Topic: Carb help please

[Cowboy48]

Ok, I think I have an accurate description of what my k5 is doing.  The first half of the throttle is good, responsive power but above that it feels like it hits a governor and just flattens out for a bit until it eventually the power comes through, almost reluctantly.  I am twisting the throttle slowly and smoothly all the way up but that does not seem to change the flat spot.  If I shift when it hits that flat spot I can feel the power come on smooth.  To my novice brain this seems like a high rpm problem with the carbs.  Here are some facts that may assist anyone who thinks they can help me.
1. The plugs look perfect, light brown low carbon.
2. New airfilter.  The bike had the same problem before the new filter.
3. 4-1 exhaust


Another way to describe the sensation is to imagine that you are suddenly a gear to high and the bike just "bogs" or "lugs".

Thank for any help.

[number13]

Hmmmm...I am gonna guess fuel starvation.
Do the symptoms occur at a specific RPM??
Does the exhaust require rejetting?
Might also check for a dirty petcock screen or
possibly floats set too low in the bowls.

Best o luck1

[crazypj]

What exhaust is it and do you have the baffles in? ( or is it so loud you can 'hear the power' i.e. sounds fast)
PJ

[Cowboy48]

I don't know what the muffler is.  It does sound fairly loud under power but quiet at lower rpm & idle.  The muffle was a big dent in it so I am looking to replace it anyway.  Should I try to just find a muffler or look for an entire set of pipes?   If so, any recommendations anyone?  I do like to "hear the power" so something a bit on the sporty side would be cool.

As far as the tach goes...I don't know what rpm it is exactly but I would say that the problem is somewhere around the 4,000 mark.  I would also venture to say that the problem is always around that range.

[crazypj]

 I would only change the silencer. I prefer stealth biking ( long story, but if they dont hear you coming you may be gone before they wake up ) And I work until after midnight, the damn HD guy down the street wants everyone to know when he leaves for work or whatever
Sounds like you may have needle position wrong or damaged needles/needle jets? The rpm is too high to be a sticking advancer unit (have you put a timing light on it to verify its advancing correctly?)
PJ

[TwoTired]

The plug reading would be more meaningfull if the the engine was run in the problem mode long enough to show a relational mixture indication.

If it is slightly starving for fuel, too lean; Plug center insulator shows white.
If it is going rich; plug center insulator shows black deposits.

These indications need 15-30 seconds of run time (on initially clean plug) and then the engine shut off immediately to preserve the plug reading.

Slightly starving the engine for fuel raises the combustion temps to burn off the deposits.  However, if the fuel starvation is severe, there is not enough to sustain combustion, or burn off any deposits.

It would be interesting to know the carb fuel levels during your problem event.

Is your fuel tank vent clear?
Is there any restriction in your fuel supply to the carbs?
Does it have the problem with the tank set to Reserve?
How full is your tank?
Do you know the carb float levels are correct?
Is the behavior any different without the air filter installed, or with partial choke applied?

Enough for now... I'm going to bed...zzzzzzzzz

[Cowboy48]

Wow tt, you ask a lot of questions 

Is your fuel tank vent clear?

Didn't know I had one.  I'll check into that.

Is your fuel tank vent clear?

Not that I know of but I see where you are going with this.

Does it have the problem with the tank set to Reserve?

Another thing I will check on today.  I've never had it in reserve before.

How full is your tank?

That doesn't seem to matter. 

Do you know the carb float levels are correct?

I have no idea

Is the behavior any different without the air filter installed?

I didn't run it with the air filter off for fear of sucking something in the carbs.  Wouldn't that be risky considering the problem only occurs while going down the road under considerable power?

or with partial choke applied?

The bike will not run with the choke applied period.  I usually have to choke it to start it but it will not run for more than 2 seconds with the choke on.  It usually stalls real fast so I then turn the choke off and start it again and give it small throttle till it warms up.  It's frustrating because I have to stay with the throttle for the first 2 minutes or it will slowly stall out.  After the bike is warm, any choke is immediate stall.

Thanks a lot for all the input tt.  I'll post the other answers later. 

Now if you could just solve my wiring problems over the internet....

[Cowboy48]

The rpm is too high to be a sticking advancer unit (have you put a timing light on it to verify its advancing correctly?)
PJ

I have not done anything with the timing since I bought the bike 6 weeks ago.  Another tool I need to purchase, my wife will be thrilled