"J" bike with pods+exhaust jet size?

Hi all, just seeing what you people that have J bikes with pods and exhaust run for mains and needle heights on your BS34 carbs. I recently got a dynojet put in, so the DJ needle is on the 2nd from the top slot, and I have 40 pilots and mikuni 135 mains. The bike is still lean, I can ride np, but it's too lean for me to keep it that way. I am essentially trying to find out if I should try for 137.5 or 140 mains, and if one slot down on the needle would correspond with what works well for you guys.

Thanks! Carbs are interesting beasts! but I am enjoying learning about how they work.

#140 main jets and #40 pilot
jets. My needles only have one slot but they are shimed, cant remember how many tho.
Tom

Thx, I was hoping for your input since my bike is your bikes twin essentially! Before you bored the bike out, was the 140 just right, or to rich?

It was a bit rich the 137.5 might be just rite for ya.
Tom

if it where me i would run 40/140 and ask otto what needle position...he knows these pretty well....40/140 is a real good start point for pods and pipe on the bs 34...i ran a set for a while with that jetting and it wasnt bad....i did need needle adj, but i didnt run them for that long....with that jetting and whatever needle otto suggests, its only a matter of fine tuning with the mixture screws to get where you need to be....hope this helps....g/l....keith

I doubt that you running too rich. On my 1150 with .420 cams and Kerker "K" series pipe with open pods. I also have a head that flows well above 100 CFM I am running 142.5 (Mikuni) Mains and 37.5 pilots. My needles are as far down as I can get them and I am still running too rich at the low transition. I wish I could get the needles even lower. The needles that I use are nowhere as rich running as the DJ needles are either. I think that I might go even smaller on the pilot. Once I get to the point that the needles take affect I am fine it is at the point between the pilot and the needle that I have a rich stutter. My screws are set at 2 1/4 turns out. I have my own needles that I make because I think that the DJ needles are junk and don't work right. They are set up for stock bikes that produce very low vacuum. Once you have an engine that produces more vacuum they are way too rich. If you are running the DJ jets than they are completely different than the Mikuni jets and they flow completely differently. A 140 DJ is nowhere close to a Mikuni 140. The reason I do not trust the DJ kits is because they are tuned ONLY for the modifications stated in the instructions. Any other mods and they leave you on your own. This is why I build my own kits dependent on the mods to the engine. I made plenty of calls to DJ when i started building these carbs and they could not answer any questions without Dyno testing results. this tells me that they have NO practical knowledge and rely strictly on technology for tuning very specific engine configurations. I think that for your configuration you might want to drop the needles down two notches and go to about 135 Mikuni mains and back down to stock pilots. Open the screws to about 2.5 turns to start. See what that gives you and go from there. If things get worse than go the other way on the needles. If they get better than you know where you stand on the needles.

EDIT: Deleted... Nevermind...

otakar wrote:

I doubt that you running too rich. On my 1150 with .420 cams and Kerker "K" series pipe with open pods. I also have a head that flows well above 100 CFM I am running 142.5 (Mikuni) Mains and 37.5 pilots. My needles are as far down as I can get them and I am still running too rich at the low transition. I wish I could get the needles even lower. The needles that I use are nowhere as rich running as the DJ needles are either. I think that I might go even smaller on the pilot. Once I get to the point that the needles take affect I am fine it is at the point between the pilot and the needle that I have a rich stutter. My screws are set at 2 1/4 turns out. I have my own needles that I make because I think that the DJ needles are junk and don't work right. They are set up for stock bikes that produce very low vacuum. Once you have an engine that produces more vacuum they are way too rich. If you are running the DJ jets than they are completely different than the Mikuni jets and they flow completely differently. A 140 DJ is nowhere close to a Mikuni 140. The reason I do not trust the DJ kits is because they are tuned ONLY for the modifications stated in the instructions. Any other mods and they leave you on your own. This is why I build my own kits dependent on the mods to the engine. I made plenty of calls to DJ when i started building these carbs and they could not answer any questions without Dyno testing results. this tells me that they have NO practical knowledge and rely strictly on technology for tuning very specific engine configurations. I think that for your configuration you might want to drop the needles down two notches and go to about 135 Mikuni mains and back down to stock pilots. Open the screws to about 2.5 turns to start. See what that gives you and go from there. If things get worse than go the other way on the needles. If they get better than you know where you stand on the needles.

I started out with 37.5 mains 2.5 turns and DJ138 mains. This was not runnable, I had to turn the idle mix screws to 3.5 just to be able to drive away, and now have them at 4 which is perfect. The DJ138 main is basically a 129 according to the chart you posted a couple weeks back, so it was WAY too lean, I got mikuni 135 jets and put them in the other day, and they are a bit better, but still not right. The needles are where DJ instructs on putting them, if I went leaner it wouldn't run. The reason I say it's lean is because my plugs are white on the tips, and when I start the bike and want to take off, when shes cold it stutters for a bit at half throttle, but as the bike warms up it gets better. Full throttle pulls are not as powerful as I thought they would be, it's basically just a continuation of a half throttle pull...The carb tuning guide dave posted suggests starting at the mains, and working backwards, hence me trying to figure out my main jets. I need to order a float valve from z1 so I am going to order 137.5 and 140 mikunis in the process.

That colortune thingy would help with this situation right?

You may not be producing enough vacuum than. so go the other way on the needles. put your needles as rich as they will go. It sounds to me that your slides are not reacting properly. You may try even 142.5 or 145 jets or maybe the float bole levels are too low. It will be time for some major experimenting. What size did you drill the vacuum ports in the slides to?

Out of curisoity...

Sorry but your project and this post have me confused... Which baffle are you tuning to again?

"Full throttle pulls are not as powerful as I thought they would be, it's basically just a continuation of a half throttle pull..."...

This is basically the correct operation!
Is the pull linear, does it op on accelration or deceleration, is there a lull or hesitiation in this RPM range... If not, your just about right, maybe a jet size but close...

As for your mid range, at a constant 5Krpm, is it skipping as if starving of fuel/semi blocked fuel filter or a constant RPM purr... If skipping, richen up your needle clip position.

Then go after the idle and slow RPM range...

The drill bit that DJ gave with the kit...

So I should try putting the clip on the needles on a lower slot then and see?