November 18, 2013 at 4:53 pm #15972
Spec Honda, Fuel is MS98 Swedetech gravity fuel system Temp 80 degrees humidity 65%. Other hondas were running a 175 main 60 pilot with needle clip 3rd down so that’s where I started. It lacked power and plug read lean. I kept going up on the main and performance improved and the plug read richer. I settled on 190 main 60 pilot and second clip from top. Performance is strong and plug reads slightly rich.
Why should my jetting need to be so much richer? Float level is correct fuel supply is solid no vacum leaks The only diffrence between mine and the other stock motos is that they’re using pump around and I’m using gravity feed.
BrianNovember 18, 2013 at 5:08 pm #15974
190 is rich for FL I never ran more then 180 58 pilot 3rd and nice brown colored plug, listening to your motor on sat sounded rich like loaded up, if your not going to compete run the 110leaded added safety the 98 has had some web report of detonating a bit.November 18, 2013 at 5:45 pm #15977
Hi Marc You may have heard it when I was still playing with it. I’m going by performance and the plug. At 180 my plug was lean and it was still bogging a little. I gained power as I got richer 185/58 was probably the best performance but it was still reading on the lean side.
BrianNovember 19, 2013 at 4:52 pm #16043
8oz/1 gallon? if your bogging in corners its pilot not main jet, and could be gearing as well I liked the 1.60 fd at ADR high 46s lap times is what I turnedNovember 19, 2013 at 5:40 pm #16050
No 32:1 which I think is 4 ounces per gallon That’s what Swedetech recomends.I’m 16/24 gearing which is 1.50 Maybe I’ll try 25 or 26. I think your right about it being to rich. I ran it today and stepped down to a 182/58. Saturday was the first time I ran it and I really didn’t want to stick it. When I went richer I may not have run enough laps for the plug to read. It was a little warmer and more humid today but not by much. Today I was low 47’s on Mojo D3’s Low 46,s on Hoosier 60A’s. I try to run the D3’s over there because that track eats tires.
BrianNovember 20, 2013 at 5:13 am #16066
I was eves dropping on a conversation at the track over the weekend between some shifter drivers who are also mechanics…they were talking about always reading the piston top as opposed to the plug…I couldnt get specifics, but they were reading the burn pattern on the piston crown using a small scope light down in the plug hole…maybe you know what Im talking about maybe not, but I plan on asking more questions as Ive never heard of taking a reading that way.
just found this:November 20, 2013 at 6:24 am #16069
From what I have read, reading the crown of the piston for signs of detonation goes as follows:
A) If you see tiny pits/pitting on the exhaust side of the crown, interpret this as the main jet being too lean.
B) If you see pitting on the intake side of the piston crown, interpret this as the pilot jet and the needle being too lean.
If I recall correctly, I read this from Memo Gidley’s Secrets of Speed for Shifter Kart Racing.
I hope this helps.
~AndyNovember 20, 2013 at 6:13 pm #16111
If I recall correctly, Jason at Swedetech has always told me to use VP ms-98 and never run pump gas of any kind, racing or not, AND to always mix the fuel at 6 ozs to 1 gal.
I found that gearing plays a big part in how the Honda performs. You want to keep it on the pipe as much as you can and if you lug it a lot, it will give you a rich condition. I think I’m jetteat with a 76 main jet now with clip in the middle. Have to check my notes for the pilot. I’m in central Fl.December 16, 2013 at 3:48 am #17852
there used to be an engine builder in FL years ago that built motorcycle racing engines. He sat me down one day a long time ago when I was racing MX and explained how jetting and premixed fuel work/burn. Basically, the more oil you run, the less gas there is to burn, so you may think you’re mixture is rich, but actually you’re lean due to less gas in the mix. Something to keep in mind, and we always ran our mx bikes somewhere between 40 and 50 to 1, and they ran really well. WKR, Woody Kyle Racing……December 16, 2013 at 4:26 am #17854
Andy you are correct!
It was explained to me the same way!
To add, and simplify, they told me to think of a funnel as a main jet. Pouring a thicker solution (exaggerating but say like honey versus water) thru it will pass thru slower than a thinner solution, hence more oil will cause a leaner condition!December 16, 2013 at 8:55 am #17885
“Temp 80 degrees humidity 65%.”
Do you have a weather station? It could be 80 degrees at sea level or 80 degrees at 6000 feet, makes a huge difference in jetting.
The Swedetechs usually run a bit richer, especially with the GFS.December 16, 2013 at 4:02 pm #17925
I run a Swedetech stock Honda with the GFS at Orlando. I run a 178 main and a 58 pilot with the needle in the middle position, that seems to work really well 90% of the time. I have never gone above a 180 / 60 at Orlando.
The GFS has a pretty wide sweet spot from what I have experienced. Occasionally if it is really hot I will run a 176 / 55 with the needle in the 2nd position from the top.
If you had to run a 190 main I would say there is a problem on the fuel delivery side or you might have a slight crack in the pipe or a leak in the pipe fitting, I know I have seen really lean results when I had similar issues.December 16, 2013 at 4:07 pm #17928
Hi Jimmy I got one after I started this thread. I think we’re 20′ above sea level maybe less. Anyway I got a good base set up and now I use the Raceair to adjust. I’m still a little richer than the other Honda’s but much closer to them now compared to when I started.
BrianDecember 16, 2013 at 9:17 pm #17948
There’s a difference between 20′ and adjusted 20′
My home track is close to sea level, but the adjusted altitude will get as high as 3500′ and will also be in the negatives in the winter.
If your at adjusted 20′, that’s good air. I would run a minimum 180 main on a practice day, prob a 185 (that’s with a 99 cylinder).December 17, 2013 at 4:33 am #17955
The raceiar reads adjusted altitude I think but it seams to rely on ADR for jetting. I’m not certain but I think the adjusted altitude is near 1000′. Isn’t the ADR the end measurment we use for jetting?
BrianJanuary 1, 2014 at 10:33 am #18741
I would really try running 6-6.5oz/gal of oil and see how that helps you. I just looked at Swedetech’s chart and that’s what they recommend on there. I run 6oz/gal Motul 2T and MS98. Currently my jetting is a tad on the lean side at a 55/170.
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