Author Topic: Flat spot under 2500 rpm  (Read 7405 times)

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mathewmerrin

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on: August 02, 2017, 05:37:35 pm
Hello all I'm from India and own a 2015 GT which I purchased second hand with around 11000 kms. The bike is in stock condition except for the RE sports silencer. The performance on the highway is good.

However the bike seems under powered under 2500 rpm  at crawling speeds as if there is a flat spot. I test drove another GT from the showroom and it doesn't have this problem, very peppy from the get go.

I really enjoy riding my bike but clueless why the bike lacks the low end torque. Does the ECU needs tuning? Have you guys faced the same problem. Will really appreciate your inputs as service centres here are more good at ruining the bikes.Thanks
Yamaha RD 350
Honda CB500T (1975)
RE Continental GT
1977 CB750 Supersport
1976 CB550K
2007 Bandit 1200


Arizoni

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Reply #1 on: August 02, 2017, 07:04:09 pm
Welcome to the forum. :)

The only thing I can think of that could cause your low power at low rps's but still have good power at higher speeds is, the throttle position sensor is out of adjustment.

The sensor is located on the inboard side of the throttle body pretty much in line with the throttle shaft (on the opposite side from the place where the throttle cables attach).  It has an electrical connector on it and a screw to lock it in place.

The Service Manual says this sensor should be putting out 0.6±0.2 volts when the throttle is in its idle position.  The voltage increases as the throttle is opened.  At wide open throttle, the output should be 5.0 volts.

If this sensor is producing a reading lower than 0.4 volts at idle speed, the ECU will think the throttle is more closed than it is at slightly higher engine speeds like, when your riding around.  This will essentially "lean out" or reduce the amount of fuel the injector is injecting so there will be a noticeable loss of power.

This link should send you to one of Singhg5's posts about checking the voltage.

https://forum.classicmotorworks.com/index.php/topic,10309.msg119217.html#msg119217

Here is a link to one of Singh5's excellent videos that shows how to test the Throttle Position Sensor.

https://www.youtube.com/watch?v=TiX8oFtYZls
Jim
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1999 Miata 10th Anniversary


mathewmerrin

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Reply #2 on: August 02, 2017, 07:57:04 pm
Thanks Arizoni for such a quick reply...Thanks bro... :)
Yamaha RD 350
Honda CB500T (1975)
RE Continental GT
1977 CB750 Supersport
1976 CB550K
2007 Bandit 1200


SSdriver

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Reply #3 on: August 02, 2017, 09:40:43 pm
Arizoni has given a great answer. Hope it fixes the issue for you.

If you are considering getting the PC-V, it will make a big difference on pulling power throughout the RPM range. It will also help setting the TPS.

Welcome and Good Luck....Jimmy
2014 CGT
Stage One Kit and a bunch of other stuff.
1994 Jag XJS V12 Convertible (and U think the RE has maintenance issues...Ha!)


mathewmerrin

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Reply #4 on: August 03, 2017, 11:55:33 am
Thanks....Jimmy I'm more or less contemplating to fit the RaceDynamics Powertronics piggyback ecu which is roughly 280 USD in India. Difficult to source the PC-V locally.

Also the Indian GT doesn't have the O2 sensor whereas the PC-V has a wire for the O2 sensor. Even if I buy the PC-V no idea what I'll do with the O2 wire of the PC.
Yamaha RD 350
Honda CB500T (1975)
RE Continental GT
1977 CB750 Supersport
1976 CB550K
2007 Bandit 1200


Otto_Ing

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Reply #5 on: August 03, 2017, 12:52:21 pm
PC-V doesn't have a wire for the O2 sensor. It will work on the indian GT's same way as on the european and us versions. It comes with an O2 eliminator which is plugged in the harnes of those GT's equipped with an O2 sensor.


ace.cafe

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Reply #6 on: August 03, 2017, 04:11:03 pm
The Sports Silencer is likely a partial cause for the flat spot. Probably too lean at those rpms.
It may be able to be solved at lower cost with a Dobeck Electronic Jet.

There have been reports here of bikes with Sports Silencer having issues with the stock ECU. PC-V with Stage 1 map typically solved it. Dobeck Electronic Jet should also work. Race Dynamic might do it if you can map it.
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mathewmerrin

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Reply #7 on: August 04, 2017, 09:04:28 am
Singh5 has clearly shown how to check the TPS voltage, but how do we adjust the voltage if the numbers are a little off.

I came across a YouTube video which shows how to adjust the TPS on a KTM. https://m.youtube.com/watch?v=JWclkhd6weU

Can we use this method for the conti too.Experts please comment,I don't have much technical expertise.
 Little off topic but also wanted to post a pic of my bike
Yamaha RD 350
Honda CB500T (1975)
RE Continental GT
1977 CB750 Supersport
1976 CB550K
2007 Bandit 1200


gashousegorilla

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Reply #8 on: August 04, 2017, 05:49:12 pm
    I would just check the TPS voltage first and see if it is off with the bike running and at idle. They CAN move a bit from vibration.  If the GT 's Throttle position sensor is the same as the Bullets, and I imagine it is.  There is a Torx headed set screw that holds it in place , in a slotted opening on the TPS.  If it needs adjustment, you would SLIGHTLY loosen that set screw until it's free, and then move and slightly pivot the TPS  forward or back to adjust the voltage.   SLIGHT movements make a big difference here.. so go slow if you need to adjust.  6.5 vs 6.0 on a bullet can make a difference when your not in closed loop.   Slightly higher readings will richen the mixture and slightly lower reading will lean the mixture across the range.  The TPS can be adjusted independently from the throttle plate, which I wouldn't mess with unless you have .
« Last Edit: August 04, 2017, 05:58:29 pm by gashousegorilla »
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


KD5ITM

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Reply #9 on: August 04, 2017, 06:00:27 pm
The issue I have with mine which is a little off topic is, when you're sitting at a stoplight and you want to blip the throttle really quick a lot of times the the bike will act like it wants to stall or will stall completely. With mine when you blip the throttle from 0% throttle it wants to try to stall. If you roll on the throttle just enough to raise the RPM about fifty or a hundred, it won't stall. It only wants to try to stall when you try to blip the throttle really quick from 0% throttle. I've heard of other people having the same issue. Just wondering if there's a fix for it. I do have power commander and filter and Hitchcock exhaust installed. I've done more ridding since February then I normally have since buying the GT it seems like this issue is very slowly starting to be more of an issue the past couple of months. Not very often but once in a while it will even stall as I start to roll on the throttle leaving a stoplight. It's just something about when you first try to crack the throttle from 0%, it wants to try to stall. When I'm rolling away from a stoplight it won't try to stall, just once in a very great while it will stall but it doesn't act like it wants to stall each time. It's only when I try to blip the throttle is when it wants to try to stall. Maybe I could take a video of it.
« Last Edit: August 04, 2017, 06:10:47 pm by KD5ITM »
2014 Continental GT 535
1979 Hurst/Olds W-30 “R” code
1967 Oldsmobile 442 W-30
1964 Volvo B18 544 Sport
1961 Willys Jeep Wagon


gashousegorilla

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Reply #10 on: August 04, 2017, 06:09:24 pm
  IMHO.... to me it sounds like your rich in the low rpm's and throttle positions, or the bike is not yet warmed up or both.   Same with a flat spot under 2500 RPM's...
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


SSdriver

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Reply #11 on: August 04, 2017, 09:23:22 pm
KD...
I assume you are running the standard stage one map on your PC-V.
GHG is correct about fuel mix causing this type issue.
Try tweaking the fuel at the 0-5% throttle opening. Maybe 5% fuel at a time, and see how it responds. If it doesn't help, just reset the Map back where it was.
...Jimmy
« Last Edit: August 04, 2017, 09:25:31 pm by SSdriver »
2014 CGT
Stage One Kit and a bunch of other stuff.
1994 Jag XJS V12 Convertible (and U think the RE has maintenance issues...Ha!)


KD5ITM

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Reply #12 on: August 05, 2017, 04:21:59 am
I think when I'm stalled the map I added a little bit of fuel from idle RPM to about 1500 RPMs. Don't remember how much I added but it wasn't much at all. The stock Matt I believe had the setting at 0. The reason why I added a little bit of fuel was for the same problem occurring before the map was installed. And to be honest with you it happens more when the bike is well warmed up and driven several miles then it does when it's idling warming up just after starting it. How to make any difference I always let the bike warm up about 5 to 7 maybe 10 minutes max, before taking off on it.
2014 Continental GT 535
1979 Hurst/Olds W-30 “R” code
1967 Oldsmobile 442 W-30
1964 Volvo B18 544 Sport
1961 Willys Jeep Wagon


gashousegorilla

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Reply #13 on: August 05, 2017, 07:21:22 pm
   Has it been any better or worse since you added fuel in the idle area's  ... or about the same ?
 Does it ever just putter out and die on you when you come to a stop without blipping the throttle ?
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.


gashousegorilla

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Reply #14 on: August 05, 2017, 08:30:49 pm
Hello all I'm from India and own a 2015 GT which I purchased second hand with around 11000 kms. The bike is in stock condition except for the RE sports silencer. The performance on the highway is good.

However the bike seems under powered under 2500 rpm  at crawling speeds as if there is a flat spot. I test drove another GT from the showroom and it doesn't have this problem, very peppy from the get go.

I really enjoy riding my bike but clueless why the bike lacks the low end torque. Does the ECU needs tuning? Have you guys faced the same problem. Will really appreciate your inputs as service centres here are more good at ruining the bikes.Thanks

  Kind of a LOW rpm to be riding these bikes at ... No ?   Especially in a higher gear .  That's lugging the bike.    Do you really spend any length of time UNDER 2500 RPM's ? Are you sure it's a flat spot ?  Or does it feel like  low power down there ? 
An thaibhsí atá rattling ag an doras agus tá sé an diabhal sa chathaoir.