Husqvarna 350 that I learned on had a similar problem. If i pulled up too hard on a undercut... It would totally cut off all my power. Come to find out that i had broke some anti-vibe springs and mounts... Which created just enough extra movement to pull back on the throttle linkage ... And reducing the throttle position down to idle. Once i replaced everything.. Saw has been back to normal ever since. When i was young and learning... I would get the saw pinched often and yank and pry till it came out . Undoubtedly the root of my problem !
Im wondering since that Makita was a rental saw that perhaps got used the wrong way... If thats a possability with the anti-vibe ?
Its easy to check if it is !

 

When I did the P&C swap I had to take off all of the anti-vibe springs, so I know they're all in good shape.

 

So when you cut, the chain stops and the saw sounds like the brake in on? To me it sounds more like an issue with lack of fuel. If you have 180psi comp now, it's definitely not P/C related. Have you checked the fuel pickup filter or the little catch screen in the carb? Possible that your carb tune is just out of whack.

If you're set on the clutch being the issue; Maybe try to just clean the drum and clutch shoes with brake cleaner and a rag. If the shoes are glazed over really bad, you could take some steel wool or scotchbrite to scuff em up just a little.

 

While I'm in the cut, it normally rips. But sometimes when starting a cut is when this happens. Or if I lean into it too hard during a cut.

The filter looks fine, and is actually a different filter after the swap, so I don't think that's the issue. I am running the saw a little rich during the break in, I'll probably lean it out some after a couple more tanks. It probably would hurt to throw a new spark plug in there as well.

 

Do you have a different bar and chain to use? I once picked up a used saw that did the same thing. Turned out the chain was binding on the bar when I gave it some pressure.

 

Yeah, I've run both a 20" and 28" b&c with similar outcomes. It was a slight annoyance with the 20", but was becoming a problem over the weekend with the 28"bar when dropping a 30" ash tree. I was nervous enough since it was leaning towards my house and we had chains and a winch pulling it the other direction and I was cutting on a steep incline. But it made matters worse when the saw wouldn't consistently cut through the trunk. Several times in just the back cut I had to keep backing the saw up a little to get it revving again, and go back to cutting.

 

Hmmm, diagnosing over the internet on something like this is tough. No offense, but it could just be you hahah. It's worse when you start a cut? Are you going into the cut full throttle? Also, any saw can bog out if you lean on it enough.

My 440's tend to do this when the bottom spikes on the dawgs grab just right and pulls the saw down in the cut. I'm going to reprofile them or something to help remedy this, it gets pretty annoying on a felling cut. I've never run the Dolmar, but the dawgs don't look like they have that sharp angle to them the 440's do that would cause this.

Just thinking out loud here. Hell, someone could come along and say my suggestions are crazy talk...