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That's the only comment that caught my eye. Modded reeds could possibly flow more air (the hard part to get into an engine, fuel is easy). 'Blueprint'?? I have no idea what that means, but I've worked with various types and thicknesses, even shaped my own, but 'blueprint'? I'd love to see a...

Yep, the 455/460 is the same engine design.

Also check the metering orifice under the metering valve. A smaller orifice will give a longer 'ramp' of the fuel off of idle. I expect that the biggest difference between carbs (for a given model) is the metering spring, the metering orifice and the air bleed/transition holes.

I remember the first time I experienced a 'cool change' in Oz. The temperature was 42C and humid, just awful. I went into an office building for a meeting and while there the fellow said as he looked out the window "looks like the cool change arrived". When I left the building a half hour later...

You have to remember that the factories are restrained by EPA guidelines. Thus, the carbs (airbleed/transition holes, springs, jets) are set up to work within those guidelines. When the factories set the idle, they are doing it with the EPA designed carb. You have to think outside that EPA box...

Whizz kid? Crikey, it recently took me three months to find a leaking welch plug - one that I had put in! The different ways to set the idle works well on Zamas as their idle mixture is a separate circuit from the low speed circuit. However, when you are working with the Walbros, you are also...

I see where you're going with this. Yeah, see if you need to increase the L circuit when you are out in the field to get the best powerband for cutting. If increasing the L circuit doesn't help with the performance, then you might consider cutting the spring back a bit so you can get more...

When I was racing desert bikes I remember a couple of stories. Here's one, Mitch Mayes the top racer at that time ran out of fuel about 4 miles before the finish. He pushed his bike over to a motor home and got some fuel, then asked for some oil to put in the fuel. Nothing but Automatic...

I got mine from Bailey's. I noticed they have various lengths up to 20" in NK for Stihls. Even on my NK stumping chain with the cutters filed all the way back to the witness marks, I still have all the cutters on the chain. Of course, just like on any chain, if you hit dirt with them the edge...

Well, considering you have an issue with the clutch that needs to be resolved, if the existing torque causes a good clutch to slip with 3/8s, then going to a chain with less resistance in the wood may be an answer. I remember a bloke on AS about 5 years ago that liked 3/8s on his saw because it...

Sorry Brewz, I didn't see your question about the H screw. In most cases, yes, the H screw controls the flow to the main discharge nozzle. However, there are variations of carbs that have an auxiliary jet to add additional flow to the High speed (venturi) circuit. You ran into that on the 039...

I should add that having a good throttle response is desirable when you stop the saw buried in the cut and you have to get the saw cutting again. For example, if you are working a back cut and stop to check the hinge, being able to get the saw cutting again from a dead stop without moving the...

Yep, you got it. (although the stiffer spring did not make the L circuit richer, you did that with the needle) The whole ramping in of the low speed circuit is much more complex in boat and kart racing. Take a boat or kart coming out of a turn, the fuel mixture has to be spot on to give the...

Maybe you can try your Dad's clutch and see if it holds any better. If not, then I think your carb mod has done more than you expected. - (I wonder how much an o39 metering spring costs?) If the torque is now too much for the clutch, then the only thing I could recommend is to raise the cutting...

The Chinese clutches can be a hit and miss affair. I had one where one of the shoes was sitting a bit further out than the others and would tend to drag at idle. The other one I put on the 029 was a complete stuff up, the drum was actually out of round. I had to 'lap' in the clutches with some...

The taper is not critical to tuning. It is only used to set the adjustment to around 1 to 2 turns out. If you can tune it easily, then don't worry about the taper. If you had less than a half a turn, you might consider using a slower taper needle to make adjustments a little easier.

On this side of the Earth, we're on our way to bed. See ya, tomorrow...

Brewz, you got everything right except this - The stiffer spring only affects the 'ramp' (or slope) of the fuel coming in from the low speed circuit. The spring affects the 'ramping' in of that low speed circuit fuel. If the diaphragm section (diaphragm, metering orifice and valve and the...

Yeah, once you get your head around it, it's bloody addictive. Take a look at Rich and now Brewz, they're hooked! All it took was a little bit of time and maybe a few bucks for some parts and they got some great results. That Walbro spring kit is a excellent idea. When you work out a spring...

I should have mentioned that Rich was working on a Zama carb which has entirely different circuits to the Walbro. In the Zama the idle mixture screw ONLY affects the idle mixture. The low speed fuel flow is controlled by the jets he drilled. On the Walbro the low speed needle affects the idle...