Erratic throttle response - looking for a starting point

Hi All,

At the end of a ride the other day, the response to throttle input was jerky on/off for about 1/2 mile, then bogged way down with almost no response and stalled upon stopping. It did restart and I limped home, thankfully not far.

There were no codes thrown on the dash, so I'm at square one. I do have a manual and will dig into diagnostics using it, but thought I would consult here also for thoughts on any likely things to check first. I've read all about the FI system, but have spent my life with carburetors till picking up this gem last fall.

Thanks everyone.
Mike

 

What year is your Bike???

Did it cough and splutter before dying, possibly meaning a fuel issue Or did the engine die instantly, possibly meaning Ignition?

What is the age and state of your battery? Are the battery terminals clean and tight?
Also measure your charging voltage with both hot and cold engine.

Incase the ECM picked up an intermittent fault code, you may want to extract the stored historical codes from the ECM, record any, then clear the memory, this will be handy for future fault detection meaning, only new faults will now be stored.

 

1999. Almost certain it is fuel. Cough and splutter, yes.

Terminals are spotless, and I've checked charging previously but could do so again. Stator and R/R are a few months old.
thanks

 

Was it not long after a fuel fill? my KLX does that nearly every time, as we're buying corn or water now, but rarely 100% fuel.

And my CB-1 dies just like that when the R/R goes kaput. absolutely worth checking the charging system with a good battery and keen eyes.

 

Agree with bmart.
Very easy to get a bad batch of fuel these days, especially in country towns with low volume turnover, and especially since Ethanol crap is everywhere.
See if you can siphon what you can from the tank then try a fresh batch of preferably non Ethanol blended fuel - reassess your bike.

When the fault happens are you Always hearing your Fuel Pump Prime at switch On and the Fi light always goes out after Fuel Prime?
Are there any other strange indications happening with the fault?

NOTE - Honda's logic with fault codes is that when you are riding and the ECM detects an Active Fault, the Fi light will come On and Not flash while the fault is active. Once stationary AND the side stand is lowered the Fi Light will now flash the DTC code. You DON'T want a distracting flashing light while riding a motorcycle, makes good sense.

 

Hm. Not even sure where to get straight gas these days, except for an airfield about 50 miles from here... worth a shot I guess, though never had this problem in 8 months of running E10 fuel.

Yes, prime is audible and light goes out as it should. I've seen the Fi light in action with a MAP sensor issue, and cleared memory previously so would only see new faults. Just no sign of it this time.

I'll get out to see if I can reproduce the issue on a short ride and get any more data.
thanks all

 

https://www.pure-gas.org/ the app sucks worse than the site, but you can see who has it and what octane it is.

 

Ethanol fuel is OK if you manage it. If the bike has been sitting a week or two, the ethanol will saturate with water and then additional water will not be dissipated. It sinks to the bottom of the tank, which will cause starting or poor running.... can be cured with a couple ounces of isopropanol which dissipates water many times what ethanol can. That's the quick fix you can try. Then you'll know if it's something else (not likely).

Try fresh fuel and 3-4 ounces of Seafoam (naptha and Isopropanol) if you're not going to ride for a while......

The other thing is a proper starter valve sync.... the manual is misleading, so here's a read. If done correctly, should run like butter.
https://www.vfrdiscussion.com/index...rter-valves-sync-incorrect-for-last-22-years/

 

Finally got the time to get out again a couple times, and the problem got worse--throttle cutting in and out, pull in the clutch and stall. Usually would restart ok right away and be ok for some time after. The bike finally threw the one-blink MAP sensor code (sensor is only a couple months old, NOS), so I ran the voltage tests at the connector following manual instructions. Almost no voltage in the first combo (pink/ground), no voltage in the others--indicating poor/loose connections at the ECU, according to the manual. Does this indicate likely ECU failure? Not sure what I can try next since I don't have a test pin box to do the last test in the sequence.
Thanks for the help!