Ok guys. I'm slightly confused here. First, I'll cover the springs. I know that the slide springs can be extremely difficult to reinstall and have a habit of jumping out at you when removing the vacuum cover. After removing the vacuum cover today to make some needle adjustments, I couldn't help but notice that it didn't come flying out, nor did it give me difficulty when it came time to reinstall. I know the dynojet kit includes slide springs, but is this how they typically behave? Second, regarding the stage one setup, some of you may have seen the difficulty I'm having from other posts. I get what seem to be backfires thru the rear carb between 3 and 4k rpm. After tearing the carbs out, I noticed some blackening on the bottom of the butterfly on the rear carb. In my mind that backs up my theory. What I would like to know is if anybody has ideas of how to tune to fix this. Here's how I'm setup now. 185 main jet for rear carb, 180 on the front. Pilot jets are stock. Needle clips are set 3 notches down from notch closest to the tapered end of the needle. Pilot screws are set 2.25 turns out. Still backfires and seems to get better if I run with choke pulled slightly out. So guess maybe I'm a little lean? also some white smoke puffs I didn't have before. I know I asked s mouthful, but any and all thoughts are welcome and appreciated.

 

Oh I forgot to mention that i didn't actually install the jet kit, a shop did. Hence my confusion over the slide springs. I only know what jets are in there cuz I tore it down and had a look so I could explain my current setup. Thanks guys

 

Yet another stupid question. On the dynojet instructions, it says to put the clip on 4th groove from top. Is the top the tapered end of the needle or the base? That makes a difference in where I'd end up placing the clip. I know, stupid right? I'm still new to this and wanna get it right. Thanks guys

 

-from the top means the very top of the needle as it sits in the carb
-the springs are much lighter than stock to allow faster lift of the slide - they are longer if I recall but less tension and easier to keep from popping out when installing
-you could give more info on the running problem you are having - backfiring on decel isn't such a big deal with an aftermarket exhaust. be more specific of how it idles, transitions at low throttle settings, is the midrange very strong/crisp, does it run hard to redline in 3rd or 4th gear with stuttering? Does it cruise at 4-5K without surging.
that info will help people help you best with tuning suggestions. Maybe its all in the other post you mention, but I didn't see that and people are less likely to spend time searching through that for you - just spell out what is the problem.
If a shop did it did they dyno tune it also? do you have AF and hp tracing - might help trouble shoot.
It sounds like DJ rec 4th notch down and you are at 3rd? that could be making it a little lean.

good luck

 

thanks bill. The backfires occur during acceleration. Between 3 and 4k rpm. Right about the time it transitions to the main jet. The bike will sort of surge, coupled with an audible clunk from under the tank which I can feel between my legs. Soon as I get out of that zone, all is well. Bike will pull hard to redline, no matter what the gear. It's those small throttle openings that cause it. If I just take off fast, it won't happen in first. In other gears, if I stay above the aforementioned rpm range it won't happen there either. It really makes for terrible in town driving. Idle seems good. The shop did dyno tune it. I will post the printout tomorrow, as I have no net connection at home and I'm posting this from my iPhone. Hopefully that is more concise. I appreciate your help.

 

Download the DJ kit instructions from their website. Actually, here it is. http://www.dynojet.com/pdf/1185.pdf They call for using the fourth notch down for a stock engine with slipons. Like Bill said, this could be causing your lean problem.

The Dynojet springs are much shorter than the stockers and are much easier to install. The tapered end of the needle is the bottom. Start with their recommended settings and go from there.

 

Thank you. I actually already looked at the dynojet instructions online. However, I still was unsure of which end was which. The picture just confuses me further. I tend to overthink things to the point that i make it difficult for myself. I will change needle settings and see what happens now that I know which way to go

 

Just had that ah ha moment. Thanks bill, killer. Makes so much sense now (slapping myself in forehead). I'll see how that works. Should probably turn those pilot screws out another half turn too according to the dj instructions. I'll keep ya posted. Thanks again.

 

Sounds like you are on to the problem with the neelde clip position and mixture screws.

At 3-4000 rpm you will not be on the main jets yet.

 

stock springs are muuuuuuuuuuuch longer than the replacement DJs

 

I second that. I have messed around with both quite a bit. DJ's almost fall right in. You gotta stick a screw driver throught the stock ones in order to control them. I think they are about twice as long. Maybe more.

 

I think your mains may be too big as well, it isn't related to your problem I just think under higher throttle amounts it will be too much fuel. The miss is definitely needles your mixture screws will not affect things much at 3 to 4k. You could go down at least one main jet size then fiddle with your needle until it is rich enough it stops missing.

 

Thanks so much for all your help guys! I'm happy to report that she's running great! Raised the needles to 6th groove and turned pilot screws out to 2.5. No more struggling between 3 and 4k. No backfires either. Guess I'll get it on the dyno to ensure I'm not too rich, but I'm just thrilled it's not backfiring.

 

If I were to go down to smaller or even stock mains, does the fact that the slides have the auxiliary lift hole drilled in them cause an issue? Same question regarding the dj slide springs. Also, what about 48 pilots? Let me know what you guys think. Thanks.

 

Ok, so to answer your question the DJ springs must be used if the slide has been drilled. The main jet size will not change how the slide lifts. Also concerning the main jet size, from my experience the stock mains are large enough for people just running aftermarket pipes. I also have a bmc filter and still run stock mains. The thing is it may not produce the most HP but it runs really strong and I get decent mpgs plus the only real way to find more power is to dyno tune. So I would try running it the way you have setup for now, keep track of your highway MPG and then go from there. If it is below 38 mpg on the freeway I would consider a smaller main jet. Or if it just feels weak up top under wide open throttle then I would change the mains smaller as well since you almost for sure are not to lean now. So go ride, and report back... thats an order

 

Yes drill sergeant! Haha. Thanks for the info man. I logged 110 yesterday and 65 miles today. Throttle response and power seems great throughout the entire range. Mileage seems down somewhat. I'm scheduled for dyno time on the 7th. I'll wait and see what happens. Given the number of times I've pulled the carbs apart I could probably handle the jetting changes.

 

Quick question for anyone who knows. The dynojet slide springs, what is the purpose of them being shorter? I'm trying to develop an understanding of how these things work. Is it to lessen spring tension to facilitate quicker opening of the slides? If that is the case, why is this essential? Carbs are foriegn to me. I've a much clearer understanding of efi. Thanks guys

 

my understanding (and it is about as muddy as can be for these things) is that the weaker springs combined with the hole drilled in the slides is just for what you said: to open the slides faster. This would "sharpen" the response.

Some people have had luck with the DJ kit, not drilling and not changing the springs. But if you change the springs you must drill, and if you drill you must change the springs.

The Factory kit doesn't have new springs nor do you drill the slide, and it also gets good results, just a different track I guess. (I have a factory kit that I have not yet installed)

 

Well I don't think DJ was trying to make the slides open "faster" I think they got tired of reinstalling the stupid stock springs over and over when running development for their kit. So they cam up with a solution to the long spring. The extra hole actually makes it harder for the slide to lift that is why it needs a softer rate spring. Again it works exactly the same.

 

Thanks guys. Asking questions is the only way to learn, right?

 

I'll buy that and have thought the same thing. Whatever the case, the DJ springs are much easier to install than the stockers and save lots of time and swearing.