Stihi Carb

[cannonball2]

Seems experimenting with carbs is a fun pass time for me. Having been in the small engine trade am well versed on Walbro and Tillotson carbs. Now that the Chinese have started making clone chainsaw parts I decided to gamble 15.95 shipped on a carb for an 041 Stihl. Seemed a good choice as the 041 is 61cc.
Cobbled up a manifold for it and gave it a run. After a few tweeks on the hi/lo needles I had an excellent running gt5. Super clean carburation from idle to a much improved top end. No flats or 4 stroking and a perfect idle.
Was really suprised at the throttle response. I expected it to maybe be an issue as the carb is 21mm. Pretty big for a stocker. However these type carbs run larger bores than a M/C type. Shortly after getting in a few hi speed runs the chain let go.

I have gotten the NT carbs running pretty good, but there is no comparison to this carb. Time to repair the chain and figure out an air filter. I plan on ordering a couple of more and one for a Stihl 660 for the 90cc Stihl Frankenstein build. To heck with changing jets!!
.

 

[cannonball2]

[

So l have been riding this setup quite a bit today. It's absolutely perfect!! I fabbed up a shorty intake and an air filter made from a Crosman pellet tin. It all fit easily into the normal space of the NT carb. Air filter is neat because it has a screw on lid that makes getting at the filter easy.

So the conclusion is if you are looking for a easily adjustable carb that runs light years better than most this is it. No freeking jets to ever have to fool with!! Light fabrication is all that is necessary and the stock throttle cable works. Plus it's only 16 bucks shipped! The exhaust limits this bike a bit as it's restrictive. Can't wait to get this carb on the Zeda 80 with the boost pipe.

 

[catman78]

Nice job. That's why this hobby is great...
A few questions
What adjustments are on the carb?
Are they all 21mm?
Does the model # determine internal jetting size?

 

[cannonball2]

It has the normal lo/hi needles. The carbs for the 041 I presume are all 21mm. I have no idea on the jetting.
I based the purchase on the 041 chainsaws displacement(61cc) as being in the ball park for the 66cc engine. Turns out it was right on.

 

[catman78]

When you get a chance take closeups of connection to intake.
Most of all, get a video up and crack throttle so we can hear her...

 

[cannonball2]

Here's a pic of the intake. Probably easier to describe the mod. A 3/8 piece of delrin cut into a matching carb flange and bonded to a piece of 3/4 copper water pipe which just happens to be 21mm in id. That is bonded over a stub of stock intake. The transition between the larger 21mm tube and the smaller stock tube is faired into a smooth taper with JB and polished. This flows noticibly better than the temporary rubber hose link up.

Also the pulse port for the pumper side of the carb is in the throat so no pulse line is needed. The nipple on the top plate is a vent. Will try to get a video up soon.

 

[cannonball2]

This thing really rips for a stocker. It revs higher (speeds per gear) than it ever has. Will rev to 35 in 2nd but tops out at 42 in third. Tells me I am over geared. Probably need to go up to a 38t sprocket instead of the 34. I am throughly stoked by how it runs!

 

[cannonball2]

Ran errands off and on all day yesterday on this bike. Running is impeccable. A big advantage is jetting and ambient temps. Was 52 degrees when I set the carb up and has been cooler until yesterday when it hit mid 70s. All it took was a quick tweek of the needles to account for the change.

Running fixed winter jets would have given a rich 4 stroking engine in a large swing like that. My area can swing many degrees in a short period. Great to have the easy adjustability.
Will try to get a short video maybe today.

 

[cannonball2]

Here's a video. Carb flange got loose on the manifold. Still ran great. Since fixed. Sounds like a chainsaw sorta. Runs somewhat better on the stock slightly modified muffler vs the long poo poo pipe. I belive it ran hotter as it is more restrictive. Needs a Zeda boost pipe.

 

[curtisfox]

WOW ! This has been my thought for a long time, to use chain saw carb. Just never made any seance to have to change jets every time you turn around, when you can just turn a screw. I believe FFV8 did this also, and was making manifolds for them. Way to go cannonball2, big confirmation for me.
By the way my new Still has a prejetted carb, no adjusting..........Curt

 

[cannonball2]

Hey Curt
Yeah running Walbro carbs has been done for a while so this is nothing new(actually I believe this one is a Tillotson clone). Its just that the carbs are so cheap now it was time to do it.

There are adapters out there for both mounting the carb to the engine and for mounting an air filter which pretty much makes it a bolt on. I just used what I had to make it work.
It's a great running set up.

 

[curtisfox]

As long as it works, ya would of made my own also. Always thought Tillotson were better carbs, at least on snowmobiles anyway. Sure glad for the good report, confirms what i was thinking all along. That and the Tecumseh clone carbs for 4 stroke, around $10........Curt

 

[cannonball2]

Now just waiting on the second carb and billet manifold for the Zeda 80. It should really wake it up!

 

[cannonball2]

Got the carb and the manifold yesterday and fabbed another set up last night for the Zeda 80 bike. Used a billet manifold which I drilled the bore to 17mm, got pretty thin!
I bonded another delrin flange/copper pipe section over it. JB weld is used to smooothly make a transition from the 21mm to the 17mm bore. This time the delrin was bonded to the copper with E6000 a tenacious adhesive of thinner consistancy. The JB got squeezed out of the joint on the last manifold as it's such a tight fit. Made another pellet tin air filter which is very unrestrictive.

The pic shows the large bore of the carb. If this was a 21mm slide it would overwhelm this basically stock motor. The diaphragm type carbs meter fuel properly with large bores. This was designed for a 61cc saw which has much more agressive porting, but works perfectly on a 66/70cc MB engine.

Also I raised the compression on the other bike and it woke it up even more. Even better response acceleration and 2mph on the top. Really hoping the Zeda rocks.

 

[curtisfox]

What do you use inside the pellet tin Foam? Looking good, should make a world of difference.......Curt

 

[cannonball2]

Not sure what you are asking Curt. Foam is lawnmower prefilter lightly oiled.

Here's the set up installed. Fuel line is loose to bleed the air to keep from pedaling so much while the carb picks up fuel. Will evevtually change all fuel lines to Tygon. Hope this carb runs as well as the other. For 16 bucks you never know.

The Zeda is a real power house stock, right at 70ccs. Wonderfully smooth bottom end. This one has slightly raised compression and the ports cleaned for flow. Will find out how it does as soon as the roads dry.

 

[curtisfox]

That's it, just lawnmower foam, nothing specific. Sure looks good on there ..........Curt

 

[cannonball2]

Have been riding this bike daily to a house we are renovating, covering around a100 or so miles.
It has run perfectly the whole time.

So the conclusion is this carb works well, is fairly easy to adapt, and is certainly cheap enough. It has a range of adjustment to handle stock to modified engines. Also its easy to adjust.
Will defiantly be getting on for my BT 80 bike which is still running an NT carb.

 

[curtisfox]

AWESOME ! Sounds like no reed valves needed here. LOL Just think if everyone did this, wouldn't be much to talk about on the forum. LOL. Sure a lot of guys having trouble with carbs. Thanks Cannonball2............Curt

 

[cannonball2]

Thanks Curt.
Am glad to finally have a CG that runs great. The usual carb choices leave a lot to be desired for overall runability. This one is good over the entire range..

The Zeda actually picked up a bit of top end.