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11-09-2016, 08:04 AM

#91

Joystick TX

Join Date: Aug 2008

Location: Diamondhead, MS

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Quote:

Originally Posted by edgersh

what is the correct timing for a da 85 cc engine I set it up for 28 degrees btdc the engine ran hot after 5 minutes I retarded it and it still ran hot.

I did a quick search on Google and it is odd that the ignition timing for the DA 85 does not seem to be listed anywhere. I'm sure DA can provide the answer.

It has been my experience that most overheating problems were due to insufficient air flow. A good "rule of thumb" to use is to make sure that the air "exit" area, at the rear of the engine, is three or four times larger than the "intake" area at the front of the engine. The intake opening should be centered on the engine cooling fins for best results.

A lot of engine installations "look like" they meet the 1:3, or 1:4, ratio, a circle has more area than a rectangle with the same perimeter, but the best way to check it, unless you're a math genius, is to measure it. Just get some 1/4" square ruled paper and trace the intake and exit area shapes and count the number of squares inside each one.

If that ratio is within the “rule of thumb” ratio, then it is possible that the air intake opening is too small. In that case you can enlarge it, just make sure to open up the exit to maintain the ratio.

It is important to maintain the proper ratio in order to make sure that the air velocity, past the cooling fins, is high enough to provide cooling.

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