912 UL Engine Vibrations - Kitfox IV

38 posts in this topic

Posted

I've been down sick since the first of the year.  Dying was an option I'm regretting not taking at this point.

 

I put in all of the new parts in the gearbox only to discover a leaking fuel pump.  I have the pump off my project plane ready to install but have not been able to work outside to finish it up.  I was hoping to work on it this weekend, but I can still barely breathe outside without coughing to the point of passing out.

 

If you look over at TKF, the other guy, from Washington state, with the same problem had great success with his gearbox.  I'm very hopeful...

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Posted

Were you leaking from the weep hole or body crimp? Is Rotax still offering the discount price for pump? Very timely for my pump failure last year, heck, I even bought a spare.

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Posted (edited)

Fuel was coming out the weep hole...

 

New pumps are back ordered for several months.

Edited by Av8r3400

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Posted

I am "that other guy" from washington. After replacing the same parts as Larry, reshimming the gear box and putting it back together, my plane seems to be turbine smooth. I have not been able to flight test it however- as it is just too damn cold. Hopefully Larry gets better soon and has the same result.

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Posted

Hey "other guy", thanks for posting up, let us know how the plane flys when it warms up enough for ya!  :BC:

 

Larry, hope you kick the bug in the ass and get back to working on the birds soon!  I think its a crap shoot on who is going to finish a project first.. My 800 conversion, your mangy fox, and ... well any of the planes that Doug is working on :lmao: 

 

:BC:

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Posted

Scott--  Hey I forgot you signed up over here on the dark side of the flapperon community.  Why don't you share your tale of gearbox woes...

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Posted (edited)

Scott-- Hey I forgot you signed up over here on the dark side of the flapperon community. Why don't you share your tale of gearbox woes...

As probably most of you know from TKF- I have been fighting a vibration problem on my Kitfox since I bought it last year. I have done SB#54, rebuilt the carbs, changed plugs, sent the gearbox off to be reshimmed, etc. My problem was I did not know what was normal as I have never owned a Rotax before- all my experience was with Lycoming and Continental. After checking with a few other Rotax owners, and seeing the problem Larry was having, I figured out I might have the same problem- so I pulled my gearbox back apart again and discovered the same spalling that Larry found in his, so I ordered a new dog gear and gearset. After a two and a half month backorder wait from Rotax, I finally get the new parts- and have to machine a spacer to make everything fit. Nothing is easy with Rotax!!! The good news is I spent the last couple of days putting everything back together, putting the doors back on and bleeding the brakes. Ready to fly!!! Hopefully tomorrow!!!!post-736-0-58701700-1389759852_thumb.jpgpost-736-0-37328300-1389759867_thumb.jpg

Edited by 68niou1

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Posted

Very cool paint job. I remember seeing a picture of your plane somewhere else not too long ago. Hope the test flight goes well for you.

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Posted

Hey thanks Lostman! Flight went well- just need to relearn how to fly and not have lazy feet!!

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Posted

Okay! She runs again. Pretty smooth, too!

Everything I touch seems to break, though. I changed out the fuel pump only to find the main fuel valve was leaking. Took that out and rebuilt it with new o-rings only to find during the test run that the supply line at the "T" between the carbs is leaking. Sheesh!

I ran out of time before I could get into that, but at least the gearbox issue seems fixed!

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Posted

good news on the gear box! hope ya get the other issues sorted out quick and get back in the air. 

 

:BC:

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Posted

Good news, well mostly. At least the big elephant in the room has been put in it's place.

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Posted (edited)

Okay to finally close the loop on this.

Back in January my initial thoughts of success were not to come true. Engine roughness, between 2000 and 3000 rpm was still there. It was different, but still a problem. Prior to the gearbox I was getting what would be best described as a vibration. After the gearbox it was more of a rough running situation. I don't know which came first, but the roughness was still there.

I had put new plugs in the motor, more out of frustration than anything, so I thought maybe there was a bad one or something. When I pulled the new plugs, I noticed one side was definitely darker than the other. Okay, that's carbs!

Off they came again. I got new boots from JBM, even though my old ones looked fine. I tore into both carbs again, and found... Nothing wrong. This time I reversed sides on the carbs, to put the throttle arms and chokes to the outside for ease of adjustment. This required the reworking of the cables and plumbing. If nothing else, if the dark plugs changed sides too, I would know I have a bad carb, or if they didn't, maybe something internal to the motor.

Well, the roughness is nearly (95% +) gone now. A little more tweaking on the air screws will fix what's left.

The good news is its fixed. The bad news is I don't really know what I fixed to get here.

Edited by Av8r3400

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