Anyone know what rpm i should be getting out of a DA100 twin on a 27x10 prop? Im getting about 4650rpm, which seems a little low so I thikn the engine needs some tweaking, i have a suspicion that in the air one cylinder isnt always firing as it should. Its a new engine has only had jsut over a gallon through it so far so some running in is still to be done but i still think the performance is wide of the mark.

cheers
alan

You are about 2.5K-3K low in rpm, something isnt right. Are you getting fire from both cylinders? is the carb butterfly opening all the way?

Well, on starting it seems to sometimes run on one cylinder for the first 10-20s, then the other fires up. So im wondering if there is something wrong with one plug, causing one cylinder to sometimes not fire. The butterfly is fully opening. I cant think of any other reason why it would be so low in rpm. If it was a running in issue id expect 300 or so rpm low but not 2-3k low.

You need to do some tests, which are quite easy. How are the needles set, if you are running extremely rich it could react as you describe. Try changing your plug wires and see if the "bad" cylinder changes and follows that particular plug wire. If it does, you very likely have an ignition problem. If the "bad" cylinder stays the same, try changing plug, or at least check color and gap and adjust. Check for any leaks around cylinder to crank case gaskets, they will show as being dirty. If you are unable to find and fix the problem alone, seek the help of knowledgeable people in your area, and if that fails, send the engine to your distributor for a check.

DKjens

Thanks for that, actually i jsut thought the same thing as you suggested. So i tried swapping ignition plugs around and hey presto it follows the ignition. So ignition sent back to distributor today, hope to get a replacement fast i hate to be GROUNDED! There dont appear to be any leaks around gaskets other than to the exhaust. My remaining concern is that perhaps the ignition is responsible for the cylinder going out (or not coming on) but the custom exhaust is perhaps responsible for lack of performance. I will return to supplier to find out...

You will want to at least check your plugs if not replace them since it has been running very rich w/o a cylinder running. Depends on how long it has been running like this.

Thx, will do.

plugs are black and covered in a very thin layer of soot, presumeably this is normal? Have cleaned them up with a bit of emery. Not sure of correct guage for the gap but there seems to be an appropriate gap in both plugs.

If you could clean them ok, give them a try, if it doesn't run the way you expect it to, put in some new plugs. I've always replaced the plugs after the 2 ignitions I have killed b/c the one on the dead side always looks pretty bad.

Your ignition module is going belly up...

You don't want dry soot on your plugs. That means you're way too rich on your high needle. The gap for your plugs is set using a #11 X-Acto blade for the gap measurement.

thanks for that, ill look into the mixture setting as well. Im guessing that it can be set as usual to peak rpm and then backed off 300rpm for optimum setting.