Did your pregen lag at ~5k on roll on?

[Lychee]

I said "did," and not "does," because I want to know how you tuned it out!

I have two pregens in the stable and they both have varying amounts of lag at 4-6K rpm, starting a roll on in a ~30mph turn in 2nd or 3rd gear. Everywhere else pulls great!

Carburetor cleanned
valve adjustment professionally done recently
mixture screws 2.5 turns out
2 washers under the needles

Suggestions appreciated - Thanks

[csmith12]

Any exhaust and/or airbox mods?

[Lychee]

Stock.

[choneofakind]

...just a touch. More like a little hiccup. No matter how much I futzed, there was always a TINY little bobble if I kept a constant 4-5k, and then did a really gradual roll on. I found I made it a little better by adjusting the mix screws a bit. I think that's int part because of the change in ignition timing at 4200 or whatever because I could never get rid of it completely. At first, I was worried about my jetting and kept adjusting it. After reading someone's theory about that hiccup (the timing thing I just mentioned) on the ninja250.org forum, I stopped worrying about my jetting there.

Now I'm all EFI so no issues there anymore

[Lychee]

Originally Posted by choneofakind

...just a touch. More like a little hiccup. No matter how much I futzed, there was always a TINY little bobble if I kept a constant 4-5k, and then did a really gradual roll on. I found I made it a little better by adjusting the mix screws a bit. I think that's int part because of the change in ignition timing at 4200 or whatever because I could never get rid of it completely. At first, I was worried about my jetting and kept adjusting it. After reading someone's theory about that hiccup (the timing thing I just mentioned) on the ninja250.org forum, I stopped worrying about my jetting there.

Now I'm all EFI so no issues there anymore

I'm still futzing! Did you adjust mixture screws leaner or richer? Maybe there is nothing I can really do. Damn this CV carb or whatever model it is.

[Jiggles]

Probably you would want to go richer. Have you adjusted your mix screws for idle?

[Lychee]

It seems to run better when it is leaner. I tried quarter turn increments all the way to 3.75 turns out where the idle ran like garbage. It came back from the shop at 3 turns out. Seems to run best at 2.5 turns out but I haven't tried any leaner.

[Jiggles]

Originally Posted by Lychee

It seems to run better when it is leaner. I tried quarter turn increments all the way to 3.75 turns out where the idle ran like garbage. It came back from the shop at 3 turns out. Seems to run best at 2.5 turns out but I haven't tried any leaner.

A certain rich point will give you the best mix. When I was fooling around with mine I observed that I had the highest idle around 11.8-12.0 AFR. That was around 3 turns out. Only problem was on hot days or in high elevation it would get too rich and barely idle at all so I corrected it by setting my idle afr to around 13.5-14 which was 2 turns out.

Are you using alex.s's method? Where you turn out each screw a quarter turn until the idle stops rising?

[Lychee]

OK, I'll try 2 turns out. Although wouldn't that would be leaner for me? (compared to 2.5 turns out)

I don't have an AFR gauge so I have to use the seat of the pants test method. Usually I simply just make an adjustment and then ride for awhile (couple days) to test it. This is because it is pretty hot in the carb area when the bike is warmed up, which makes it difficult to adjust until the engine is cooler. After the adjustment I have to warm the bike up all over again. Real pain. I keep telling myself it is a tinkerer's bike.... lol.

[Jiggles]

Yea, a bit leaner than where it feels best is probably safest. If you go up like say Mt. Hamilton, your bike will idle like poop and may not even run

[choneofakind]

For the record, Jiggles is right here. I did mine by the method of turning them out until I found the highest idle and left it there.

On my track day, It was like 85 and the bike was being run at track loads, (WOT) all day. In the afternoon, my bike decided not to idle. Turned the screws in 1/4 turn and it was perfect again. Aim for whatever gives the highest idle and turn it in a bit.

[Lychee]

OK, so after some running in the sunny but cold weather, it seems to run a little better at 2 turns out instead of 2.5. Although sometimes the idle stays at 2k or hovers there for a moment before coming down to 1.5. The lag is still there, especially when cold. When the bike is warmer, the lag seems less pronounced. I suppose I should try a carb sync. Never done that before.

[pimpybra]

I have this problem, but only in the cold around 6-7k, it just kinda lags/stutters a bit. I asked /r/motorcycles on reddit, they just thought it was a powerband issue.

I'm all stock as well, and when I bought the bike 1,700 miles ago, PO said the carbs were entirely redone/cleaned/etc.

I might have to tinker with the idle mix screws when I eventually do more work on it.

[Lychee]

Originally Posted by pimpybra

I have this problem, but only in the cold around 6-7k, it just kinda lags/stutters a bit. I asked /r/motorcycles on reddit, they just thought it was a powerband issue.

I'm all stock as well, and when I bought the bike 1,700 miles ago, PO said the carbs were entirely redone/cleaned/etc.

I might have to tinker with the idle mix screws when I eventually do more work on it.

I've been tinkering with the screws for awhile now and although it does run better and pull harder than before, the initial lag is still there, especially when the bike is cold. From the responses from other veterans here, I don't think I will be able to tune it out any more than I already have.
After looking at the carburetor, I seem forced to conclude that there may be an inherent delay between the throttle butterflies opening and the increased vacuum raising the slide. In effect, a flaw resulting from the design.

[pimpybra]

Originally Posted by Lychee

I've been tinkering with the screws for awhile now and although it does run better and pull harder than before, the initial lag is still there, especially when the bike is cold...

Then maybe I just won't sweat it for the time being. Bike runs great otherwise, and I'll save that fun for when I finally get around to doing my valve check/adjustment...

[Bunjee]

sounds like either your transfer ports are gummed up (they are insanely tiny holes) or your carbs are out of sync. if you know how to work on carbs at all, rip them down to the castings. i use kerosene personally, but someone else may have a better product to use, but soak them in some type of solvent for a bit, and hit the jet holes with some compressed air. rinse and repeat. if they still give you issues, have them synced. carb sync is often over looked, but vitally important to a good running engine. i say clean first though. if you dont know what a transfer port is, they help provide a little extra fuel when coming off the idle circuit and moving onto the needle. and then the same when moving from the needle to main. if those ports clog, you run a little lean when coming into your next jet and it lags. if it ends up being a sync issue, do it right or have someone with vacuum gauges do it. there is no way to do it by ear, period. dont ever let anyone tell you there is. they are lying, or ignorant to fact. i am a technician, not a mechanic. theres a world of difference. by march i will be certified by kawi themselves, so i know more than most backyard mechanics. i hope i can add a whole new level of knowledge to this site, and if you, or anyone else has any questions i will do my best to answer them. if i dont know, ill tell you honestly. im good, not god. hope this helps, and let me know what the result is! good luck.

[Lychee]

Happy to report that removing all the washers seemed to have done the trick. Apparently it was running too rich. Odd that leaner seems to work better for my ride during these colder days. Perhaps the washers were never necessary for my bike. I'm putting off the carb sync a little longer for now. @pimpybra try aiming for leaner.

[pimpybra]

Originally Posted by Lychee

@pimpybra try aiming for leaner.

Man, and I was hoping to not muck with my carbs, since the PO said the carbs were fully rebuilt/cleaned before I bought it in September. Then again, I've found things on the bike that he should have taken care of as a mechanic, like a loose front axle castle nut, chain was way too tight, etc.

Now I just need the time to mess with it, and some warmer weather so I don't freeze to death in the garage!

Glad you got it taken care of! Did you check your sparkplugs and see if there was an indications of rich/lean?

[choneofakind]

Spark plug readings are only good if they're taken immediately after running at the specific load/throttle that you want to test. For instance, if you want to test the mains, go WOT to 13000, cut the engine, coast to a parking lot, and check the plugs right then and there; not very feasible unless you have access to a dyno.

Think about how many times it fires while idling or cruising. Those are both times when the engine runs in the 14+ AFR range. Just riding up your driveway and idling for 5 seconds will throw off a plug reading, even if you're running a 112 main with the stock airbox (way rich)

[Lychee]

Originally Posted by pimpybra

Man, and I was hoping to not muck with my carbs, since the PO said the carbs were fully rebuilt/cleaned before I bought it in September. Then again, I've found things on the bike that he should have taken care of as a mechanic, like a loose front axle castle nut, chain was way too tight, etc.

Now I just need the time to mess with it, and some warmer weather so I don't freeze to death in the garage!

Glad you got it taken care of! Did you check your sparkplugs and see if there was an indications of rich/lean?

Well I didn't check the spark plugs, I made the adjustment based on how it felt after I reduced the idle mixture to 2 turns out. I had assumed it was a too lean problem and all of my prior adjustments went toward the richer side. Apparently I was wrong and @Jiggles had the answer. The first washer was already there when I took apart the carb for the first time so I simply removed it.

[Jiggles]

Sweet

[FvnnyL3tt3r1ng]

Did anyone mention adjusting the float height? I read under the factory pro directions this could be done to lean or richen the mix (mainly for the low end)

[choneofakind]

I have not touched float height because I didn't need to.

I did read about it in the factory pro tuning guidelines though.