Triumphrat

FrankBlack

I'm trying to sort out some low-rpm lumpiness on my Bonneville post-ARK and want to try some less strong carb needle springs in an effort to allow the needle to come in to play easier/ quicker. This follows numerous attempts to play around with the pilot mixture and a suggestion from a mate on the site.

Basically at 1/8-1/4 throttle and 2-3000 rpm there's a real lack of smoothness e.g. 30 mph, 3-4 gear, 2-3000rpm = lumpy. Feels like I'm going over a bumpy road (when I'm not). I guess it's right in where the pilots taper off their influence and the needle starts to come in. Have tried 1 and 2 shims - no good. Have tried various adjustments leaner and richer on the pilots - no good. Have tried going up or down on the main jets - no good. So, my last port of call is the needle spring.

Any suggestions welcome (please be specific on the springs so I can find and order them on the net).

All the best.

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Silver Bonneville 2007
Togas/45 pilots/145 mains/Turns:0.75L&1.25R/50 mpg avrg/FARK/Latest DYNO

Pokeyjoe

Jenks Bolts talked about drilling out the 2.5mm vacuum hole to 3mm to allow the piston to move quicker. Don't know if that would help or not. Can't exactly undo it either.

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John

Some people are like Slinkies. They're really good for nothing. But they still bring a smile to your face when you push them down a flight of stairs.

FrankBlack

Thanks John. Exactly as you say - drilling the slides is a pain to undo and I'd rather not drill them until I try everything else.

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Silver Bonneville 2007
Togas/45 pilots/145 mains/Turns:0.75L&1.25R/50 mpg avrg/FARK/Latest DYNO

propforward

The bonneville dynojet kit has softer springs in. It might be worth emailing them to see if they will sell just the springs. I am not aware of anyone else doing it.

I know some people have chosen to use the dynojet kit without the springs - maybe try sticking a wanted ad out there, see if anyone wants to give them up.

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I can't stand cheap people. It makes me real mad when someone says something like, "Hey, when are you going to pay me that $100 you owe me?" or "Do you have that $50 you borrowed?" Man, quit being so cheap!

mikeinva

i had the dyno jet springs in my stock carbs they worked

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Why do I feel young on my bike

propforward

I used the dynojet kit, including needles and springs, in my carbs, and I was very happy with overall improvement to throttle response, and the bit of extra power. However, I did not go as far as Frank has done with tuning - I'm not pulling the airbox off of mine. The theory sounds good though.

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I can't stand cheap people. It makes me real mad when someone says something like, "Hey, when are you going to pay me that $100 you owe me?" or "Do you have that $50 you borrowed?" Man, quit being so cheap!

FrankBlack

Thanks for that guys. I'll try a want ad for dynojet springs. Any other theories on the low throttle roughness between 2-3000rpm welcome in the meantime...

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Silver Bonneville 2007
Togas/45 pilots/145 mains/Turns:0.75L&1.25R/50 mpg avrg/FARK/Latest DYNO

Holyman

Phone DynoJet in the UK. You can buy all the kit parts except the needles as spare parts.

oldroadie

Every time I look at your dyno run it seems like you're really rich in that exact range and I wonder if you've tried putting the 40 pilots back in just to test that approach; 40s with more turns out on the screws?

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2001 Bonneville
2004 Bonneville America

FrankBlack

Appreciated Holyman. Just emailed them...

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Silver Bonneville 2007
Togas/45 pilots/145 mains/Turns:0.75L&1.25R/50 mpg avrg/FARK/Latest DYNO