Cruising speed with BB 351
#31
07-04-2011, 05:34 PM
Join Date: Apr 2011
Location: Fort Atkinson, WI
Posts: 349
+1 and I 'd like to add that I don't think people are advising you to go 15T in front for the purpose of 'going faster.' With larger bore, the engine handles the higher gearing easily and it results in turning lower RPMs at any given speed in the same gear. My gas mileage went up when I added a tooth up front. It's nice to cruise along at 5400RPM in 6th gear at 60mph. The bike (with 300cc and above) will handle all but the very largest of hills in 6th gear with no problem at all. I have the KLX300 jug on mine and it does just fine so a 351 should handle it that much easier.
#33
07-05-2011, 05:09 AM
Join Date: Apr 2011
Location: Fort Atkinson, WI
Posts: 349
That's not a typo. I don't fully understand the carb components. Maybe you or someone else can educate me and push me in the right direction. I will not buy a 351, jets, or do anything until everything is clear in my head and I understand every thing. Yes, I know I take things slow!1. What jet's would I need with the 351. ( I would use stock carb )
2. What does the pilot jet do?
3. What does the main jet do?
4. What does the needle jet do?
5. What does the jet needle do?
6. What does the pilot air screw do?
I know, everybody can go ahead and laugh, I can take it!
#34
07-05-2011, 12:12 PM
2007 Green Machine, read this:
http://www.mikuni.com/fs-tuning_guide.html
SF has a smaller rear wheel. (17")
Bike turns 6,000 rpm speedo reads 60 or 61 mph. Tack goes down to 5750, speedo drops to 59 at the same time.
Before with 14/39 it was about 6500 @ 60 mph.
My numbers are as I see them. My speedo is off 7%, so 70 mph = 65.
David
http://www.mikuni.com/fs-tuning_guide.html
How about 'take' 600RPM. If you're running the stock 39T rear and bumped to15T in front, the RPM should be around 5400 at 60MPH. The shock 14/39 combo gives you about 6000RPM at 60mph....unless the SF has a larger rear sprocket than the D-tracker...or our speedo's read way different. 
Bike turns 6,000 rpm speedo reads 60 or 61 mph. Tack goes down to 5750, speedo drops to 59 at the same time.
Before with 14/39 it was about 6500 @ 60 mph.
My numbers are as I see them. My speedo is off 7%, so 70 mph = 65.
David
#35
07-05-2011, 01:44 PM
[QUOTE=2007 Green Machine;449358]b
1. What jet's would I need with the 351. I would get a DynoJet Kit, and use the STAGE 2 Instructions.
As far as you other questions, read this: Care & Feeding Of The Keihin Carb
1. What jet's would I need with the 351. I would get a DynoJet Kit, and use the STAGE 2 Instructions.
As far as you other questions, read this: Care & Feeding Of The Keihin Carb
#36
07-05-2011, 01:46 PM
Now that's another thing I have no idea about. I just rebuilt the carb in my 87 kawasaki mojave 250 4-wheeler, but I just went to the dealer told them I needed a rebuild kit and $17 later my 4-wheeler was back up and running. The rebuild kit was stock and I just replaced all of the components in the kit. I know the names off all the parts but really don't know what they do. That's not a typo. I don't fully understand the carb components. Maybe you or someone else can educate me and push me in the right direction. I will not buy a 351, jets, or do anything until everything is clear in my head and I understand every thing. Yes, I know I take things slow!
1. What jet's would I need with the 351. ( I would use stock carb )
Go ahead and get this Dynojet kit. Amazon.com: Dynojet Research Intake Performance Kit - Stage 1 2206: Automotive
This will cover all of your jetting needs, allowing you to replace your main jet, drill the slide for better throttle response with the included drill bit, and drill out and remove the cap covering the fuel/air mixture screw.
Along with ordering the Dynojet kit, you may want to go ahead and order the Kouba Fuel/Air screw extension. It basically allows you to easily adjust your fuel/air mixture while leaving the carburetor on the bike.
This can be purchased here:
"T"-Handle FuelscrewAir/Fuelscrews
Last but not least, go ahead and order a #38 Pilot jet. This may or may not be necessary but it's always nice to have in case your bike is running lean after the 351 kit. You most likely wont need this if you are stock 250.
I am not sure where this can be purchased as I am still looking myself, but someone should speak up and tell you where you can get it
2. What does the pilot jet do?
-Pilot jet controls bikes fuel from 0-25% throttle. If you are running lean in that range, you need to up your pilot jet. Most likely wont have to unless you get the 351 installed.
3. What does the main jet do?
-Main jet controls throttle from 25% on. It is used in conjunction with the needle.
4. What does the needle jet do?
There is no needle jet.
5. What does the jet needle do?
-Just used in conjunction with the main jet. The Dynojet needle has 6 grooves. The higher up the needle you place the clip, the leaner you will lbe running because the needle will plug the main jet more. The farther down the clip, the richer you run because the needle doesn't plug up the main jet as much.
6. What does the pilot air screw do?
-This is more commonly known as the fuel/air screw. It controls fuel/air mixture to a certain extent. You should replace this with the Kouba fuel/air screw.
I know, everybody can go ahead and laugh, I can take it!
That's not a typo. I don't fully understand the carb components. Maybe you or someone else can educate me and push me in the right direction. I will not buy a 351, jets, or do anything until everything is clear in my head and I understand every thing. Yes, I know I take things slow!1. What jet's would I need with the 351. ( I would use stock carb )
Go ahead and get this Dynojet kit. Amazon.com: Dynojet Research Intake Performance Kit - Stage 1 2206: Automotive
This will cover all of your jetting needs, allowing you to replace your main jet, drill the slide for better throttle response with the included drill bit, and drill out and remove the cap covering the fuel/air mixture screw.
Along with ordering the Dynojet kit, you may want to go ahead and order the Kouba Fuel/Air screw extension. It basically allows you to easily adjust your fuel/air mixture while leaving the carburetor on the bike.
This can be purchased here:
"T"-Handle FuelscrewAir/Fuelscrews
Last but not least, go ahead and order a #38 Pilot jet. This may or may not be necessary but it's always nice to have in case your bike is running lean after the 351 kit. You most likely wont need this if you are stock 250.
I am not sure where this can be purchased as I am still looking myself, but someone should speak up and tell you where you can get it
2. What does the pilot jet do?
-Pilot jet controls bikes fuel from 0-25% throttle. If you are running lean in that range, you need to up your pilot jet. Most likely wont have to unless you get the 351 installed.
3. What does the main jet do?
-Main jet controls throttle from 25% on. It is used in conjunction with the needle.
4. What does the needle jet do?
There is no needle jet.
5. What does the jet needle do?
-Just used in conjunction with the main jet. The Dynojet needle has 6 grooves. The higher up the needle you place the clip, the leaner you will lbe running because the needle will plug the main jet more. The farther down the clip, the richer you run because the needle doesn't plug up the main jet as much.
6. What does the pilot air screw do?
-This is more commonly known as the fuel/air screw. It controls fuel/air mixture to a certain extent. You should replace this with the Kouba fuel/air screw.
I know, everybody can go ahead and laugh, I can take it!
If you get the Dynojet kit I linked you to along with the Kouba fuel/air screw, you'll want to use something close to this set up:
-Fuel/air screw 2.5 turns out
-#128 DJ Main Jet
-Needle with clip 3rd notch down with two washers on top
This works for most people depending on where you live. I live ~900ft above sea level.
#37
07-05-2011, 01:54 PM
Now that's another thing I have no idea about. I just rebuilt the carb in my 87 kawasaki mojave 250 4-wheeler, but I just went to the dealer told them I needed a rebuild kit and $17 later my 4-wheeler was back up and running. The rebuild kit was stock and I just replaced all of the components in the kit. I know the names off all the parts but really don't know what they do. That's not a typo. I don't fully understand the carb components. Maybe you or someone else can educate me and push me in the right direction. I will not buy a 351, jets, or do anything until everything is clear in my head and I understand every thing. Yes, I know I take things slow!
1. What jet's would I need with the 351. ( I would use stock carb )
2. What does the pilot jet do?
3. What does the main jet do?
4. What does the needle jet do?
5. What does the jet needle do?
6. What does the pilot air screw do?
I know, everybody can go ahead and laugh, I can take it!
That's not a typo. I don't fully understand the carb components. Maybe you or someone else can educate me and push me in the right direction. I will not buy a 351, jets, or do anything until everything is clear in my head and I understand every thing. Yes, I know I take things slow!1. What jet's would I need with the 351. ( I would use stock carb )
2. What does the pilot jet do?
3. What does the main jet do?
4. What does the needle jet do?
5. What does the jet needle do?
6. What does the pilot air screw do?
I know, everybody can go ahead and laugh, I can take it!
How a carburetor works: Carbs explained - Ninja250Wiki
#38
07-06-2011, 01:49 AM
Interesting that it's for a Ninja250, when I got mine off of a KLR650 site.
#39
07-07-2011, 05:29 PM
Join Date: Oct 2009
Location: Sonoran Desert, Arizona
Posts: 262
Dude! I ask questions like these all the time. Let me try and help you out! Haha answers are in bold.
If you get the Dynojet kit I linked you to along with the Kouba fuel/air screw, you'll want to use something close to this set up:
-Fuel/air screw 2.5 turns out
-#128 DJ Main Jet
-Needle with clip 3rd notch down with two washers on top
This works for most people depending on where you live. I live ~900ft above sea level.
If you get the Dynojet kit I linked you to along with the Kouba fuel/air screw, you'll want to use something close to this set up:
-Fuel/air screw 2.5 turns out
-#128 DJ Main Jet
-Needle with clip 3rd notch down with two washers on top
This works for most people depending on where you live. I live ~900ft above sea level.
2007 Green Machine said:
4. What does the needle jet do?
jhoffy22 said:
There is no needle jet.
If you are interested, the part number for the needle jet is 16017-1439.
Ron
#40
07-07-2011, 10:18 PM
Also, when I talk about speed, I am talking actual speed ( not what the speedo says )
I also have the stock 14-42 gearing.
Before the big bore, the bike was happiest between 55-60 mph. I could run 65 mph but there wasn't much power left on tap. If I tucked and there wasn't a head wind I might touch 70 but there was no way I could hold it there.
After the big bore, the bike is now still happiest at around 60 mph. It still has enough power on tap to pass people though. It will easily run right up to 75 mph now. Thats about where it runs out of steam. Plus I could hold it at 70 mph all day if I wanted to, headwinds and hills aren't much of a concern anymore, even in 6th gear.
I feel much more confident with a big bore at cruising speeds.
I am going to try the 15 tooth front sprocket here soon and see what it does.
For jetting, all I ended up doing was going up one dyno jet main jet size and raising the needle one clip position.
Runs like a champ