Hi guys. Well I just completed building my Trinity 420 Long Rod and I am now tuning it. I am running the stock carbs for right now. Trinity recommended 330 mains with the needle all the way up (clip all the way on the bottom). Well just to play it safe I started with 340s, clip on the bottom, 30 pilots, screws 1 1/2 turns out. I am at about 1500ft and today was 70 here. I did a plug chop after a few seconds of full throttle and the plugs were very white. There was a small hint of red/tan on one side of one of the plugs.

Obviously this means that I am lean on the main jets. How many jet sizes should I jump up? 350? 360? 370? Even Bigger? Its not the money of the jets. Its the fact that I am driving 5 hours to Little Sahara OK Friday. Luckily one of the dune shops has all of the above sizes but I would like to minimize the disassembly/ reassembly routine so I can ride! ANY advise is greatly appreciated! Thanks alot!

Adam Biossat
P.S. What about the pilots? I already fouled a set of plugs and it is smoking alot but throttle response isn't too bad.

 

Are you sure you ran it long enough to get a decent reading? Personally, I'm not a fan of plug chops because I think that especially with clean burning fuel and oils it takes a long while to get a real reliable reading.

I try to run fairly hard while doing regular riding for a while then pull the plugs and see how it's doing. I probably tune more by feel than the plugs anyway; mainly how it feels on top. If you just rebuilt, it's probably not a bad to go real rich for a little while anyway.

I'm no expert, but having the needle clip all the way up seems a little extreme to me; seems like it would be a little lean through the midrange???? Like I said, you will probably jet better by the feel of it than reading the plugs.

 

My 420 regular rod ran on 320 mains at sea level..

I'd think you'd be rich.. but I could be wrong..

Brad

 

Thanks for the replies so far guys. I was running on a paved surface at about 3/4 throttle for a while and then ran full throttle for about 3-4 seconds. I was concerned that if I ran longer at full throttle I might hurt something if it was lean. Anyway, if I had run longer at full throttle is it possible that the plugs could have gotten darker? I was thinking that the plugs could only get lighter if I ran longer.

Do you think that I could be leaner at 1/2 to 3/4 than at full throttle?

Thanks alot for all your information!

Adam