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TR2/3/3A TR3A carb problem

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TFR

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Randall sent me a nice used carb to replace one that was damaged. The old carb had a crack where the main jet extends into the carb body.
The engine is still fouling the number three and four plugs. The one and two are nicely brown.
Both carbs are set the same with the same jets and float levels. The mixture bolts are both backed off the same on the bottom ( jet lowered the same level)
Any ideas on what to do next to help eleviate the plug fouling?
 
Are the carbs synchronized?
 
Larry - another thing to check - is the needle "shoulder" set correctly into the piston? If it's too far up in the piston, the mixture will be too rich. And of course is the needle correct. Randall probably already gave you the needle and jet correctly set up, but wouldn't hurt to verify.

And of course, be sure the jets are fully up ("choke" completely off). If the choke linkage isn't correctly set up, you can find one carb jet remains "down", and thus mixture is too rich.

Also, are the float bowl and float mechanism putting the right level of fuel in the jet? And of course, does the vacuum piston move freely up and down in the chamber? (lifting the pin and letting go gives a solid "thunk" when the piston falls back to the jet bridge)

Other guys with much more experience than me will chime in, but these are things I went through on my own TR.

Tom
 
NutmegCT said:
Randall probably already gave you the needle and jet correctly set up, but wouldn't hurt to verify.
Click to expand...
/bcforum/images/%%GRAEMLIN_URL%%/blush.gif Actually, no. Larry asked for a carb body & piston, so that's all I sent him. Since I wasn't sure of the condition of the needle & jet, they weren't included.

My first question is : What happens when you try the "lift the piston" test ?

Did you reuse your old needle & jet ? Perhaps they were the problem to begin with.

Any chance the jet housing assembly isn't assembled right ? Did the housing lock firmly in place when you tightened the big nut (after centering the jet) ?

I think Tom has covered all the other points.
 
Randall, I never expected anything more than you sent.

Now, I checked the needle height and they were set slightly different. Had no idea they could vary in height. I work on motorcycle ans the bike needles use a clip to set the length.
Anyway, set them to the same length using a caliper. The steps are at the bottom of the brass sleeve in the piston.

I had to reset the fuel mix and will test drive it when the rain stops.

Thanks and will post when I have any conclusions.
 
Larry - what's the situation now? How does the piston "lift and drop" test turn out?

What method did you use to balance the two carbs? Carb synchronizer (floating ball), Synchrometer (needle gauge), rubber hose?

When you reset the fuel mix, what method did you use? Colortune? Exhaust analyzer? Idling RPM change? Plug color? etc.?

Tom
 
Tom,

I've been a race motorcycle mechanic and a quality engineer for along time. Have a lot of experience with two and four carb rack carb synching.
When I synch the carbs I use a .035" pin under the butterfly and set the two to be at the same opening. Been using that method on race bikes for years.
I don't own a synch device. Have tried the mercury level / vacuum types along with needle gauges on a vacuum line.

To my TR3 carbs. I tried to lift button and the carbs and nothing changes in the idle speed.
The old fashon plug check after a ride is used to determine mix ratios. Have used a wide band o2 device on modern bikes and cars but not on this car.

TFR - Larry
 
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