1000 RPM idle too low ?

[22R88]

I just got a low mileage 2004 250 Ninja running again after setting for years. Intro thread link (https://www.ninjette.org/forums/showthread.php?t=240484)
So Ducatiman refurbished the carbs and the bike starts easily no choke needed just let it warm a minute before it is ready to take the throttle. I have the idle set at 1000 RPM's and it purrs. Blip the throttle and it revs fine then returns to 1000. Will this hurt anything ? I know spec is 1200-1300 but I figure within reason the lower the better. Just worried bout oil pressure.
I haven't really ridded it yet maybe after running a while it will be too low after engine is good and hot ?? Can't say enough about Ducatiman's Custom Carb service.... I woulda never dreamed it would ever run this smooth after all this time and all I have read about wandering idle issues people seems to have with these 250's

Thanks,
22R88

[Ghostt]

I have mine set at about 1,400, seems to like it just fine, the bike is made to idle at a certain RPM, I suggest you try, and see.

http://faq.ninja250.org/wiki/What_is...I_adjust_it%3F

[verboten1]

you will want the idle set to spec for shifting, charging, oil pressure, etc etc.

also, there is no big flywheel to keep this tiny engine running, so coming off throttle at cruise could allow it to stall possibly

[dcj13]

If you like it at 1k and it doesn't die, then don't worry about it. You can change it any time you want.

[choneofakind]

^^^ werd. as long as it doesn't die and it returns to that rpm consistently, go with it.

Personally I'm at the opposite end of the spectrum and make mine idle around 1500. It's nice and easy to see the needle overlay on one of the hash marks and the throttle response seems acceptable and it returns to that speed consistently.

Whatever works for you and your bike. Personally I'd turn it up.

[22R88]

Appreciate all the responses. I am just gonna wing it and see how it acts when I start riding it. Thanks,

22R88

[csmith12]

Here... Take it for a ride. If the bike and rider are happy then go with it. If there is ANY reason to question it, raise it up to spec. It's just not worth the worry, there are bigger fish to fry.

[ninjunk]

the other comment i would have is to make sure that your adjustments are all correct, you should tune your air bleeds until the idle is as high as possible and ideally you'd want to put a vacuum gauge on there and sync the carbs.

If you just threw them on straight out of the box they cant possibly be adjusted in, unless ducatiman is really that awesome.

[Ghostt]

Yes he is, the only tuning once you get them back is the idle mixture screws

Dialing in the idle mixture screws

Your initial setting should be 3 full turns out from the bottom, remember just slightly tighten them, don't go all Conan on them.



Then warm it up, slowly turn 1 side pilot screw in until the rpms drop, then back out till RPM's peak (and no further)* Twist throttle...see how it reacts...tweak to taste.
Repeat on other side... test ride. You're looking for best throttle response and transition from just cracked to 1/4 throttle opening or so.*

Thats a quickie, 10 cent tutorial on setting pilot screws.**

Also a vacuum sync is improper way to synchronize the carburetors, bench synchronization is the proper way,

You can sync with the carbs in hand. Back the idle adjustment off to close that carb then match the second carb to it with the sync screw. You can then turn the idle adjustment up while using a thin feeler gauge (maybe .002") between the throttle plate and the throttle bore, adjust to just fit, and then check the second one and adjust to match. If you have good feel for this it will run fine once installed.

It would do folks well to take a minute to review and understand what a sync tool does, how it works. And take another minute to look at the carb linkage and sync adjustments available to fix irregularities that might occur. It can help take some of the mystery out of this as well as stop unnecessary carb sync screwups.

Meaning, that the carbs were right once, the butterflies were matched and it performed well, but then changed. Undecided And the problem somehow occurred in the butterfly direct shafts, or the sync screw turned or wore that pad that it rests on, or the carburetor pairing/ bridging brackets twisted in relation to each other, and enough so that the butterflies no longer operated in sync, such that performance noticeably suffered. And a fix will be accomplished by changing the butterfly position, the only thing the sync adjustment does. Hmmm. Really? Undecided

Meanwhile, the tool measures vacuum at each individual runner. That's all it does, how it works. And vacuum is effected by a huge list of things, butterfly position being only one of them, and the only one addressed with that tool while turning those sync screws. The rest of that list includes, valve adjustment, jetting, float level, compression differences between cylinders caused by wear as well as factory CC differences in the head, intake runner, as well as flow by port variations, etc. Variations in cams, wear or factory tolerance. Then there's the potential big one, pilot jets and pilot screw mixture settings. All of those effect the vacuum and will be read by the sync tool, accurately identifyng the difference that exists, and with the only adjustment being used to "correct" the problem, move the butterfly relationship, one to the next.

It's that clear understanding that has me of the opinion and long time practice to not touch the sync screws on a set of carbs that were right once and were never dismantled from the rack. And jet cleaning as well as float needle changing doesn't require that they be dismantled. And further, if I DID dismantle a set of carbs, I just matched the butterflies on the bench at assembly, using a feeler gauge, and then never touched them again, never gave them another thought.

That method, properly executed, will have THAT portion of the complete equation, balanced flow to each cylinder in a multi-cylinder/ carb application due to butterfly position, satisfied entirely adequately. And in fact, it has worked for me every time I've done it on every bike (as well as individual runner/ butterfly V-8 intakes, all eight) that I've ever owned or any that I've fixed for others. And the times I fixed for others was usually after an attempt by others to sync the carbs, chasing a problem, or sometimes not even chasing a problem, but one they created wth a sync tool, chasing a problem from that list, that was never a butterfly position change problem. Those linkages are so direct and simple that they don't know how to screw themselves up. Not enough to care about.

I'm sure this will start a lot of controversy so I won't argue it, just offering it for those who understand the whole picture that I outlined and might make good use of it. It is what I've done, on every engine I ever worked on, including blue printed racing engines as well as regular old, high mileage street stuff. I've had at least four, four cylinder bikes with over 100,000 miles that ran quite well, the whole time, and never had a carb sync performed. When they did finally get a total disassembly, this is how I set them up, on the bench. Over the years I've straightened out at least a half dozen messed up ones, probably more, and on the bench, after fixing the original problem which was fouled pilot jets.

I only posted this because it seems like its coming up fairly often, especially with problems from a sync gone bad. One I would suggest was never a sync problem to begin with. A big or sudden change in performance is NEVER a sync problem. NEVER. Remember that. Cool If there is a problem, and you connect the gauges? YES, there will definitely be an imbalance indicated. But because that hole has a problem that is from the rest of the list. A bad plug, a plugged pilot jet, a screwed up float, a bad valve or setting, etc. Every one of them effecting the vacuum in the intake but NOT from a sudden move of a butterfly position, a sync adjustment.

[ninjunk]

Vacuum synch is to synch the jetting together not the throttles. Throttles should be synched before you put the carb on (or never touched from factory), the vac just makes sure you are pulling the same vac (running as strong) on both carbs. The closer you get to perfect tuning the stronger vac you'll pull. You can just turn the screws in and out and hear the idle pick up, but the vac gauge takes some of the guesswork out of it.

I don't really understand that quote but apparently the poster who has built 'blueprinted race engines' thinks that the vacuum gauge is use for adjusting the throttle balance screw? Its not, its used for the fine jetting adjustment.

Even still when adjusting the pilots, I do it with the bike fully warmed up and i give them an extra touch of a turn to the rich side just so it tips in off idle a little better, and runs better on cold starts. IMO your perfectly tuned when your cold idle is a little bit higher than your hot idle.

[Ghostt]

Yeah that's my write-up, I'm saying that using vacuum sync has its faults, and reasons why, it's the set the both butterflies exactly the same, which is the point of synchronization.

Adjustment to the jetting, Is a best guess, if your not using an exhaust gas analyzer.

Adjusting the idle mixture screws you can get real close by ear, assuming your listening.

[xorbe]

After I did valve adjustment + sync, my bike would also idle around 1K, but it was a lot happier around 1.4K, as the idle could vary a bit on temp, phase of moon, etc.

[ninjunk]

You know, Mr Ghostt, this was bothering me, partially because i felt bad about the smartass response, and partially because I'm more or less self taught and have picked up some bad habits/preconceptions along the way. I'm not sure if i ever was actually taught how to synch carbs, or if i learned it from a book or something on the internet or what.

So, I asked two friends of mine, one who races later-model sportbikes (he has a '04 cbr600, an '01 R1 and an '01 RC51) how he does a carb synch- he said that on his R1 he has to do it frequently as you loose the setting when you remove the carbs, and he said that he only adjusts the throttle balance. He also said that by turning it 'one **** hair' the bike will go wildly out of tune, and since its a four, you absolutely need the synch tool to tune the throttles. Certainly less forgiving than our ninjas, and since you can't do it on a bench, the vacuum gauges are the only tool available. The mix screws many of the modern sportbikes can't be reached with the carbs on the bike, so best case you can set them, try them out, take the whole bike back apart, make a small change... ugh... there is a reason I don't mess with modern sportbikes (the ninja doesn't really count)


The other guy I asked is the best motorcycle mechanic i know, a guy who has raced on a national level and owns a moto shop and does vintage restoration and customs that have been on 'bikeexif'

He texted me back 'both'

haha. Not a big texter, next time i see him in person i'll ask him for a better explaination of how he goes about tuning with a vac. gauge. I can get more out of him when he's got a beer instead of a phone in his hand.



On the older bikes (cb's; gs's; kz's) that i've worked on, seems like the vac didn't respond a lot to the throttles being synched. Hell my CB450 had a goofy piece of bent metal strip connecting the carbs and you just kinda bent it back and forth to get the carbs running together. The mix jet however would take it from burbling like a kitten to choking and sputtering in less than a 1/4 turn.



Long story... well... long, i apologize for my snotty response and I learned a lot doing some digging. I think if you try adjusting the pilots with the vac gauge on there, you will see how beneficial it can be, my two cylinders are running about a 1/4 turn off from each other on the pilot... the idle still hasn't broke the paint dot from the factory, i should probably see where it is at and i might find a bit more throttle response.

[Ghostt]

No worries, I didn't, and almost never get offended by responses to my post/write-ups.

I understand that some will stand by what methods for for them. My write-up of carburetor synchronization is my method, and I present the reasons why, and the faults with vacuum synchronization. The final choice is yours, and yours alone.

Thank you for explaining your actions, and as always I respect your rights to have an opinion, as well as everyone else.

Sláinte!