Low Compression? (Bike runs rough)

[jnr1114]

Hello,
My bike (2009, 250) has recently been giving me some trouble. I will start from the beginning.

When the bike started acting up, it was running on one cylinder. I replaced the sparkplugs and took out and cleaned the carbs and the other cylinder was firing. (The spark plugs I took out were from a previous generation ninja 250, which was really weird I was running those for a year with no problems, but I replaced it with the proper plugs.). It was running normal for a about a day, and then it lost power one morning. The bike starts up instantly with the choke on. When the choke is taken off after a bit of warming up, the bike will sometimes die, idle low, or idle in the normal range, but it's rough. When the throttle is pinned, the bike chokes, then starts to climb of the rev range, but is slow and sputtery. Can't redline it, it stops accelerating after it hits just near the redline.

I either messed up the carbs (all I did was take the bowls off to clean em, they were already flawless)
Or, the compression is low, making the bike run weak.

I just performed a compression test. One cylinder is reading about 145-150, and the other is 125-135. Is this considered to low of compression?

I think the bike may be running lean, as I took the newer sparkplugs out and they are already starting to get white (normal with new spark plugs?)

The engine has 15k on it. I'm assuming it's the valves because both cylinders are reading very close.

Any suggestions on troubleshooting before I take the bike apart again? Getting the carbs out was hell. I'd like to avoid that. haha

[HoneyBadgerRy]

Your compression is on the low side, but still OK. Valves out of adjustment would cause lack of compression, and the bike to run s**tty.

If the plugs are white the bike is running lean, and that could be caused by dirty carbs, or mid jetted carbs. Do you have any engine (intake or exhaust) modifications on your bike?

[crazymadbastard]

time to check them valves for sure

[Racer x]

When you are doing the valve check. You should pull the carbs. I would check the pilot jets also.

[xorbe]

OP is going to double his whp when he does the valve adjustment! It was like a bike upgrade when I did mine.

[HoneyBadgerRy]

I find it funny you guys let your bikes get like that. If you put e10 or old gas vs fresh e0 93 octane in my racbike I could tell you after two laps around a MX track.

[jnr1114]

Originally Posted by HoneyBadgerRy

I find it funny you guys let your bikes get like that. If you put e10 or old gas vs fresh e0 93 octane in my racbike I could tell you after two laps around a MX track.

I maintain my bike very well. But I've only had it one year.

[jnr1114]

Originally Posted by HoneyBadgerRy

Your compression is on the low side, but still OK. Valves out of adjustment would cause lack of compression, and the bike to run s**tty.

If the plugs are white the bike is running lean, and that could be caused by dirty carbs, or mid jetted carbs. Do you have any engine (intake or exhaust) modifications on your bike?

No mods. Bike was well kept and stock when I got it. In fact he had never even taken the fairings off and he bought it new.


I will do a valve adjustment and take the carbs off. Can I get rid of the stock airbox with pods without effecting the performance? I don't wanna get a jet kit. But I can't stand this god damn airbox.

[jnr1114]

Originally Posted by jnr1114

No mods. Bike was well kept and stock when I got it. In fact he had never even taken the fairings off and he bought it new.


I will do a valve adjustment and take the carbs off. Can I get rid of the stock airbox with pods without effecting the performance? I don't wanna get a jet kit. But I can't stand this god damn airbox. And for the record when I took t he carbs off last month they were absolutely flawless. That's why I'm hesitant to assume that it is the problem.

[HoneyBadgerRy]

Originally Posted by jnr1114

No mods. Bike was well kept and stock when I got it. In fact he had never even taken the fairings off and he bought it new.


I will do a valve adjustment and take the carbs off. Can I get rid of the stock airbox with pods without effecting the performance? I don't wanna get a jet kit. But I can't stand this god damn airbox.

You WILL NEED to rejet with pods. A jetkit will make your life much easier. Pods did seem to add some power, but mostly just noise.

[HoneyBadgerRy]

Originally Posted by jnr1114

I maintain my bike very well. But I've only had it one year.

I was refrencing @xorbe .

[xorbe]

Originally Posted by HoneyBadgerRy

I was refrencing @xorbe .

It was like that when I bought it as the 3rd owner. I learned to ride, then tackled the valves. Which worked out fine, as it was less power to start on.

[jnr1114]

Is there any why I can kind of diagnose the carbs before taking them out? Testing for insufficient fueling? The valve adjustment looks pretty scary. If I can just get the bike running like it was before I'd be happy. And maybe take it in for an adjustment later on.

[jnr1114]

Also just for the record, I did a spark test again just to be sure, good looking sparks. But the right sparkplug holds a charge for a few seconds after the bike is completely turned off and gives a spark like 2 seconds after the bike is off. Does it every time. Shocked me good.

[HoneyBadgerRy]

Originally Posted by jnr1114

Is there any why I can kind of diagnose the carbs before taking them out? Testing for insufficient fueling? The valve adjustment looks pretty scary. If I can just get the bike running like it was before I'd be happy. And maybe take it in for an adjustment later on.

The only thing you can test in carbs is if the petcock is working, and if the float seals are working. So no, you have to take them off, clean them, and run pressurized air through all the pathways, then run carb cleaner through all the passages until the fluid comes out clean.

Once you have the carbs off I highly recommend that you replace all the JIS screws on the slide caps and the fuel bowls with stainless steel allens. You should be able to pick them up at a local hardware store, but since you need 16 of them, it would be much cheaper to pick them up as an online fastener store or amazon. (I personally go to a fastener store most of the time, because I know the quality of the bolts, vs hoping that the ones on amazon are chinese crap that will randomly snap on me and cause me a huge headache).

[jnr1114]

Carbs are out. Floaters are working, main jets look brand new (as does every part in the carb), but I can't access the pilot jets. I don't have a screw driver small enough to fit down the hole. But I did spray carb cleaner threw everything. I'm starting to doubt it's the carbs.

[HoneyBadgerRy]

Originally Posted by jnr1114

Carbs are out. Floaters are working, main jets look brand new (as does every part in the carb), but I can't access the pilot jets. I don't have a screw driver small enough to fit down the hole. But I did spray carb cleaner threw everything. I'm starting to doubt it's the carbs.

Turn the mixture screws all the way in and look and the carb cleaner, then turn them 3 turns out, and it should come out a different hole. (I am having a blonde moment right now and don't remember your problem, but this might help with starts, and it will help prevent a problem in the near future.)

[jnr1114]

What if I rule out compression, carb, and spark? What else should I be looking into? Anything electronic?

[HoneyBadgerRy]

Originally Posted by jnr1114

What if I rule out compression, carb, and spark? What else should I be looking into? Anything electronic?

Compression, fuel, spark, and valves. That's pretty much all there is to check. The ninja CDI is pretty basic, if it works, its not the cdi.

[jnr1114]

Originally Posted by HoneyBadgerRy

Compression, fuel, spark, and valves. That's pretty much all there is to check. The ninja CDI is pretty basic, if it works, its not the cdi.

Okay.

I just put the carb back in after cleaning. Bike won't start at all now... -_-

[HoneyBadgerRy]

Originally Posted by jnr1114

Okay.

I just put the carb back in after cleaning. Bike won't start at all now... -_-

I have this problem myself. Turn it over for a while, walk away and let the fuel settle in the bowls, come back in an hour or two and she will start right up.

[Ghostt]

NewGen has a PRI setting on the petcock, make sure it's set to PRI once you have it running, switch back to ON.

[jnr1114]

Got the bike started, had a loose connection. Still runs rough despite cleaning the carbs...

[HoneyBadgerRy]

Originally Posted by jnr1114

Got the bike started, had a loose connection. Still runs rough despite cleaning the carbs...

Check the valves, with a 10mm tool to take the valve cover off, a 9mm wrench, a 9mm deep well (I used a snap on), long handle skinny flathead, and feeler gauges its a pretty easy job.

Edit: I noticed you have a newgen, I take that back, I never did the valves on a newgen.

[rgx107]

I don't think it is the valves, they shouldn't go from good to running on one cylinder over night. Typical symptom should be difficulties to start when the engine is hot.

And yes it's a hazzle to adjust the valves, and they are due at 15k. But I still think it sounds like an air leak or issues with the fueling. I don't know much about these carbs though.

[Mohawk]

Originally Posted by jnr1114

Got the bike started, had a loose connection. Still runs rough despite cleaning the carbs...

What connection was loose ?

[crazymadbastard]

Did you check the valves? They may be too tight and causing the low compression. Until the valve clearances are right, nothing you do will get it to run right.