Mid to high throttle/rpm stuttering issue

[Juney]

My bike: '14 SM with 30k miles, 3x3 mod, k&n air filter, stock BSR carb (150 MJ, jd blue needle in 3rd position, cw 434 big bore, fmf header, crd silencer.

 

I have been struggling with the same problem for a while, and have found and fixed several issues along the way, but the original problem persists.

 

Around 5k-6k rpms, and/or mostly open throttle, my bike misses, pops a lot, stutters, whatever you want to call it.

 

My first thought was I was too rich on the MJ. I tried a 145, and it felt really thin on top and just ran out of steam. Maybe I don't know how to diagnose rich and lean from the butt Dyno. I tried a 155 MJ, didn't fix the problem and felt sluggish. I went back to the 150 and tried a whole bunch of different settings on the needle. No dice.

 

I thought everything was magically working fine today after I went back to the 150. I rode around for about 20 minutes and the problem showed up again. This has been typical of the problem. When I first start the bike and ride around, it seems fine. Then it sort of gradually decides it doesn't want to be ridden.

 

Given my jetting attempts and the 'warm up' required for the problem to start, I'm wondering if it isn't a carb issue after all.

 

I've read gas in the oil can cause similar symptoms, but it has had the problem just minutes after an oil change.

 

I haven't looked into the stator yet, but could that be it? I haven't tested anything with the multimeter yet, but could a worn out stator cause this? I was thinking as it gets some heat in it, something goes out of whack?

 

Could it be another wire? Spark plug lead? Something with the ignition coil?

 

Just scratching my head thinking where else to look.

 

Thanks

[1hp]

have you ever cleaned the strainer inside the fuel tank?

[Juney]

have you ever cleaned the strainer inside the fuel tank?

I haven't! I'm not running the stock petcock, and I know there is a little screen on that. I'd there something else I should look into?

[1hp]

most petcocks have a strainer inside tank.

[ohiodrz400sm]

Last time you changed the oil was there fuel in it?

 

How long have you owned the bike? Did it ever run right? Jetting doesn't sudden change.

Once you're past the "bad spot" does it run ok near the redline?

 

 

[Juney]

Last time you changed the oil was there fuel in it?

 

How long have you owned the bike? Did it ever run right? Jetting doesn't sudden change.

Once you're past the "bad spot" does it run ok near the redline?

 

 

It didn't look or smell suspicious. I have it a good sniff because I'd read about gas getting in.

 

I've had the bike almost a year. I ended up replacing the cylinder because there was a head gasket leak, she the original one was pretty high mileage.

 

The issue I'm trying to fix existed before any of that, but not the whole time I've had the bike. I know jetting doesn't just 'go bad' unless there is some other issue. I thought maybe my issue was wrapped up in the leaking head gasket, over heating, etc. It doesn't seem to be at this point.

 

The jetting send to be good anyways, as nothing I do changes the issue I'm having, and every other combination of MJ and needle has been noticeably worse. That's why I'm thinking it's not jets (maybe float level? Maybe a clog somewhere, though the problem only happens in mj/needle territory, so idle circuit likely isn't at fault).

 

Before today, it seemed to run fine past 6500 rpms or so. Today it didn't like that much either. I might try to record some video of it tomorrow.

[Stuwy123]

Sounds like a stator to me.  

A fried stator will make your ignition cut out at a certain RPM for a pretty narrow band.  

At speed, it feels like your tapping the brakes, fast and instant loss of power then instantly back to normal.  

If you want to check the stator (takes 30 minutes tops), dump the bike on it's throttle side and pull off the stator side cover.

A fried stator is apparent by the black and charred insulation around the stator.  

If no crispy bits, put it back together and stand the bike back up (let sit for 1/2 hour before starting again).

[Juney]

Cool. I'll try that tomorrow. Is the 30 minutes to let oil seep back around everything again?

Sounds like a stator to me.  

A fried stator will make your ignition cut out at a certain RPM for a pretty narrow band.  

At speed, it feels like your tapping the brakes, fast and instant loss of power then instantly back to normal.  

If you want to check the stator (takes 30 minutes tops), dump the bike on it's throttle side and pull off the stator side cover.

A fried stator is apparent by the black and charred insulation around the stator.  

If no crispy bits, put it back together and stand the bike back up (let sit for 1/2 hour before starting again).

 

[Juney]

Well, I tried a few things. 

 

First off, I remembered I already thought it could be a problem with the tank/petcock. I have a safari tank and petcock in addition to the stock tank currently on the bike. I had tried putting them on a month or tow ago and still had the same problem. It wouldn't be hard to check again or check the screen, so maybe I'll try that.

Before I pulled the side cover off to take a look at the stator, I tried busting out the multimeter and measuring things at the CDI. According to my manual, there should be at least 5.0 Volts across the pickup coil and 1.4 V across the signal coil when cranking the bike. I struggled a little bit to get the electrodes into the connector, but measured a pretty consistent 0.4 V across the pickup and 0.3 across the signal. Either something is wrong with those coils, my multimeter doesn't work right, or I'm not getting a good connection. (I did disconnect the electrodes and try sticking them in again and got the same readings).

I went to pull the stator cover off, but couldn't get it! Am I right in that the only bolts I need to remove are the 7 8mm bolts around the outside? I also tried taking the cover off the starter motor, since I thought there may be some other bolts in there, but one of the screws is stuck and started stripping. I let a friend borrow my impact driver, so I will have to get that back from him and try again.

[ohiodrz400sm]

Well, I tried a few things. 

 

First off, I remembered I already thought it could be a problem with the tank/petcock. I have a safari tank and petcock in addition to the stock tank currently on the bike. I had tried putting them on a month or tow ago and still had the same problem. It wouldn't be hard to check again or check the screen, so maybe I'll try that.

Before I pulled the side cover off to take a look at the stator, I tried busting out the multimeter and measuring things at the CDI. According to my manual, there should be at least 5.0 Volts across the pickup coil and 1.4 V across the signal coil when cranking the bike. I struggled a little bit to get the electrodes into the connector, but measured a pretty consistent 0.4 V across the pickup and 0.3 across the signal. Either something is wrong with those coils, my multimeter doesn't work right, or I'm not getting a good connection. (I did disconnect the electrodes and try sticking them in again and got the same readings).

I went to pull the stator cover off, but couldn't get it! Am I right in that the only bolts I need to remove are the 7 8mm bolts around the outside? I also tried taking the cover off the starter motor, since I thought there may be some other bolts in there, but one of the screws is stuck and started stripping. I let a friend borrow my impact driver, so I will have to get that back from him and try again.

Drill the head off the screw. You will be able to turn the threaded portion out with your fingers. Been there, done that. Replace with socket heads.

 

You are correct, there is 1 bolt behind the starter clutch.

[Stuwy123]

The whole disassembly and re-assembly takes like 30 minutes.  

PS: I totally forgot about the fuel, best to remove the fuel tank before dumping the bike on it's side or it'll pee gas everywhere.

[Rib Eye]

You've probably seen this thread:

 

[Juney]

Alright, stuck bolt dealt with, and the cover is off. I noticed a definite dark spot on the right/upper side in this pic. Also a zip tie crumbled away when I touched it. Would this be what's causing my issue?

The fact that the rest of it looks good might correspond with the fact that the bike runs well except for a band from 5500 to 6500.

Any suggestions on replacements if this is the issue? I was looking at RM stator for $109, Ricky stator for $175 or OEM for $250+. I also saw some on eBay for like $40 but that seems suspiciously low.

Again, any advice is appreciated.

[Stuwy123]

Am currently running a Caltric brand stator for $37 shipped. 7k km on it so far. No issues.  

I can replace it about 4 times before buying an OEM stator will be worthwhile. 

[Juney]

Good to hear!

Am currently running a Caltric brand stator for $37 shipped. 7k km on it so far. No issues.  
I can replace it about 4 times before buying an OEM stator will be worthwhile.