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Carburetor issue.


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Posted

I have bought several engines from a reputable rebuilder, and for the most part am well satisfied. However: One of the engines I installed on my Avid/Kitfox Frankenplane had idle issues from day one. Lots of power and ran well, but I couldn't get it to idle smoothly below about 3000 rpm, and although I had the idle stop screws all the way in, I still had to add throttle to keep it from shaking the front off the plane.

So today I decided to make a project out of the mess. So I tore the carbs off and disassembled both. Checked the jets and needles and set everything according to the manual. In the process of re-assembling the carbs to the engine I looked at the enricheners, which were still on the plane. I don't know why, since I don't use them, but I had to disconnect them to get the carbs out.. AHA ! The rubber bottom on one was worn clean through and the other was missing completely. Now I had a complete "new" engine still in the crate at home, so a thunder-run home to steal the enricheners. NO GOOD ! The enricheners on that engine were in exactly the same condition, shot !  Fortunately my ample junk box yielded a pair of manual enricheners in new condition, so in they went.

The engine now idles at about 2200 rpm, and I had to re-set my jet-needles. Also in the process I found the carb boots to be bell-mouthed. In fact it shook the carbs off the engine twice, and no way could I get them tight enough. Fortunately I had a new set.

Point is, the guy does a marvelous job of rebuilding the engines, but the quality control on the accessories is somewhat lacking. In fact I got one set of carbs that had different jets in one. A few minutes checking might save you a lot of headache.. If I hadn't accidentally checked those enricheners or if I had just thrown the "new" carbs in complete, I'd still be scratching.

Too soon old and too late smart

Bob McCaa

 

 

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Posted

Unfortunately I have heard stories just like yours. I actually seen on fresh rebuild that bolts were finger tight only. The best carb boots are from JBM industries in Ohio. He makes them out of a different material than standard Rotax boots. They last about twice as long as normal and seem unaffected by sunlight. Plus they are cheaper also.

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Posted

Great advice Allen, JBM has served me well, and at great prices, top quality:

 

http://jbmindustries.com/

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Posted (edited)

When I bought my kitfox, the previous owner had the mechanic, that did the annual, rebuild the carbs, and on my flight home I stopped for the night and the engine quit on landing roll out and when I popped the cowl this is what I found:blink: The bolts in the carb boot where only hand tight and had back out after 2.5hrs of flying. 

 

50hrs after the carb rebuild it started to run rough at idle a few weeks ago, and when I took the carbs apart to see what was up, 75% of the o-rings where cracked. 

20190731_170407.jpg

Edited by FireFoxIV

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