Too much power for clutch springs?

[sawfun]

I have an 090 that was recently ported but now the old and new clutch keep running on. Is it possible to have too much power at idle thereby overcoming the springs. I know it is in a centrifugal clutch drag car but in a saw?

 

[CR888]

HP output does not really matter. Saw clutches engage at a certain rpm usually 3-3.6k. The clutch shoes are are prevented from stretching the springs as they are held back by the clutch drum. Power does not really change their function. Springs can fatigue over time and need replacing and they will tend to engage at a lower rpm than spec. If your clutch is engaging or not disengaging its either springs or worn shoes. Pretty simple devices, but clever all the same.

 

[CR888]

Adjust your idle screw and reduce rpm to 2600-2800. That should solve your issue or you need to replace springs/clutch.

 

[sawfun]

Thanks but I do not have a tach, however the idle is as low as the engine will go and still run. The clutch in complete and brand new, also the old one that worked before no longer does as well. So I may need to buy a set of springs and shorten them. My only issue with this is getting the temper correct after their modification.

As fare as power goes, I have experienced a centrifugal clutch sensing power or I would call it, kick. The same 4 disk clutch in a blown alcohol engine at idle will not activate at all where in the nitro engine, at idle, it works perfectly and gives you clutch pedal. Both engines idling at 2500 rpm. Same pieces of metal turning the same speed. So yes centrifugal clutch springs can seemingly be overcome, in my experience, by engine power at any rpm. Even with this 090's rpm so low it is about to die, the clutch is locked up. I loaded it down with a block of wood and it did not slow it down. This engine will just plain lug down.

 

[Frogfarmer]

You are trying to compare apples to oranges. The function of your 090 clutch is RPM based and from what you afe telling us the mods to the engine have raised the idle speed. You need heavier springs.

 

[Redfin]

Sounds more like a tuning issue than the clutch if you cant get to idle down.

 

[CR888]

^^Yup......richen the L to bring down motor speed.

 

[sawfun]

I tried that but will try again. This thing pulls even when it's going pop pop pop and about to die.

 

[Redfin]

Your clutch worked fine before mods? Nothing is binding?

 

[sawfun]

Yes the old clutch worked fine but now behaves like the new clutch. Nothing I can see is binding. I have tried another new clutch drum and have had that clutch off over dozen times now trying to figure this out. I likely have to modify a set of springs and or re-drill a carb jet but think the latter will not help in this case as the saw really seems to go down to very low rpms.

 

[ABarrick]

Can you move the chain along the bar by hand when the saw is shut off? If it moves freely, the problem is premature engagement. If it is tight, something is dragging mechanically. Are you positive it is assembled correctly? If there is a shim washer missing, misplaced, or installed when it shouldn't be it could be causing the drum to be locked to the crank shaft.

 

[sawfun]

I am not going to run a bar & chain when I cannot stop the clutch, especially the 72" bar that is for it. But yes everything spins free and nothing is binding missing, added, or out of place.. It seems that the clutch springs now need to be stronger than stock to hold the clutch at idle.

 

[sawfun]

I have the complete OEM old clutch (that was on it) & drum and a complete brand new OEM 090 6 shoe clutch and new drum. The new complete clutch behaves, just as the old one that worked before, now does. So a new OEM clutch has been tried. I am fairly sure both sets of springs are not bad, just no longer strong enough for a correct stall speed.

 

[Deets066]

I have the complete OEM old clutch (that was on it) & drum and a complete brand new OEM 090 6 shoe clutch and new drum. The new complete clutch behaves, just as the old one that worked before, now does. So a new OEM clutch has been tried. I am fairly sure both sets of springs are not bad, just no longer strong enough for a correct stall speed.

I had to put a new oem clutch in mine too, it had the 070 clutch in it. Too much power for the 070 setup, new oem 090 clutch fixed my problem but was expensive

 

[VinceGU05]

manual says idle is 1800 rpm and engage engagement is 2500 rpm. best you get a tach.. very handy. only 30 to 40 bucks.
when the spring is out straight they are around 6" long.. all it needs to do is stretch 5 to 10mm in length and its sheet. thats what i found on my 2100.

edit: i just ran mine..dead cold it took a minute or 2 for the idle to come down to 1800 or there abouts. it looks like my clutch start engaging at 2100 rpm. so my springs are getting tired. checked it with a Works Connection tacho.

 

[CR888]

An 090 is one saw I'd really want a clutch working properly.

 

[sawfun]

Yea, especially with a 72" bar. We shall see how it goes at the gtg. There will be some smart experienced folk there and tachs.

 

[Lightning Performance]

I'd put it together and start it. The chain will grab some of that clutch pulse. It might be a borderline "walking" chain. Then you will know it needs more spring.

I would not assume anything because it's not bone stock anymore.

 

[sawfun]

Turning the idle screw a quarter turn lower and adding that 72" bar & chain seemed to solve the issues. The saw runs perfectly.

 

[Stump Shot]

Just worked on an 015 a little while ago and when I got 'er running experienced the same kind of issue. Turned out it was missing a washer that went to a step in the crank shaft behind the clutch and had actually wore in to the clutch a bit allowing it to bottom out on the drum causing it to turn at all rpm's. I had to look at an exploded view of it to discover the missing washer. I replaced the clutch with washer from a donor saw and it worked like it was supposed to. Not saying this is your problem, but maybe check for a similar interference/fit issue. To help diagnose I pulled the spark plug and used the pull start to see what was going on with that clutch.