MS460 to 066 carb swap??

[Erick]

I need for someone who has both a 046/MS460 and an 066/MS660 (or the carbs for both) to measure the carb throat's on both saws for me.

Also the width of the carb mount studs on both, are they the same??

I need to know how much more air a 066 carb will flow vs. an 046 carb.

Also if someone could look at things like linkages, lines, physical size, etc., does it look like a pretty straight forward swap.

From what I've seen I know I will have to turn the fuel line elbow 90* but looking at the IPL's everything else seems to be in about the right place to make it work. What about the impulse line?? haven't got a good look at where it's located on the 066 yet.

Anybody who's done this swap have any "words of wisdom" for me??

 

[Four Paws]

I need for someone who has both a 046/MS460 and an 066/MS660 (or the carbs for both) to measure the carb throat's on both saws for me.

Also the width of the carb mount studs on both, are they the same??

I need to know how much more air a 066 carb will flow vs. an 046 carb.

Also if someone could look at things like linkages, lines, physical size, etc., does it look like a pretty straight forward swap.

From what I've seen I know I will have to turn the fuel line elbow 90* but looking at the IPL's everything else seems to be in about the right place to make it work. What about the impulse line?? haven't got a good look at where it's located on the 066 yet.

Anybody who's done this swap have any "words of wisdom" for me??

Why are you wanting to put the 066 carb (WJ) on the 046 (HDA)?

Attached is some tech info that may help you...Looks to me that the mounting holes are in different locations, although they are the same width apart.

 

[Outlaw5.0]

I have always wondered how a 650/660 carb would work on a ported big bore 460.

 

[pgg]

Here's an 066/660 carb, throat 21.5mm, studs 31mm apart, fuel connection adjustable for angle, impulse connection on lower lid and adjustable for angle, choke connection on R/H side

 

[timberwolf]

I have run WJs on 60 cc saws and HT's off 088 on 80cc saws. Fine for racing, but not worth the hastle for a work saw.

Go over carb and Low speed operation becomes a problem, as the same air moves through a bigger hole air velocity drops, that means less draw on the jets in the venturi and under the throttle plate to pull fuel out. So you end up needing to crank the needles out. Also as the air velocity is lower fuel break up is poor, which leads to stumbling idle, flooding, hard starting ect.

If the saw gains RPM and pumps more air with the bigger carb then you are doing something, but if the carb is not the bottle neck, little will be gained at top end but losses will be incurred at lower RPM. That said if the saw is ported to race a big carb will work, if it's ported to be a work saw, not so much.

 

[timberwolf]

Here is a WJ from 066 that was made to flow a little beter, this is an option too for the 046 keeping the original carb.

Just stream lining the carb made about an extra 10% difference over a stock carb on a fairly well ported 066 work saw.

 

[Outlaw5.0]

So even with a big bore kit that is ported, it is too much?. Just trying to learn, I have a bigbore kit on the way.

 

[timberwolf]

I don't find much difference flow wise BB or standard jug, Sure the BB jugs have a few more CC's but in general they rev a little slower and also pump a little less efficently due to the same restrictions in transfers, base, exhaust...being applied to a greater displacement. Even power wise what they gain in torque is pretty much lost in speed.

If it is a work saw then going bigger is likely not going to gain much. If it is a grey area saw where the limits of a work saw are being pushed, then yes there are a few percent to be gained, but it will suffer for general use and pushing RPM up is going to push life expectency down fast.

If it's a race saw, then no question a bigger carb will let it turn higher RPM and pack more fuel and air in.

Puting a bigger carb on though without increasing the intake tube diamiter though is not addressing the issue.

 

[scootr]

Agreed

I agree with Timberwolf, you will lose velocity. That will pretty much kill your low end power. Look at a Quadrajet carb, tiny primaries for velocity and low end torque. The Secodaries are like silver dollars and open only at very high RPM.

 

[Ghillie]

I agree with Timberwolf, you will lose velocity. That will pretty much kill your low end power. Look at a Quadrajet carb, tiny primaries for velocity and low end torque. The Secodaries are like silver dollars and open only at very high RPM.

and the secondaries only open as the air flow increases (quadrajet)

 

[pgg]

I like the streamlining thing but what's the best way to start a saw without a choke plate?

 

[timberwolf]

2 ways, thumb in the hole, or a squirt of fuel down the bore. Thats the price to be paid to go fast.

 

[Four Paws]

2 ways, thumb in the hole, or a squirt of fuel down the bore. Thats the price to be paid to go fast.

Well, here is a 3rd way...but it is not nearly as easy as the 2 ways you mentioned.

 

[Erick]

Hey fellas thanks for the replies, I wanted to let this run a bit to see what would develop.

pgg, thanks for the measurement and the photos that helps a bunch.

Paws, thanks for the link I have that stored in my computer but it didn't cross my mind to check it for some reason.

TW, This is going on a big bore turning around 15,500 I was looking at the option of boring the 046 carb and rejetting or just going up to the 066 carb. I'm not looking for more RPM it's just a little "thin" up top and finicky about tuning with the carb maxed out, I can't help but think a little more air with a little more fuel in it will help. There's plenty of room in the intake and exhaust for more fuel but I wasn't able to work the transfers as I would have liked so you may be right about the transfers being the bottle neck with the bigger carb. I may yet go back in and raise the transfers a little to get more time/area and put them where I want. I've been sneaking up on this saw slowly and have reached the point that I really feel I need more fuel and air.

It looks like I would gain 1mm into and out of the carb and around 3mm in the venturi if I go with the 066 carb, whereas I would get probably 2mm max boring the stocker. I can jet to whatever is necessary fuel wise, just trying to figure out how much air I'm gonna need. It runs good now, but I think it can be a lot better with more carb.

I'm starting to think I may just bore the stocker, I want this saw to look dead stock.

I would value your opinions here.

 

[blsnelling]

...I want this saw to look dead stock.

But we already know what that "stocker" looks like:greenchainsaw:

 

[Erick]

But we already know what that "stocker" looks like:greenchainsaw:

Thaaats not iiiit.

 

[Four Paws]

I'm starting to think I may just bore the stocker, I want this saw to look dead stock.

I would value your opinions here.

Just drill the carb and see how that does for you. If you bore it, be careful - there are passages under the surface that you don't want to open up - specifically the little nib in the venturi - you'll see it.

 

[blsnelling]

Thaaats not iiiit.

LOL. I was worried about that!

 

[Outlaw5.0]

How much can the stock 460 carb venturi be bored before getting into the passages?.

 

[Outlaw5.0]

Why are you wanting to put the 066 carb (WJ) on the 046 (HDA)?

Attached is some tech info that may help you...Looks to me that the mounting holes are in different locations, although they are the same width apart.

What is the exact size on the 460?, they list few different sizes for the HDA carb?.