Bogging on start

Betlog · March 15th, 2010, 03:58 PM

Hi guys, couple of questions I hope you all can help me with.

Problem: When starting the bike, the bike has trouble starting. There are times when I have to hold the starter for 4 to 6 (or so) seconds before she would start. Sometimes, holding it down for that long still won't start the bike. Setting the choke to different distances sometimes helps but sometimes actually kills the bike. When I move the choke all the way to fully open, it's actually acting in reverse of what I expect. That is, the bike drops below idle.

Background: I just installed a Dynojet Stage 2 Jet Kit and an Area P standard exhaust. The jet kit called for the idle mixture screws to be set to three turns. When I adjusted the screws, I noticed from the factory that they were set unevenly, that is, one screw was set further in, while the other was out more. After adjusting, they are currenlty both set to three turns.

Question: Is this a problem with my idle mixture screws set to too rich? Should I back them up? Or is this a case of carb syncing (I have yet to do that). I will attempt Vex's DIY in regards to adjusting the screws but wanted to check first to see if it's something else.

Momaru · March 15th, 2010, 04:01 PM

The factory sets the idle mixes differentially, just as the stock needles are not identical. Once you've rejetted they should be the same on both sides.

I'd try rolling the idle mix screws in a turn; 3 turns out is pretty severe for a 'base' setting (usually it's suggested to step up to the next size pilot jet if you have to go that far for a happy engine). The info I usually use/see says start with 2 turns out from closed and back 'em out (towards 3 turns) a little at a time (I usually use 1/6 turn increments) from there until you hit the sweet spot.

kkim · March 15th, 2010, 04:03 PM

Can you get the bike to run long enough to fully warm up? If so, what is your idle set to at that point?

To adjust the mixture screws I used this alternate method...

http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

Betlog · March 15th, 2010, 04:24 PM

Quote:

Originally Posted by kkim

Can you get the bike to run long enough to fully warm up? If so, what is your idle set to at that point?

To adjust the mixture screws I used this alternate method...

http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

Thanks Kelly, trying to visualize this adjustment, if say I adjust one screw and get it to a point where the engine runs fine, why would I need to adjust the other screw? Wouldn't adjusting the other screw mess up the adjustment that I just made to the now-perfectly adjusted screw? Or while adjusting the other screw, do I just keep on turning until I hear it mess up my adjustment of the other screw? Lastly, given Momaru's statement above, how bad is it for the screws to not be exactly set the same way?

P.S. The bike idles fine at around 1300 or so when fully warmed.

kkim · March 15th, 2010, 04:43 PM

you need to tune both carbs so they pass almost the same mixture. At that point, the carbs work together. Any difference between the 2 results in a less than mixture that the engine needs. use the links provided to "tune" the circuits... I wouldn't worry that they are not exactly the same amount of turns out, only that the settings give you the desired results.

Don't forget to sync the carbs too.

Betlog · March 15th, 2010, 04:49 PM

Quote:

Originally Posted by kkim

you need to tune both carbs so they pass almost the same mixture. At that point, the carbs work together. Any difference between the 2 results in a less than mixture that the engine needs. use the links provided to "tune" the circuits... I wouldn't worry that they are not exactly the same amount of turns out, only that the settings give you the desired results.

Don't forget to sync the carbs too.

Thanks Kelly, I read the link you've provided. But I am still a bit confused as how to get them adjusted at the same time since I am adjusting one screw, getting the result I want, then adjusting the other. As I mentioned in my previous post, if one screw is already adjusted properly, wouldn't adjusting the other screw "undo" the adjustment I made with the first screw? Or do I adjust one screw, get that perfect and adjust the other until I notice it affect the "perfect" adjustment from the other screw?

Also, with Vex's carb sync tool, do you think any "oil" will work? Rather than throw it, I have a few unopened motor oil that I can use.

kkim · March 15th, 2010, 04:57 PM

Don't know the "why" behind tuning both independently to work together, only know that it works.

You do one carb, get the results you're looking for, then do the other. Worked for me.

Any liquid will work for the sync tool, though the higher the viscosity, the shorter the tubing needs to be. Try the oil you have... the worst that can happen is that you'll suck motor oil into the engine if the carbs are way out of sync.

Momaru · March 15th, 2010, 05:18 PM

Quote:

Originally Posted by kkim

To adjust the mixture screws I used this alternate method...
http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

Same method, I just failed at explaining it. That's actually where I got the method I use.

Betlog · March 15th, 2010, 05:27 PM

Quote:

Originally Posted by Momaru

Same method, I just failed at explaining it. That's actually where I got the method I use.

Which method? There are two mentioned there... cylinder misfire OR blipping the throttle?

Betlog · March 15th, 2010, 05:33 PM

Oh one more thing... maybe a stupid question. The bike does not have to be level when doing the carb syncing and idle mixture tuning, right?

Momaru · March 15th, 2010, 06:06 PM

Heh, fair enough. I usually go with the blipping method, if only because it's more fun imo

I usually tune on a rearstand, but I don't think it matters much. Just so long as you don't use slider pucks as stands and lay it over for tuning.

However you do want your carb syncher level.

HKr1 · March 17th, 2010, 05:27 AM

Quote:

Originally Posted by Betlog

Which method? There are two mentioned there... cylinder misfire OR blipping the throttle?

The best way for a carb:

Quote:

Turn in each screw(one at a time) until the cylinder for the screw being adjusted starts to miss, then turn it back out 1/4 turn.

Also if your at 3 turns out, its time for a new(bigger) pilot jet.

kobachi · March 17th, 2010, 05:32 PM

I have a bike I bought with this same jet/exhaust setup, and have the same "problem". Is there a risk of hurting something trying the starter for this long? I've never been able to /not/ get the bike started though, sometimes it just takes a few tries. I was under the impression that all of these bikes are a bit touchy starting up cold...?

March 15th, 2010, 03:58 PM	#1
Betlog ninjette.org guru Name: Dude!! Location: Southern California Join Date: Dec 2009 Motorcycle(s): 2009 250r Posts: 443	Bogging on start Hi guys, couple of questions I hope you all can help me with. Problem: When starting the bike, the bike has trouble starting. There are times when I have to hold the starter for 4 to 6 (or so) seconds before she would start. Sometimes, holding it down for that long still won't start the bike. Setting the choke to different distances sometimes helps but sometimes actually kills the bike. When I move the choke all the way to fully open, it's actually acting in reverse of what I expect. That is, the bike drops below idle. Background: I just installed a Dynojet Stage 2 Jet Kit and an Area P standard exhaust. The jet kit called for the idle mixture screws to be set to three turns. When I adjusted the screws, I noticed from the factory that they were set unevenly, that is, one screw was set further in, while the other was out more. After adjusting, they are currenlty both set to three turns. Question: Is this a problem with my idle mixture screws set to too rich? Should I back them up? Or is this a case of carb syncing (I have yet to do that). I will attempt Vex's DIY in regards to adjusting the screws but wanted to check first to see if it's something else.

March 15th, 2010, 04:01 PM	#2
Momaru ninjette.org certified postwhore Name: Paul Location: Roanoke, VA Join Date: Jun 2009 Motorcycle(s): 2008 Candy Plasma Blue 250R Posts: A lot.	The factory sets the idle mixes differentially, just as the stock needles are not identical. Once you've rejetted they should be the same on both sides. I'd try rolling the idle mix screws in a turn; 3 turns out is pretty severe for a 'base' setting (usually it's suggested to step up to the next size pilot jet if you have to go that far for a happy engine). The info I usually use/see says start with 2 turns out from closed and back 'em out (towards 3 turns) a little at a time (I usually use 1/6 turn increments) from there until you hit the sweet spot. __________________________________________________ Proud member of the Blue Army

March 15th, 2010, 06:06 PM	#11
Momaru ninjette.org certified postwhore Name: Paul Location: Roanoke, VA Join Date: Jun 2009 Motorcycle(s): 2008 Candy Plasma Blue 250R Posts: A lot.	Heh, fair enough. I usually go with the blipping method, if only because it's more fun imo I usually tune on a rearstand, but I don't think it matters much. Just so long as you don't use slider pucks as stands and lay it over for tuning. However you do want your carb syncher level. __________________________________________________ Proud member of the Blue Army

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March 15th, 2010, 04:03 PM	#3
kkim Join Date: Nov 2008 Posts: Too much.	Can you get the bike to run long enough to fully warm up? If so, what is your idle set to at that point? To adjust the mixture screws I used this alternate method... http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

March 15th, 2010, 04:43 PM	#5
kkim Join Date: Nov 2008 Posts: Too much.	you need to tune both carbs so they pass almost the same mixture. At that point, the carbs work together. Any difference between the 2 results in a less than mixture that the engine needs. use the links provided to "tune" the circuits... I wouldn't worry that they are not exactly the same amount of turns out, only that the settings give you the desired results. Don't forget to sync the carbs too.

March 15th, 2010, 04:57 PM	#7
kkim Join Date: Nov 2008 Posts: Too much.	Don't know the "why" behind tuning both independently to work together, only know that it works. You do one carb, get the results you're looking for, then do the other. Worked for me. Any liquid will work for the sync tool, though the higher the viscosity, the shorter the tubing needs to be. Try the oil you have... the worst that can happen is that you'll suck motor oil into the engine if the carbs are way out of sync.

March 15th, 2010, 05:33 PM	#10
Betlog ninjette.org guru Name: Dude!! Location: Southern California Join Date: Dec 2009 Motorcycle(s): 2009 250r Posts: 443	Oh one more thing... maybe a stupid question. The bike does not have to be level when doing the carb syncing and idle mixture tuning, right?

March 17th, 2010, 05:32 PM	#13
kobachi ninjette.org member Name: Craig Location: Seattle Join Date: Dec 2009 Motorcycle(s): Blue 2008 Ninja 250R Posts: 86	I have a bike I bought with this same jet/exhaust setup, and have the same "problem". Is there a risk of hurting something trying the starter for this long? I've never been able to /not/ get the bike started though, sometimes it just takes a few tries. I was under the impression that all of these bikes are a bit touchy starting up cold...?