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Discussion Starter #1 (Edited)
Hope you're all doing well in these times we're all going through. I'm editing the thread to make it shorter as it was too long initially.

My issue is my bike doesn't respond to throttle input past mid range. Revs will go up but the bike will NOT accelerate. Happens in all gears and at all speeds.

Going WOT (wide open throttle) is even worse and dangerous as the bike literally takes 2 seconds to accelerate (while RPMs shoot up) and then the bike buckles forward.

Never did this before. Bike was running like a raped ape before I did the following:

All I did is removed LED lights from relay switch on handlebar. Removed tank too. Put everything back together checking all rubbers/wires plugged.

I put the battery back on and by mistake I had left keys turned on. So when I connected the + terminal... yep... Decent spark I got. No signs of burnt anything, ECM looks OK (wiggled it while throttle in neutral, no hiccups).

Installed battery properly. Went for a ride and BOOM, bike will rev up (RPMs go up) when past mid range throttle but the bike won't accelerate.

Would appreciate your help. Many thanks!

PS... The bike is ALL stock. Carb, exhaust, air, etc all stock.
 

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The way you have it worded It seems you have a clutch that is slipping.
>> Revs will go up but the bike will NOT accelerate.<<<<
With throttle situation I suspect that an ICM wire has broken possibly
associated with the TPS.
Inspect carefully and hopefully you will see a broken wire.
Sometimes the strands have broken and are making intermittent contact.
The insulation could have a reduced diameter right at the weather seal o-ring.
It will not be the first time an ICM wire broke from a battery change or maintenance.
 

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Discussion Starter #3
The way you have it worded It seems you have a clutch that is slipping.


With throttle situation I suspect that an ICM wire has broken possibly
associated with the TPS.
Inspect carefully and hopefully you will see a broken wire.
Sometimes the strands have broken and are making intermittent contact.
The insulation could have a reduced diameter right at the weather seal o-ring.
It will not be the first time an ICM wire broke from a battery change or maintenance.
Many thanks for your reply, Hans.

Yep, it feels like clutch is slipping but 2 seconds later, the bike picks up the acceleration and launches forward. Only happens from mid range throttle and up. It's a 2 second delay and then BOOM, the bike launches to pick up the RPMs.

I revved the bike in neutral while softly wiggling the ICM and there was no issue. No misfiring, no backfiring, no popping, no hiccups.

However, if I roll throttle WOT (till very end of range) in neutral, the sound that the bike makes is sort of intermittent grunting rather than the usual linear grunting. It really feels like things turn bad as soon as past mid range of throttle.

I checked ICM and from outside it looks fine, including wiring. As said, I even wiggled it softly revving in neutral and nothing, all was good.

How can I check the ICM better to check all wiring OK? DO I have to open it? I read these things are expensive f*ckers to replace.

My concern is my mistake of having left the keys turned on the bike while inserting the battery. As soon as I went to connect the + terminal. It created a spark about 5 inches tall.

No smell of burnt anything or smoke. I installed battery (keys out, my mistake) and all good. Everything works and lights up. Bike starts perfectly, idles as usual, and responds to low throttle input perfectly and smoothly. But pass the mid range in the throttle and bike doesn't accelerate as RPMs rise.

Could I have burnt something in the electrical wiring due to mistake of battery short?

I read about a module that sits atop the cylinders in the VTX 1300 that manages throttle input to air/gas mix. Could that have been toasted due to battery short?

Also, the LED lights that I removed went to a handlebar switch acting as a relay. I unplugged the LED lights from a plug (two plugs) inside the headlight case which I believe belongs to the handlebar switch (so it isn't the Honda plug and play one). I work on my bike and installation was done by Honda dealer years ago.

That plug inside the headlight which goes to the handlebar switch is now sitting with nothing plugged to it since I removed LEDs. Could this be drawing voltage/power from the battery unnecessarily?

I just don't understand why it's doing this since the bike was running like a top and never one single issue like this.
 

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The TPS on the carb is for ignition timing advance.
I do not know of any module that sits on top of the cylinders to manage A/F.

Five inch spark?? Something melted and it flew like a comet.
A sharp point contact can create heat that could hurl a small spark.
Ohm meter to check the TPS. Or back-probe and check voltage.
I posted a msg on your PM.

Slide diaphragm not lifting??? Slow response if it has holes in it.
Fuel flow??? All Vacuum hoses connected.

Go back and check every place you were.
Connectors in the headlight bucket. A bare wire not insulated may have created the
high current for a spark.

I back probed using an led lead. A small gauge stiff wire will do to check the voltage from ICM and see if TPS working as expected. Unlatch the ICM connector for the Ohms test to TPS.
 

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Discussion Starter #5
Hans, many thanks as usual. I'm going to post my findings upon checking the ICM with pics attached.

Unplugged ICM from chip box. Pins look good, no corrosion. Posting pics below.

Wires connecting to outer side (with rubber boots) look fine. I did some gently pulling and they would not budge and seem solid fixed. They're tight though with no slack and I can see how these break easily. Always try to be careful with these.

The inner side of the of the wire connector, I shed some light to it and all holes with wires connecting to it look the same. So the TPS wires look the same as the rest of wires fixed inside there. I'm also attaching a pic of that.

Incidentally, I discovered there was a teeny tiny spider living in the silicone casing of the ICM chip box and there was a tiny web. Cleaned it up but didn't find the spider. Not worried though because of the following.

I put everything back with battery and all. Neutral, rev the bike slowly all the way to end of throttle range. Same intermittent noise. Sounds like hitting rev limited. I'm posting a sound file of it.

I also got my ear close to the ICM unit when throttle at WOT and I can hear a very low high-pitch sound.

It sounds like electricity shortening OR it could be just a heat shield vibrating. Not sure, hopefully you can hear it in the sound file.

I'm posting a pic of the handlebar switch. When I removed the wiring from the LED lights going to it, I remember the handlebar switch also had another cable going down towards the frame of the bike as I had the tank off.

I didn't do this installation and it was years ago. Never a problem. I have an array of plug connectors next to the battery box which I don't even know what are for. I have a 12v power outlet on handlebar too but that's about it.

Posting pic of a plastic harness which is what???

I pulled tank up slightly to check rubber to PAIR valve, which once pulled out when I put tank on. Nah, it seems to be good. Checked T-hoses and all plugged good.

I will remove the tank soon (busy with work), but the bike was running PERFECT before I took those damn LEDs out (had to as they're not DOT certified so won't pass MOT).

Please see pics and hear sound file in next post.
 

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Discussion Starter #6
Pics of ICM, chip box's pins, handlebar witch for LEDs I removed (with suspect wire that follows down to tank), and what the hell is that plastic harness connector for?











 

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Discussion Starter #7 (Edited)
Video of revving bike in neutral gradually from closed throttle to end of range throttle (WOT).

When it's at WOT, you can hear the intermittent sound of the engine as if hitting rev limiter. You can also hear a low volume buzzing sound as if electric shortening OR it could be some heat shield vibrating or something else.

You can especially hear the buzzing sound at 00:35 seconds into the video in the third attempt at WOT.

Please click on the volume sound to hear the video as the video is muted by default.

 

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Pics of ICM, chip box's pins, handlebar witch for LEDs I removed (with suspect wire that follows down to tank), and what the hell is that plastic harness connector for?













You have Hans attention, so that’s a good thing. The light switch looks like a stock Hondaline passing light bar switch. (If you’re interested in selling, I’d buy it). Disconnecting that switch from the headlight bucket shouldn’t effect anything other than the lights.

In the last pic, one end of that connector goes to the battery, what’s at the other end? It looks like a battery tender plug.

I agree it sounds like you’re hitting the Rev limiter, but you are also reving it up in Neutral, it wouldn’t take much to get there. When you put the tank back on, did you make sure the gas lines was straight and not kinked? Vacuum hose to the petcock is good and not cracked?


Sitting on my VTX making vroom vroom noises.
 

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Discussion Starter #9
You have Hans attention, so that’s a good thing. The light switch looks like a stock Hondaline passing light bar switch. (If you’re interested in selling, I’d buy it). Disconnecting that switch from the headlight bucket shouldn’t effect anything other than the lights.

In the last pic, one end of that connector goes to the battery, what’s at the other end? It looks like a battery tender plug.

I agree it sounds like you’re hitting the Rev limiter, but you are also reving it up in Neutral, it wouldn’t take much to get there. When you put the tank back on, did you make sure the gas lines was straight and not kinked? Vacuum hose to the petcock is good and not cracked?


Sitting on my VTX making vroom vroom noises.
Thanks. Handlebar switch is actually aftermarket. I believe it's BBP or Kuryakin. It's been a long time and never had any issues with it.

The wiring of the handlebar switch was taped as it was two wires. One going to headlight and the other down to frame. I didn't pay much attention to it when tank was off but I recall the handlebar switch wire running down to the frame was soldered to a big wire. Not sure if that's something to do with affecting TPS or if it's soldered to TPS main wire?

I do recall when I would go WOT on neutral on the bike for testing purposes, it would do a linear grunt and not that intermittent rev-limiter sound. But I may be wrong here. I've only done it couple of times when working on other stuff.

I will be taking tank off to ensure all rubber lines are good, but very busy this weekend. When I took the pics and video right now, I also lifted the tank slightly and checked PAIR rubber line, which was good. It once unplugged putting tank back on which created a lot of popping and bad running.

I shed some light between cylinders to check T rubber lines, all plugged. Also fuel lines and venting lines all plugged.

Even if the rubber lines were rotting somewhere, I think this issue is too much of an issue from simply having removed tank and taken LEDs out. The same day before I took the LEDs out, the bike was running perfectly.

In fact I never had one single issue regarding throttle input or running of the bike. And then out of nowhere, I take LEDs out and the bike now takes 2 seconds to respond to throttle input and accelerate past mid throttle range? RPMs go up as normal but it takes the bike 2 seconds to catch up and then she's all good running??

Below mid range of throttle, the bike responds to input flawlessly and immediately. It's only once I go past second 1/2 of throttle range that she won't respond immediately and take 2 seconds as RPMs go up (very dangerous to do WOT now too).
 

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I am not a fan of WOT in Neutral.
I suspect that many items could rattle at different rpm ranges.
Connectors in the HL bucket, helmet lock, clutch lever, are some examples.
I did notice on the Battery Negative post a wire terminal under the large negative cable.
The large cable should be on post first.
That Black plug is not OEM, follow it to the end. Probably more leds.
 

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This is why I question the fuel and vacuum lines. Like the throttle is wide open but the fuel is not getting to the carb. The vacuum line to the petcock may look good on the outside, they crack on the inside. With the age of the bike, I’d be taking a closer look, or just replace it.

If the bike is reving up before the transmission catches up, as noted before, that sounds like a clutch issue. Nothing electrical will cause that. Seems old that this suddenly happened after disconnecting a switch.


Sitting on my VTX making vroom vroom noises.
 

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I added ACO valve issues, two of those earlier this year.
Slide valve diaphragm with too many holes will not lift the slide valve.
A few holes in the diaphragm could cause a delayed response.
intake manifold clamps could be loose.
 
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Discussion Starter #13
This is why I question the fuel and vacuum lines. Like the throttle is wide open but the fuel is not getting to the carb. The vacuum line to the petcock may look good on the outside, they crack on the inside. With the age of the bike, I’d be taking a closer look, or just replace it.

If the bike is reving up before the transmission catches up, as noted before, that sounds like a clutch issue. Nothing electrical will cause that. Seems old that this suddenly happened after disconnecting a switch.


Sitting on my VTX making vroom vroom noises.
Thanks for following up, but my clutch is new, only 15k on it (installed a new one, all stock). I actually have the Glenns CR and is it a useful little thing. I checked to see if clutch was disengaging just in case right when I noticed the surge and it's all good. Checked throttle cables all good.

Clutch works perfectly. Never one single issue of surging or hunting RPMs in the past. Till when I did this removing of LEDs thing.
 

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Discussion Starter #14
I'm going to get a voltage multimeter ASAP and check the ICM unit. Quickly glanced the owner's manual and it says there's a voltage range for every throttle position. I think this would be the best way to discard any TPS issues or ICM. What you guys think?

Bike has been running like a top forever and right before I removed the LED lights. I'm going to see if I can remove tank in these couple of days and inspect cables and rubber hoses. I'll take more pics to post here.

I was looking at the location of the TPS sensor and it seems to be under the tank, any chance I could have hit it and damaged it?

BTW, the bike doesn't backfire, pop or run rough. It just does this crazy thing of delaying acceleration while RPMs rise for two seconds when I roll throttle past mid range.

Any more thoughts or ideas are much appreciates.
 

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I'm going to get a voltage multimeter ASAP and check the ICM unit. Quickly glanced the owner's manual and it says there's a voltage range for every throttle position. I think this would be the best way to discard any TPS issues or ICM. What you guys think?

Bike has been running like a top forever and right before I removed the LED lights. I'm going to see if I can remove tank in these couple of days and inspect cables and rubber hoses. I'll take more pics to post here.

I was looking at the location of the TPS sensor and it seems to be under the tank, any chance I could have hit it and damaged it?

BTW, the bike doesn't backfire, pop or run rough. It just does this crazy thing of delaying acceleration while RPMs rise for two seconds when I roll throttle past mid range.

Any more thoughts or ideas are much appreciates.
Just a thought. When you connected the battery the first time, you said you had sparks but nothing burnt. The symptom's you are describing seem to be clutch related. Have you checked your clutch cable for smooth operation. High current from the battery may have travelled through the cable and cooked the inside of the cable. It might be sticking and not engaging the clutch immediately.
 

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I was taught that high revs with no load is TERRIBLE abuse of an internal combustion engine. Good luck tracing down your problem though.
 

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I was taught that high revs with no load is TERRIBLE abuse of an internal combustion engine. Good luck tracing down your problem though.
I consider it abuse to my bike even on the Highway myself. In the 10 years I had my Yamaha Raider (93,000) I only hit the rev limiter once, passing a vehicle. And that was just lack of paying attention to shift.
 

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Discussion Starter #18 (Edited)
So I tore the thing apart inspecting everything. I didn't remove the air box to inspect carb as I didn't have all the time in the world. But here's a couple of things.

1) Checked all rubber lines connected to tank. The fuel vacuum hose had those tiny cracks where it mates to the metal tit. Trimmed the cracked end off. The PAIR rubber line also had some of that. Trimmed it off too.

2) Went thru electrical wiring. The unknown harness in previous post was for a 12v power socket. All seemed good. Haven't had a chaknce to check TPS ohm output in ICM as have no voltmeter. Will try to get it in these coming days. Should be a quick check.

3) Cable clutch is all good. Removed cover and while a bit of greasy black goo next to engine oil case, seemed fine. Just dirty. Apparently user manual says I can check continuity at the clutch lever too, so will do that with voltmeter aside from ICM checking TPS.

4) Put everything back together. Went for a test ride. Same issue.

I was able to flog the bike at different speeds and without fail, RPMs go up as expected with NO acceleration when passing first 1/2 of throttle range. The bike doesn't accelerate for 2 seconds when gone past first 1/2 of throttle range, and then, ALL HELL breaks loose and the bike launches forward to catch up. So much that I had rear tire spinning in 2nd gear in the wet going slow. Too dangerous.

It doesn't it at an indicated 40 mph without fail, on what looks like EVERY gear !??

The acceleration delay feels similar to a turbocharged engine lag. Like the f*cking thing goes bananas after 2 seconds of no acceleration and then accelerates as if turbocharged. Is this really concise with a clutch issue? I thought clutch slipping did not include the bike suddenly accelerating dangerously after 2 seconds.

Also and very important, within the first 1/2 of the throttle range, the bike responds flawlessly. Perfect clutch response and throttle response on ANY gear on that first 1/2 throttle range.

I'm going to order new rubber lines for everything and check slide valve diaphragm. I need to get new rubber lines for PAIR valve too as it's getting too short due to nipping it a third time now.

I also found a few ants on the frame and there seems to be a small ant's nest about 4ft away from the bike. Found a few going up the kickstand. Currently bike stored outside with cover.

I've read of ants clogging things up though a rare occurrence. More power to putting new rubber lines but you think ants could cause clogging of rubber lines/carb/air box?
 

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Discussion Starter #19 (Edited)
I was taught that high revs with no load is TERRIBLE abuse of an internal combustion engine. Good luck tracing down your problem though.
It is terrible abuse if done all the time. But I had to somehow show what would happen on neutral. I NEVER do that purposely aside from this instance. No engine oil pressure pumping when doing that hence should be avoided as much as possible.

Flogging bike at speed is fine as is hitting rev limiter on the occasion (at speed too). Moderately, of course. I don't partake in this in as much as the rest of you do, but know a few who do.
 

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Discussion Starter #20
One more thing regarding what I'm experiencing.

The day before I experienced this issue, I remember that when I arrived home, I stopped the bike, went from 2nd gear to neutral, and then I heard the clutch doing 3 loud clunks in a row. The same CLUNK when going from 2nd to 1st instead of 2nd to neutral.

Usually 2nd to neutral makes no noise at all. This time it was 3 consecutive clunks. The bike has done this only two or three times and never paid any attention to it as VTXs are noisy by nature. But hey I might as well also report this in case you folks think it could indeed be clutch related or cracked rubber lines in those Ts.

I sure hope it's the cracked rubber lines as I don't look forward to replacing clutch.

Also clutch springs only have 15k on it new (put for preventive measure). Bike currently at 30k mileage. Replaced engine oil some 6k ago (synth, 15-40 Mobil). Also changed oil filter 6k ago with engine oil.
 
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