DIY Shimming the carb needles.

[kkim]

lol... good ole duck.

very simply, there are 3 parts to the carb jetting. the idle, midrange and top end. the idle circuit is handled by the idle mixture screw and the pilot jet. the midrange by the needle that we are talking about shimming and the top end by the main jet.

the idle circuit and midrange are lean from the factory. instead of doing both, we are raising the needles with the washers to richen where the needle comes into play with the idle circuit. By raising it, we let in more gas/air mixture earlier when we turn the throttle, which in turn makes more power. the net effect is that the bike's power feel "fatter" from right off the bottom.

On the other hand, the stock 98 main jet is a bit too rich from the factory, so pulling the snorkel out actually leans out the bike a bit and makes the 98 main just about perfect for the top end.

Pulling the snorkel, though, will lean out the mixture from idle to top end and the idle and midrange will suffer if you don't compensate for it by richening the mixture by shimming. That is why in my DIY on pulling the snorkel I recommended only pulling it after the needles were shimmed.

The best time to remove the snorkel is when you do the shimming.

On my bike, with an area p QC exhaust, I ran with 3 washers under each needle with the snorkel removed. It ran fine in that configuration and at no time did the top end suffer from being too lean with the stock 98 main jets.

The above advice is all with you using the stock airbox. If you remove the airbox, everything changes.

Do it, you'll be fine.

[CaliGirl]

I think I will attempt to shim the needles this weekend...are there any long term adverse effects to removing the snorkel if I am shimming the needles as well?

[Kurosaki]

I've had my snorkel out for about 6000 miles. No problems yet.

[kkim]

Originally Posted by CaliGirl

I think I will attempt to shim the needles this weekend...are there any long term adverse effects to removing the snorkel if I am shimming the needles as well?

give me the intake and exhaust mods made to your bike and I can kinda give you a ballpark area on how many washers to use.

[Jiu Jitsu Player]

For a slip on exhaust- is shimming the needles and and pulling the snorkel enough to run the slip on without a decrease in performance?

[kkim]

yes.

[CaliGirl]

Originally Posted by kkim

give me the intake and exhaust mods made to your bike and I can kinda give you a ballpark area on how many washers to use.

I'm all stock. Should I start with 2 washers if I pull the snorkel as well??
Posted via Mobile Device

[kkim]

yes, stock w/ snorkel pulled, try 2 washers to start. be careful when loosening the screws on the top of the carbs. Long #2 phillips and lots of downward pressure before you turn the screw. If it starts to slip out, apply more downward pressure until it turns w/o trying to slip out of the screwhead.

those screws have caused more problems with this mod. second biggest problem... use the correct sized washers. 3mm or 4mm washers will do. I used 3mm.

GL

[CaliGirl]

Lots of downwards pressure and correct washer size-Got it!!

Hopefully I'll be able to get this done this weekend.
Posted via Mobile Device

[kkim]

Yep, I think that's it...

oh... take lots and lots of revealing, closeup pics. And some of the bike too.

[miks]

^

[paterick4o8]

I just added two 3mm today... took me forever to find them as Radioshack, and Lowe's & Home Depot only go as small as 4mm. Anyways what a day just to find them.. I eventually found them at Fry's Electronics (if you guys have that store in your area).

You guys are right, the carb screws are a PIA!, but after time, I was successful. After I put the tank and seat back on I was about to take it for a test run when it started raining . As another test, I decided to start it without choke, since I've heard shimming makes starting easier even without choke. It started, but the engine had some struggle to stay running, though it did stay on. Not sure if that is normal on a cold start without choke, or if it really should start up and not struggle at all. However, I'm a bit skeptical as to if I need to add another washer since the thickness of the ones I bought from the electronic store seem pretty slim. I have a FMF Apex slip-on btw. Hopefully roads are dry enough tomorrow for me to see how it performs.

[kkim]

You still need to use some choke at start up. it should warm up faster though. Once it warms, try revving it a bit and see if it will rev past 5-6K. Some people that have had problems couldn't rev past that mark.

no matter what the thickness of the washers, you're in a better (richer) situation than you were before shimming. You should see some improvement with the addition of the washers.

did you pull the snorkel off too? I would recommend doing so at this time so you can compensate for that too in your final shimming.

[paterick4o8]

Just tested throttle response on my bike after adding those 2 washers from the electronic store and removing the snorkel. I feel the smoothness start to kick in at just about 2.5k. I'm thinking it's best to add another. I know that this mod can also involve personal preference as to what the rider likes, but do you agree I should add another?

[kkim]

did you ride the bike around until it's fully warmed up (10-15 minutes) and then test the throttle response while actually riding the bike or did you just warm it up in the garage and are basing your findings on a static load?

[paterick4o8]

yes I let it warm up. I rode it down my block, testing with the throttle in first gear.

[kkim]

at this point, you know best about what it might need. You won't screw anything up by adding another washer, as if you go too rich, the bike will just feel really flat at the rich spot with no chance of engine damage. You will want to change it back, though, if you are too rich.

Experiment... there is no set rule about this as every bike differs a bit. 2.5k is pretty low for this bike, though. you actually ride it at that rpm?

Did the shims help with the takeoff smoothness and power at the lower (below 5K) rpms?

let us know your results.

[paterick4o8]

Originally Posted by kkim

2.5k is pretty low for this bike, though. you actually ride it at that rpm?

Did the shims help with the takeoff smoothness and power at the lower (below 5K) rpms?

let us know your results.

haha no I dont ride it at that rpm, but I just like a smooth take off from idle. they did help with smoothness prior to 5k, it's just I didnt feel it start until 2.5K.

I'll try adding another and see how it goes. maybe even upload some pics if I take some.

[kkim]

that would be helpful if you take some pics of removing the screws from the carb tops and the springs and clips inside the carb tops once you get them off. seems like there are still some that are a bit spooked about what to do once the tops are removed.

mahalo

ps- when I was playing with shimming, I would just put the tank and seat back on and go out and test. Saved putting the bottom fairings back on. you just need to use hand signals for turns as the blinkers won't work with the front blinkers not hooked up.

[Sound Wave]

Originally Posted by kkim

..you just need to use hand signals for turns as the blinkers won't work with the front blinkers not hooked up.

don't forget to open and close your hand to simulate the blinking. ok, dumb joke.


hey, about the petcock leaking gas... i helped visus today with shimming of his carbs. when we removed the larger hose on the petcock, fuel started dripping out. quickly at first, then about once every 3-4 seconds. that didn't happen when i did mine and when i helped ninjabrewer. i did it in the exact same order as the last two bikes. large tube on the side, larger tube on petcock, and smaller tube on petcock.

it didn't stop dripping, so we set the tank down (with a 2x4 on one end so the petcock was off the floor) and i put some paper towels under it to catch the gas. when we were ready to put the tank back on, i checked and it had stopped dripping... although, when i touched the tip of the petcock, it dripped a couple more times.

i wonder why it is that there are so many faulty petcocks? i wonder if the amount of gas in the tank has anything to do with it? visus' tank was pretty full. although, ninjabrewers was pretty full as well. i don't know. doesn't make sense to me.

[kkim]

I've taken my tank off when it was pretty full and have never had a problem. diaphragm inside the petcock could be defective. wonder if it has anything with the ethanol we use in Hawaii... hope not.

Diaphragms fail... fact of life.

BTW, how did the shimming go and is he happy with the results?

[Sound Wave]

shimming went ok. like ninjabrewers fairing and your windscreen rubber nut, one of his ripped in half. we were able to get it back on though by holding the broken piece in place from behind while screwing in the screw (props to nb on that one).

as far as his impression, i don't know. he left after we were done. he said he was going to give a report later on.

yeah, i was really surprised when his petcock started leaking. i wasn't prepared for that. when we crack open another oxygen tank at work, i am going to take the rubber nipple cover in case i ever come across that situation again.

[paterick4o8]

Ok tell me if this is not weird.. I added the 3rd washer on. I start up my bike w/ choke on. Before, even without shimmed needles, when I had the choke on to warm up the bike, it would hit at least 4K, maybe a little over. Yet this time, it only went up as high as 3.5K with choke on to warm it up. Is this normal?

[Sound Wave]

mine is the same. 4k+ stock, 3.5k now.

[Visus]

Sound Wave and I shimmed my needles with 2 washers each needle and removed the snorkel. Thanks a lot to him!
It does feel smoother, however, coming from a standing stop in first gear, it seems to feel and sound like it wants to stall. Is that normal or am I not used to having the snorkel out?

[kkim]

Originally Posted by paterick4o8

Ok tell me if this is not weird.. I added the 3rd washer on. I start up my bike w/ choke on. Before, even without shimmed needles, when I had the choke on to warm up the bike, it would hit at least 4K, maybe a little over. Yet this time, it only went up as high as 3.5K with choke on to warm it up. Is this normal?

doesn't really matter. what matters is that after the bike warms up it idles at 1500. does it?

btw, it isn't good for the bike to idle at 3.5-4.5 at startup. I play with the choke lever once the bike is started to try to keep the idle revs at about 2-2.5K. it's a touchy thing and just a slight movement of my choke lever will let the idle drop significantly at one point.

Don't treat the choke lever as a digital device, but more like analogue.

[kkim]

Originally Posted by Visus

Sound Wave and I shimmed my needles with 2 washers each needle and removed the snorkel. Thanks a lot to him!
It does feel smoother, however, coming from a standing stop in first gear, it seems to feel and sound like it wants to stall. Is that normal or am I not used to having the snorkel out?

how many shims did you put in and any exhaust mods?

the shimming should have made the off idle power a bit stronger. Yes, removing the snorkel does seem to reduce the midrange a bit, but you are suffering power loss at the low end. that is a bit strange.

[Visus]

Originally Posted by kkim

how many shims did you put in and any exhaust mods?

the shimming should have made the off idle power a bit stronger. Yes, removing the snorkel does seem to reduce the midrange a bit, but you are suffering power loss at the low end. that is a bit strange.

No exhaust mods. 2 shims each needle.

Would replacing the snorkel help?

[Sound Wave]

i don't think putting the snorkel in would help from a standing stop. that is strange. i guess try using more throttle when starting off... you shouldn't have to, but it may help.

edit: pm sent

[kkim]

hmmm... all the vacuum hoses get hooked back up correctly? when you first started it after the shimmimg, did it idle okay?

[Visus]

Originally Posted by kkim

hmmm... all the vacuum hoses get hooked back up correctly? when you first started it after the shimmimg, did it idle okay?

Rode it again. Idles ok. I am able to go from 0 to highway speeds fine, so it may not be a loss in low end power. Could be that I just need to slip the clutch & give more throttle like Gary said. That and the throatier sound is maybe throwing me off.

[kkim]

Originally Posted by Visus

Could be that I just need to slip the clutch & give more throttle like Gary said.

mmmm... that's exactly the point of shimming. it should make it so you require less revving and clutch slipping to get the bike moving from a stop.

as a test, stick the snorkel back in there and see how you like it. it's not hard, but it's not easy, either. You don't need to get it back in there perfect, just stick it in the best you can and see if that improves the low end power you're seeking.

[ahskeetz]

So i was able to go home this weekend for less than 24 hours. I spent the majority of the time working on the bike. Here is what I got done:

1) I shimmed the needles to 3 washers, It runs great I notice a significant increase in power, especially in the mid range, I don't really have to keep it in the high rpm range to get power out of it. However, with this performance increase, there is a trade-off. I got about 42 MPG today, traveling on about 95 miles from my home to school, the whole time i was goin about 85, just to give you all an idea of the rpm range it was around 10k the whole time.

2) I also got to put on flush mounts .

3) I did a fender eliminator and bought license plate light bolts to use as my license plate lights.

The bike runs great, and is beautiful, I'll post pics when I get a chance. Thanks for all your help everyone who contributed to the forums.

[kkim]

yes, there is always a trade off with any engine performance mod. the question one must answer is... is it worth it?

I think you'll find your mpg will fluctuate dependant on how vigorously you twist the throttle.

have fun, ride safe.

[paterick4o8]

Originally Posted by kkim

doesn't really matter. what matters is that after the bike warms up it idles at 1500. does it?

btw, it isn't good for the bike to idle at 3.5-4.5 at startup. I play with the choke lever once the bike is started to try to keep the idle revs at about 2-2.5K. it's a touchy thing and just a slight movement of my choke lever will let the idle drop significantly at one point.

Don't treat the choke lever as a digital device, but more like analogue.

Ok, then I guess this is normal since it does idle at 1.5K or close to it.. it's not way off or anything. (I actually keep it a little below like 1.4 or 1350, so it was about right for me.)

Yeah I know what you mean about choke lever.. it's pretty sensitive. When I warm up, I also adjust to also keep it at 2.5K until fully warm.

[paterick4o8]

Originally Posted by ahskeetz

I shimmed the needles to 3 washers, It runs great I notice a significant increase in power, especially in the mid range, I don't really have to keep it in the high rpm range to get power out of it. However, with this performance increase, there is a trade-off. I got about 42 MPG today, traveling on about 95 miles from my home to school, the whole time i was goin about 85, just to give you all an idea of the rpm range it was around 10k the whole time.

Did you remove the snorkel? http://www.ninjette.org/forums/showthread.php?t=10090

As Kelly says, this helps the bike run leaner, so it may help some.

[Buffalony]

Originally Posted by kkim

yes, stock w/ snorkel pulled, try 2 washers to start. be careful when loosening the screws on the top of the carbs. Long #2 phillips and lots of downward pressure before you turn the screw. If it starts to slip out, apply more downward pressure until it turns w/o trying to slip out of the screwhead.

those screws have caused more problems with this mod. second biggest problem... use the correct sized washers. 3mm or 4mm washers will do. I used 3mm.

GL

Thanks kkim this answered my question.

did you mean a 3mm or #4 washers will work?

[kkim]

Originally Posted by Buffalony

Thanks kkim this answered my question.

did you mean a 3mm or #4 washers will work?

No, I meant either a 3 or 4 mm washer, but I see I was mistaken. I would recommend using a 3mm, if you can find it. if not, someone measured a #4 washer and I do believe you are correct that a #4 washer will work, too.

yes, a #4 will work...
http://faq.ninja250.org/wiki/Washers_for_carb_needles

[Sound Wave]

Originally Posted by kkim

hmmm... all the vacuum hoses get hooked back up correctly? when you first started it after the shimmimg, did it idle okay?

yes. the vent hose (i believe that is what it is called), the fuel and the vacuum hose are on correctly.

Originally Posted by kkim

mmmm... that's exactly the point of shimming. it should make it so you require less revving and clutch slipping to get the bike moving from a stop.

yeah, it was just a thought.

todd, yeah maybe sometime this week we can meet up after work and switch bikes so we can see if and what the difference between the two is. but yeah, kelly is right... it should be easier, not trickier, to start from a stop. i can also give you a hand sticking the snorkel back in if you want. going to pm you again.

[kkim]

Originally Posted by Sound Wave

yes. the vent hose (i believe that is what it is called), the fuel and the vacuum hose are on correctly.

on the left carb, when you take the top off, I had to disconnect two vacuum hoses to that round thing that hangs off the left side of the carb. could those hoses been switched? I know they are of a slightly different diameters, but did you get them back on correctly?

in this picture it's the little round thing right above the clear filter...