Jump to content
Buckaroo

Rumbling idle this morning?

Recommended Posts

She’s a 2006 CTSW with 750 hours and 75 since last carb balance and new plugs just a few hours back. 

This mornings warm up for a flight she would rumble in the warm up ranges. I just couldn’t put my finger on it it just felt a bit strange and sounded a little off. 

I suspect a carb balance problem but can you fine folks advise what else might be going on? I have a carb balance gauge from Lockwood I just need to study up on that procedure.

 Thanks 

 

 

Share this post


Link to post
Share on other sites

I guess I should of mentioned that this morning was maybe the first dead calm morning we’ve had in months. Yes I know what that wind rumble is. This felt almost the same but with nothing wind. Also it would kinda come and go at a steady rpm.

Share this post


Link to post
Share on other sites

Could be several things. First to check float bowls and float weight. Then a carb sync. Then see what's going on. Could be a clogged idle jet? Could have been a tad flooding? Do the first things first. They are free and easy plus you need to start somewhere and the common causes are best checked up front. You should be able to weigh floats and check the carb sync in 40 minutes.

Share this post


Link to post
Share on other sites
13 minutes ago, Roger Lee said:

Could be several things. First to check float bowls and float weight. Then a carb sync. Then see what's going on. Could be a clogged idle jet? Could have been a tad flooding? Do the first things first. They are free and easy plus you need to start somewhere and the common causes are best checked up front. You should be able to weigh floats and check the carb sync in 40 minutes.

I’ll look at those items. I did take the left carb bottom off and had kind of a scary time with it. The fuel drip plan seemed in the way and I was afraid that I would bugger something getting it out. Then since the hard to get to drip bolt the pan is broken I loosened the other and got the pan and carb bottom out. No dirt visible on that right one. Now I need to learn the carb float weigh procedure. 

Now concerning the left bowl will the carb rotate enough where the bottom will clear the drip pan? 

Share this post


Link to post
Share on other sites
36 minutes ago, Roger Lee said:

 

I have no idea how I missed this video but thanks again Roger! I guess I can man hand things a little more! I’m always afraid to get aggressive with this unit!:giggle-3307:

Share this post


Link to post
Share on other sites

Have you done a video on the carb balance? A friend helped me last summer do the balance but I don’t think it was perfect. He had taken a couple day course and had forgotten some detail. I remember he was trying to adjust one carb to the other but was hesitant to take the safety wire of the adjusting screw. 

Share this post


Link to post
Share on other sites
40 minutes ago, Runtoeat said:

+2 on "worth every penny" joining the Rotax Owner's website.

I joined a year ago and do enjoy reading the material. 

I’m heading out to the hanger to do my first carb balance. I’ve looked over several videos but have a couple questions:

1. I’m using the Lockwood dual gauge instrument. How does the two hoses fit to the crossover? The video is a carbmate with only one I believe. Mine have two with the large diameter fittings. 

2. Do I cut the safety wire on both carbs or are you only interested in adjusting one carb to the other? If only one which one do you go to or does it matter? 

3. Is the safety wire required as I’ve seen videos where it’s not used. 

Thanks 

Share this post


Link to post
Share on other sites

I have the gauges. I connect to the left side. Remove the carb support spring and loosen the clamp, then slide the balance tube off. The hose on the gauges with the aluminum fitting slides in the hose, and the hose slides on where the balance tube was removed. The aluminum fitting should be attached to the hose for the right gauge.

I'm not sure how yours is wired, but you should not need to cut the wire. I adjust by loosening and tightening the two nuts to change the length.

Which one to adjust depends on your idle RPM. If it is right where you want it you will need to adjust both.

If RPM is low lengthen the cable on the carb with the high number. You do this by loosening the rear nut and tightening the front nut. 

If RPM is high shorten the cable with the low number. You do this by loosening the front nut and tightening the rear nut. 

If you are shortening the cable make sure it is not pulling against the throttle stop. Start with small adjustments, don't turn the nuts more than 2-3 flats. As it gets closer you may have to do even less.

Share this post


Link to post
Share on other sites

Call me. It will be ten times faster and easier to understand. Have your gauge in front of you.

 

Share this post


Link to post
Share on other sites

Thank you Tom and Roger! I went out to the plane this morning and decided to first take out the idle jets. I blasted cleaning fluid through the holes and inspected the bowls. Put it all back and fired it up. Smooth as a Rolex watch. 

Some of that jobs challenges!

1. Getting the flicking bowl springs off. Kinda scraped carb bodies with screw driver.

2. Got a bloody knuckle on the drivers side jet screw as the fire wall cables refused to allow it to rotate enough to get the screw driver in. Ended up taking a plastic scrub brush handle and kinda prying her!😬

I feel really happy something I did actually worked thanks to you guys! 

I will be tackling the synchronization soon. Thanks Roger for allowing me to call. Thanks Tom for the detailed instructions!

Here is my tool.

I was confused as to where the other fat aluminum piece went.

09C31BD3-E496-4096-957F-600B7BAA3963.jpeg

Share this post


Link to post
Share on other sites
1 hour ago, WmInce said:

Buckaroo,

Didn't Lockwood provide instructional pictures with your gauge set?

No!🤔

Share this post


Link to post
Share on other sites

Since I evidently got some debris in one or two of my idle jets is this an indication that something is going bad in my fuel or hardware systems? 

I hope this is just a normal anomaly that sometimes happens!

 Thanks 

Share this post


Link to post
Share on other sites
16 minutes ago, Buckaroo said:

Since I evidently got some debris in one or two of my idle jets is this an indication that something is going bad in my fuel or hardware systems? 

I hope this is just a normal anomaly that sometimes happens!

 Thanks 

its a cause for concern.  a common source would be rubber from fuel lines damaged when installed at the 5 year change.

What was the nature of the debris?

Share this post


Link to post
Share on other sites

Has the plane been sitting? 

Idle jet clogs show up withing a few seconds of a carb sync at engine start. This is why you should always use gauges and not electronic devices to sync. You couldn't see this on an electronic device.

The hole through the idle jet is so small I take a 16 ga. wire and strip it back 2". Then I take one strand of that wire to rod out the idle jet. This is how tiny the idle jet hole is. Old fuel will clog it which is what happens most of the time. Unless it is pretty big most small things pass through the main jet. Rubber doesn't clog idle jets. Not enough flow to vacuum the rubber pieces up.  You can unscrew the idle jet that sits right behind the main jet with the same procedure in the carb removal video.

Share this post


Link to post
Share on other sites
1 hour ago, Roger Lee said:

Rubber doesn't clog idle jets.

post-6-0-21009000-1352328704_thumb.jpgpost-6-0-16502000-1352328668_thumb.jpg

 

When my fuel system was polluted with rubber shavings it ran extremely badly at idle.

Share this post


Link to post
Share on other sites

There is no way rubber particles could ever go through or into the idle jet. The hole is only one strand of wire in size. About  .02. It sit well above the main jet and the rubber wants to go down into the well where the vacuum is. The idle jet flows such a small quantity that the rubber or other particles tend to sink to the bottom as they are in the picture.

Share this post


Link to post
Share on other sites

Joe from Lockwood told me to never use a wire to clean the holes. He said it would trash it.🤔

Share this post


Link to post
Share on other sites

This morning I go out to fly and the idle run up is fine. Then after takeoff I notice my EGT is in the yellow. This is after a short 700 foot climb. I turned back to the field then on decent running power back through the 4500 to 4000 range she rumbled pretty noticeable. 

Many ideas folks?

7135C714-FABE-4D98-9DB9-08ABA6057C62.jpeg

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

×