sprocket chain bar combo not working


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9:56 AM
Jul 25, 2023
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I have a McCulloch Pro Mac II (46cc) which has been running nicely with original 18 inch bar and .325 chain . I have used it to mill some 14 inch logs, but now I have a larger log and the bar is too short. So my (slightly crazy) plan is to put a 25 inch bar on it and angle grind off half the teeth. It will be very slow but hopefully not overload the engine
so a 25 inch bar means 3/8 chain and a new drive sprocket. I thought I purchased everything right but when I tighten the chain it binds.

If I pull the chain over just the bar cog then I would say that its a correct match. Therfore I suspect that the chain and drive sprocket are not matched. But Its difficult to confirm this. Or maybe its the bar and the chainsaw in some way

Here are the specs:-

stihl bar 63 cm 1,3 mm 3/8'' 84DL

chain Stihl 3/8'' Rapid Micro (RM) 1,3 mm 84dl Sågkedja

sprocket (3/8", 6T)

I hope someone can see where I have gone wrong. Or suggest how I can troubleshoot the problem


PS some more info that is probably not relevant:-
the bar doesnt fit the saw well as the bar sausage hole is wider then the diameter of the 2 bolts. So the bar ends up pointing "up" a bit
The chain tightening hole on the bar is too far out, but I used a dremel to extend the hole towards the bar center line
the chain is on the long side. Maybe I can shorten it if and when I reach the stop

Bob Hedgecutter

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7:56 PM
Sep 12, 2021
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Way Down South New Zealand
Slightly crazy does not start to cover it.
I suggest you stop what you are doing before you wreck the saw and or yourself.

You are using a bar that does not fit, hacked up a chain that does not suit and trying to drive it with an incorrect spur drive to the point of constructing something dangerous.
Your only saving grace thus far is the chain profile is wider than the machine was designed for and when you tighten the saws side cover down it is clamping the chain in place so it cannot turn.

If you are serious and this is not some kind of troll post- stop what you are doing, buy a saw to suit the bar you bought that is designed to run 3/8 chain and do what you are wanting to do in regards to milling with a 24 inch bar- a plastic consumer grade saw is NOT that saw.

Bar must suit the studs, bar mount and oil supply gallery.
3/8LP is NOT standard 3/8 and your spur is 3/8LP and your chain 3/8 standard.