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Old 09-06-2014, 02:43 PM   #2
blight
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Join Date: May 2004
Location: death zone, Minnesota
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Re: 1982 xv920 single tm40-6 (tuning help please)

UPDATE:

there are 5 notches on the jet needle. the issue WAS happening between idle and 3000 rpm. The jet needle was set to the 3rd from the highest position (blunt end down). I adjusted it to the 4th position and the issue lowered from idle to 2500 rpm. Then I adjusted it again to the final and lowest position, or if you prefer the highest needle height (factory needle for this unit) it then dropped it down another 500 rpm. It is now an issue from idle to 2000 rpm.

I am running a 6 of 81' seca rear diff and rim/tire setup. In second gear I am going about 15 or so mph (according to my gauge). This is about 2000 rpm.

I will say aside this final miner adjustment, this thing is quick. It for sure feels relatively light (and I am coming from a 200 pound purpose built 130cc two stroke supermoto bike) for its size, the tq of the vehicle is rather pleasant.

Something I did not mention in this thread is I am also running the 2-1 mac exhaust. open header, this thing is loud, like pissed off many neighbors. I have done lots of exhaust research in the past as I have made my 280z sound like a ferrari. For a deep mellow sound but not (too) loud, the material for the muffler should be made of carbon fiber. For a higher pitched (ferrari esk) sound, you stainless is middle ground, then titanium is the most ferrari sounding. The reason for this is just how the sound waves are absorbed into the material itself, regardless of packing material. There are many other factors as well and that is not what this thread is about. I digress, I found a carbon fiber muffler that is 9" long, 2" inlet, and 2.75" outlet. To run this muffler I have to use an exhaust reducer, I think it will be worth it.

for those that care.

muffler
http://www.amazon.com/gp/product/B00...A26ZGWDZX82YQN

reducer
http://www.amazon.com/gp/product/B00...A311393O04YIYG

Now back to trying to tune this sucker.
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