Does a Stihl have to have an impulse line to run?

[e36]

I am actually combinding a stihl piston and cylinder head to a weedeater engine. My question is with just the piston and cylinder head is an impulse line required?

Thank you in advance

 

[Armosh]

You definitely need a way to pulse the carburetor. I think it will depend on what carb you want to use. Some have an orifice on the intake side that seals against the cylinder to pulse the carb others have a dedicated line. Sounds like an interesting project. Post some pictures too. Good luck.

 

[2StrokeFondler]

Sometimes the impulse line comes from the crankcase, not from the cylinder. But as Armosh wrote: you need an impulse for the fuel pump part of the carb.

 

[Armosh]

Sometimes the impulse line comes from the crankcase, not from the cylinder. But as Armosh wrote: you need an impulse for the fuel pump part of the carb.

I had neglected to mention that, 2stroke is 100% correct.

 

[e36]

i will be using everything the weedeater has, i.e. the same carburetor and pulse bulb set up, the flywheel is the same size so a win there. I believe this will work, wrist pins are the same size.

 

[cookies]

did you measure the stroke and the piston to cylinder head "squish"

 

[Wood Doctor]

You definitely need a way to pulse the carburetor. I think it will depend on what carb you want to use. Some have an orifice on the intake side that seals against the cylinder to pulse the carb others have a dedicated line. Sounds like an interesting project. Post some pictures too. Good luck.

Agreed. I rebuilt a Stihl 038 seven years ago and thought it was ready. However, it did not run right, and I discovered that the impulse hose line was shot. After I replaced that line, the engine ran flawlessly. Note that I believe the new M-tronic saws do not use impulse hose lines.

 

[stihltech]

It depends on the saw. Some still do use hoses.

 

[Sidecarflip]

Even 4 stroke engines use an impulse hose (specifically 4 stroke vocational engines like are on Zero Turns and other small engines) use an impulse line to actuate their external fuel pumps instead of using a mechanically driven (from a cam lobe) to drive the fuel pump. Reason being, it's less expensive to produce and the external pulse pump is easier and less expensive to replace. Pressure differential in the crankcase or in the cylinder is a very convenient (and inexpensive) way to actuate a fuel pump or use pressure differential actuation in the case of a 'pumper carb' which is common place on 2 stroke chainsaw engines.

 

[Armosh]

Even 4 stroke engines use an impulse hose (specifically 4 stroke vocational engines like are on Zero Turns and other small engines) use an impulse line to actuate their external fuel pumps instead of using a mechanically driven (from a cam lobe) to drive the fuel pump. Reason being, it's less expensive to produce and the external pulse pump is easier and less expensive to replace. Pressure differential in the crankcase or in the cylinder is a very convenient (and inexpensive) way to actuate a fuel pump or use pressure differential actuation in the case of a 'pumper carb' which is common place on 2 stroke chainsaw engines.

Very true. The 20 horse Vanguard on my Ferris uses an impulse line to drive the fuel pump.

 

[Sidecarflip]

If you ever have to replace it, whatever you do, buy the Stens replacement or the OEM one, not a Chinese edition. The Chinese ones seem to fail pretty quickly.

 

[Armosh]

If you ever have to replace it, whatever you do, buy the Stens replacement or the OEM one, not a Chinese edition. The Chinese ones seem to fail pretty quickly.

I have had terrible experience on the few times I've used chinese parts, always OEM if possible. The only exception is sometimes you can buy a knockoff muffler for a saw that is just an empty can instead of the very expensive and restrictive OEM one.

 

[Sidecarflip]

Interestingly, Echo offers both a CAT and non CAT muffler but the non CAT is sold aftermarket.

 

[ZeroJunk]

Yeah, which Stihl weed eater ? Most if not all 4 Mix have a separate tube coming straight from the crankcase to the bottom of the carb.

Most 2 cycles it comes directly through the manifold to an opening in the carb through a little hole in the gasket.


A photo would be nice. Can't picture what you are doing.

 

[Armosh]

Interestingly, Echo offers both a CAT and non CAT muffler but the non CAT is sold aftermarket.

I think Husky does with some saws too like the 570, but they are stupid expensive.

 

[Retiredboomer1]

I am actually combinding a stihl piston and cylinder head to a weedeater engine. My question is with just the piston and cylinder head is an impulse line required?

Thank you in advance

if you study your carb, the bottom diaphragm is a FUEL pump and if the Impulse hose is dead /missing ,cracked or clogged
the pump is now dead, and so be the carb.

see youtube vid, showing graphically how a diaphragm carb works , , the pumper is first

 

[Retiredboomer1]

I am actually combining a stihl piston and cylinder head to a weed-eater engine. My question is with just the piston and cylinder head is an impulse line required?

Thank you in advance

no base engine told. is this a franken-Stihl garden tool project, asks the blind?

 

[Retiredboomer1]

i will be using everything the weedeater has, i.e. the same carburetor and pulse bulb set up, the flywheel is the same size so a win there. I believe this will work, wrist pins are the same size.

but no weedeater model told , is this is test for the blind?