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phazed
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33 Posts
Discussion Starter · #1 ·
Just got the engine back in my phazer today, and was about to set the pilot screws back to spec (1 1/2 turns out). Like an idiot I overtightened one of them when screwing it in all the way and broke the head off. Now I have the majority of the pilot screw stuck in the carb and not enough sticking out to put a pair of vice grips on it.

My question is, anyone have any good ideas on how to get the rest of that screw out? The sled still runs, but I'm afraid to try driving it. I've read that the pilot screw only effects a/f ratio at idle for the most part and at WOT it doesn't do much. Not sure how important it is for me to get this fixed right away.

Please, share your opinions and flame away! :thumbsup:
 

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Super Moderator
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18,335 Posts
Welcome to the forum.


If you try to remove the broken part, be gentle in what ever you do. The aluminum of the carb is very soft and won't take much abuse.

You may be able to use a small screwdriver and turn the top of the broken part to get it to thread out.

If that doesn't work you can try to get a small chisel or sharp screwdriver onto the top of the broken part. Use a small hammer and tap the chisel to make a groove in the top of the broken part. That may allow you to turn the screw out.

I would avoid using a drill, although a reverse cut drill designed to remove broken studs may work. It's been my experience that the drill tip wanders too much and ends up damaging the hole. As a last resort, if you can center-punch or flatten the broken part to get the drill centered, a reverse drill may work.

Hopefully, someone else can pop on with a good idea or two.. good luck!
 

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phazed
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33 Posts
Discussion Starter · #3 ·
i did have the thought of using an easy out.. but i usually just end up making a huge mess whenever i use them. i tried pounding a small flathead into what was left of the screw and found out how soft the aluminum of the carb really is. i'm keeping an eye on e-bay for a cheaper set of used carbs.

aside from all of this mess, me and my buddy managed to rip the motor out yesterday to remove a bent steering shaft, and got it all back together & running today. then i broke that stupid screw :rofl:

thanks for the advice!
 

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Mr. Budget Mechanic
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152 Posts
By tightening the air screw all the way in, you have made the idle fuel mix as rich as it possibly can get.
Sorry to contradict you Dan but don't Phazer's have fuel screws? Mine have the pilot screws on the engine side of the carb, which means screwing them in leans the mixture.

And lastly, a little bit about the difference between fuel screws and air screws:
Two stroke carbs normally have air screws and four stroke carbs normally have fuel screws. You can tell if a carb has an air screw or a fuel screw by it's location on the carb. An air screw will be on the intake side of the carb while a fuel screw will be on the engine side of the carb.
They sort of work opposite one another. An air screw adjusts how much air is being delivered thru the pilot circuit: in is rich (less air) and out is lean (more air). A fuel screw adjust how much fuel (or air/fuel mixture) is being delivered from the pilot circuit. In is lean (less fuel) and out is rich (more fuel).
from Snow Tech Magazine

[/IMG]

I had a broken pilot screw on my '86 Honda ATC250 SX; I was just able to remove the broken piece out of the carb by sticking the tip of a pushpin into the pilot hole from the inside of the throat of the carb body and carefully squeezing the pushpin with a pair of needlenose pliers. It took a bit of effort, and I broke the plastic off a couple of pushpins, but with patience, steady hands, and a bit of determination I was eventually able to dislodge the broken pilot screw tip. Didn't think it was going to work to be honest, but it did the job. Be careful not to scratch the carb throat and also try not to enlarge the hole too much with the pushpin. I believe I filed down the diameter of the pushpin a bit with a dremel first before I attempted to poke the broken pilot needle out. It'll enlarge the hole a tiny bit, but as long as it isn't too much bigger you should be able to tune it to run properly just by adjusting the screw in a bit more than you normally would.

Free '84-'99 Phazer Manual download here:http://www.snowmobileforum.com/yamaha-snowmobiles/39584-1984-1989-yamaha-phazer-manual-pdf.html

I wouldn't buy another set of carbs yet, try punching the broken pilot out with a pushpin first; it worked for me.

Good luck, let us know how it works out.
 

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Super Moderator
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If the screw controls air to the pilot jet, it's an air screw. Closing the air off just makes it richer at idle. If it's a fuel screw, closing the fuel off will make it leaner and could cause a problem. I have not worked on that type of carb, so I can't tell you what it controls. If it's a fuel screw, I would get it repaired before riding, just to be safe. Where's Yamadad when you need him ;) Looking at the diagram that Cutlass posted, it sure looks like a fuel screw.

You may be able to call a shop or the dealer to get some information on what the screw controls.
 

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Mr. Budget Mechanic
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152 Posts
It's definitely a fuel screw. I have worked on the carbs on my '87 Phazer and can attest to the fact that turning the pilot screws out enrichens the mixture, and turning it in leans it. I wouldn't run the sled with the pilot screw broken off in it. It'll likely be too lean on that one side and you'll run the risk of overheating and damaging the motor. You could try running it for a few minutes and check the plug color: if the electrode is really white or silvery gray then it is dangerously lean; a cardboard or chocolate brown color is ideal and if the electrode looks like that the mixture is good. Chances are that if it is jetted properly a plugged pilot screw hole is going to lean out the cylinder; at least at idle/low RPM's, if not throughout the whole RPM range. In fact, if the pilot jetting is correct, it shouldn't even run with the pilot screw completely turned in (see #3 second paragraph below): How to adjust pilot screws
This is from Snow Tech Magazine
"The low speed tuning (idle to 1/4 throttle setting) is calibrated by pilot jet changes and adjusting the air screw. Operate the throttle between idle and 1/4 and see if the engine revolutions increase smoothly. If the pilot jet circuit is too lean, increase in the engine speed will be slow and irregular. If the pilot jet circuit is too rich this would create heavy exhaust smoke as well as a dull exhaust noise. If you cannot maintain speed in this 1/4 throttle area while the throttle is held constant, the pilot jet circuit is too lean.
To find a good starting point on the air screw, warn up the engine to operating temperature and adjust the air screw in (richer) or out (leaner) until the idle RPM is at its highest point (do not open more than three turns). One point to watch on air screw adjustment, if the engine idle to 1/4 throttle performs best with the air screw adjusted 1/4 turn or less it may be an indication that the pilot jet is too lean and the opposite holds true if the air screw ends up near three turns the pilot jet may be too rich. It’s easier to adjust the airscrew than to change pilot jets to find out if you are too rich or lean on the pilot circuit.

_______________________________________________________________________________________________________________________________________________


OK. On to the procedure!

1) Warm up the engine to full operating temp.
2) Turn up your idle a few hundred RPM using the throttle stop screw (basically you want a fast idle). This will make it easier to hear small changes in RPM. Watch for overheating--pointing a big shop fan at your engine will help it from getting too hot during the fast idling. The whole procedure shouldn't take too long though.
Each time you change the screw setting 1/4 or 1/2 turn or so, wait about 5 seconds to let the idle speed normalize. It usually take the carb and engine a moment to react to the change.
3) Turn the fuel screw IN until the idle starts to drop and miss. The engine should die if you bottom out the screw. Your pilot jet is too big if it doesn't die when the screw is bottomed out--it should die before it gets that far in.
4) Then begin turning the fuel screw OUT. The idle should peak and become smooth. Keep going and look for the idle to begin to drop/miss again.
5) The goal is to find the setting that provides the highest and smoothest idle. If it's unclear exactly were that point is then set to the midpoint between step #3 and step #4. For example, if the idle starts to drop at 1 turn out and starts to drop at 2 1/2 turns out then 1 3/4 of a turn out should be the correct setting.
If the peak/smoothest RPM is reached somewhere between 1-3 turns then your pilot jet is correct (the 1-3 turns applies to most carb types). If you end up less than 1 turn out then your pilot jet is too big and you need a smaller one. If you end up more than three turns out or the fuel screw seems to make little difference as you continue turning it out than you need to go up (bigger) on your pilot jet.
To re-emphisize: If the idle never drops when you're turning the fuel screw in, you need a smaller pilot jet. If the idle never drops when you're turning the fuel screw out, you need a bigger pilot jet.
Typical fuel screw settings are in the 1 1/2 to 2 1/2 range.
6) Once you've got the fuel screw set, re-adjust your throttle stop screw (idle screw) to an appropriate idle speed.
And that's it! Your pilot circuit is now VERY close to ideal. From here you can experiment with how small adjustments affect low-end (i.e. small throttle openings) response and make adjustments for weather. The hardest part is usually gaining access to the screw while the engine is running. Also, you may really have to listen carefully to detect the rpm changes in the idle. 100 or 200 rpm differences can be tough to detect when the change happens over several seconds.


And lastely, a little bit about the difference between fuel screws and air screws:
Two stoke carbs normally have air screws and four stroke carbs normally have fuel screws. You can tell if a carb has an air screw or a fuel screw by it's location on the carb. An air screw will be on the intake side of the carb while a fuel screw will be on the engine side of the carb.
They sort of work opposite one another. An air screw adjusts how much air is being delivered thru the pilot circuit: in is rich (less air) and out is lean (more air). A fuel screw adjust how much fuel (or air/fuel mixture) is being delivered from the pilot circuit. In is lean (less fuel) and out is rich (more fuel).
Try the pushpin trick; at this point you've got nothing to lose.
 

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phazed
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33 Posts
Discussion Starter · #9 ·
I dont think a pushpin is going to do anything, it's still threaded in the hole completely.

But I'll try it, along with other things. Worse comes to worse I'll go get a smaller easy out and try that.
 

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I don't think I'd risk riding it without getting it out and a new one installed at the correct setting. I'm not saying its impossible, but you'll likely jack up the side of the screw hole trying to drill into it. I've been watching E-bay lately and there have been plenty of carb sets for sale on there. It sucks having to go that route, but how much time do you want to tie up is also the question, trying to back that stupid screw out. You could keep that set around for parts. If it was another part someplace else on the sled, I'd say try and back it out, but the carb is a place you don't want to take chances, with the possiblity of burning a piston then you'll be setting instead of riding. Good luck!
 

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phazed
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33 Posts
Discussion Starter · #11 ·
I don't think I'd risk riding it without getting it out and a new one installed at the correct setting. I'm not saying its impossible, but you'll likely jack up the side of the screw hole trying to drill into it. I've been watching E-bay lately and there have been plenty of carb sets for sale on there. It sucks having to go that route, but how much time do you want to tie up is also the question, trying to back that stupid screw out. You could keep that set around for parts. If it was another part someplace else on the sled, I'd say try and back it out, but the carb is a place you don't want to take chances, with the possiblity of burning a piston then you'll be setting instead of riding. Good luck!


that's pretty much how i feel about it to. i actually got a set coming from eBay, bought them yesterday. will just try to fix my carbs and then keep them on the shelf of spare phazer parts that is slowly getting bigger.
 

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Mr. Budget Mechanic
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152 Posts
I dont think a pushpin is going to do anything, it's still threaded in the hole completely.
I was skeptical too, and to tell ya the truth the pushpin was kind of a desperation move; the needle thin tip of the broken-off fuel screw was wedged in that tiny little hole like it was welded in, and I kept breaking off all my tiny drill bits on it that I had that were small enough for the job when I first tried drilling it out; maybe I was just lucky, but in the end it worked, and that's all that mattered. I thought that at best I'd get the pushpin stuck in the pilot circuit hole and broken off too; then I'd have 2 broken pins stuck in the carb.

Just to be clear, I used the power of the needle nose jaws (and not my thumb) to push the broken piece of fuel screw out. I wrapped a small piece of rag around the parts of the carb that the pliers would make contact with, and placed the pushpin tip on the primary screw circuit hole from the inside of the carb throat; then centered one side of the jaw on the end of the pushpin, and the other on the outside of the carb body, and squeezed hard. Took many, many, many attempts and a couple of pushpins (plastic kept chipping off, was hard to keep pushpin in place and pliers centered on it), but eventually the broken sliver of metal popped out, and the pushpin itself did not get stuck in the hole. It took a while to get the broken screw to begin moving and it was discouraging at first, but once it did (and it was just a hair to begin with), I knew that I was going to be able to get it out. And since it was a fuel circuit, if the hole got enlarged a bit it wasn't the end of the world; it would enrichen the low speed a bit which I'd adjust by just leaning it out by turning in the fuel screw a bit more than normal.
 

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phazed
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33 Posts
Discussion Starter · #14 ·
Just got the "new" set of carbs from eBay on last night. Took them apart and cleaned them really quick (they didn't need it at all) and she's running great. Me and my bud cruised our phazers down the street for a quick victory lap even though there wasn't nearly enough snow. Runs awesome. Just need to do some fuel screw tuning once we get enough snow to actually ride the things.

Thanks for all the suggestions.. I'll probably attempt getting the broken screw out from the old carbs sometime this weekend.
 

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Mr. Budget Mechanic
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152 Posts
Good deal man. Sounds like you bought from a good seller; those puppies shipped fast.

Now just pray for more snow, eh? :cool:
 
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