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Discussion Starter #1
I was hoping to get some advice regarding a small bike problem I’ve got. Be glad for your thoughts. I installed a shorty slip-on exhaust as well as some shorty levers. Motorcycle performed pretty amazingly at first, but as I was riding on PCH there was a sudden, very noticeable drop in power. I didn’t think too much of it at first, other than that the exhaust itself may not be giving enough back pressure to the engine, so I went home.

The next day was riding up the 405 at freeway speed and again power just cut out. This time, however, I couldn’t do more than 20 mph. I managed to get to the Ventura freeway using the shoulder and pulled over. I noticed a small amount of white smoke coming from the exhaust. I want to diagnose the problem so I know how to fix it.

  • I adjusted the clutch cable, no change
  • Replaced old levers and readjusted clutch cable, again no change
Here are the symptoms I know:
  • Very little power, torque, and speed
  • Engine power decreases as I shift up
  • Lots of revs, up to 6000, just to get to 20-30 mph
I started reading online and saw all the following possibilities, was hoping you might help me either narrow in to the issue, or give me a procedure I could narrow in with?? Any help very welcome

Clutch:
  • Disk
  • Cable adjustment
Throttle
- Extra slack in the throttle cable

Air Filter
- Clogged

Carb:
  • Plugged jet in the carb
  • Broken carb spring
  • Vacuum leak in the carb or intake boot
  • Dirty carb
  • Engine Oil in the combustion chamber
Spark Plug
  • Poor timing advance
  • Loose
  • Dirty
I hope you’re having a good weekend. Again thank you for any help you can give.

Best,
Alex
 

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The white smoke is a worry though. Generally that indicates coolant getting into the combustion chambers through something like a blown head gasket.
Check your coolant reservoir level first. Is it using any oil? How many miles on the clock and is it still under warranty?
It really does not sound ideal, I'd be wary of riding it.
 

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The white smoke is a worry though. Generally that indicates coolant getting into the combustion chambers through something like a blown head gasket.
Check your coolant reservoir level first. Is it using any oil? How many miles on the clock and is it still under warranty?
It really does not sound ideal, I'd be wary of riding it.
^THIS^ white smoke is not good, butt how much white smoke? Barley noticeable, or a white plume spewing out the tail pipe?
When I first started reading this (Major loss of power at high revs.) I was thinking "a pinched vent line at the gas tank? Or bad fuel? Also, we've read about a few peeps on here with fuel pump issues, so yer fuel pump may be go'in out? Only revving to 6K sounds like fuel starvation to me. Butt the white smoke....
What year, how many miles on this Z400?
 

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I was hoping to get some advice regarding a small bike problem I’ve got. Be glad for your thoughts. I installed a shorty slip-on exhaust as well as some shorty levers. Motorcycle performed pretty amazingly at first, but as I was riding on PCH there was a sudden, very noticeable drop in power. I didn’t think too much of it at first, other than that the exhaust itself may not be giving enough back pressure to the engine, so I went home.

The next day was riding up the 405 at freeway speed and again power just cut out. This time, however, I couldn’t do more than 20 mph. I managed to get to the Ventura freeway using the shoulder and pulled over. I noticed a small amount of white smoke coming from the exhaust. I want to diagnose the problem so I know how to fix it.

  • I adjusted the clutch cable, no change
  • Replaced old levers and readjusted clutch cable, again no change
Here are the symptoms I know:
  • Very little power, torque, and speed
  • Engine power decreases as I shift up
  • Lots of revs, up to 6000, just to get to 20-30 mph
I started reading online and saw all the following possibilities, was hoping you might help me either narrow in to the issue, or give me a procedure I could narrow in with?? Any help very welcome
So I think you can rule out carb, because these are fuel injected bikes.....which also means unless your fuel pump has mysteriously went bad around the same time or you dumped gas into the bike with mud in it, you can rule out fuel issues or delivery.

With the install of levers and exhaust I would think its related to one or the other.

Possibly levers....or a pinched fuel like or maybe something with the cables...

You say lots of rev's to get the bike moving....which could be a slipping clutch, but in order to determine that the symptoms and behaviors have to be the same.

So when you are accelerating are the RPM's high and the bike just does not feel like its moving?
With the bike in gear and the clutch released(so not pulled as if you are changing gears), if you crack the throttle open wide and quick, do the RPM's jump, but the bike does not move or pull hard?

If so, that is a slipping clutch, and could be how that lever is installed and the cable slack or lack thereof.

Or, when you crack the the throttle the engine bogs and does not feel like its pulling or reving, so you have to hold the throttle wide open and eventually, very slowly, over time and struggling, the bike gets to a higher rpm?

Usually when fuel delivery is a problem, or a cylinder is dropped and or the rings are fried, valve guides and its mixing oil with gas like a 2 stroke, the bike will bog down and feel like it just cannot run, chugs, does not want to idle sounds and feels rough, smoking excessive(not when its a fuel delivery issue, unless the fuel is really bad), when you rev it, does not respond and rpm's slow to jump, etc. Does not snap open the engine rpms and go .....whaaaAAAAAA-BOPPPPPPP!

Can you post a video of how its behaving and sounding?
 

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If you are reving to 6,000 and in a high gear but only going 20 mph, then it's a clutch problem. Revs and speed are linear with the clutch engaged. If this is not the case, then there is something wrong with the clutch.
 

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WHAAAAABOPPPP?
Yes sir, describing in words the sound the engine makes when you rip the throttle wide open in neutral and it quickly smacks up against redline, instead of bogs down, coughs and sputters its way there like a wounded animal......like this CBR250RR when he hits redline....


Surely you have seen the old Batman series episodes where their fights have sounds spelled out.............same thing........
 

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Yeah, I gotcha. Kinda reminded of something different. Not Batman though. Ha
Could be that too...whatever that might be......I conveyed the point or at least the response he should be getting when he twists the throttle as opposed to maybe what is happening?

Unknown, he posted once and then vanished.....or twice, asked another question in another post and then "poof" just like that gone.......
 

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Could be that too...whatever that might be......I conveyed the point or at least the response he should be getting when he twists the throttle as opposed to maybe what is happening?

Unknown, he posted once and then vanished.....or twice, asked another question in another post and then "poof" just like that gone.......
Ghost poster! ?
 

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Discussion Starter #13
Hey everyone who posted, I just wanted to say thank you for all the comments. I wanted to give you an update. So it turns out the clutch was destroyed. A gasket also blew. I had them both replaced. I ended up getting an aftermarket clutch that did the job. It's working great now. I'm keeping the oil fresh to make sure all the crap that got lodged is out.

Just a quick update for you all.

Thank again,
Alex
 
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