Bigger carb for a stock MS460?

[TJ the Chainsaw Mechanic]

Thoughts? Both of mine are muffler modded. Is there a bigger carb I can put on them stock or will that be a waist of time?

 

[jacob j.]

Hmm...I guess it depends on how much work you want to do. The horizontal intake studs limit carb width that way, but if you want to relocate the studs to a diagonal configuration, you could probably squeeze an 066 carb in the airbox.

You could also bore and drill an existing stock carb.

 

[Terry Syd]

Try drilling out the EPA approved .25mm limiter jet on the low speed circuit. You will pick up some more torque and resistance to bogging.

The carb venturi is actually fairly large - 17.45mm and has a nice offset discharge nozzle that allows it to flow quite well.

 

[Landmark]

Try drilling out the EPA approved .25mm limiter jet on the low speed circuit. You will pick up some more torque and resistance to bogging.

.

Is 046 the same or was it pre epa?

 

[Poleman]

There are some tricks you can do if you can find a Zama carb from an earlier 046 that work well. The ones without the compensation vent on top.

 

[TJ the Chainsaw Mechanic]

Thanks for the ideas. We have a ton of carbs at the shop that would be rebuildable and I could modify. I'll see about finding a zama off an 046.

 

[mdavlee]

I have a modded Zama on mine. It won't flow enough for methanol and nitro though

 

[Terry Syd]

Is 046 the same or was it pre epa?

I don't know, but I modded a cheap Chinese 460 carb ($A20) for a 029/390 conversion. If you don't want to drill on the OEM carb you could pick up a Chinese carb and try that. It would be interesting to see the comparison of a modded Walbro and the modded Zama. The modded Walbro might require a stiffer metering spring to bring up the low speed circuit flow to match the modded Zama.

This is when I would like to have access to a dyno to see the difference in the power curves. For my 029/390 I'm presently running a modded HD-5 that came on the 029. Not bad, after drilling out the limiter on the low speed circuit. Besides the difference in venturi sizes and discharge nozzle placement, the 460 carb has bigger air bleed/transition holes and a weaker metering spring. The HD-5 has smaller air bleed/transition holes but a much stronger metering spring. If I had a dyno and a box of metering springs I could probably find the 'perfect' carb for the saw. I'd probably end up with a drilled HD-5 with a different metering spring - but once I had the right recipe, everyone would know and could duplicate it. - Of course, on that series of saws it is the air filter that is the bottleneck for air flow.