Won't rev out... !

G

GGRider01

New member
This is a new and exciting development out of the blue. I'll list the things I have checked or replaced while diagnosing this! It was one day running fine, and the next it is popping and sputtering. Starts and idles great. No jetting changes were made because it was running acceptably.

It is strictly RPM related and not effected by throttle position. After stian's recent saga the first thing I went through was the silencer. It is a TurbineCore 2. Fully disassembled, blew all kinds of trash out of it with a pressure washer. Let dry, new packing.

Ignition:
New plug
KTM and GasGas CDI tried
Stator (OEM) with exciter coil
Metered exciter, pickup, ignition coil, plug cap, HT
Grounds, grounds, grounds!

Exhaust:
New silencer packing
New header/FMF Gnarly (it was on my list/needed one anyway)

Carb/Intake:
Drastic jetting changes with no effect - 165 and 180 main jets.
Thorough cleaning, disassembly and reassembly short of removing needle jet tower. (Peered through it, not quite scientific but it looks :confused:)
Clean/oiled filter
Reeds
Float level checked, adjusted to close prematurely for curiosity's sake, no discernible change.
Adjusted to deliver excess fuel, bike would not start and dumped tons of fuel - invalid test

Engine:
Compression
Powervalve visibly checked - operational.
Inspected only through exhaust port but the piston still has factory machining marks. Looks like new with only a bit of color between the rings and top of piston looks a bit dark brown.
Drained crankcase, no residual oil (this is a first!) :eek: This throws the biggest red flag????


I'm baffled and disgusted. :(

At this point the only bad idea is no idea. I'll try it if you name it.
 
Last edited:
GGRider01 said:
This is a new and exciting development out of the blue. I'll list the things I have checked or replaced while diagnosing this! It was one day running fine, and the next it is popping and sputtering. Starts and idles great. No jetting changes were made because it was running acceptably.

It is strictly RPM related and not effected by throttle position. After stian's recent saga the first thing I went through was the silencer. It is a TurbineCore 2. Fully disassembled, blew all kinds of trash out of it with a pressure washer. Let dry, new packing.

Ignition:
New plug
KTM and GasGas CDI tried
Stator (OEM) with exciter coil
Metered exciter, pickup, ignition coil, plug cap, HT
Grounds, grounds, grounds!

Exhaust:
New silencer packing
New header/FMF Gnarly (it was on my list/needed one anyway)

Carb/Intake:
Drastic jetting changes with no effect - 165 and 180 main jets.
Thorough cleaning, disassembly and reassembly short of removing needle jet tower. (Peered through it, not quite scientific but it looks :confused:)
Clean/oiled filter
Reeds
Float level checked, adjusted to close prematurely for curiosity's sake, no discernible change.
Adjusted to deliver excess fuel, bike would not start and dumped tons of fuel - invalid test

Engine:
Compression
Powervalve visibly checked - operational.
Inspected only through exhaust port but the piston still has factory machining marks. Looks like new with only a bit of color between the rings and top of piston looks a bit dark brown.
Drained crankcase, no residual oil (this is a first!) :eek: This throws the biggest red flag????


I'm baffled and disgusted. :(

At this point the only bad idea is no idea. I'll try it if you name it.
Click to expand...

You didn't mention reed condition.
Are you using a non resistor plug cap? BAD!!

Have you had the barrel off? Did you use thinner Base gaskets? Too high compression can cause this.

The stator coil has a tendency to die, but measure fine, take it off, put it in the oven at 50 degrees and try measuring again... Search for my post on high rpm misfire, been there and it ain't fun!!!
 
From my experience, high compression may limit high rpm overrev but it will not cause a variable misfire from one day to the next. Increasing the compression may require you to shorten the plug gap but you would identify that as soon as you increased the compression.
 
motopsycho87 said:
You didn't mention reed condition.
Are you using a non resistor plug cap? BAD!!

Have you had the barrel off? Did you use thinner Base gaskets? Too high compression can cause this.

The stator coil has a tendency to die, but measure fine, take it off, put it in the oven at 50 degrees and try measuring again... Search for my post on high rpm misfire, been there and it ain't fun!!!
Click to expand...

Reeds are fine. Things on the list have been checked as OK.

I only use BR8EG plugs.

I should also mention, zman, that it is very consistent ever since it began.
 
Yes, I was running a Clarke tank when it began. It had a silly decorative vent cap. I reinstalled the OEM tank and tried that without the cap as well. No inline filter, just the coarse filter built into the petcock. It came out clean when moving it to the other tank. Blew through it fine.

Top end has not been off since winter.

Things on my to do list:
Try a different carb
Try tight plug gap to isolate a voltage issue
Disconnect pv rod and run it hard
???
Retard/advance timing
Inspect top end
 
Does it act exactly the same every time? If you are sure air flow in and out of the engine is good, then I'd say it's an electrical issue.
 
It behaves exactly the same every time. Once I try a known-good carb, I will be 100% sure it is electrical.

Another option is to get a cheap RPM meter. The kind that wrap around the HT lead, and see what it does at high revs.

This is a new stator in the bike,. Not sure what to make of it. I've been through a few, and they usually just take a dump without warning. Is this known behaviour for a failing exciter?

A lot to look forward to this weekend :rolleyes:
 
From the symptoms you describe, I would bet on restricted exhaust flow, power valve, shipping packaging in pipe? free flowing muffler?
Have a close look.

One other quick check, take it out in complete darkness, run it and check coil/plug wire. If the current is going somewhere it shouldn't you'll see it.
 
Zman said:
I bet his left and right testes!!!
Click to expand...

Either way, someone's gonna be short a marble if this is it. Let's hope! Sorry Slapshot ;)

This was one of the first things I checked though :confused:

Can't do anything more this evening but a few more ideas have come to mind. Tomorrow I will run it without the silencer. It has been gone through but who knows. Also bought fresh gas. It could've been bad out of the pump and it smells... weird. 91 ethanol free. Going to recheck the PV assembly.

Alarmingly, the stator cover let loose a small bit of water. Thought it was gas at first, but everything is fine and I still have spark. Need to glob some RTV on it.
Could a wet flywheel cause voltage to leap to it? I know very little about electricity.
 
A wet flywheel should have no effect. A wet stator can be a problem, but usually from corrosion. There is a 6mm threaded hole under the engine that can let water in, you should plug it if you ride in wet conditions. I vented mine to the airbox.

If the powervalve linkage hangs up you won't reach revs under load. I would expect that the engine would still rev up on the stand in neutral. Your idea of a simple rev meter is a good way to find out.
 
It was behaving the same with or without load on the motor.

Anyway, uh.. instead of hiding my shame, I figure some closure would be nice..


Bad gas. :o:o:o:o

In my defense, it ran about a 1/4 tank fine before the symptoms began. Not buying from that Shell station again. No one goes to the ethanol free pump, so a number of things could have happened to it. Really old, water in the holding tanks, etc.

I keep hearing about this threaded hole but never can find it.

At least some things I've been wanting to get done got taken care of.
 
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