Injector chokes / Dolmar

[Spruce_Goose]

I was just unsticking a stiff throttle return spring on a 111i Dolmar today when I noticed the choke lever wasn't closing any valve. At first I thought something was missing but then I discovered the concept of the injection choke. Huh, never new it existed.
So i am just curious, is Dolmar the only company to use this and does anyone think there are any disadvantages or advantages to this style? Why use it, why not?

-goose

[sablatnic]

I like them. Normally easier to start, but can take some more pulls to start, when they have been standing for a long time, probably because of sticky need valve and diaphragms. A squirt of petrol or a hand over the intake when pulling normally takes care of that.

In 'the old days' Partner used a combination. A lever depressed the measuring diaphragm to open the needle valve when the choker was closed.

[Jiles]

I have two DCS520i Makitas that have the injection. I have found that if they don't start FIRST or SECOND pull you can shake the saw vigorously and it will build enough pressure inside fuel tank to send to carburetor.
I usually just shake before starting, matter of fact, I usually shake all my saws regardless of brands.

[sablatnic]

Never thought of shaking the saw, but will try it, Thanks!

[motard]

Sachs Dolmar has (had) the patent on the 'injector choke'.

And most SDs used a Tillotson carb back in the day.

They work on a cam so when you rotate the lever CCW it opens the 'injector'.

Some had a small pin while other used a screw to orient them properly in the carb port.

[motard]

I don't see any dis-advantage to the design.

When working properly they are the best starting saws bar none.
The only fly is finding parts, I think they are still available, but can't say for sure. (go to the Tillotson web site)

I have been through a couple dozen of those carbs and only had one I couldn't get right.

I ended up putting a 120 Super carb on that one. (pull choke)


I personally have never dealt with one newer than the 116/120si series.

[motard]

http://store.chainsawr.com/products/dolmar-116si-120si-chainsaw-tillotson-hs-236c-carburetor-kit-with-filter-mount-bolts-intake-manifold-throttle-link