Carbs

10 posts in this topic

Posted

For those that run 582's with Bing carbs, do you use the choke system or do you use a primer for starting?  I've always used the chokes but considering a primer system this time. Would save a lot of headaches with the cables and control and mounting. A simple installation since I am using a gascolator.

Share this post


Link to post
Share on other sites

Posted (edited)

Primers work real well with a 582.  Very quick starting often once you learn how many pumps to make.  Especially noticeable if you have pull start.   On the Avid you have a fuel valve right close to the throttle in the center, so there is a good place to T into a fuel line there.  Had the primer close to the center as well then.  Here was my MK IV when I first got it showing valve and primer locations.  JImChuk

New Avid 008.jpg

Edited by 1avidflyer
2 people like this

Share this post


Link to post
Share on other sites

Posted

I find the primer perfectly adequate as long as you know there is fuel all the way up to the carb. I had a devil of a time starting my 582 sometimes, especially re-start, and since I installed a 2 to 4 psi firewall boost pump with my 670, not a single problem. The pump assures that the fuel lines and carb bowl are full, something the slight gravity pressure doesn't seem to assure.

Share this post


Link to post
Share on other sites

Posted

I like to have both a primer and an Enrichener   (what a lot of people call a choke) on my airplane.  I had a 670 in my skidoo.  It had a pull starter and a primer only, no enrichener.  When starting I always opened the hood so I could see the clear primer line while I worked the plunger.  As soon as i could see fuel in the primer line...usually about 3 or 4 plunges...it would start first pull, but I had to have my hand on the plunger to give it another shot if it started to die.

On my 503 rotax kitfox I had both.  In cold weather it took a lot of electric starter cranking to start with the enrichener.  So I used the primer to save wear and tear on the electric starter. 

Another good thing about a primer is you can keep the engine running with it encase of a fuel pump failure.

So, why do I say I like to have both enricher and primer?  Here's Mike Stratman's article to explain.  https://www.cps-parts.com/cps/pdf/Part60.pdf

Direct link to the whole series of Mike's Rotax Tech articles. https://www.cps-parts.com/catalog/rtxpages/articles.php

1 person likes this

Share this post


Link to post
Share on other sites

Posted

I always install an electric boost pump on my aircraft, especially 2 stroke models. The Deloroto carbs have a different animal for an enricher. Basically called a starting tickler(don't ask me) and works a tad different than on a Bing carb. Yes, a choke (enricher) can help solve some rich/lean issues and even drop EGT's in an emergency situation in flight. But a primer can do similar things when used correctly. Either one can flood an engine if used incorrectly. I usually tweak my engine so that its running balanced on both cyl's. Next day the humidity or temps can change it a little. And I am a firm believer in having your EGT's as close as possible. Unbalanced EGT's put extra stress on the crank when one cylinder isn't producing as much power as the other cylinder. May not mean squat, but with a two piece crank pressed together, every bit of stress reduction helps. Also makes the engine run smooth as hillbilly mountain dew!

Share this post


Link to post
Share on other sites

Posted (edited)

I've ran both. I prefer a primer for ease of use and set-up for new installations. I also keep the cylinders balances as close a possible. Makes them run smooth. Allen, do you manually adjust your slides to the same height or do you use a manometer?

Edited by NorthIdahoAvidflyer
spelling

Share this post


Link to post
Share on other sites

Posted

I adjust them with the pencil method and manually. After running and warm up I adjust the slides according to what the EGT's are saying. Normally get them within 10 deg  separation.  A lot depends on how well the cables were fabricated and the control slop.  Long runs on the small cables can make it difficult to get them to match. With a less than perfect cable setup you can have them matched at mid range and be off at full throttle or the other way around. If they don't stay sync'd thru full range then its a cable issue.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

A word of caution on using egt for carb balancing. These gauges are not generally accurate enough. Swapping the probe position front to back we'll give an idea of how matched they are. They may be close, but you need to be sure.

Share this post


Link to post
Share on other sites

Posted

Allen is right about the cabling and balance. My method for balancing was to use a home made manometer to balance the carbs at idle. That way at idle where balance is important to smooth operation they could be perfectly balanced. I made sure that at idle there was a tiny bit of slop in both cables so the carbs were on both idle stops.

My manometer was a super simple piece of tubing that I bent into a U shape with a valve across the top that I would open and progressively close to increase manometer sensitivity. The tops of the U connected to the primer connections on the carbs. I put a mixture of gas and two stroke oil into the U to get a nice thick viscosity to make balancing easier. 

Once I got the idle silky smooth on the idle stops at the RPM I wanted, I would adjust full throttle with the cables so the slides just disappeared from view at the EXACTLY the same time as the throttle was advanced to full.

This was pretty simple and worked great for me. i did not worry about the mid range differences created by cable slop, and my EGT's were never very far apart and the engine ran great over the entire RPM range.

 

1 person likes this

Share this post


Link to post
Share on other sites

Posted

A word of caution on using egt for carb balancing. These gauges are not generally accurate enough. Swapping the probe position front to back we'll give an idea of how matched they are. They may be close, but you need to be sure.

Gauges are only accurate when reading "0"' Even digital gauges are only as good as the connections through the entire system. What you are really looking for anyhow is a unexplained change in EGT's. Once you have a baseline, whatever that is, then you are watching for a sudden change in one or both. 

1 person likes this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now