quick fix?

[red]

Hello,

From dfw, tx. I picked-up a near new 2010 for my daughter (and son) but she might not get it back. It is admittedly a lot of fun and is living happily with a few other bikes.

While it had less than 300 miles when I bought it, I can't help but think that it needs a little idle mixture bump as it seems EPA strangled down low and cold blooded starting. Or maybe it is just me used to about 5 times the displacement? Or maybe get out the carbtune and make sure they're synced? I have read a bit of the forum and I really do not want to twiddle it to death and would probably not bother to ever rejet or shim the needles or change out the can, just destrangle it if there is standing wisdom on making it more drivable especially cold and below 4k.

IME, a lot of the US spec in the past has needed the epa caps removed and a little twist of the idle mix screws.

And maybe it is just me not used to winding it up into the powerband.

Although I read some of the articles, can I easily get to the epa caps without pulling the carbs off? I have a 90 degree adjusting screwdriver. Or does a stock de-strangle not make all that much difference, or do I really need to pull the carbs and raise the needles for casual riding.

Thanks for any advice.

[dubojr1]

You can easily do the shimming without pulling the carbs. I would suggest shimming the needles, pulling the snorkel, and changing the front sprocket to 15T. All easy stuff with BIG differences.

http://www.ninjette.org/forums/showthread.php?t=5586

[Snake]

Here is a link to removing the cap and adjusting the screws without taking the carbs off.

http://www.ninjette.org/forums/showthread.php?t=10246

[red]

Originally Posted by dubojr1

You can easily do the shimming without pulling the carbs. I would suggest shimming the needles, pulling the snorkel, and changing the front sprocket to 15T. All easy stuff with BIG differences.

http://www.ninjette.org/forums/showthread.php?t=5586

Are you guys generally putting one shim for just general putt-putting around? All I am really looking for is for eliminating what seems to me as epa strangling.

Thx.

[HKr1]

Stock needles are horrid, swap those out for some others (takes 30-40 minutes tops). Also the stock cdi with 35 deg advance hurts the cold running in lower rpms, that brt cdi with 42 deg advance takes care of that

[kkim]

Originally Posted by red

Are you guys generally putting one shim for just general putt-putting around? All I am really looking for is for eliminating what seems to me as epa strangling.

Thx.

http://www.ninjette.org/forums/showthread.php?t=9465

[2WheelGuy]

The 250s are cold blooded. The bike will never start like a Fuel Injected 4 cylinder bike but it can be improved.

While I have no problem riding off with the choke half on my girlfriend is a nervous rider and wants the bike running perfectly before she leaves the driveway. I have found no way around the 5 minute warm-up session for her.

When she got the bike from the dealership is was almost unrideable for her. All I did was set the idle screws to 2 1/2 turns out and move the idle closer to 2000 rpm for her to be totally happy with the bike.

You do need to remove the carbs to remove the EPA caps. Once the caps are out you can make adjustments with an angled screwdriver.

I've found that shimming/changing the needles makes a tiny improvement but isn't necessary with the stock exhaust.

[red]

Originally Posted by 2WheelGuy

The 250s are cold blooded. The bike will never start like a Fuel Injected 4 cylinder bike but it can be improved.

While I have no problem riding off with the choke half on my girlfriend is a nervous rider and wants the bike running perfectly before she leaves the driveway. I have found no way around the 5 minute warm-up session for her.

When she got the bike from the dealership is was almost unrideable for her. All I did was set the idle screws to 2 1/2 turns out and move the idle closer to 2000 rpm for her to be totally happy with the bike.

You do need to remove the carbs to remove the EPA caps. Once the caps are out you can make adjustments with an angled screwdriver.

I've found that shimming/changing the needles makes a tiny improvement but isn't necessary with the stock exhaust.

Exactly the info I was looking for, and exactly where I am at right now in the time-for-twiddling budget. Thanks.

[kkim]

how is removing the cap plugs for the mixture screws a "quick fix"? You will most likely need to remove the carbs to be able to remove them. I know there is a DIY on how to remove them w/o taking the carbs out, but I've also seen people fubar the drilling out the cap and damaging the carb body while doing so. If you go this route, be very careful when you drill the caps.

I agree w/ Craig that the fix is to redo the mixture screw settings, but calling it a "quick fix"??? I don't agree with that.

[dubojr1]

Originally Posted by kkim

how is removing the cap plugs for the mixture screws a "quick fix"? You will most likely need to remove the carbs to be able to remove them. I know there is a DIY on how to remove them w/o taking the carbs out, but I've also seen people fubar the drilling out the cap and damaging the carb body while doing so. If you go this route, be very careful when you drill the caps.

I agree w/ Craig that the fix is to redo the mixture screw settings, but calling it a "quick fix"??? I don't agree with that.

Just for my own knowledge... Is adjusting the mixture screws accomplishing similar results of shimming the needles with no mixture adjustment?

[red]

Originally Posted by kkim

how is removing the cap plugs for the mixture screws a "quick fix"? You will most likely need to remove the carbs to be able to remove them. I know there is a DIY on how to remove them w/o taking the carbs out, but I've also seen people fubar the drilling out the cap and damaging the carb body while doing so. If you go this route, be very careful when you drill the caps.

I agree w/ Craig that the fix is to redo the mixture screw settings, but calling it a "quick fix"??? I don't agree with that.

Thanks for the warning on being careful.

I eyeballed with my brightest flashlight and there seems to be a lot of room under the carbs to (gently) drill a small hole with one of the 90 degree adapters or maybe a dremel with a 90 degree, then do the sheet metal screw thing (by hand) and wiggle out the EPA cap by hand after removing the lower tupperware.

On larger bikes I've done the idle mix/epa cap thing times after removing the carbs on both mikunis and keihins. But normally there was NO space even to adjust them in situ and it did make a large difference on warm up and off idle manners. But you are right about being careful especially if this is new territory.

I don't have the 90 degree drill tool but any excuse for another one, and the HF right angle jobbie looks interesting for $12. I have a 90 degree mixture screwdriver for the deed after the caps are out.

Famous last words... but it looks like it could be a 30 minute thing at most to set them to 2 1/2 out, requiring no parts other than a little 90 degree adapter. Not pulling the carbs would seem to be lower hassle.

[red]

Originally Posted by dubojr1

Just for my own knowledge... Is adjusting the mixture screws accomplishing similar results of shimming the needles with no mixture adjustment?

I believe these operate in primarily different ranges. The idle mixture is down low off idle and stop having an effect very early. But that is just what I know about other non ninjettes.

[kkim]

you're attacking the problem from 2 different directions as the pilot circuit and needle interact at that crucial period of when the bike is just taking off from a start.



what I like about the shimming method is that not only does it richen the off idle response to improve take off, but due to raising the needle taper with the washers, the bike is richer a bit higher into the rev range where I feel the stock jetting is also lean. (2-5k).

the aftermarket jet kit guys must think so, too, because if you compare the stock needles with those supplied by them, you can see they are thinner throughout the taper making them deliver more fuel as you ramp up into the mains.

[00nothing]

Have to agree with shimming i have never worked on a bike really before and shimming was quite simple as long as u have the right size washers the snorkel was a bit of a pain but once u get pissed off enough about having your fingers go sore u just rip it out and realize how easy it really was

next step is going to be a 15t sprocket but my wife who is a brand new rider loves her bike now and immediately noticed a difference in how much nicer everything was with those simple mods

[slow_2k10]

going to put it straight foward with u... the cold bloodness is mainly du to the needles... if u are planning on keeping bike stock jus tput 1 washer in each needle... the bike will start up easier and ride easier... yes u will still have to warm it up for idle to be perfect but all of the missing power and bogging down will dissapear..


the idle screws are something hardly anyone touches.. the shims on the other hand 9/10 people have.. and is much easie rto do than the screws..

[red]

Well the pilot mixture can be done with out pulling the carbs, but it is certainly fiddly on the right, not too bad on the left. You need to remove the left and right lower panels.

You definitely need to have the 90 degree tools to remove the EPA plugs and a 90 degree pilot screwdriver. It takes more time to undress the bike than it does to do the deed.

I put mine at 2 1/2 out to begin with. Any further adjustments won't require any disassembly as they can be reached with the pilot tool.

Interesting many here go for shimming first rather than adjust the low speed circuit - probably a result of how the (no) low power curve is on these. I have a couple of older brand T bikes and the first thing everyone does to them is to set them up to "euro-spec" where the EPA caps are removed and pilots reset to about 2 1/2 or 3% CO. It cures all their starting problems an low speed stumbling and transforms them.

I will give it a test and see if I need to pull the tank and shim next. I picked up a bag of ss washers last night. What's the consensus on a stock can - 1 shim at most?

My only objective right now is to make it as easy and smooth to drive as possible for my oldest.

[g21-30]

Here's my 2 Cents. If you wish to keep the stock exhaust. Buy a DynoJet kit and ONLY use the needles/washers/clips and set the mixture screws to 2 1/2 turns out. Remove the snorkel. With the stock 98 jets, you WILL be rich.

If you have the CDI problem, then consider the BRT TIS or retro fit an '88-94 CDI.

And VeX's method of removing the caps will not hurt anything, since you're using a self-tapping screw (not a drill). Worked for me!

Good Luck!

[kkim]

Originally Posted by red

I will give it a test and see if I need to pull the tank and shim next. I picked up a bag of ss washers last night. What's the consensus on a stock can - 1 shim at most?

1 at least... maybe 2 depending on the bike, though with you already readjusting the mixture screws, maybe none. You tell us how it works out as I think you're the first that has gone this route first instead of shimming the needles first.

yes, if all you're doing is looking to make the bike smoother and easier to ride, leave the exhaust stock and do not remove the intake snorkel. You may need to lean out the main jets later if you find the top end a bit strangled/flat, but for now work on the pilot and needles to make the bike more rider friendly.

Good work!

[kkim]

Originally Posted by g21-30

And VeX's method of removing the caps will not hurt anything, since you're using a self-tapping screw (not a drill). Worked for me!

did you not see the post where a forum member broke the carb casing at the mixture screws while drilling the caps out and was leaking fuel from there when he reassembled it?

[g21-30]

Originally Posted by kkim

did you not see the post where a forum member broke the carb casing at the mixture screws while drilling the caps out and was leaking fuel from there when he reassembled it?

I did see that, but I remembered he "drilled" with a drill bit, not a self-tapping screw in the MOS. If I'm wrong (dementia ), then I stand corrected and would say don't do it.

[kkim]

Originally Posted by g21-30

I did see that, but I remembered he "drilled" with a drill bit, not a self-tapping screw in the MOS. If I'm wrong (dementia ), then I stand corrected and would say don't do it.

yep, it does sound that way.

http://www.ninjette.org/forums/showthread.php?t=47488&

why would a self tapping screw be any different, though?

[g21-30]

Wow, it was a drywall screw (length not stated!! ). The self-tapping screw (ala VeX), actually popped the cap out, before it was completely thru the cap. It only penetrated maybe 1/16" in my case. I was turning the MOS by hand (not a drill ).

Definitely understand a drywall screw via MOS with an electric drill could penetrate pretty deep!

Oh, the self-tapping screw is no way as sharp as a drywall screw.

[red]

Not trying to induce thread creep, but from my experience you could definitely get a self tapping screw to bugger up a carb in a power screwdriver (what I had the MOS chucked in) if you weren't careful. I used a different (slightly larger) screw, not thread cutting to grab the cap and remove it. Carbs are not very hard metal, but harder than an pot metal EPA dork cap.

I was very careful to try to stay in the near-center of the little cap but it I can see how someone that has not done this before could flub it up and not know what is under the cap and how deep, etc. Including someone like me by accident.

OB public service announcement: Someone that's not familiar with what they are doing should probably remove the carbs and do it on a bench in good lighting, with a professional driver on a closed road

[kkim]

How's the bike running, DJ?

[red]

Originally Posted by kkim

How's the bike running, DJ?

Here's my full report.

I don't want to over attribute the results. I am a firm non-believer in the phrase "seat of the pants dyno" . The differences seem pretty subtle but I was surprised to find the low speed mixture screws out farther than I thought they'd be under the caps - they were ~~ 2 out, IIRC, and I set them to 2.5.

But the change it is no worse. It will start with very little/no choke and is not horribly reluctant to get underway, which seems about right. Granted, I have only a few days and very little experience with the 250R/J bike and don't really know what is normal. All of my related experience is mostly with carbed bikes are all displacements +3x the size, and of course modern magical FI bikes too. So this behavior is what I would expect for properly set mixture screws.

When it is cold started it will immediately idles reasonably but will still bog a lot when the throttle is twisted for about a minute until it warms (it is 95-100 in Texas now, btw, everything is pre-warmed). The idle has been set closer to 2k than 1k and this seems to help initial drivability and is not too high to be detrimental to normal deceleration. I think it is still boggy moreso than I would expect even with CV carbs. It is also very slow to return to idle - the throttle does not "snap shut" by any stretch.

Once fully warmed it is still lethargic/lazy between about 2k-4k (I presume this is normal??), and at 4k the switch is tripped and power comes on nicely all the way up. It is quite drivable but if I had my wishes it would be pulling smartly, linearly, and proportionally from 2k up (obviously within the capability of a 250), which would not be unlike the powerband of a properly tuned street bike like I'm familiar with, just 250 sized. Of course past 8k it goes like stink (this means good).

I couple of days ago I thought it was pretty hazardous off idle when I brought it home and felt it was strangled. I am too big for the bike but I took that into consideration.

I am generally of the opinion that factory engineers have better analysis equipment know a lot more than I do and design airboxes (I presume most airboxes these days have some helmholtz resonator properties - not unlike http://www.desmoducati.org/airfilter.html) that usually make the best drivable powerbands for everyday use, so I will probably never mess with the intake side unless there is a graph to go with it. I've seen a lot of bikes mucked up by fiddling with pods and other stuff that really confuses the powerband and jetting over the full spectrum of drivability and usually reduces actual power, and get modded into a mess. But again, I know nothing about these bikes and could be totally wrong.

If there is a simple solution to the 2k-4k spot I will probably do it, and I presume it will be 1-2 shims under the needles? And I will need to wrestle a couple quiet hours with the bike back from its riders to do this. If shimming is likely to not make any significant difference here, I will leave it alone.

Opinions on the 2-4k spot?

[Snake]

Great write up Dj.

[kkim]

Originally Posted by red

Opinions on the 2-4k spot?

yes, I feel shimming will help in that rev range.

very good, detailed feedback on the mixture screw adjustments. if anything, you need to try tune the mixture screws before you move on to shimming as they may be not at the optimum setting right now at 2.5 turns out. from what you describe, it may still be a bit lean?

http://faq.ninja250.org/wiki/How_to_...r_idle_mixture.

if you decide to shim, start with one shim and add another if you think one doesn't improve the bottom end enough for you.

looking forward to your future work.

[red]

Not sure I will get weekend time to fiddle more, but I will keep at it and see if it gets any better if I get some spare time. Next week is a travel week for me.

From what I've seen I can spread the top of the fairings while the lower part is still attached, remove the seat and remove the tank and get at the carb tops within a few minutes, unless there is a gotcha I don't know about.

I've also got a morgan carbtune in the tool box I would probably stick on to see how they're balanced, any general wisdom unique to these as to what's the best approach/tolerance to calling them synced? I'd probably default to keeping them near each other in the first half of the rev range and be happy if it stays that way for the rest.

[kkim]

when I sync mine, I try for equal amounts at idle. as the revs go up to 3k, they are unequal you already know. I did test for equal settings at 3k and idle and I preferred the bike when it was synced at idle. I set my idle at 1500rpm.

yes, you can do the shims by spreading the top side of the fairings out a bit, but it's relatively easy to fully undress the bike.

http://www.ninjette.org/forums/showthread.php?t=9933

how do the kids like the changes you've made? Have they noticed any difference?

[red]

Originally Posted by kkim

how do the kids like the changes you've made? Have they noticed any difference?

I don't think they have a clue. They just like to ride and ride but luckily don't explore the boundaries of the envelope. yet.

[red]

Where/how should these rubber U-shaped bumpers go?

They are on the back rear upper corners of the fairing, one on each side, and their stickum has apparently come loose and they are just rattling around loose.

[TenaciousD]

Originally Posted by red

Where/how should these rubber U-shaped bumpers go?

They are on the back rear upper corners of the fairing, one on each side, and their stickum has apparently come loose and they are just rattling around loose.

Mine went in the trash. They just fell out on their own when I took the fairings off the first time and I couldn't figure out where they should go back to. I don't think the bike misses them.

[red]

I looked up the fiche and found the right orientation for those bumpers U facing forward and over the crease in the fairing) and glued them. After locating the general area there was a little paint key mark where they were to go.

I tested a bit this morning and it did seem like the idle mix was still showing signs of being too lean, so I reset them both to 2.75 out.

I pulled the tank and looked at the possibility of shimming the needles with the carbs in place. After a bit of testing the stubborn screws with no JIS bits, and examining the lack of room to maneuver, decided to wait until I find a need to extract the carb rack and get them on a bench and test the mixture later with a longer test ride.

This evening I had a chance to put a few miles on it and it seems just about perfect for what I'm expecting. It does not make much power between 2-4k (pretty docile, but it is hauling my giant self), but it seems quite linear. Good for it's current role for someone less than half my weight. I am going to leave it alone for now.

The transmission seems to make a pretty significant whine/gear noise in all gears at all speeds. Normal?

[red]

What's the general consensus on what causes a slow return to idle (10-20 secs).

May be time to pull the carbs again. Oops, should probably start a different thread. sorry mod.