Stihl 4 Mix Brushcutter Piston stop dimensions?

[martin Phillips]

Hello All,
i am working on a 4180 series 4 Mix engine and need a piston stop to lock the engine to allow starter cup removal. These engines have a 10mm spark plug thread and the stihl part number for the stop is 4180 890 2700. i have a lathe and i reckon i can make one quicker than i can get one delivered but i would like to know ( confirm) the distance from the spark plug 'seat' to the end of the stop and the diameter of the portion that goes into the cylinder. Please see the picture for clarification.

Please can i ask if any of you kind folks have one of these stops, please can you take a couple of measurements for me?

Many thanks.

 

[Fish]

Just take a ratchet/socket, and put it on. Rap the handle to the left with a few sharp raps with the hammer handle, that nut easily spins off. I use my drill driver, it has impact action.

 

[jmester]

1.100 length or 27.94mm
.316 diameter or 8.02 mm
Hope it helps

 

[martin Phillips]

Thanks for your advice and the dimensions.
Stihl are quite explicit in stating that impact wrenches should not be used on these engines so i thought i would do it 'by the book' this time.
Having said that, i have never had a problem using an impact wrench, especially when removing chainsaw clutches i think its kinder to the engine internals than forcing the piston against a stop.
Thanks again

 

[Fish]

Well the starter cup is the easiest one to take off.... Just tap on the ratchet a few times.....

 

[AVB]

Thanks for your advice and the dimensions.
Stihl are quite explicit in stating that impact wrenches should not be used on these engines so i thought i would do it 'by the book' this time.
Having said that, i have never had a problem using an impact wrench, especially when removing chainsaw clutches i think its kinder to the engine internals than forcing the piston against a stop.
Thanks again

And on the blowers your not going to get the fan off with an impact. The last BR600 fan was on so tight I was worried about putting an hole through the piston. It takes a breaker bar and the piston stop to break these free. Not enough compression for the impact break them free. Matter of fact the impact actually sheared the dog bone flywheel key when I tried the 1300 ft-lb impact. And just the cost these flywheels justify the piston stop cost.

 

[CR888]

Stuff some starter cord in there till it locks up. Easy peasy. Just do it when piston is closish to TDC.

 

[Fish]

Stuff some starter cord in there till it locks up. Easy peasy. Just do it when piston is closish to TDC.

No worries about those valves?

 

[AVB]

Stuff some starter cord in there till it locks up. Easy peasy. Just do it when piston is closish to TDC.

No worries about those valves?

Personally I won't risk to it to avoid buying a $10 tool but of course I work on several units every year and that tool can used on other 2 cycles with the 10mm plug hole too.

I reckon doing it TDC compression may work but I would prefer to back off the valve clearance but then you would need a very narrow feeler gauge to readjust them. OH heck I said to myself why waste valuable shop time and just brought the tool.

And to Martin it is great that you can make the tool yourself. I would do the same thing for some those special need tools that are not readily available. I just trying figure what setup I need here to do the various design cuts without costing me a small fortune. I am lucky enough to have a neighbor that is a machinist that can take my artwork work with dimensions and turn it into the tool I need if I ask nicely.

 

[Fish]

I would just take the nut off......