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General Category => Yamaha FJ1100 / FJ1200 Running Problems => Topic started by: chocker on August 01, 2013, 06:30:35 AM

Title: Bike won't accelerate
Post by: chocker on August 01, 2013, 06:30:35 AM
Hi,
I have a 93 FJ and when I'm in 4th gear at about 3000 RPMs doing about 60 - 70 km/hour trying to accelerate it will not go any faster. I pull on the throttle and no more acceleration. To get out of this I downshift then upshift and it works. This has happened to me a few times. It seems to happen when the bike is cold. After that one time it never happens again during the ride. Has anyone else had this problem?

Thanks,
Mark
Title: Re: Bike won't accelerate
Post by: jscgdunn on August 01, 2013, 08:54:58 AM
Be great to hear what other folks think....both of our '92s do this from time to time.  I feel it is related to the complex system used to ensure you do not run out of fuel...the ignition drops down to two cylinders.  Does not seem to matter if the tank is full or not.  After a few seconds it comes back and runs fine.

Jeff
Title: Re: Bike won't accelerate
Post by: ribbert on August 01, 2013, 08:55:41 AM
Quote from: chocker on August 01, 2013, 06:30:35 AM
Hi,
I have a 93 FJ and when I'm in 4th gear at about 3000 RPMs doing about 60 - 70 km/hour trying to accelerate it will not go any faster. I pull on the throttle and no more acceleration. To get out of this I downshift then upshift and it works. This has happened to me a few times. It seems to happen when the bike is cold. After that one time it never happens again during the ride. Has anyone else had this problem?

Thanks,
Mark

There's your problem, you've got to twist it.

Seriously, your not leaving the choke out too long are you? That would sort of be consistent with what you describe.

Noel
Title: Re: Bike won't accelerate
Post by: jscgdunn on August 01, 2013, 09:20:56 AM
Quote from: ribbert on August 01, 2013, 08:55:41 AM
Quote from: chocker on August 01, 2013, 06:30:35 AM
There's your problem, you've got to twist it.

Seriously, your not leaving the choke out too long are you? That would sort of be consistent with what you describe.

Noel

Noel,
Not the choke, for sure, in our case.

Jeff
Title: Re: Bike won't accelerate
Post by: chocker on August 01, 2013, 10:21:38 AM
The choke is off at that point.

Mark
Title: Re: Bike won't accelerate
Post by: andyb on August 01, 2013, 03:17:21 PM
Weird.  Slides getting stuck down?

Title: Re: Bike won't accelerate
Post by: FJmonkey on August 01, 2013, 07:33:57 PM
Quote from: andyb on August 01, 2013, 03:17:21 PM
Weird.  Slides getting stuck down?

I was thinking of the slides not moving freely, then breaking loose and working properly again.
Title: Re: Bike won't accelerate
Post by: RichBaker on August 01, 2013, 07:38:29 PM
Quote from: jscgdunn on August 01, 2013, 08:54:58 AM
Be great to hear what other folks think....both of our '92s do this from time to time.  I feel it is related to the complex system used to ensure you do not run out of fuel...the ignition drops down to two cylinders.  Does not seem to matter if the tank is full or not.  After a few seconds it comes back and runs fine.

Jeff

The ignition does NOT drop 2 cylinders!! I wish people would stop perpetuating this MYTH.....  The fuel pump is shut off, which causes the float bowls to run dry, which signals the rider to switch to reserve.   :dash2:
Title: Re: Bike won't accelerate
Post by: jscgdunn on August 02, 2013, 10:40:19 AM


The ignition does NOT drop 2 cylinders!! I wish people would stop perpetuating this MYTH.....  The fuel pump is shut off, which causes the float bowls to run dry, which signals the rider to switch to reserve.   :dash2:
[/quote]

I stand corrected and better informed...thanks.  I am pretty sure I picked up that nugget on this fourm somewhere.

Jeff
Title: Re: Bike won't accelerate
Post by: Dan Filetti on August 02, 2013, 03:28:32 PM
Quote from: jscgdunn on August 02, 2013, 10:40:19 AM


The ignition does NOT drop 2 cylinders!! I wish people would stop perpetuating this MYTH.....  The fuel pump is shut off, which causes the float bowls to run dry, which signals the rider to switch to reserve.   :dash2:


So, what you're saying, is that the bike drops 2 cylinders to SAVE ON GAS, when it's low -Ahhh  -That clears that up -thanks!

:rofl2:

Dan
Title: Re: Bike won't accelerate
Post by: ribbert on August 02, 2013, 11:32:30 PM
Quote from: RichBaker on August 01, 2013, 07:38:29 PM

The ignition does NOT drop 2 cylinders!! I wish people would stop perpetuating this MYTH.....  The fuel pump is shut off, which causes the float bowls to run dry, which signals the rider to switch to reserve.   :dash2:

I never had occasion to look into this, nor am I interested until mine stops working. But as Rich, and no doubt others know, there is a distinct difference in the symptoms or feel of how electrical vs fuel interruption to a running motor present.
The indication that you need to switch to reserve in entirely consistent with fuel starvation, not electrical interruption. It also explains the short delay and 'progressive' return to full power after switching to reserve, while the carbs refill. If the switch restored power to the coils, restoration of power would be instant, like flicking a light switch, which it's not.

I agree with Rich 100%

Noel
Title: Re: Bike won't accelerate
Post by: Dan Filetti on August 03, 2013, 07:04:15 AM
Noel-  I was poking fun at Rich a bit, -he was so emphatic...  In the event you did not get the subtlety of it...
Title: Re: Bike won't accelerate
Post by: fintip on August 03, 2013, 12:11:38 PM
I've never used my reserve switch, but I had heard this myth in the past.

For the '86-'88, however, do remember that there is no fuel pump, and it is controlled by a solenoid in the petcock--the reason why our petcock is so expensive. (Gives us an extra plug to deal with when reinstalling the tank, as well.)
Title: Re: Bike won't accelerate
Post by: Pat Conlon on August 03, 2013, 12:56:48 PM
All the FJ fuel reserve functions, being either petcock or fuel pump, are over rated. I don't like them.
Title: Re: Bike won't accelerate
Post by: fintip on August 03, 2013, 03:15:53 PM
You know, I'm not really strongly opinionated on them one way or another, though I have read (obviously) many pages worth of acrimony towards them.

But are the reserve solenoids on the '86 petcocks known to fail? And even if they do, does unplugging the sender solve the problem? My impression is just that people don't like nanny-features on their bikes, not that there is anything actually wrong with the features other than unnecessary complication from not doing it via mechanical means like every other bike out there.
Title: Re: Bike won't accelerate
Post by: ribbert on August 03, 2013, 08:56:30 PM
Quote from: Dan Filetti on August 03, 2013, 07:04:15 AM
Noel-  I was poking fun at Rich a bit, -he was so emphatic...  In the event you did not get the subtlety of it...

Dan, the humour was not lost on me. That's why I replied to his original post. My post was entirely unrelated to your comments and not in response to them.

Single posts do not have much impact when challenging the status quo and I thought I would just add my own observations to help debunk this idea about the coils. Most likely though the coil theory will continue to circulate until it is decreed false by a higher authority.

Noel
Title: Re: Bike won't accelerate
Post by: RichBaker on August 05, 2013, 08:35:15 PM
Quote from: Dan Filetti on August 02, 2013, 03:28:32 PM
Quote from: jscgdunn on August 02, 2013, 10:40:19 AM


The ignition does NOT drop 2 cylinders!! I wish people would stop perpetuating this MYTH.....  The fuel pump is shut off, which causes the float bowls to run dry, which signals the rider to switch to reserve.   :dash2:


So, what you're saying, is that the bike drops 2 cylinders to SAVE ON GAS, when it's low -Ahhh  -That clears that up -thanks!

:rofl2:

Dan

I see what you did there......   :drinks:
Title: Re: Bike won't accelerate
Post by: chocker on August 06, 2013, 11:25:25 AM
Hi,
just to be clear. When this happens to me, I do not switch to reserve. As I have said I down shift then upshift and it works again and doesn't happen again during the ride.

Mark
Title: Re: Bike won't accelerate
Post by: fintip on August 06, 2013, 12:38:38 PM
Right, forgot the original point of this thread.

Can you describe more the nature of the feeling the bike gives? I remember a friend's '83 R100RS that needed a top end rebuild would kind of act like this; originally I thought it couldn't pull up to redline in 4th or 5th, but if I slammed the throttle back in third and didn't shift until the revs were high enough, then I could shift up and have access to the top.

It's a symptom of an underpowered bike, I think. Might have low compression. Would fit with hot vs. Cold symptom, as well.
Title: Re: Bike won't accelerate
Post by: Pat Conlon on August 06, 2013, 01:03:13 PM
Hey Mark, I would start with the basics.... adjust your valves, then sync. your carbs, set your idle fuel/air mixture (blip test) then set your idle speed.
See if that helps...
Proper Carb syncing is the most important.

If there is no improvement I think Andy may be on the right track. Definitely Carb related.
Something could be happening with the slides. Sticking? Perforated diaphragms? A blockage in the vacuum circuit?

Your FJ should pull cleanly from any and all RPMS, if not, something's wrong.