Just received my engine back from Desert Aircraft having warranty service provided. The engine was almost 2 years old and has been well flown. I returned it to DA because the engine power and rpms were reduced to around 6000 and the cylinder showed pinkish signs of overheating.

DA reported that the engine had excessive carbon build up and a partially stuck ring. They also found an air leak from apparent over tightening of the carb bolts that distorted the carb reed block. They replaced piston, ring, pin, and worked on the carb block and reed.

Back when the engine was new, the carb bolts loosened up enough to permit the gasket to sag and admit an air leak. Upon contacting DA the rep cautioned against over-tightening the carb bolts and distorting the carb reed block.

The dilemma is this. If you tighten the bolts (with blue lock tite) enough secure the carb, the carb reed block becomes distorted and thus introduces an air leak. It seems that a small amount of torque on the bolts will cause this.

Have other DA-50 owners had to contend with this problem and what was the remedy? Does it seem that the carb block is not solid enough to support sufficient tightening of the bolts to prevent air leaks and the bolts from backing out? Has anyone tried to fabricate a plate to go between the carb and the reed block to distribute pressure and prevent the block from distorting from bolt tightening?

Thanks - Jaketab

Ive had to tighten 3 now in the last 3 months, I my own and 2 belonging to others however I think this happens if you get close to overheating, BTW none of the ones I worked on had gone pink.

A new DA 85 arrived at my house today. It’s a fine looking piece of work. Upon examining the carburetor mounting, it has an approx 1/8 inch aluminum plate between the carb and the reed housing block. The plate’s apparent purpose is to prevent the block from distortion due to over tightening of the carb bolts.

Believe me; it does not take much torque at all to over tighten these bolts. The new DA 85 manual specifies for only 6 in. lbs. of torque on the carb bolts. Seemingly, a plate similar on a 50cc would help eliminate air leaks and reed block distortion.

Thanks - Jaketab

I think the plate is a good idea. I will fabricate one and give it a try as I don't like the way the block deforms.

Cobra,

When I get home I’ll post a pic of the DA 85 that shows the plate between the carb and the block. Let me know what you make a plate out of and if you have success with it. It would require one additional gasket which DA could supply.

Thanks - Jaketab

Thanks. As they say, A picture is worth a thousand words.

The below pic is a new DA 85 showing plate between the carb and the reed block. If a plate similar to this were on a DA-50 I believe the problem with overtightening the carb bolts and distorting the block would be eliminated. The other pic shows how the gasket sagged on my DA 50 and allowed air to lean the mixture.

Jaketab