Carb troubleshooting

[wtm442]

Put a wet rag under the bowl to get any gas that spills out. You should check the primary float level first. After it is adjusted correctly, then check the secondary float level.

The straight slotted screw on the top of the fuel bowl is the locking mechanism, and the 5/8" nut is the float adjuster. Turning the nut clockwise will lower the level. Use a box wrench and a big flat bladed screwdriver when making the adjustments.

Ideally, the adjustments should be done with the engine running, but it can be done with the engine off which is much safer, especially for a novice.

So engine is OFF.
1) Slowly remove the PRIMARY float level inspection screw. If a lot of gas starts to flow out of the hole before you get the screw out, the float level is too high. Tighten the inspection screw. Make the float adjustment using big screwdriver and 5/8 inch box wrench. Loosen the locking screw just a little (maybe 1/8 of a turn) and then turn the wrench no more than 1/8 of a turn clockwise to lower the float. Tighten screw with big screwdriver. Most novices will make too big of an adjustment and will turn a high float level into a low float level with a 1/2 turn adjustment.

2) Now you need to use up the excessive amount of gas in the bowl that made the level too high before the adjustment. So clean up any gas spilled and remove the rag. Now start the engine and let it run for a few minutes if you have a mechanical pump. Of course, this adds heat to the carb and makes adjustments harder. Many experienced tuners will slowly remove one of the lower float bowl screws and let all of the gas run into a cup. Tricky for a novice. On the other hand, if you have an electric pump, just turn on the pump without starting the motor.

Repeat step 1 and 2 until level is correct

OR

3) If no gas came out of the inspection hole when the float level inspection screw was removed, the level is either correct or too low. The gas in the bowl should just come up to the bottom of the hole. By bumping the car a little (or rocking the boat a little), a trickle of gas should come out of the hole if the adjustment is correct. If no gas comes out, the level is low. Make the adjustment with big screwdriver and 5/8" wrench, turning the wrench in the counter clockwise direction to raise the level. Put inspection screw back in the bowl.

4) Now you need to put more gas in the bowl. Remove the rag. Now start the engine and let it run for a minutes if you have a mechanical pump. On the other hand, if you have an electric pump, just turn on the pump without starting the motor.

Repeat step 3 and 4 until level correct.

Now you need to check the secondary bowl. See next post. I'd hate to lose all this typing if there was a computer glitch in the site.

[wtm442]

Secondary float adjustment same as the primary float except for one important bit of info.

If the secondary float is too low, use the steps above for the primary float level.

If the secondary float level is too high, you cannot use up the gas just by running at idle. You have to get the secondaries to open up. That means taking the car or boat out for a ride and floor it a few times.

Of course, if you feel brave, just remove one of the lower float bowl screws and let the gas drain into a cup. You probably will have to make a special cup if the carb bowls are close to the manifold. Then replace the screw. Now start the engine and let it run for a few minutes if you have a mechanical pump.

On the other hand, if you have an electric pump, just turn on the pump without starting the motor.

Repeat the steps for the secondary bowl until the levels are correct.

Now take the boat or car out for a 10 minute cruise. Make sure the secondaries are opened up a few times.

Now check the level again, but with the engine running. Many novices make the adjustments too quick or over-adjust. This last step is important, just to check your work with the floats before you move on the acc pump adjustments, jet changes and secondary actuation changes.

[gene8084]

wtm442, Thanks for taking the time for such a detailed reply. I actually only have a single bowl on the 6317...guess it doesn't really look like a 4150.

Thanks again.