Bonneville America Forums Forums Technical Forums Performance Mods Help interpreting dyno results 07 America

I am currently running an 07 America with AI removed, Freak Kit with dual K&N's, Bubs long slash cut's, and I believe stock pilots and a 160 main. These were all installed by the dealer at the time of purchase so I haven't been in to the carbs to confirm the jets. It has been running great; no issues except a little lag in throttle response at about 50 mph and a little backfire ocassionally on starting. I have not played with the mixture screws because everthing seems to be running great. I decided to dyno it the other day just to make sure everything was running optimally. I did think the 160 mains might be a little large given all the postings I've seen. Our Triumph dealer doesn't have a dyno so all the initial rejetting and adjustment was done based on their experience and ears. The dyno results look like it is pretty close. The place I took it to have it dyno'd is a Big Dog dealer near my house. They do mostly Big Dogs, Harleys and other V-twins. They said it ran smooth and pulled great. Actually two of them said it was the smoothest they had seen and said it pulled more consistently through the run than most bikes they see. They would not dyno tune it because they don't have experience with the parallel twins. The tech said I was running a little rich and suggested I go down one size on the main jets. The air fuel ratio seems to run consistently rich but not too far below optimum. Seems to me changing the mains will correct the rich setting a high rpm but what should I do for the lower end. Change the pilot or adjust the screws? Any help will be appreciated. By the way they charge $50.00 for a dyno diagnostic. I think that' pretty reasonable. I have included a link to my dyno results. Thanks to Staffo for posting those.

http://www.bonnevilleamerica.com/forums/...part=3&vc=1

Sorry can't see your dyno results.

i would tune out the pop on startup, or try giving it lss choke and see how that does. 155 mains may cure the slight lag you have also

Frank

Yeah, and happy new year to you too MIke

Hi Bill,

Here's what I think and it's based on my last dyno which gave me some great numbers and in particular the ones that count ie Torque at 54 footpounds.

Now whilst some pooh pooh dyno figures and to some extent there are certain arguements that back up these, on the whole I believe a dyno done by a properly qualified operator by the latest machines will give an accurate reading on a bikes performance.

So given my dyno was done with SS pipes, which many will agree are virtually identical to Bubs, the settings I had at the time (and btw still have with staintunes) are:

150 mains ( I agree 160's are too rich), 45 pilot jets, and I think this is really important, and whilst many don't like shims I had one on the stock needles.

That's it. Nothing out of the ordinary really but for me, great response across the entire band which feels right, and bum dynos as we all agree don't lie.

As far as adjusting your pilot screws, well each bike is different and many times each carby is slightly different from each other also. So, to adjust them just takes time and getting a feel for when it's right. If you want to pm me on how I believe it can be done successfully, I'll be only too willing to discuss.

Finally, good tuning is best done with clean air filters and don't forget about synchronising the carbs also.

Good luck mate and btw, I've pm'd Phil (bonnyusa) about trying to increase the size of the dyno printout and the table.

cheers

Staffo

Thanks, for the information. I really need to get in and see exactly what is in the carbs right now. I'm waiting on the stainless steel screws before I start. Any idea what would cause the pop on start up?

Mixture not burning, then igniting in the exhaust.

Bill, I only have this problem when I don't use the choke cos I think it's still warm enough to start without it.

Just a thought but, you know you don't need to use the throttle to start our bikes don't you? In other words just pull out the choke and press the start button. Just checking.

Yes, I never use the throttle to start. I usually use full choke and just press the starter.

I reckon if you put in 45 pilot jets and then had your mixture screws adjusted properly, you would loose the popping when starting.

I tried that. Well not taking the screw with me, but I took the specifications I found posted here and tried several hardware stores and fastener stores. I could not get the correct length. They said they could order a box of 1000.

I bought mine slightly long and ground them down shorter.

I think I got the screw sizes from one of your old posts. I'm going to check a couple more stores when I'm out and about.