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Scooters - 125 to 300 => Downtown 300 => Topic started by: cuse309 on August 12, 2014, 09:10:14 PM

Title: Hesitation during hard aceleration
Post by: cuse309 on August 12, 2014, 09:10:14 PM
I just purchased a used 2012 Downtown 300i with 3400 miles on it. I love this bike. I's my first experience with any kind of motorized bike. I notice that during accelerating from a stop that it hesitates between 20-30 mph, then runs smoothly after that. It also seems to hesitate if I'm cruising at any speed, and then try to accelerate quickly. This may be futile, but I'll try and spell out how it sounds during acceleration. Vroooooooo-oo-oo-oo-oo-oo-oo-oooooooooom
Any ideas?
Title: Re: Hesitation during hard aceleration
Post by: Adept on August 13, 2014, 06:35:30 AM
First of all I would change the spark plug to NGK CR7EIX or CR8EIX.
As I red your post, I would think some variator cleanging, clutch cleaning (with sandpaper!!)...

But wait for the others to write some...
Title: IF
Post by: boo on August 13, 2014, 01:19:45 PM
the hesitation is slight, it might be normal.
Some DT and GT owners install sliders to eliminate this.
Title: Re: Hesitation during hard aceleration
Post by: kfc.android on August 13, 2014, 03:08:14 PM
Quote from: Adept on August 13, 2014, 06:35:30 AM
First of all I would change the spark plug to NGK CR7EIX or CR8EIX.
As I red your post, I would think some variator cleanging, clutch cleaning (with sandpaper!!)...

But wait for the others to write some...

Agree with Adept, maybe you want to take a look at the belt, and perhaps transmission clean up :)
Title: Re: Hesitation during hard aceleration
Post by: mnpugdog on August 13, 2014, 05:41:19 PM
I have the same issue .the shop hooked it up to the computer and found nothing. I am now wondering if it could be the injector.  I am going to put in sliders and see if that atleast evens thngs out a little. Using non-ethynol gas has helped some.
Title: Re: Hesitation during hard aceleration
Post by: cuse309 on August 13, 2014, 07:44:12 PM
Quote from: mnpugdog on August 13, 2014, 05:41:19 PM
I have the same issue .the shop hooked it up to the computer and found nothing. I am now wondering if it could be the injector.  I am going to put in sliders and see if that atleast evens thngs out a little. Using non-ethynol gas has helped some.
Forgive me, as I'm new to all of this, but whar are sliders, and what do they do? I'm going to start as low tech as possible, and add some chevron with techron fuel system cleaner, and see if that helps. I'll update later...
Title: Re: Hesitation during hard aceleration
Post by: kfc.android on August 13, 2014, 08:47:55 PM
sliders normally refers to slider rollers (Dr. Pulley has good reputation in terms of sliders)
I would use seafoam than other brand/formula, all my car/mc are fine with seafoam for several years.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 24, 2014, 01:57:13 AM
Hey guys, anybody found an answer in the meantime?  Yes it is there on "some" Downtowns, but what is the difference between them and what causes it? The D/T's don't have knock-sensors, or do they? Because it feels exactly like that, retarding of ignition and then advancing back to normal again.
Title: Re: Hesitation during hard aceleration
Post by: zombie on October 24, 2014, 02:17:35 AM
Stig has been fighting that for a few months now. He bought a Honda because of that same issue.
There is no "knock" sensor but everything in his, and others suggest a TPS or sensor issue. It could all come down to code in the ECU.

Try the SeaFoam, and read up here. It could also be a simple air leak in the manifold or coupler. Try tightening everything you can get your mitts on, and see.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 24, 2014, 02:36:59 AM
Thanks Zombie,
I think I have found the answer.  A UK fellow has posted the following (below), and it makes a LOT of sense to me! I had a similar issue on a BMW R1100GS, and also there the TPS/MAP setup was crucial for smooth running  I just need to find that sensor on the D/T where it is located and do what he did.

credit goes to "jimmyuk" with post Re Downtown 300i:  Flat spot/hesitancy/surging at 4500/5500 rpm

>>>>start extract of copy<<<<
Anyway after checking all connections and the injector etc....it became apparent that one of these sensors....the MAP sensor(the one with the locking tab on it) had a direct effect on the running of the bike depending on its position.It can be rotated through 180% more or less.I reset this position to the maximum engine speed obtainable (ticking over).
Put the bike back together and tried it out.......Well i cannot believe the transformation it has now got a beautifully linear throttle response all the way to 6k were theres a tiny bit of a flat spot and then continues as it should.
Absolutely NO trace of the hesitancy/surging at the 4500/5500 range and has restored my faith in the machine.
>>>>end of copy<<<<
Title: Re: Hesitation during hard aceleration
Post by: zombie on October 24, 2014, 04:53:43 AM
It's a promising lead. I hope it sorts out your issue, and thank you ever so much for sharing it.
Title: Re: Hesitation during hard aceleration
Post by: RubenC on October 25, 2014, 03:59:41 AM
Check your spark plug wire
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 25, 2014, 01:29:56 PM
RESOLVED (at least 95%)

I want to make sure folks understand some Downtowns have this problem, some don't  No, it is not as simple as a faulty spark plug wire, or replacing roller weights, or any other minor defect.  It has to do with the mapping of "some D/T's" of the fuel injection during the process of acceleration in relation to throttle position. 
D/T owner "enslin" who posted on the same topic in another thread messaged me back that they received a new computer from KYMCO under warranty and apparently that resolved it. However, below is a hint how to minimize the surging/hesitation/flat spot characteristics.

I do not have the time today to write a long essay, but in principal the British fellow "jimmyuk" I quoted above is right, the MAP sensor position makes a huge difference. On top of that, the TPS sensor position has also an influence.
After about 6 hrs of extensive adjusting and on-road "testing" I have found (at least for this D/T) a setting that works very well, MUCH BETTER than it was, about 95% perfect, and very tolerable now.

 You can find pictures on-line of the MAP sensor e.g. in the service manual, it sits right atop the air intake assembly with a metal locking tab and one Phillips screw. In the first step turn the MAP sensor around in small increments while the engine is running until you reach the highest idle rpm. My best position is about 11o'clock of the wires coming into the MAP sensor (looking from the left side of the scooter into the engine compartment), different from 1-o'clock where it was originally.  Eventually the computer will lower the high rpm to an acceptable idle rpm.  Take it for a test ride (just pop the seat on the scooter to make it easy) and try. Test different positions of the MAP and make notes or pictures what you feel so you can go back. This should make a noticeable difference already.

If it is getting better but not enough, the next step is to go to the richer side of the setting of the TPS, still in factory specs. But that is another chapter...
Title: Re: Hesitation during hard aceleration
Post by: zombie on October 25, 2014, 10:26:13 PM
You're the MAN !
Title: Re: Hesitation during hard aceleration
Post by: donjack on October 26, 2014, 09:27:56 AM
I can vouch for the "jimmyuk" solution, when I got my dt I had the same problem, found his post and the problem was gone!! Although it took a couple of attempts, I ended up rotating my map sensor about 180 degrees, my main problem was that I forgot to do the 'tps' reset, after that it was like a new scoot!!
Cheers,
Don.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 26, 2014, 12:49:59 PM
Glad to hear donjack! 

Did you change the TPS position/voltage too? Otherwise just moving the MAP sensor I believe a TPS reset is not necessary.
Title: Re: Hesitation during hard aceleration
Post by: donjack on October 26, 2014, 01:09:58 PM
No, I never touched the tps or anything else. I do believe that the tps reset procedure worked tho' I have now got into the (bad??) habit of doing a reset after I do anything on her, change plug, battery etc, after all it only takes a few seconds!!
Cheers,
Don.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 26, 2014, 03:25:23 PM
Sure, does never hurt to clear "a bad memory" ;). 

For those here on the thread what you do to reset TPS memory:
Title: Re: Hesitation during hard aceleration
Post by: Mysterio on October 29, 2014, 03:45:24 AM
i have the same problem
and i would like to ask some questions
what is the TPS ?
where is the map sensor ?
what and where is the richer ?

actually i have had vibrations while take off but changed the clutch for one with better material and wider space and its gone
but still the hesitation while hard or full acceleration
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on October 31, 2014, 10:18:46 PM
I recommend you search for the on-line PDF Service manual, actually search MAP and TPS sensor adjustment or similar, and it showed up for me.  There it is with pictures.

The MAP sensor is where you start and it sits on the very top of the Intake, as I said with a metal locking tab.  The only thing you really can do is to move it in increments and see how the bike performs on the very same stretch of road.  It is trial and error. Probably several comparison tests are necessary until you see which position is best.  Make notes.

You do not need to re-install the whole luggage compartment bucket for test drives, just put the seat back in place and it will lock in, and it does not even need the nuts to be put on. On-off is quick like that.

IF you really want to move the TPS (a Torx T25 key is required to loosen the screw)
Richer setting is moving the TPS counter-clockwise in VERY small increments.  DO NOT go clockwise past the point where it came set from the factory (it will throw an engine error code that can be time consuming to remove); you need to make sure you make a reference mark where it is factory set to be able go back to that if necessary.  DO NOT disconnect the plug of the TPS. Reset the computer for the TPS every time after an adjustment as described in my former post.


Title: Re: Hesitation during hard aceleration
Post by: Ronnie on December 31, 2014, 01:27:15 AM
I have a  2013 DT with the same hesitation, easy fix is on the throttle body is the map sensor loosen screw and turn it 180 degrees left
lock it in place tighten screw be careful not to loose O ring.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on December 31, 2014, 02:01:47 AM
Quote from: Ronnie on December 31, 2014, 01:27:15 AM
I have a  2013 DT with the same hesitation, easy fix is on the throttle body is the map sensor loosen screw and turn it 180 degrees left
lock it in place tighten screw be careful not to loose O ring.

You were just plain lucky if you changed it 180 degrees counter-clockwise and it worked. When I went to 180 degrees mine stalled constantly and didn't start properly after it had warmed up.

Usually there is a sweet spot that one needs to find by moving the MAP sensor in either direction in small increments. Then test ride the scooter and see it it got better or worse, and find the best position. It's usually trial and error until one gets the best result.
Title: Re: Hesitation during hard aceleration
Post by: BettinANDlosing on December 31, 2014, 03:15:10 AM
Are you sure what your turning is the map sensor? And bit the tps? The map (manifold air pressure) has nothing to do with how it's oriented. The tps (throttle position sensor) does however. I don't see how or why the map would be adjustable or why that adjustment would change anything.
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on December 31, 2014, 03:37:26 AM
I can't tell you exactly what it does, but it does clearly change "something".  (PS: I am very familiar with the TPS, have adjusted that too, and yes, it also has an influence on the behavior under acceleration).)

What I saw is that there are holes under the MAP plastic cap that are when turned then aligned in a different position. I assume they change the vacuum and with that the voltage to control the computer, and with that the FI. It sure made a positive difference, but not with just one adjustment.

That's my theory based on observation...
Title: Re: Hesitation during hard aceleration
Post by: BettinANDlosing on December 31, 2014, 03:42:16 AM
That's the only thing I could think too, maybe when it's turned it covers or uncovers holes in it.. Idk i wish Kymco used a megasquirt style system that could be tuned with the right tool.
Title: Re: Hesitation during hard aceleration
Post by: Ronnie on December 31, 2014, 10:43:59 PM
Quote from: windwheeler on December 31, 2014, 02:01:47 AM
You were just plain lucky if you changed it 180 degrees counter-clockwise and it worked. When I went to 180 degrees mine stalled constantly and didn't start properly after it had warmed up.

Usually there is a sweet spot that one needs to find by moving the MAP sensor in either direction in small increments. Then test ride the scooter and see it it got better or worse, and find the best position. It's usually trial and error until one gets the best result.

My DT has stalled after a warm start I just give it a little throttle when starting and its OK and doesn't stall during operation.
Title: Re: Hesitation during hard aceleration
Post by: zombie on December 31, 2014, 10:49:47 PM
All of these scoots have their little quircks. You have to keep in mind, their not Ferrari's.
Title: Re: Hesitation during hard aceleration
Post by: CROSSBOLT on January 02, 2015, 04:08:15 PM
Like Zombie said, Windwheeler, you the MAN! Genius is a great idea, experimentation either proves or disproves it. I do not experience any hesitation in my DT300i so probably will not try it subscribing to, "if it ain't broke, don't fix it" philosophy. Still, a nice "tool" that is not in the service manual.

Karl
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on January 03, 2015, 03:50:21 AM
Quote from: CROSSBOLT on January 02, 2015, 04:08:15 PM
Like Zombie said, Windwheeler, you the MAN! Genius is a great idea, experimentation either proves or disproves it. I do not experience any hesitation in my DT300i so probably will not try it subscribing to, "if it ain't broke, don't fix it" philosophy. Still, a nice "tool" that is not in the service manual.
Karl

Karl, what model year is yours?  I think KYMCO did change something in the computer from 2013/2014 model years on.  Yes, if you don't experience it, don't touch it   ;-)
Title: Re: Hesitation during hard aceleration
Post by: nushipwright on January 03, 2015, 11:05:57 PM
Is it safe to do TPS/ISC reset if only in doubt? When not "necessary" so to speak?

For those not having the manual, excerpt from service manual:

TPS/ISC RESET
The  throttle  position  sensor  (TPS)  and  idle air bypass valve (ISC) have to be reset when throttle  body,  MAP,  TPS,  ISC  or  ECU  has been reinstalled.


TPS/ISC RESET PROCEDURE

1.  Put  the  side  stand  up  and  engine  stop switch is at “RUN”.
2.  Turn the key to the OFF position.
3.  Fully open the throttle.
4.  Turn the key to the ON position.
5.  Release the throttle after waiting for eight seconds.
6.  Turn the key to the OFF position.
7.  Turn the key to the ON position.
8.  TPS and ISC have been reset successfully.

If fail to reset, repeat the steps from 1 to 8.
Title: Re: Hesitation during hard aceleration
Post by: zombie on January 04, 2015, 06:23:57 AM
"Is it safe to do TPS/ISC reset if only in doubt? When not "necessary" so to speak?"

Perfectly safe. It's the same as doing a tune up, whether you need it or not.
Title: Re: Hesitation during hard aceleration
Post by: CROSSBOLT on January 04, 2015, 09:48:59 PM
Windwheeler, mine is a 2014. Several times I have experienced high and or surging idle which was corrected by the reset prodedure. Haven't had to do it for quite a while so its little brain maybe "learned" something!

Karl
Title: Re: Hesitation during hard aceleration
Post by: windwheeler on January 04, 2015, 11:49:07 PM
Quote from: CROSSBOLT on January 04, 2015, 09:48:59 PM
.... so its little brain maybe "learned" something!
Karl

LOL! That is too funny!

...probably,
"or..., it learned something until the next power-outage...." 
   
;D
Title: Re: Hesitation during hard aceleration
Post by: bpt323 on June 03, 2016, 05:33:38 AM
on the map sensor.... I combined cleaning the tiny holes & slightly chamfering them with a razorblade.
I then rotated it about 45 degrees(if you examine the sensor itself you can only technically rotate it a certain amount of degrees before it forces itself out of place.
The hesitation became alot better.  altho it is most certainly still there....
Im anxious for someone to develop a standalone type of ECU for this thing that will allow tweaking & sensor checks.

anyhow the mod works, and certainly helps.
Title: Re: Hesitation during hard aceleration
Post by: pipster326 on June 03, 2016, 11:22:15 AM
What kind of spark plugs do my fellow downtown 300 riders use? Which ones fit and work the best? I was looking at ngk iridium cr7eix, but it said it would not fit my DT 300. Is that true? Let me explain... On amazon,you can put your vehicles in their"garage" when I put the downtown in and hit spark plugs( ngk cr7eix) it said this does not fit vehicle!!! Any thoughts and or recommendations would be appreciated

  -Rich


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Title: Re: Hesitation during hard aceleration
Post by: TANWare on June 03, 2016, 12:31:37 PM
The NGK CR7EIX may not be the designated plug but it works fine.
Title: Re: Hesitation during hard aceleration
Post by: pipster326 on June 03, 2016, 02:56:09 PM
Thanks, TanWare


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Title: Re: Hesitation during hard aceleration
Post by: donjack on June 03, 2016, 03:06:22 PM
Pilsner, I'm the same as TANWare, cr7eix.
Fits perfectly!
Cheers
Don.
Title: Re: Hesitation during hard aceleration
Post by: donjack on June 03, 2016, 03:08:55 PM
Sorry, Pipster!
Title: Re: Hesitation during hard aceleration
Post by: Snorvey on June 04, 2016, 04:30:13 PM
I did the reset on the throttle today. It's made quite a difference. That, along with the replacement fuel cap, has made a helluva difference to its slow to medium speed rideability.
Title: Re: Hesitation during hard aceleration
Post by: pipster326 on June 05, 2016, 10:57:23 AM
OK,thanks guys. I am going to go with the CR7EIX Iridium plug.

  -Rich


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Title: Re: Hesitation during hard aceleration
Post by: pipster326 on June 11, 2016, 10:14:01 AM
I'm going to change the oil and filter,again. It's been about 1,000 miles since my last one. I am also going to change the stock spark plug with NGK CR7EIX iridium. Hopefully I will find the time and complete by this weekend

  -Rich


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Title: Re: Hesitation during hard aceleration
Post by: starorb on June 22, 2016, 10:26:30 PM
I DONT think you can upgrade the no# on your plug. IF you have a 7, a BETTER plug is a BRISK=go to Amazon, type in performance plug. You will see 2 plugs 1 yellow, IF you have a NGKcr7hsa or another 7 rated plug, order it. Only 1 comes and its a match for ANY 7 plug. The no# is the heat rating, the more, the hotter, which can burn out ur engine over time if NOT match right. CALL BRISK in Texas and tell them your plug, if you dont have a 7 and they will give a match.