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Author Topic: [SOLVED] '86 K100 won't go faster than 60 mph  (Read 23919 times)

Offline Steenbeen

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[SOLVED] '86 K100 won't go faster than 60 mph
« on: July 29, 2016, 11:20:09 AM »
I just got my bike working again. However, when I fully twist the throttle, it seems like I'm only twisting it halfway. While driving it's revving slower and slower the higher the revs get. How can I exclude that the previous owner tinkered with the throttle bodies? The little spring on the left side doesn't seem te compress, as opposed to the right side. I've added photos of the bodies at full throttle. Is this normal? I've never ridden a k100 before, but if I look at videos on youtube, my acceleration seems really slow compared to the bikes on youtube.

Also, what is exactly the function of the TPS? What would happen to a normal running bike when the plug of the TPS is pulled?

Thanks.

Edit: added photos, site acted wierd.
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Offline kennybobby

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Re: '86 K100 won't go faster than 60 mph
« Reply #1 on: July 29, 2016, 06:21:18 PM »
Is the little vacuum tube wrapped with a metal spring coming off the rearmost throttle body intact, or is it cracked and leaking.  The visible side is easy to check, but the rear part to which it runs is difficult.  A leak will cause very high fuel rail pressure and engine will not make good power above 4k rpm...
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Offline Martin

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Re: '86 K100 won't go faster than 60 mph
« Reply #2 on: July 29, 2016, 08:07:08 PM »
Check for air filter blockage, I believe you guys can have nesting problems with critters and or fuel filter blockage.
Regards Martin.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #3 on: July 30, 2016, 07:31:54 AM »
Thanks for the suggestions.

The vacuum tube seems fine at a first glance. I think the previous owner said he cleaned the air filter and replaced the fuel filter, I'll ask.
What would happen if the fuel pressure is too high?
It's pretty strange. It will rev over 4000 rpm in lower gears, but very slowly. Not at all what I expect from a 66 kW bike. It's not really faster than my 11 kW Honda CBR125R. When on the highway it tops out at about that many revs.

I checked the TPS. It didn't click at all first, now I adjusted it so it clicks when the throttle is slightly turned. However, I tried driving without the plug attached to the TPS, and it didn't seem to make a difference... Should it make a notable difference? If so, maybe the switches inside are corroded.
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Offline K1300S

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Re: '86 K100 won't go faster than 60 mph
« Reply #4 on: July 30, 2016, 08:14:04 AM »
unless my eyes are deceiving me, something ain't right with your tb's.  when you open the throttle, all the tb's should open together, in synch.  just from your pictures, it does not look like that is happening.  a video of the tb's while you twist the throttle would be helpful.

i also see severely cracked caps on your vacuum ports.  that tells me that all the rest of the rubber in the intake system is probably cracked too and needs replacing.  you could have some massive vacuum leaks.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #5 on: July 30, 2016, 08:48:09 AM »
Link: https://www.youtube.com/watch?v=_NpRS6qa06M&feature=youtu.be
Let me know if it's not clear enough. Is the speed of which the revs are increasing normal?
I'm not sure about vacuum leaks.. Wouldn't that cause wierd irregular behaviour? It drives fine, just kind of slow.
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Offline Inge K.

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Re: '86 K100 won't go faster than 60 mph
« Reply #6 on: July 30, 2016, 10:05:39 AM »
Have the throttle mechanism at the handlebar been dismantled?
If so, have the mechanism been properly set afterwards?

The toothed wheel attached to the chain is marked with a line, this line
should correspond with a line on the toothed part on the throttle handle.
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Offline Laitch

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Re: '86 K100 won't go faster than 60 mph
« Reply #7 on: July 30, 2016, 10:54:37 AM »
Quote from: mlytle on July 30, 2016, 08:14:04 AM
. . . something ain't right with your tb's.  when you open the throttle, all the tb's should open together, in synch.   

. . . all the rest of the rubber in the intake system is probably cracked too and needs replacing.  you could have some massive vacuum leaks.
+1
+1
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #8 on: July 30, 2016, 10:55:46 AM »
It wasn't. There was a lot of grease in there so I didn't noticed the line. I just set it to the first position it 'clicked' into. Not sure if it did make a difference, I can twist the throttle about 90 degrees, which seems kind of small compared to my other bike and other bikes in particular.
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Offline Laitch

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Re: '86 K100 won't go faster than 60 mph
« Reply #9 on: July 30, 2016, 11:06:16 AM »
Quote from: Steenbeen on July 30, 2016, 10:55:46 AM
It wasn't. There was a lot of grease in there so I didn't noticed the line. I just set it to the first position it 'clicked' into. Not sure if it did make a difference, I can twist the throttle about 90 degrees, which seems kind of small compared to my other bike and other bikes in particular.
I can't learn from your response to Inge if you have properly aligned the throttle mechanism yet, Steenbeen. Have you?

What the "my other bike" you mentioned?
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #10 on: July 30, 2016, 11:21:21 AM »
Sorry, I see now that it wasn't really clear. It's now properly aligned. It was set a tooth too 'early' at first.
My other bike is a Honda CBR125R. My fathers bike, a V-strom, also has a larger maximum throttle angle. The angle of my K seems kind off small, but as this is my first K, I'm not sure if it's normal. If not, then that would be the problem.
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Offline Laitch

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Re: '86 K100 won't go faster than 60 mph
« Reply #11 on: July 30, 2016, 11:43:04 AM »
Quote from: Steenbeen on July 30, 2016, 11:21:21 AM
Sorry, I see now that it wasn't really clear. It's now properly aligned. It was set a tooth too 'early' at first.
My other bike is a Honda CBR125R. My fathers bike, a V-strom, also has a larger maximum throttle angle. The angle of my K seems kind off small, but as this is my first K, I'm not sure if it's normal. If not, then that would be the problem.
My K75 throttle rotates 90º and that's as far as I'd want it to rotate.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #12 on: July 30, 2016, 01:28:37 PM »
Good to know. That shouldn't be the problem then. Would it act like it does if the throttle bodies weren't correctly synced? How do I know if they are synced correctly?
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Offline Martin

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Re: '86 K100 won't go faster than 60 mph
« Reply #13 on: July 30, 2016, 05:31:32 PM »
Before you go any further replace the rubber caps.
Regards Martin.
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Offline K1300S

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Re: '86 K100 won't go faster than 60 mph
« Reply #14 on: July 30, 2016, 08:34:12 PM »
Quote from: Steenbeen on July 30, 2016, 08:48:09 AM
Link: https://www.youtube.com/watch?v=_NpRS6qa06M&feature=youtu.be
Let me know if it's not clear enough. Is the speed of which the revs are increasing normal?
I'm not sure about vacuum leaks.. Wouldn't that cause wierd irregular behaviour? It drives fine, just kind of slow.

if that is as far as they open, you have a throttle problem.  should open a lot more than than.

as to vacuum leaks.  if there is a big leak, then the mixture goes lean and power goes away....which is the symptom you are having.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #15 on: July 31, 2016, 03:13:10 AM »
I can't push them any further by hand than you can see on the video. By them I mean the mid and right bodies. I can however push the left one a bit more up, compressing the little spring. What could 'block' them from opening any further? I think the previous owner may have mounted it incorrectly.
As for the air leaks, I'll be sure to check the rubbers and replace the caps.
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Offline Inge K.

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Re: '86 K100 won't go faster than 60 mph
« Reply #16 on: July 31, 2016, 03:25:44 AM »
Try to remove the TPS and see if that makes any difference to the throttle opening.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #17 on: August 14, 2016, 07:12:23 AM »
I was on vacation, so here's an update. I did a dyno run, since I had to classify it as <35 kW for my license, and I figured I should do a run before I fix the problem. Turns out, maybe my brick is from 1886 instead of 1986, because it has 18 hp, and should top out at 120 km/h. Graph is attached. I'm going to replace the caps on the bodies, but I'm not sure that would cause a problem like this.
I'm betting on that the throttle isn't able to fully open, so after replacing the caps I'm going to take a look at the inside of the bodies.
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Offline Laitch

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Re: '86 K100 won't go faster than 60 mph
« Reply #18 on: August 14, 2016, 07:27:37 AM »
Quote from: Steenbeen on August 14, 2016, 07:12:23 AM
Turns out, maybe my brick is from 1886 instead of 1986, because it has 18 hp . . .
  :laughing-on-ground:

Did you check the throttle position sensor as recommended by Inge?
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #19 on: August 14, 2016, 08:31:47 AM »
Yeah, I just checked the TPS. Didn't seem to make a difference. However, I just found out I need a new throttle first... The teeth on the throttle bar are flattened, and it would 'skip' through the teeth when force was applied. The damage was hidden under a lot of grease.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #20 on: September 11, 2016, 01:13:10 PM »
Update:

I finally took some time again for this problem after some other repairs. I uploaded a video on youtube which shows the inside of the throttle bodies when twisting the throttle to 'full' (sorry for vertical video syndrome). Seems to be a lot less than they should. What could be blocking them? I can't push them farther than this by hand.

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Offline K1300S

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Re: '86 K100 won't go faster than 60 mph
« Reply #21 on: September 11, 2016, 01:37:10 PM »
there is your problem as we suspected.  those butterflies should open to be fully vertical at wide open throttle.   
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Offline Martin

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Re: '86 K100 won't go faster than 60 mph
« Reply #22 on: September 11, 2016, 01:43:33 PM »
Definitely not getting full throttle, now you need to check why. When you move them by hand try to see if there is anything stopping the movement. How much movement do you now have at the throttle, is it 90o.
Regards Martin.
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Offline Martin

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Re: '86 K100 won't go faster than 60 mph
« Reply #23 on: September 11, 2016, 01:50:15 PM »
I think you have a problem with the linkage set up. I went back to your first pictures and noticed the idle adjustment screw is well off its stop. try to take more pictures of the throttle body linkages with the throttle fully closed and the throttle fully open. In order to get good pictures you might have to disconnect the wiring to the injectors.
Regards Martin.
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Offline Steenbeen

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Re: '86 K100 won't go faster than 60 mph
« Reply #24 on: September 11, 2016, 03:52:19 PM »
Thanks Martin and mlytle. The photos I posted are both on full throttle. I'm not home until friday. Can you make something out of the first video I posted, Martin?
I didn't inspect the bodies thorougly yet, but there didn't seem to be anything that blocks it on the outside. The throttle movement looks like close to 90 degrees, but still a lot less compared to another K100 I checked yesterday. Just to be clear, I can't push them further by hand than I can by twisting the throttle.
How could the linkage be set up wrong? I'm pretty sure the previous owner disconnected the bodies before he sold it to me so that could very well be the problem, I guess.
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