Carburetor and Fuel System
Title: Bendix
question
I did a rebuild on a Bendix today, and have a question about the idle tube.
The diagram that comes with the rebuild kit that I used shows and states that I should just carefully insert the tube and tighten it and the main jet. The diagram does not show a spring on the top of the tube, similar to the one on the idle adjusting needle, but there was one there when I took it apart. Additionally the tube was not what I would call "tightened" when I removed it.
Further problem is that my 9 year old "mechanic's assistant" has misplaced the paper on which he wrote how many turns the tube was out before I removed it.
So, I guess my questions are as follows:
1. Do I leave the spring on it like it was, or do I go without it and tighten the tube down like the instructions say?
2. If I leave it on, what is a good starting point for tuning as far as how far out to have it?
Thanks in advance!
Dean
Post by Jonderson on Apr 16, 2004, 3:41am
Dean, you have an adjustable main, which accounts for the spring. The rebuild kit assumes that you do not have an adjustable main. Keep the spring on just like you had it before, assuming that you are using the same tube and jet. One and a half turns from seated and you should have yourself a good place to begin.
Post by Dean J on May 3, 2004, 2:54pm
Well, I did what you suggested and it fired right up and ran great--for about 20 minutes. Then it started blowing smoke and getting really hot. Oil still circulating, pressure at idle was 25psi. Temp-wise it ran cool enough before, and no smoke. Could it be running too lean? If so, can you provide input as to how to correct this? I have not used the adjustable main type jet before, and am relatively new to old bikes (if you have not gotten that yet).
Post by Billy on May 4, 2004, 7:44am
Do you have any "Intake leaks"?? That will get her too hot.
Did you Test for intake leaks??
What do the Spark Plugs look like?? The same or not?
& are they both clean=too lean
One clean & one sooty = Intake leak..
Post by Dean J on May 5, 2004, 3:55am
Billy, no I took it right out and rode it around. Plugs look good, and yes, I did a pressure test for intake leaks already, as that is apparently a common problem. So I guess it must just be too lean. I figured that would cause it to run hot, but would that cause it to smoke too? And my big question, since I now have an adjustable main: what is the proper thing to do to adjust the mixture, do I use just the adjustable main, or is it a combination of both?
Thanks for all your help guys, I am really grateful!
Dean
Post by Billy on May 5, 2004, 6:43am
Dean J, Too lean will make it run too hot & can burn a hole thru a piston.
OK, here we go, Assuming you have the "Correct" Heat range plugs in it, & gapped correctly,
& NO INTAKE Leaks,
& your timing & points are correctly set.[ALL critical]
We can proceed. Both adjustments do work together..
Idle mix screw & high speed adj. screw.
Not knowing what pipes you have makes it more difficult. But if you are running open-drag pipes you are too lean. The Bendix 16P12 w/adjustable Main jet tube.
check both adj. screws & set them both at 2 1/4 turns out. Warm up motor & Set idle for 800 rpm's approx. Then turn in & out the "Idle mix screw" till you get the "Smoothest idle"& "Highest idle" a 1/8 more. Done.
You should have a Big fan Blowing on the motor during this. Then set throttle for approx. min. 2,000 rpm's & adjust main till it runs "best & Highest rpm" a 1/8 more. Done..
Test ride & see how it performs.. Then let us know how you're doing... & what pipes you run..
But remember ALL the things listed, do need to be correctly adjusted prior to the carb.
Any time you feel the motor is getting too HOT, shut it off before any damage can occur. If you really overheated it, change the oil, first..
Your Spark plugs should look kind'a dark tan to gray.
Motor runs better a bit Rich rather than Lean..
Hope this helps.. ;D
Billy
Post by Dean J on May 5, 2004, 9:35pm
Billy: Thanks tons, that is precisely what I was looking to know!
As far as the other adjustments you mentioned, both the points, and timing were also just recently done as part of general spring maintenance. New 3-4 plugs, gapped. And you are apparently also a good guesser, as I am indeed running straight drag pipes.
I don't think I ran it long enough to harm anything, I was only a mile from home when I began to notice it having a problem, and it didn't seem to mind so much as long as there was air flowing over it. I will try these carb adjustments (probably not until Saturday) and let you know how it goes. Thanks again, you have been a great help already!
Dean
Post by Dean J on May 9, 2004, 8:03pm
Billy, (and Jonderson)
Thanks both for your help! Everything seems to be great now, and running smooth!
Dean
Post by Billy on May 9, 2004, 9:48pm
Happy Days are here again.
After 50 to 100 miles pull the spark plugs to check their color. If you got good color [I think you should] You're set for the road.. ;D Glad it was so easy.. ;D
Remember, Never tighten a spark plug all the way in a hot motor. When it cools it can/has, pulled the threads in Aluminum Heads, as it contracts/shrinks.
