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Chokes/Bogs down at mid-upper speeds (newbie)

  • Thread starter Thread starter Busbis
  • Start date Start date
B

Busbis

Guest
Hello all!

Please excuse my lack of terminology and basic knowledge, I'm new to motorcycles.

Within the past two weeks I've had an issue where, when at higher rpms in 3rd 4th and 5th gear, the bike "bogs down", "chokes" or "sputters" severely lowering acceleration capabilities. I'm thinking it could be that I drain the fuel filter in first and second gear, get up third/fourth/fifth and the petcock can't supply the engine with enough gas? It's so bad I can be going anywhere from 25-70 mph and I cannot touch the throttle without the sputtering to return sometimes. If I accelerate hard after a second or two the bike will accelerate hard in turn, however the bike is seemingly better while in first and second gear.

Before this had happened I removed the left side crank case holding the stator (lower end?) and had to replace the gasket. Coincidence or not, the bike acquired an electrical issue at the same time where only the neutral light will light up with a key turn and the headlight/brake light/speedo/tach will only light up with wiggling the positive wire (to get a better connection?). I have sanded all ends of the positive wire, so i'm also clueless on this issue..

Today I noticed the fuel filter line had a half kink in it, so I replaced the fuel filter and line and it hasn't improved the issue..could my fuel filter be too small? The vacuum hose is connected as well as a thicker hose connecting the motor to the air box (another vacuum hose?). Additionally the petcock seems to have a hardly noticeable leak, potentially from the new fuel filter line.

THANK YOU FOR ANY HELP!
Regards
 
What have you modified? Exhaust, carbs airbox?

What maintenance have you done? Valve adjust, carb rebuild, carb sync?
 
20160328_193824.jpgPrevious owner (Craigslist) mentioned the carbs were professionally cleaned. Additionally the bike has a magna flow exhaust, airbox and is chopped which was all done before I bought it.
I've done simple maintenance things, changed oil, secondary oil, fuses, new gasket for both sides of crank case, new instrument cluster, adjusted clutch cable, new battery, bolted several loose ends on, installed brake light, and I'm forgetting some things however I'd bet 75% of those are irrelevant as is.

Photo I took today for interest
 
It's very difficult to say what could be wrong. All I can suggest is for you to go through the Newbie Mistakes thread linked in my signature and see if anything needs to be tended too. A good starting point would be to go through the carbs and adjust the valves.
 
You definitely have electrical gremlins to chase out. Start by cleaning all electrical contacts. There are a few methods posted here on the boards.

Now when you say it's better in 1st and 2nd, are you getting full engine rpm range? Both easing on the throttle and jamming it hard?

Did the PO say how long ago the carbs were cleaned and how long it may have sat with fuel? Anymore than a month or two and you will need to do a full strip and dip on those carbs. Also, did he mention doing a vacuum sync on those? A bad sync will simulate all sorts of issues and leave you chaising your tail and doing potentially unnecessary things(ask me how i know)

Otherwise, by the sounds of it you either have the wrong size main jet/needle setting or your floats are set too high.

Last thing, don't forget to look at the newbie mistakes thread and verify a few things listed there, such as valve clearances mentioned by nessism
 
Last edited:
Thank you for the suggestions! I will be doing the newbie check tomorrow.

Yes, full RPM range on first and second gear as well as the others if I hold the throttle for a while (I believe on the 3/4/5 gears, actually).
I sanded the connection between my battery's positive terminal and the ..cylindrical..object.. below the ignition unit and so far that electrical issue has relaxed.

I'd believe the carb needle was the problem if this throttle issue has been bothering me since September, however it's only in the past couple of weeks. Could it just be coincidence?
 
Can electricals impact how the bike runs once it's on? Could the electrical issue be my issue? Feel free to gift me with any of your knowledge :p
 
This is the part that caught my attention:
Busbis said:
..., when at higher rpms in 3rd 4th and 5th gear, the bike "bogs down", "chokes" or "sputters" severely lowering acceleration capabilities. I'm thinking it could be that I drain the fuel filter in first and second gear, get up third/fourth/fifth and the petcock can't supply the engine with enough gas?
Click to expand...
Suggestion: ditch the fuel filter.

There is already a filter at the petcock and another one at each inlet valve, there is no need for another one.
 
electronics are a possibility, but I would think that you would be experiencing it in all gears, not just 3/4/5. have you checked both primary and secondary sides of the coils to make sure that they are within spec? because your spark could be getting weaker as the coils get hot from use and the engine heat.
 
Wonder what the spark plugs look like. Are you able to tell if you're running on 4 cylinders when the bike begins to stutter? In the original post you said airbox followed by chopped, then I saw the picture. The airbox is fully intact then?
 
Yes I believe the airbox is fully intact. It did cross my mind today that maybe I wasn't on all four cylinders! I'm trying to see how to test that plugs to notice if the arc appears.
New data today:
It seems that once I drain the gas from the carb bowls (I think that's how the fuel system works) the bike will stutter in any gear. If I hit the throttle hard, a few seconds later the bike will accelerate quickly. I tried in second and had the same issue. While throttling in fifth, I can lightly touch it and the bike seems to be accelerating properly, however any more throttle and it'll stutter. It gets worse as time goes on. I also noticed the RPMs may be slower to fall than I recall in the past, I read that this could be an indicator of the issue?


Yes, sorry. The frame is chopped, airbox is not.
 
20160329_154712.jpg
I assume this is fine for what my plugs look like? The other side looks identical.

Just before I added the gasket to the crank case, my buddy disconnected the fuel filter from the gas tank on accident, so in a panic he connected the petcock's vacuum hose to the fuel line nipple. I had forgot about this, and now believe this could be the cause of the issue?
I'll look at BikeCliff's website tonight to see how to clean out the petcock. Any insight on whether or not this could be the issue?
 
I would check your coils once you get them nice and hot. from what you are saying, it sounds as if the coils are breaking down when hot. measure the resistance of the primary winding (the part of the coil that the harness plugs into) and then measure the secondary windings of the coils (what connects to the spark plugs, and take the boots off and trim about 1/4" to get the best reading) before you start the bike when it's cold and make note of what resistances you are getting. reconnect everything and take it for a ride and get it nice and warm until it starts acting up and then either return home if possible or pull over to a SAFE place (ie parking lot, not the shoulder on the interstate), make sure you bring your meter with you for this part. shut the bike off and recheck both the primary and secondary windings of the coils. if either side has a dramatic result(way higher or way lower) when the coils are hot, then they need to be replaced.

I mention coils because this is what my kz1000 was doing before I got it on the road back in late summer 2014. as a last ditch effort, I took the dyna coils off of my gs650 and put them on the kz and low and behold the problem went away.
 
Busbis said:
View attachment 44884
I assume this is fine for what my plugs look like? The other side looks identical.

Just before I added the gasket to the crank case, my buddy disconnected the fuel filter from the gas tank on accident, so in a panic he connected the petcock's vacuum hose to the fuel line nipple. I had forgot about this, and now believe this could be the cause of the issue?
I'll look at BikeCliff's website tonight to see how to clean out the petcock. Any insight on whether or not this could be the issue?
Click to expand...

So where's the fuel line hooked to, if the vacuum hose is on the petcock? They're different diameter hoses, so I would think it would be difficult to put the vacuum on the petcock outlet.

Still would like to see the other end of the plugs.
 
phydeauxmutt said:
This is the part that caught my attention:

Busbis said:
..., when at higher rpms in 3rd 4th and 5th gear, the bike "bogs down", "chokes" or "sputters" severely lowering acceleration capabilities. I'm thinking it could be that I drain the fuel filter in first and second gear, get up third/fourth/fifth and the petcock can't supply the engine with enough gas?
Click to expand...

Suggestion: ditch the fuel filter.

There is already a filter at the petcock and another one at each inlet valve, there is no need for another one.
Click to expand...

What phydeauxmutt said; remove the fuel filter.​

Because from what I read, your engine cannot develop enough power. Multiple possible reasons for this exist, a f$!ked up mixture being one of them. The fuel filter could be responsible for this (even likely judging by other problems described). As removing the fuel filter is very easy and done quickly, do so, and spend your time on more complex troubleshooting later on. It would be quite annoying to take apart half of your bike only to find out that the fuel filter was the culprit, wouldn't it?

You can always put it back on afterwards, but in my opinion, with the quality and short storage duration (high turnaround) of today's fuel in civilized parts of this world, a fuel filter is an unecessary gimmick.
 
You might also try cleaning the gas cap vent. It is easy, you only have to remove a couple screws. Spiders like to make their nests in there. Just a thought.

V
 
roeme said:
It would be quite annoying to take apart half of your bike only to find out that the fuel filter was the culprit, wouldn't it?
Click to expand...

Would certainly be entertaining for the rest of us, just like last time, and the time before that..... Have you ditched the filter yet?

gustovh said:
You might also try cleaning the gas cap vent. It is easy, you only have to remove a couple screws. Spiders like to make their nests in there. Just a thought.

V
Click to expand...

Just run it with the gas cap popped open a little as a test.
 
gustovh said:
You might also try cleaning the gas cap vent. It is easy, you only have to remove a couple screws. Spiders like to make their nests in there. Just a thought.

V
Click to expand...
I have never done any such thing ! ! ! ANYWAY, these bike don't need, and WON'T run right with an inline fuel filter. the stock petcock flows too slow without any extra restrictions, so get rid of it. You really do need to have a look, and take a picture so WE can have a look at the OTHER end of your plugs. I'm betting they are VERY pale because it's running lean. We should see a good close up of your petcock-hose setup. If you could get the vacuum line on the fuel side it wouldn't run for $hit if at all. please do these few things for us to better help you out...

Which NW suburb are you located in? Maybe one of us could make a weekend house call to help you out...
 
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