212 Predator Adjustable Carb Project - Snowblower Forum : Snow Blower Forums
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post #1 of 26 Old 10-07-2014, 11:08 PM Thread Starter
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212 Predator Adjustable Carb Project

After reading lots of things on the internet, about re-jetting 212cc engines for running in cold weather, I thought, why not open up the stock .028 HS jet and make it adjustable.

One thing puzzles me. A 212cc Predator, with a stock .028 jet, runs fine in warm weather (above 40 degrees). The only change, seems to be the introduction of winters cold air into the carb. It seems that the idea of a heat box would solve the problem, without changing to an increased jet size.

Getting warm air to the carb might be the answer. I am working on a prototype to do just that, without the use of a heat box. In the meantime, I thought that being able to fine tune the high speed jet, might be a good idea also.

I bought this carb to test my idea. It already has the adjustable low speed jet.


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I got an M8 x 1 bolt, so I could match the threads on the bowl nut. I dug through my old carb parts and found a needle assembly, that I could adapt with the fiber washer seal.


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On my lathe, I turned the needle assembly threads down to .200, to be silvered into the hole, that I drilled part way in the head of the M8 bolt. Then drilled a clearance hole (.136), the rest of the way through for the needle.


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Once I had it silver soldered, I tested it in the carb and found that the needle was not quite reaching the jet. Had to thin out the bolt head, from the bottom.


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The completed set-up came out fine.


======================================

The HS jets seem to run from the stock .028, all the way up to .048. Not sure how much I should drill out the HS jet to. I guess I could go all the way to .048, as the adjustment will cover all of them.

Just put a 212cc on my Jake 626, and will test this carb on it this week. -- John
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post #2 of 26 Old 10-08-2014, 12:10 AM
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John
I love your work. I knew before I opened your thread I was going to be impressed.
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post #3 of 26 Old 10-08-2014, 12:15 AM
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Outstanding!
Once you fine tune everything, you'll have a great product. Start selling them to all the folks who have a predator engine.
Let us know how things work out

1972 Ariens 13/32 restored & repowered
1971 Ariens 7/24 (retired)
2011 Ariens Deluxe 24
1980 Ariens st7/24 (retired)
1985 Ariens st10/36
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post #4 of 26 Old 10-12-2014, 04:51 PM Thread Starter
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Quote:
Originally Posted by Waterlooboy2hp View Post
After reading lots of things on the internet, about re-jetting 212cc engines for running in cold weather, I thought, why not open up the stock .028 HS jet and make it adjustable.

One thing puzzles me. A 212cc Predator, with a stock .028 jet, runs fine in warm weather (above 40 degrees). The only change, seems to be the introduction of winters cold air into the carb. It seems that the idea of a heat box would solve the problem, without changing to an increased jet size.

Getting warm air to the carb might be the answer. I am working on a prototype to do just that, without the use of a heat box. In the meantime, I thought that being able to fine tune the high speed jet, might be a good idea also.

I bought this carb to test my idea. It already has the adjustable low speed jet.


=====================================

The completed set-up came out fine.


======================================

The HS jets seem to run from the stock .028, all the way up to .048. Not sure how much I should drill out the HS jet to. I guess I could go all the way to .048, as the adjustment will cover all of them.

Just put a 212cc on my Jake 626, and will test this carb on it this week. -- John
======================================
I ended up using a #56 drill (.0465) to open up the HS jet seat. I got time today to go ahead and install the new carb, with adjustable high and low speed jets.

At the same time, I had finished up my idea for getting warm air to the carb intake, without the use of a traditional heat box.

I had started with a small piece of 1" electrical conduit and added a flange. Next, I found an old choke shaft and used the plate from an old throttle shaft, that just happened to fit perfect in the tube. This damper control is more for testing, than for anything else.

When cold weather gets here, I want to be able to run the engine without adding warm air to the carb intake and see if adjusting the new HS jet is enough to smooth out the engine. If not, I can open the damper and introduce the hot air, and take it from there.




=========================================

I added a hole to the side of the muffler guard, that was 1/4" larger in diameter than the flange pipe. (I did not want the pipe to touch any part of the muffler, or its cover). I also put a 1" hole through the side of the carb cover. (both inner and outer walls).

I bolted the flange pipe directly to the carb cover at first. I wanted to see if anything was going to melt. After 1/2 hour of run time, nothing had melted, but I could feel a tiny hot spot on the plastic. It was right next to the flange, at the very top. Turned out, that there was a pocket between the two cover walls, that trapped the heat.

To be safe, I put a piece of .062 Phenolic between the flange and the cover (it can be seen in the 1st photo). Also cut away a spacer between the two walls and added 3 layers of the Phenolic, to fill the void. Now the heat would not get trapped in the pocket.



I can`t really test the system out, until we get some cold weather. Right now, with the damper open, the hot air mixes with the normal incoming cold air. If need be, I can always stuff some filter foam, into the holes where the cold air comes in, to restrict it more.

The overall set-up is nice and compact. Time will tell if it works , or not. - John


Last edited by Waterlooboy2hp; 11-29-2014 at 08:46 PM.
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post #5 of 26 Old 10-13-2014, 12:11 PM
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Impressive detail work!!! Why didn't you thread the inside of the bolt and just put the needle in there?

'77 Ariens 924032 "Brick House" Re-Powered with a TEC 10HP and oversize auger pulley
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post #6 of 26 Old 10-13-2014, 12:31 PM
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Beautiful work!
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post #7 of 26 Old 10-13-2014, 01:58 PM Thread Starter
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Originally Posted by nt40lanman View Post
Impressive detail work!!! Why didn't you thread the inside of the bolt and just put the needle in there?
==========================================

That style of needle has an o-ring on it, and would require a 1/4" hole to be drilled down into part of the bolt thread. No material left to support the bolt threads.

After making the first one, I found a style of needle in my stash, that will work with just a thread in the bolt. The seal is still an o-ring, but needle spring pushes it against the head of the bolt, on the outside. It can be used in the bowl bolt that comes with the carb, or an 8mm bolt from the hardware store.



As carb needles are expensive, even if you could find one of the right type and size, I have now refined the whole process a bit further. I am going to make some needles from #10-32, stainless steel Allen cap screws, that have a partial thread. They were shipped to me today. The o-ring, washer and spring are easy enough to find.

Prototypes pave the way for improvements. -- John
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post #8 of 26 Old 10-14-2014, 09:46 PM
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Makes me wish I had a lathe

'77 Ariens 924032 "Brick House" Re-Powered with a TEC 10HP and oversize auger pulley
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post #9 of 26 Old 10-31-2014, 10:01 PM
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So did you test it out yet?? Roger
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post #10 of 26 Old 11-01-2014, 01:05 AM Thread Starter
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Originally Posted by rhenning View Post
So did you test it out yet?? Roger
========================================

As far as the adjustable carb jet, it works like a charm. The engine runs so smooth, that it sounds like an electric motor. It was 80 degrees that day, so I suspect it is adjusted to be pretty much the same as a stock .028 jet would be.

I will have to wait for some temps well below 40 degrees, in order to see how adjusting the high speed jet and feeding warm air into the carb will work out.

In the meantime, I am preparing to make some 10mm to pipe thread adaptors for extending the oil drain plugs. I am planning to make them from 5/8" aluminum hex bar stock. I ordered some material today. -- John
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