Bonneville America Forums Forums Technical Forums Performance Mods Epco jetting question... Yes another newb

Hoping for some Epco guys to chime in on this:

Just installed the Epco slash cuts on my 08 TBA (has K&N drop in filter and the AI & snorkel removed). As you are well of aware of and I soon found out... backfires & stalls at idle occasionaly.

Okay here's the meat & potatoes of the plee for help:

What mains & pilots are you using or suggesting? I have "read" any where from 145/42 to 155/45... I am confused & just don't see the point of ordering the dynojet complete kit as I don't intend to add anything else to the engine at this point. Newbonneville sells the mains & pilots for a lot less than ordering a whole kit of parts that I won't use. Again any experience or help would much appreciated.

Thank you in advance.

Hi MD,

I'd recommend checking out:

http://www.dinqua.com/

And then download and run the Jet Calculator.

It's very small and it allows you to input all of the variables for your bike's setup and then gives you and idea of where you stand.

I'll let other folks chime in with their experience, but Dinqua's calculator seems to be a pretty generally accepted tool for your situation.

-B

Thank you, for the link...

But now I am a bit more confused,

The calculator shows a recommended Main jet of 129 with a 42 pilot or a 130 main with a 45 pilot.

I have read that on 2008 America's are with similar mods are using 145/45 or 150/45?

Hi Austin,

Whilst I don't have epcos, I believe they are a straight through type pipe and with the snorkel removed and the drop in K&N you will now be running lean. Also considering you are popping and stalling etc are symptoms of a lean condition too.

So, from what I've learnt from others you would more than likely want at least 42/45pilots and 130 mains jets as a start.

Personally the 145/45 or 150/45 setting sound a bit optimistic to me primarilly due to the drop in filter not being as well breathing as say pod filters.

There is a bit of debate on this one but most people with these settings have the K&N pod filters.

I'm sure some with epcos who have already been down this track will chime in soon enough.

Regardless, you wouldn't want to ride your bike for too long with your bike in this lean condition as over time you will damage the valves.

staffo

First decide on the correct main jet. Staffo is probably right that a 130 main would be a good starting point. Test ride the bike and try a few full throttle pulls. if it pulls to redline cleanly with a 130 main (even if its not quite right at light throttle) leave it in and either

1) turn the pilot mixture screws out maybe two and a half turns and put in a TBS or Thruxton needle.

Or

2) Put in a 45 pilot jet leaving the pitol mixture srcrew alon and put a shim under the stock needle.

Either of these setups will probably work pretty well for you and will be light years better than the stock settings.

Thank you for the help guys. I ordered from newspeedmaster (has a good link for a step by step photo write up as well) the D-tool, 130, 132 & 135 mains and will keep the 42 pilots. The shop where I bought the bike said that the mains could be one of the three & as cheap as they are didnt make any sense to not get them all.

Thank you for link it seems to be much more accurate than what I was thinking

Thought that I would update and provide feedback.

I put the 130 jets in and left the pilots with the stock 42 that came in the 08 america. After a couple of trips around the block & a couple turns, she smoothed out and stays running at a nice low idle. Very happy with the throttle response and the help you all provided. The calculator (and the updated version) are spot on. I didn't try the 132 or 135 mains as the 130 is apperantly perfect for my mods at sea level.

As a side note: big embaressment to be had for at least the entire ridding season. I had a buddy come over to help just as I was putting the faux chrome air filter covers on and it was decided that we would go for a spin to see how my install went. As the seat was currently at Mean City Cycles getting reshaped it was also decided that a T-shirt would make a good seat. It did an okay job of being a shop rag but not much of a seat. We headed out and down the street, I would give her a little of the go juice and she would just fall on her face. After a couple of attempts and adjusting the choke ect, ect. I was slowly growing with a good amount of frustration at this point, while thinking that tearing it all back a part, by the way to only drop in two different screws that to the naked eye I couldn't tell much difference apart from the ones I pulled out & replaced already all becuase I wanted pipes. My buddy leans over and asks " aren't you sitting on your air filter"? I reply well yeah! "It seems like the motor isn't getting air, is there supposed to be a gap under the seat and the filter?" As he established his pure genious and I cemented by ignorance (and was partialy glad that with the shorts I had on, it was the shirt that was sucked down into the filter and not me), I pulled out the shirt and she began to idle like an exotic sports car. Turned down the idle and then all was well! Went for a short run with no shirt to call a seat, snapped the throttle thru the gears and decel back down for assurance... and all is good!

Thanks for help.

Good to hear. The next thing you will want to do is adjust the idle mixture screws and place at least 1 shim under your needles. You probably notice a flat spot some where around the 1/2 throttle mark.