moog5050
Active Member
I would try a 31 int and see what happens.
jets
- Thread starter Bhawkins854
- Start date
francoblay1
The Spaniard
Ok, tomorrow I will try to find one in a neaby city.... I did take the vent plug off. I am going to do a test right now and see if there is any difference. I am sorry for the neighbours) its almost 2100 hrs here LOL
Moespeeds
Well-Known Member
I say go lean only because lean is easy to detect. Running it down the road lean for a few miles isn't going to hurt anything. If you blindly go richer you end up chasing ghosts because the bike will run great rich and will only show symptoms at certain rpms or not at all. If you drop until you know you're lean, then you have a solid baseline to start working from. When I jet a bike I take it to the gas station on the highway across from my house so I'm not driving my neighbors nuts, with tools to open the carb and a handful of jets. I blast up and down the road, pulling back into the gas station to make jet changes. Shut off the petcock 1/4 mi from the station and you'll have an empty bowl when you pull in, so there is no need to keep dumping the bowl to change the jets. You never really know if you're rich until you run it all the way down to lean. Try it, you may be surprised. Also remember that the intermediate jet will have the greatest impact on how the bike runs, it's the jet you are on most of the time.
francoblay1
The Spaniard
Right, I am not sure if it is my imagination but taking the vent plug off made a change! it seems to run smoother and does not sneeze as much at 2.5-3K rpm... mind you I had to stop running up & down as the road is already frozen (caught an ice patch and scared the shit out of me) Tomorrow will keep working on it.
Moespeeds
Well-Known Member
Remember cold weather will put you on the lean side, so if you just touch lean then you'll be good when the weather breaks. Pulling the vent will smooth the transition between jets, I don't know why this works I'm sure someone else can elaborate. I went to the S&S site to find the tuning guide and they only have this lame quick guide up.
Here's a wide open throttle test for checking the main jet. It's a simple test and easy to do, I mark my throttle in 1/8" increments with a sharpie for this test. This is actually from the roadstar site but it will work for a BD just fine.
To get best results, we need both load and RPMs. Given that the needed RPMs would equal extremely high speeds in fifth gear, I prefer to do it in 4th.
On the freeway in 4th gear, accelerate at WOT (wide open throttle) to 75 or 80 mph (the higher the better). Acceleration needs to maintain for a couple of seconds to use up the squirt supplied by the accelerator pump. (ignore this, your accel pump should be off!) I like to start around 55 or 60 mph. After getting up to the appropriate speed, back off of the thottle 1/8th turn. While doing so, pay attention to your RATE of acceleration. You will still be speeding up, as you are still in a nearly full throttle position, so rate of acceleration is the key (feeling of acceleration or momentum).
Bike wants to increase rate of accelleration. Main jet is lean and you need to increase main jet size.
Bike wants to maintain accelleration, or feels like you have done nothing different when backing off. Your main is right on the cusp, slightly lean.
Bike looses some momentum (may still be accerating, but at a slower rate). The main is not lean.
This test will not help to identify a rich main, only a lean one.
Here's a wide open throttle test for checking the main jet. It's a simple test and easy to do, I mark my throttle in 1/8" increments with a sharpie for this test. This is actually from the roadstar site but it will work for a BD just fine.
To get best results, we need both load and RPMs. Given that the needed RPMs would equal extremely high speeds in fifth gear, I prefer to do it in 4th.
On the freeway in 4th gear, accelerate at WOT (wide open throttle) to 75 or 80 mph (the higher the better). Acceleration needs to maintain for a couple of seconds to use up the squirt supplied by the accelerator pump. (ignore this, your accel pump should be off!) I like to start around 55 or 60 mph. After getting up to the appropriate speed, back off of the thottle 1/8th turn. While doing so, pay attention to your RATE of acceleration. You will still be speeding up, as you are still in a nearly full throttle position, so rate of acceleration is the key (feeling of acceleration or momentum).
Bike wants to increase rate of accelleration. Main jet is lean and you need to increase main jet size.
Bike wants to maintain accelleration, or feels like you have done nothing different when backing off. Your main is right on the cusp, slightly lean.
Bike looses some momentum (may still be accerating, but at a slower rate). The main is not lean.
This test will not help to identify a rich main, only a lean one.
moog5050
Active Member
Franco I defer to Moespeeds. I am no tuning expert. It just seemed logical that you are lean due to the coughing and cold air, so I figure if the small jet change works, you are golden. But Moespeeds knows his stuff. Its just a slightly more time consuming procedure, but the proper one I am sure. Good luck.
Moe,
I plan to take your adive and try this procedure when spring arrives. Thanks.
Moe,
I plan to take your adive and try this procedure when spring arrives. Thanks.
ringo
Active Member
29.5 int is to small for sea level, 31-32 would be a better choice. Also, get the accelerator pump adjusted correctly. Mine had a lag or weak spot when slowly rolling on the throttle in say 5th gear @ 55 mph. It also would occasionaly pop back thru the carb.
Adjusting the ac. pump cleared all that up.
Adjusting the ac. pump cleared all that up.
moog5050
Active Member
http://www.bigdogbiker.com/forums/fuel-air/30505-s-s-carb-tuning-tips.html
one more link that may be helpful
one more link that may be helpful
Bhawkins854
Member
Going back to my intermediate jet I brought up earlier, is it common for a bike with motor work to need larger than .032 intermediate? Shaved heads and jugs 10.3:1 comp.060 larger valves, comp cams springs, port and polish, 600 cam, daytona twin tech ignition, and a custom 2 into 1 exhaust from donnie smith cycle. Just seems Dennis kirk and other places only sell to a .032, I built the motor so I'm hoping its just lean and its not other issues
Bhawkins854
Member
Awesome. I will also look around
Moespeeds
Well-Known Member
I can't comment on what bike needs what, in my experience every bike gets a different setup. Until you find that lean baseline, it's very hard to know how you're running. Rather then just blindly going up a jet just because you got motorwork, I'd drop it down a jet and see if it runs. There's a big difference in the throttle response and overall feel of a rich bike and one that's spot on. Definitely worth the time it takes, and once you learn it applies to anything with a carburetor.
francoblay1
The Spaniard
UPDATE
Today I have been running the dog at 41 degress temp (5 Celsius)... after taking the vent plug yesterday night, it runs LOTS better... BUT.... my mixture screw is still all the way out to stop sneezing through the carb. I am waiting for a 31 Inter Jet to arrive to me in a couple days (I am running a 29.5 at the mo) I hope this helps as I think it is still running lean?
Today I have been running the dog at 41 degress temp (5 Celsius)... after taking the vent plug yesterday night, it runs LOTS better... BUT.... my mixture screw is still all the way out to stop sneezing through the carb. I am waiting for a 31 Inter Jet to arrive to me in a couple days (I am running a 29.5 at the mo) I hope this helps as I think it is still running lean?
Germanbiker
Active Member
What do your spark plugs look like??
Spark Plugs
Check it out. Dont' go with E10 (ethanol gas).
Jochen
Spark Plugs
Check it out. Dont' go with E10 (ethanol gas).
Jochen
francoblay1
The Spaniard
Got that, I am running 98 Octane (the best here in Spain, and with less percentage of Ethanol) .... As far as I know!!
I will do further investigation in this subject!!! Good point! :up:
Further on after looking at the guide.... #3 Carbon fouled.
Last edited:
ringo
Active Member
looking back at the original post, you said the motor idles fine and runs OK but pops back thru the carb. You say you think its lean, but state the plugs are black, #3 I think, which is carbon fouled. Something seems amiss here, a lean condition and black plugs dont normaly go together. Keep in mind the carbs idle circuit may not operate as well anymore after all the engine mods, and a poorly performing exhaust will only make tuning worse. I believe you said you are turning the idle mixture screw out all the way, which is making it richer, thats a sign of an intermediate jet that is to small.