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Author Topic: [SOLVED] Running poorly under 5k rpms until warmed up  (Read 18646 times)

Offline frankenwing

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[SOLVED] Running poorly under 5k rpms until warmed up
« on: September 21, 2016, 10:45:51 AM »
When I bought the bike, it would start and run without any trouble. After I brought it home, I immediately started taking it apart to renew it. Cleaned out the injectors, cleaned off the throttle body, hell... cleaned everything. Last night I was able to get everything back together and tried to fire it up. I tried all night. And it wouldn't start 💔

Here is what I've noticed so far:
• I checked all the spark plugs - And they have spark
• All the spark plugs are wet, so I know they're getting fuel
• Occasionally, while trying to start, it will backfire through the intake (and I can actually feel the backfire through cylinder 1's intake boot! So I probably need to replace that boot)

I know the spark plug wires are in the correct order, and I'm certain the wiring to the coils is correct (but I'll double check when I get back home tonight).

I'm thinking the next thing I need to check and do is the Throttle Position Switch adjustment. When I was going through and cleaning the bike, before I realized what it was, i started unscrewing the TPS until I noticed that I just undid something that clearly needed to be set in a specific position. I screwed it back in roughly in the same position I found it. But I'm betting this wasn't good enough, and that I need to adjust it. Questions about the TPS:
1: If it's just a little bit off, will it prevent the bike from starting?
2: I've read tons and tons of posts about how to adjust it, but to make sure I understand correctly, do i:
- Loosen the screws, and turn it all the way counter-clockwise
- (With throttle closed) Slowly turn the TPS clockwise until it clicks (then tighten screws)
- Open throttle all the way to hear a second click?
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #1 on: September 21, 2016, 12:10:33 PM »
Are you absolutely sure the plugs wires are in the right order and connected to the correct coils?   

You wouldn't be the first to have two cylinders crossed and it sure sounds like that is your problem.  That is where I would concentrate my troubleshooting efforts.
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #2 on: September 21, 2016, 12:12:17 PM »
Thats one of the things ill be checking tonight. But I'm pretty certain they are. I noticed when taking the bike apart that both the plug wires and ignition wires (to the coils) were different lengths and made it super obvious where each of them went.
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #3 on: September 21, 2016, 12:15:28 PM »
Yeah, super obvious, except that one of the plug wires is folded back.  I think it is #3 that is longer than #2.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #4 on: September 21, 2016, 12:28:12 PM »
 Shit, now that you say that I'm second-guessing myself.  I think I might have the plug wires ass backwards
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Offline Laitch

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #5 on: September 21, 2016, 01:03:04 PM »
Take a look here, frankenwing.
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #6 on: September 21, 2016, 01:31:29 PM »
Yep, pretty sure I put them on backwards. Please take one of my man-cards away from me, and forget this thread ever happened...
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #7 on: September 21, 2016, 01:33:27 PM »
What thread?
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Laitch

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #8 on: September 21, 2016, 01:41:47 PM »
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Offline Martin

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #9 on: September 21, 2016, 04:22:07 PM »
The bike will run without the TPS connected or even without a TPS.
Regards Martin.
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #10 on: September 22, 2016, 01:13:53 AM »
So yeah, it was actually the plug wires. Fires right up and got to ride it tonight!

However, below 5-6k rpms its definitely not running quite right. Feels a little bogged down.

I'm inclined to think it's because of loosening the TPS when I took everything apart.

In my original message, do I understand the procedure correctly for adjusting it?

From tonight... [emoji16]



Sent from my iPhone using Tapatalk
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Offline Laitch

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #11 on: September 22, 2016, 05:40:26 AM »
Quote from: frankenwing on September 21, 2016, 10:45:51 AM
I've read tons and tons of posts about how to adjust it, but to make sure I understand correctly, do i. . .
Add to your tonnage with this instruction, frankenwing. It isn't complex but good hearing makes it easier.
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Offline kennybobby

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #12 on: September 22, 2016, 06:52:17 AM »
The TPS just affects idle and WOT, nothing in between.

Backfire thru the intake may have dislodged or damaged the air flow meter.  pull the air box and check for cracks in the plastic or bent aluminum vanes in the AFM.

Can you do a plug chop to check the spark plugs and determine if it's running rich or lean--that will give you a clue of where to look also.
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #13 on: September 22, 2016, 10:05:42 AM »
Quote from: kennybobby on September 22, 2016, 06:52:17 AM
The TPS just affects idle and WOT, nothing in between.

Backfire thru the intake may have dislodged or damaged the air flow meter.  pull the air box and check for cracks in the plastic or bent aluminum vanes in the AFM.

Can you do a plug chop to check the spark plugs and determine if it's running rich or lean--that will give you a clue of where to look also.

That makes sense. I do have a spare AFM unit and case fortunately. And some MAF cleaner. I'm going to start there, run it again and if its unchanged I can plug chop on my way back. 👍🏼
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #14 on: September 22, 2016, 11:13:17 AM »
How not quite right is it running?   

Have you balanced the throttle bodies since you got the plug wires straightened out? 

Looking forward to hearing what your plugs look like.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #15 on: September 22, 2016, 11:24:47 AM »
Quote from: The Mighty Gryphon on September 22, 2016, 11:13:17 AM
How not quite right is it running?

Acceleration under 5k rpms is just sluggish. It's hard to tell for me if its from lean or rich conditions. I'm inclined to think maybe running lean. But I don't have any info to back that up yet, not until I can do a plug chop.

Quote from: The Mighty Gryphon on September 22, 2016, 11:13:17 AM
Have you balanced the throttle bodies since you got the plug wires straightened out?

I haven't touched the throttle bodies at all. I left that as is, since it was running fine before I took the bike apart.
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #16 on: September 22, 2016, 11:34:47 AM »
Did you disconnect the throttle cable?  If so, how is the throttle action at the throttle body butterflies?  Any looseness in the cable?  Anything hanging up?
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #17 on: September 22, 2016, 11:36:18 AM »
Quote from: The Mighty Gryphon on September 22, 2016, 11:34:47 AM
Did you disconnect the throttle cable?  If so, how is the throttle action at the throttle body butterflies?  Any looseness in the cable?  Anything hanging up?

I did disconnect the throttle cable. It's a little stiff, doesn't snap back very easily. Which i believe is just because I need to route the cable better.
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #18 on: September 22, 2016, 03:34:50 PM »
So... it's worth mentioning that I've been riding the bike today. I picked it up over lunch, and long after it's had a chance to warm up it's seemed to clear itself up. The sluggishness is gone. However... prior to warming up it still struggles. "Choke" only helps when initially starting it up, but the acceleration will still be sluggish.

Does that sounds like anything in particular to you guys that I should investigate?
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Offline The Mighty Gryphon

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #19 on: September 22, 2016, 04:28:50 PM »
Any hesitation when the throttle is opened?  The temperature sensor may not be indicating a cold engine and enriching the mixture.
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  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #20 on: September 22, 2016, 05:19:24 PM »
Quote from: The Mighty Gryphon on September 22, 2016, 04:28:50 PM
Any hesitation when the throttle is opened?

Well, whether I'm holding the throttle at cruising speed or turning it wide open; it behaves the same. WOT doesn't stop it. It's just sluggish until it reaches 5k+ rpms.

Quote from: The Mighty Gryphon on September 22, 2016, 04:28:50 PM
The temperature sensor may not be indicating a cold engine and enriching the mixture.

This is an interesting point. And could very likely be a part of it. I bought a used temp sensor and have plugged it into the harness that came with the bike. And it does not work yet. (And I have already replaced the coolant drain plug with the temp switch). Or are you referring to the sensor at the top of the motor?
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Offline Laitch

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #21 on: September 22, 2016, 06:17:20 PM »
Quote from: frankenwing on September 22, 2016, 05:19:24 PM
Or are you referring to the sensor at the top of the motor?
He's referring to the one on top.
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Offline Brad-Man

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #22 on: September 22, 2016, 06:49:57 PM »
This may have nothing to do with it, but since this is  a new to you bike, you might want to slap on a multimeter and check battery voltage at idle and then at 1K rpm increments to 5 or 6 K rpms...

You want to verify the state of your battery and charging system.

Low voltage at low rpm's could cause iggy and EFI issues.

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Offline kennybobby

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #23 on: September 22, 2016, 10:12:09 PM »
It sounds like you are running rich up to 5k then the bike clears and runs good.

Did you check/replace the vacuum tube to the fuel pressure regulator--the tube inside the steel spring seen in Laitch's photo above?
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Offline frankenwing

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Re: Won't start • Has Spark • Plugs are wet • Occasional backfire through intake
« Reply #24 on: September 23, 2016, 10:16:07 AM »
Quote from: kennybobby on September 22, 2016, 10:12:09 PM
It sounds like you are running rich up to 5k then the bike clears and runs good.

Did you check/replace the vacuum tube to the fuel pressure regulator--the tube inside the steel spring seen in Laitch's photo above?

I did and the line seemed fine. No cracks in it. However, I do need to replace the breather hose. It's in bad shape.

I managed to get the temp gauge working last night, was just a bad wire. Since yesterday its been running pretty good. On my way to work this morning though I noticed it was running fairly hot. after about 5-10 minutes on the interstate it got up to just a hair past the 3/4 mark.



I know that the fan is running, as I made a manual switch for it and can confirm it was on. I've already flushed and replaced all the fluids. Coolant is exactly where it should be in the expansion tank. Radiator fins are pretty much clear, just a couple bugs. Whats the normal operating temp for k-bikes?
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