Two unusual problems--97 vf7 750----suddenly "won't idle", starter motor "stall"

Greetings,
In my last posts a few months ago, I had a horribly running vfr 750...that was eventually fixed
be me by removing the carb assembly, then carefully dissassembling and cleaning obviously
filthy carb passages. It was really a no brainer..the bike was let to sit for a year with the carbs
full of ethanol/gas. Ok...fine..I fixed it and the bike ran dramaticly better.

The bike then recently sat for a month and then when I rode it it ran on "less than 4 cylinders" until about
5k rpm. That went away after 20 miles. The bike IDLED perfectly and ran well.

Now, suddenly it stalls all the time. To be specific, if I play with that manual rotary adjuster,
I can get the bike to "idle" at 3k (!) rpm. If I turn that adjuster to lower than that...say 2k rpm,
it runs poorly then slowly slows down to a few hiundred RPM and quits. This takes about 8
seconds. Crazy. Why would ity suddenly do this???????

Second "NEW" problem: A lot of the time, now when I press the starter button, the starter motor goes for about 1 secthen "stops" as if it is mechanically jammed. Try it a few more times?..same result. I then
put the bike in second gear and "rock" the bike back and forth. This action seems to "free"
whatever was happening....and the starter turns successfully and it starts. Weird!!
I am thinking it is either:

Poor batttery cable connections
Bad starter RELAY
Bad starter MOTOR
Strange mechanical lockup problem

Any and all ideas welcomed.....I am pretty ghood mechanic and am a a bit "perplexed"!!!

 

ethanol fuel can clog jets quickly, a dirty/rusty fuel tank will clog jets too, and your idle jets most likely need re-cleaning unless the carb mounting boots are leaking air and making a too lean A/F ratio.

starting/stopping problem could be a sign of an impending starter clutch failure, not uncommon on VFR's.

 

Do you think hydro locking could be a possibility?

 

could be but also doubtful. inspect plugs for one much darker than the others to confirm. also find which cylinder sometimes misfires by checking header heat.

 

Thanks very much for your responses......here is an update:

1) Won't idle-----IT FIXED ITSELF...seriously....it sat for a day, I started it and it now idles! (????)
Strange!!! When it was having the problem of not idling and stalling, I tried pulling
the choke "on" in various amounts. Doing that made it immediately stall even quicker...so
I surmised that it was not stalling due to too LITTLE fuel....but TOO MUCH fuel. This is
pretty weird. Bottom line---I have no idea why it stalled below about 3k rpm ( set by
the manual cable/knob) .......and then somehow the problem went away. (!!)

2) Starter "locks up" a lot of the time. More detail....when I hit the starter, it acts fine and sounds
fine for anywhere from 1/2 second to up to 2-3 seconds then acts like it "jams" and stops. After
this happens, I then jam the shifter up to second, pull in the clutch and try to rock the bike
forward and back while "popping" the clutch. SO FAR>>>> this has cleared whatever jam
has happened and the bike starts. Ideas:
1) The trans somehow shifts out of neutral? ( but the
green nuetral light is on..so "no" I think)
2) The bike fires "backwards" sometimes and this locks up the gears (?????)
3) Their is some hard obstruction or hard debris that gets in the gear to gear mesh (???)
4) The starter MOTOR occassionally stops for some reasom as one particular commutator
area is "defective" (??????)
5) There is a defect in the transmission that causes it to lock up even while in nuetral
occasionally. (????)

Suggestions/comments welcomed of course!
-Dave

 

I had a lovely little cbf250 i used to commute on and that suddenly developed idle issues. Drove me mad not knowing. Turned out to be the choke cable had come the plunger at the carb end. Stripped it , cleaned it and reconnected it perfect again.
Sold it shortly afterwards. . . Why do we do that ?

 

Briliant!----I am thinking then that the reason it would not idle is that the choke was "on"...while the choke
handle was in the "OFF" position!! I will check the perhpas "sticky" cable today! Your comment was
veryt helpful..thanks!!!

 

Problem #2 really sounds like the starter clutch is protesting, like Squirrel mentioned above.

How many miles/kilometers on bike? Might point to a starter clutch that is worn.

How old is the battery? I've had somewhat weak batteries (that seemed to crank ok) cause the starter clutch to partially disengage producing a symptom like that. New battery spun it up faster and problem went away.

How old is oil? The starter clutch uses one way rollers that can be funky on old oil. Lower probability on this one, but something to consider.

 

Wow..new crazy sounding events:

1) I wanted to eliminate any possibility of the CURRENT reaching the started motor being low. I first tried
to start it....and the "lock up" happened every time I hit the starter. I tried this multiple times before
noticing I had drained the battery somewhat.

2) I hooked up a charger..charged at 6 amps or so for 3 hours till the charge rate displayed dropped
to about one. Assuming the battery was then charged up....I removed it.

3) I triesdstarting....and immediately got the "lock up" symptom. I then tried it again probably 20 x...no
change. I then tried to "rock" the bike to "free" the "lock up". Didn't work at first.....then suddenly
the starter turned fine..and it started after fiddling a lot with the throttle. I then noticed a crazy thing!
There was a LARGE stream of gasoline spewing out of a very small hole where the input side of the
muffler is!!!!!! I had noticed some gas on the garage floor and assumed it was left over from
me filling the tank with a portable tank.

4) I immediately shut if off.....cleaned some of the gas up....and tried to start it again..BINGO..no
"lock up" symptoms!!!!

5) I repeatedly revved it up....and the stream of liquid gasoline turned into a "mist". Repeated
turn off/start cycles resulted in ZERO "lock up" events.

6) The bike would NOT idle again at anything consistent under about 2.8k RPM. Adding "choke"
immediately killed the engine.

So.....I think I understand why my bike "locked up" during starter motor operation.....AND why it
won't idle!!!!!!!!!!!!! Reason to for both problems? Somehow, gas is being dripped or flowed
into the engine THRU the carbs and actually FILLING some or all of the cylinders! When
this happens, the compression stroke can not compress the gas ( of course) and the "lock up"
symptom occurs. Then, through rocking the bike and slightly rotating the engine, enough
of the liquid gasoline exits the cylinder.....thereby then allowing the starter to turn it normally.
Now....after it is started and running....that same mysterious big gasoline flow still is adding
waaay too much gas.....causiing it to have a super high gas to air ratio,...and causing
it to stall at low speeds. EUREKA!!! ( I THINK )

 

OK so you need to replace the leaking float needle/s. checking sparkplugs (post#4) would have shown a problem and where.

 

yep...thanks

 

Not saying you don't need new float valves, but...

Sometimes when carbs are drained and the float(s) gets completely extended, it can get stuck there. You should always tap on the carb assy with a screwdriver handle (or wood) as they are filling up after being drained. I know you've ridden it and this is probably not your problem, but always try and do this ritual, it will save a future mess.

I've seen it happen MANY times, including in my driveway.

 

Thanks very much..good tips. I had some ideas as to how to solve my problem without
pulling out the entire carb assembly .....may sound crazy... but worth a try I think:

1) Run the engine.
2) Shutoff the tank valve.
3) Run till it stops from starvation.
4) Remove all four carb bowl drain screws.
5) Using a "wire"...poke around inside the bowl cavities,
( thereby possibly dislodging the "stuck" float.)
6) Using "carb cleaner" with it's small red hose, spray
a lot in to each carb.
7) Reassemble...(and cross my fingers that I solved it)
Not much to lose if this works...or not.

 

I would avoid #5. Go ahead and spray them out. Just rap on the carbs as they fill with a handle. You can jump the fuel pump relay to fill the carbs with just the key on.

And no need to run the bowls dry. Just attach a tube to the drain nipples or stuff some rags in the V of the motor and drain them. Don't need to make everything hot while you're working on stuff.

 

Good tips...thanks very much......