Jetting?

[avdhunter]

Ok I have searched and read the numerous threads on jetting. My bike has Hellbent pipes with no baffles or inside restrictions.

It has a JBS Engineering intake which inside the skull in a large K&N filter.

My problem has been severe stumbling at around 2500 RPM no matter what gear I was in. Soooooo I started from scratch and adjusted the card as per S&S and Gas's instructions. Results were I had 6 rounds of adjustment on air/ fuel mixture screw so set it in the middle or 3 rounds in from outer spot. Then to the Accel pump .... it took 5 1/2 rounds out to get any kind of throttle response when stabbing at the throttle. Looked at the jets(stock) 28 int and 68 main(seems small even for a 107?). So I started going up on the int first til I got a 33 in it. Now I have only 2 rounds of adjustment on fuel/air screw and it takes 2 1/2 turns on accel pump. went up on the main and am at a 76 now. I hope this is enough background!!!! Soooo here is where I am at now. The bike runs like a scalded ape. No stumbling at 2500 thru all the gears except 6th which @ about 2500 is around 75 MPH. At this stage the bike just about dies unless I twist into the throttle some the it will hesitate and go on but won't hold a constant RPM around 2500 RPM in 6th gear. Also if riding between 2000 and 2500 and stab the throttle there is still a major hesitation then pulls hard as hell. Here is a pic of what I call a LEAN plug after running down the rod at 70 MPH between 2000 and 2500.

Soooo after all that I wanted you guys opinions on:
1. Does 33 and 76 seem large to still be running lean?
2. I am not sure which jet to keep going up on if that is what I indeed need to do. I am thinking intermediate but not sure since it is right at the transition from int to main.
3. I am assuming that because of the design of the intake the higher the MPH the more air is being shoved down the throat of the carb would I be right in this assumption? If so would explain the leaning out at higher speeds?!?!?!!!!?!?!
I know this is long but wanted to give as much info as possible so yall wouldn't have to ask for it.
Thanks in advance for the input!!!!:bang:

 

[slowrower]

How do your pipes look .. I find mine lean with the .076 and would hesitate on the highway so I installed the .078 and it works great, my other is .032 which seems fine. Better to run rich, too lean and valves burn. Good Luck! Cool ride and love that skull cover ... I have the desperado intake with S&S cover.

 

[Chopper Dave]

as slow said......remember....I think around 2750 rpm is the transition from the intermediate to the main jet.....that might be were you are getting your stumble from.....I'm sure others will chime in....
oh..and...cool ass skull!

 

[RCAdd1ct]

I was always taught to get the top end (main jet) tuned first.

What I was told was that if you do it the other way the transition area and just after is difficult to tune.

Is this sounding familiar?

Try to get the top end close then rework the low end. Fine tune both after the are both close.

This was on a yamaha roadstar but the principle is the same.

 

[avdhunter]

The pipes look fine. They were all sooty at the tips before I started rejetting but thinking that was because the accel pump was out so far and was dumping gas in the carb when twist the throttle. Hadn't heard to do top end first but guess it's worth a try!!!! Oh and thanks for the compliments on the skull ... here's a pic of the headlight that matches it

 

[RCAdd1ct]

Cool skull! :2thumbs:

 

[littlef66]

AVDHUNTER--I am having the exact same problem that you are. I have a D&M twisty cone airfilter. I was having the problem that you mentioned when running around 2500-2750 RPM on the interstate at 70-75mph it would keep cutting out on me. I took it to the dealer and had it rejettetd. They bumped up my intermediate jet. I thought the problem was fixed, but I noticed this weeked when I rode that it was doing the some thing with really windy conditions. It only happened a few times when I was riding with the wind, but when I was comming back going against the wind it was a bitch. IT kept cutting out and losing RPMs around 70-75. Then you hammer the throttle and it hesitates and then hang on. Please let me know if you figure out a solution to the problem. The dealer said that he probably wouldnt go any higher on the jets. My plugs seem to be tuned in properly as they have that nice cinnamon color.

 

[avdhunter]

Little - I will let ya know if I get it figured out. Headed to go get bigger jets now and will keep adjusting on it today and see what I can come up with!

 

[Vegas]

33/76 is kind of a strange combo. Not many of us are running anything but a 31/32 76/78 on our 117's. I would bump up the main jet to a 78 and see if it helps. I have a feeling that 33 is going to end up a little fat for you. If you get it to where it's running clean with the intermediate and the high rpm performance is good you may need to change your air bleed that controls when the main jet come into play. That or dump that air cleaner.

 

[Raywood]

Have you tried pulling the float bowl vent?

 

[Mongo]

Two words "Dyno tune" if you can take it to be dyno tuned it will show where you are lean or rich and what to do. There is a guy who travels to different Rallies called DND Homeland cycles, $40 and you'll know what you need to do. It was worth it just to not have to dick with the Carb anymore.

 

[Vegas]

Two words "Dyno tune" if you can take it to be dyno tuned it will show where you are lean or rich and what to do. There is a guy who travels to different Rallies called DND Homeland cycles, $40 and you'll know what you need to do. It was worth it just to not have to dick with the Carb anymore.

I agree a dyno tune is the easiest way. As long as it's a good tuner.

 

[avdhunter]

:roll: :bang: Vegas - My carb is the older style that has the fixed air bleed.
Raywood - Yes I have pulled the vent screw out and it helped but not quite right yet.
Mongo - I have had the bike DYNO'd twice at 2 diferent places and it runs great and everything checks out fine on the DYNO ... but a DYNO doesn't shove air down the throat of the carb like what happens when going 75mph with this style intake. If you look at the intake once the air goes in the eyes, nose and mouth of the skull there is nowhere else for it to go but into the carb and engine. Seems it acts like a true forced air induction which can't be duplicated on the DYNO ... well I guess I could take it back to them and bring along my backpack leaf blower and stand in front of the intake!!!!!

 

[Raywood]

:roll: :bang: Vegas - My carb is the older style that has the fixed air bleed.
Raywood - Yes I have pulled the vent screw out and it helped but not quite right yet.
Mongo - I have had the bike DYNO'd twice at 2 diferent places and it runs great and everything checks out fine on the DYNO ... but a DYNO doesn't shove air down the throat of the carb like what happens when going 75mph with this style intake. If you look at the intake once the air goes in the eyes, nose and mouth of the skull there is nowhere else for it to go but into the carb and engine. Seems it acts like a true forced air induction which can't be duplicated on the DYNO ... well I guess I could take it back to them and bring along my backpack leaf blower and stand in front of the intake!!!!!

Yeah, S&S claims that all carbs made after 03 all had airbleeds so must of sent all the remaining stock without airbleeds to the production companies like BD and AIM.

I'll tell you I have the same issue on my bike with the cone filter but it's minute and at only one rpm range. But I may still reduce my airbleed. I have one now cause I had my carb Triple X modified.

Another thought is to go with a Thunderjet and go to three jets vice two.

Or put another aircleaner on and see if this is the issue which some believe it is.

 

[Vegas]

May very well be your crazy ass air cleaner causing you problems. Throw the stock air cleaner on it and go for a ride.

 

[avdhunter]

Vegas - I am assuming you are talking about the hole that you can see in the bottom side of my bowl in this pic. I know I read somewhere that the newer carbs have a jet here where mine is fixed ... I think at 40???

 

[avdhunter]

Oh it's without a doubt the air cleaner. It ran without a hicup til I put that F%*@er on there. I just went and found some bigger jets and gonna go start trying then. Didn't know S&S didn't make 34,35,36 int jets. The guy had some but can't remember the Brand now....:loony:

 

[Vegas]

I'm with you dude....mine runs to lean on a 32 so I run a 33/78 combo. Could you try a different air cleaner without changing the skull?

 

[Raywood]

Oh it's without a doubt the air cleaner. It ran without a hicup til I put that F%*@er on there. I just went and found some bigger jets and gonna go start trying then. Didn't know S&S didn't make 34,35,36 int jets. The guy had some but can't remember the Brand now....:loony:

I don't think that would work for you avd, you are just going to foul out the motor on the lower end. I would have the bowl drilled for a air bleed which is easily done on that aluminum and then reduce the airbleed to a 38 and you should be golden.

Remember getting it to idle with that big an intermediate mean you may have the air bleed screwed turned all the way in.

Oh, and while you are turning you should turn that accelerator pump off as the instructions say. It just masks issues.

 

[avdhunter]

Raywood - As the bike sits now with 33/ 76 with the accel screw all the way in the air mixture screw is 2.5 rounds out which is middle ways of the inner and outter adjustment as per the instructions. Then in order to get any throttle response the accel pump has to be backed out 2.5 turns. To have it respond instantly it is more like 3 to 3.25 turns out which from everything I have read that is screaming for more int jetting. Is this correct?