APT smartcarb tuning advice needed

adamd1979 said:

I've had the same thing happen with my new 38 billet. Way rich. I've got the 76 metering rod and have it at 100 clicks out. Still rich, but a bit better then the 78 clicks it was set at from factory. Is this similar to what you were finding before the 200 mile mark? If it doesn't lean out right, I may try the 80 rod that came with the carb.

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Is this on your 500 ? Why a 76 rod ? I run a 80 rod at 70ish clicks. I had a 76 because of some deto. I slowly worked my way back to the 80 with a little race or fuel builder. 76 was way to rich. I know Millar ran the 76 at 76 because of the lean spot at 3/4 decel. As the jetting moved back towards the 80 it just got stronger and stronger.

I always wonder why guy try a richer needle ?

On the 300's what is APT sending out for needles ? 80's ?

summitboy said:

Is this on your 500 ? Why a 76 rod ? I run a 80 rod at 70ish clicks. I had a 76 because of some deto. I slowly worked my way back to the 80 with a little race or fuel builder. 76 was way to rich. I know Millar ran the 76 at 76 because of the lean spot at 3/4 decel. As the jetting moved back towards the 80 it just got stronger and stronger.

I always wonder why guy try a richer needle ?

On the 300's what is APT sending out for needles ? 80's ?

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I originally ordered mine for my 300 then picked up a 500. If you ordered a 38 they should be the same carb.. Rod and all... See below the email I received from them..


Thank you for purchasing a SmartCarb form APT and I’m happy to say that you’ll be able to utilize the same SmartCarb on your Honda CR500. The SmartCarb is not tuned to any one specific model bike and can be placed on different size bikes as long as they meet the carbs proper displacement requirements and fit properly.

As long as you mount your SmartCarb correctly and follow all of the instructions in your owners manual for initial tuning, you shouldn’t experience any problems on either your Honda or KTM. You probably will need a new throttle cable which is a decision you’ll have to make based on how the old cable looks and if its long enough. The Motion Pro # 10-3000 will give you an extra 4 inches in length over your OEM cable.



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I was under the impression the 300's came with the 80 rod. Not sure why guys always stray away from APT's recommendation. They know the 300 probably better than any bike. 500 is a little different story.

summitboy said:

Is this on your 500 ? Why a 76 rod ? I run a 80 rod at 70ish clicks. I had a 76 because of some deto. I slowly worked my way back to the 80 with a little race or fuel builder. 76 was way to rich. I know Millar ran the 76 at 76 because of the lean spot at 3/4 decel. As the jetting moved back towards the 80 it just got stronger and stronger.

I always wonder why guy try a richer needle ?

On the 300's what is APT sending out for needles ? 80's ?

Click to expand...

Ya, it's on the 500. When talking to Corey at the time of ordering, he said the 76 would be installed because of other feedback from other guys with 500s. He said the 500 was a bit of an anomaly to them and that he'd send the 80 with the carb for me to try. I've got 20 more clicks on the 76 before it maxes out, but it sounds like I'll end up with the 80.

I bet you will be 80-90 on the 78 and 60-80 on the 80 Rod.