MS 170 Simple Mod ?

[C George]

For some reason I cant find anything on line about this mod ,, as Ive discovered that removing the air intake insert really wakes up a ms170 / 180 a lot.

 

[Tomos770]

 

[C George]

Thanks but no comment sbout the intake insert. My main concern is about running it with it out as its a real screamer

 

[C George]

To file the flywheel groove is nuts ,,, advancing a 2 stroke timing actually kills rpms

 

[J D]

It's not an uncommon mod, some saws run fairly conservative timing on account of lower quality fuels in various places

 

[Tomos770]

To file the flywheel groove is nuts ,,, advancing a 2 stroke timing actually kills rpms

When I was a teenager....my father helped me with "how to make my Tomos mofa faster".....one of the standard procedures was/is slight timing advance....from standard 1.5mm before UTDC (upper top center-of piston) it was adviced to re-set it to 1.7mm before UTDC...for better throttle response...

What killed rpms the most was higher compression ratio (I lowered cylinder head by 1.5mm)....but that also gave better peak torque.....that was ok since I was riding my mofa in mountains

Hard to change compression on a clamshell design....but that will give you better usable torqe....

 

[Captain Bruce]

Thats a MOPED, no matter the flywheel key location..............................................

 

[Snowchaser]

Swapping in a wt215 carb and a minor muffler mod is the best mod to wake them up…. Or the easiest.

 

[hwrdpromac7900]

The easiest MS170 mod is get a MS180.

 

[C George]

Swapping in a wt215 carb and a minor muffler mod is the best mod to wake them up…. Or the easiest.

And removing the intake insert

 

[J D]

And removing the intake insert

How many saws have you done this to & have the results been consistent?

 

[C George]

Swapping in a wt215 carb and a minor muffler mod is the best mod to wake them up…. Or the easiest.

And removing the intake ink

 

[C George]

6-8 with the same results

 

[heimannm]

McCulloch provided 5 degree advance flywheels for their kart engines, the same flywheels could be used on chainsaws. Obviously there are occasions where advancing the time is advantageous.

Mark

 

[rogue60]

So you are saying your ms170 is stock with none adjustable carb? And you have removed the intake insert and now it's a screamer.
If the above is the case I hope you ain't running 50:1 lol

I've got a couple ms170's still with none adjustable carbs and have removed the insert for science and stuffs. I quickly put the insert back going on how lean the saw was running.

But yes running an adjustable carb the above mod wouldn't be a problem.

 

[J D]

Removing the insert will definitely lean things up as it exposes the compensation circuit to greater vacuum which will have the same effect as lowering the metering lever (ie restricting fuel through the metering valve slightly).
Absolutely terrible idea for a stock saw as the jets are fixed lean from the get go. A common improvement is to raise the metering lever a touch to increase fuel a fraction. I personally prefer to replace or drill the jet.
All that said, the OP has another post stating he also plugs the compensation port & drills a vent to atmosphere so hopefully that's the case here.

 

[C George]

Removing the insert will definitely lean things up as it exposes the compensation circuit to greater vacuum which will have the same effect as lowering the metering lever (ie restricting fuel through the metering valve slightly).
Absolutely terrible idea for a stock saw as the jets are fixed lean from the get go. A common improvement is to raise the metering lever a touch to increase fuel a fraction. I personally prefer to replace or drill the jet.
All that said, the OP has another post stating he also plugs the compensation port & drills a vent to atmosphere so hopefully that's the case here.

I siliconed compensation port and drilled a 1/32 hole in cover so diaphram can move richer

 

[C George]

Plus 25:1 Maxima 927

 

[C George]

Let me update this mod by saying I highly reccoment blocking off the compensator passage with silicone and drilling a 1/16th
hole in the snorkle so the diaphram can move towards rich only. Then you can safely remove the insert and not be as lean