Jetting info???
 

Hi guys,

I recently posted about my 99 curvy running a bit rough and have narrowed it down to the jets not being up to the job anymore now i have installed an aftermarket exhaust. Does anyone know the standard jet sizes used and what jets would be sufficient for the extra air flow etc.

Cheers, Jake.

Re: Jetting info???
 

Thanks for the quick reply dude!

Well after doing some reading up, and using the info you have given me, i think a good base to start on would be 142.5 main jets and 17.5 pilots. I have a delkevic slipon (no baffle) and a stock air filter so i’ll order those bits and have a faff around with them and see what happens ��

Re: Jetting info???
 

Stick with the stock pilot jet, you haven't made enough mods to tinker with that. Not sure about main but give it a go, this is for top end though. Once you get that right you can adjust the needle clip if necessary but this works all the way through the midrange so don't dive into it too fast until you have the main jet right or you'll really get in a knot. Once it is feeling good then its worth a trial dyno run to see how far off you are - be prepared to be miles away from being right though.

Re: Jetting info???
 

with a stock air filter and a slip on (baffle or not) there is no need to change the jetting. there are thousands of curvys out there doing the exact same thing without problems so look elsewhere as its not the exhaust/jets.

the only time you need to change jetting is when you have a 'full flow' exhaust and a race air filter and more so the air filter.

Re: Jetting info???
 

+10 to what Bibio says.

I asked a similar question about having to re-jet when I wanted to and have fitted a shorter"Slip-on" exhaust.I heeded what Bibio and others on here said and went ahead on my Curvy and have had no fuel delivery problems except that I tried a set of,"Iridium" spark plugs and my Curvy didn't like it,ran lean.Went back to Standard plugs and all good as I couldn't be bothered to mess around with the Mixture screw/s.

However I also have well balanced Carburetors.I bought a, Morgan Carbtune2 over ten years ago and it's still like new,

http://www.carbtune.co.uk/carbcust.html
http://www.carbtune.co.uk/


I get over 150 miles before my Fuel Low warning light comes on which is fine by me but I do give the fuel a shot of RedX from time-to-time :)

https://i.imgur.com/PAqaTTT.jpg

Re: Jetting info???
 

I'm surprised it wants jets tbh, but I think I saw a thread you posted about this? Hesitation at 6-7000 when you snap the throttle? If so that's a classic undersized mains symptom on the SV, it's the main trick I used to get a baseline setup on mine- you could probably work around it with a shim on the needles though. It oughtn't to need jets with just these mods tbh but, stuff happens.

I should have tons of standard-ish DJ jets somewhere, mine has something daft like 185s in it so all the stuff from the kit ended up too small, want me to have a dig? Changing jets is a total pain in the **** the first time, but once you've unstuck and replaced the horrible stock screws on the float bowl it's pretty simple so it's no great loss if you try it and it doesn't work out.

Re: Jetting info???
 

Moving the needle up because the midrange is lean is probably going to leave the top end lean instead. I'd go up maybe one size from stock, I doubt it needs any more than that - a lot of slip-ons make little difference to anything except noise.

Re: Jetting info???
 

Thanks for all the replies guys!

I had a revelation today, i put the baffle back into the stubby just to see if that would alter anything and straight off the bat it responded much better! Seems that the added ‘restriction’ has somehow altered the air flow as such, and the bike does respond alot better. Being a hoonigan at heart, i will be taking the baffle back out because i do much prefer the noise with it out ;)

But i digress, today my new jets came and im going to have a fiddle about with them at the weekend and see what happens and post the results :smt114

Re: Jetting info???
 

Oh yeah, it's absolutely a bodge.

Re: Jetting info???
 

So it's definitely running leaner without the baffle. Less restriction = leaner. TBH it's pretty tough rejetting using the trouser dyno alone but you can give it a go