Carburetor mods and mod theories

[idiotwithasaw]

Sounds like something I would do.

 

[Chainsaw Jim]

I thought I had it together good enough to get by without using it after using a larger sleeve. I was wrong.

 

[idiotwithasaw]

Did you use a rubber washer between the carbs, also what did you use to block the holes where the choke and throttle shafts used to be?

 

[Chainsaw Jim]

The gasket between carbs is one of those gray ones from a tillotson carb kit. I do have a rubber one ready to install.
I use pieces of fuel line that fit the holes snug and lock them in place with equal length chunks of a wood nail. That way they are removable without damaging the carb.

 

[idiotwithasaw]

ok here is one hda 198 I bought for one of my 357 to 346 carb conversation. I already have the rest of the intake tract, but I'm curious as to any mods that should be done to the carb? Do I need to notch the throttle plate? Or anything else?

 

[Chainsaw Jim]

I believe that's the same carb on my 357/272 hybrid. One thing I've noticed about it is the metering pin seat opening is half the size of the 562xp carbs... El-46, and 48. I drilled it out to match. The only other mod I did was pop the main nozzle out to drill a hole to match up with the two holes in the carb body. The jet has a hole on each side when the holes in the carb are closer together. I only drilled the third hole in order to line up perfectly with the holes.

 

[Chainsaw Jim]

I think with the direction you are going you really need a pipe on it for it to flow properly. Still a cool idea.

I decided to do it because it would only take a few minutes to set up and the second carb was ready to go from previous carb experiments. Here in the next hour or so it will be back as it was before I started unless some folks out at Bob's gtg want to check it out this way. I'm only five minutes away from there so I can bring it in either form.

I wouldn't say no to a pipe though.

 

[idiotwithasaw]

On the one I already have it set up on I'm having problems with too much fuel, not too little. That's why I was wondering about notching the throttle plate if that would give me a leaner mix at idle. Also yes I checked the meter height, it why I bought these.

 

[Chainsaw Jim]

There's a few important pieces of info needed to help your situation out. What is restricting the air flow to make it so rich? Sometimes the air injection isn't enough when you get into modifying these models and they need breathing holes cut. Is your saw ported to the point of needing a larger carb?
It may just be too much carb as it is.

 

[banana boat]

Is it OK that I have a little bit of a bone looking at that pic?

What do you mean a little bit lol

 

[Chainsaw Jim]

Has anyone ever used the flood limiter valve on an old tillotson as a fuel supplement?
I suppose there's no harm in trying. My idea is to take the same piece of aluminum can that is disabling it and drilling a very tiny hole in the center to turn it into a jet. Maybe grinding a tiny cavity around the opening in the throat of the carb to increase vacuum on the hole since it'll be so much smaller.

 

[Chainsaw Jim]

So I have this theory that carbs have a limit on how far you can hog them out. Lol
I've obviously surpassed the throttle plate limit for what it came with so I suppose I'll be fabbing one up for that.

 

[drf256]

Which carb and for what saw is that Jim?

When I've done it, WOT is fine, but idling/starting/throttle response has suffered.

 

[Chainsaw Jim]

Which carb and for what saw is that Jim?

When I've done it, WOT is fine, but idling/starting/throttle response has suffered.

It's a wj carb I'm destroying. Lol
I oversized the metering seat and the jet plug. I've heard idling problems can be fixed by plugging the other brass jet so that'll be something to try if it comes to that. I'm not heart set on this thing being a successful mod. I'm just learning a bit more about carb modding through trial and error.
I'm probably going to slap it on the piped 064 hybrid to try it out.

 

[drf256]

Cool

Did you leave any Venturi in it at all?

 

[Chainsaw Jim]

Cool

Did you leave any Venturi in it at all?

There's actually a measurable venturi left in there. I was trying to make it a straight shooter but I didn't want to bore through into the metering shaft.

 

[Chainsaw Jim]

I guess it's time to slap this thing on something to see what I did to it.
The throttle plate is nice and tight.

 

[paragonbuilder]

I guess it's time to slap this thing on something to see what I did to it.
The throttle plate is nice and tight.
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Nice job Jim! Here's hoping it works!


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[Chainsaw Jim]

Nice job Jim! Here's hoping it works!


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Can I keep you on call as a good luck mojo type dude?!

 

[paragonbuilder]

Can I keep you on call as a good luck mojo type dude?!

Lol. Sure but it might backfire on you....


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