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 Post subject: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 10:55 am 
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Joined: Wed Jul 06, 2011 3:35 pm
Posts: 3
1986 F1B with 20,000k on the dial. I've been experiencing symptoms which include running on 1-cylinder (rear cylinder is cutting out.) It's exhibited this issue in both cold and hot running conditions (40ºF-95ºF). Initial feedback was to replace the ignition pickup wires which are prone to deterioration due to engine oil exposure. While they were a bit tired, the insulation was not cracked, but the wires were upgraded with aircraft grade wire and coated with high temperature epoxy. While this was probably necessary in the long run, it didn’t fix the issue. Fast forward 16 months and most of electrics have been replaced including:
1) keyed ignition switch (modern)
2) on-off rocker switch (NOS)
3) high-low beam switch (modern)
4) coils (Dyna)
5) ignition pickups (NOS)
6) pickup wires (second time)
7) DMC electronic ignition
8) Rectifier

Fuel tank has been drained twice and both carbs were inspected and cleaned. Original vacuum operated petcocks were replaced with newer style gravity feed types. When rear cylinder was cutting out, the situation was replicated on a dyno, and starting fluid was sprayed into the rear carb to see if it might indicate a fuel starvation issue. That didn’t help. Since installing the new electronics, the bike is also charging consistently around 14V with no fluctuation.

When the bike runs on only 1-cylinder it feels like an ignition problem, because it will sometimes sputter back onto both cylinders. It doesn’t happen at any particular time because it happens at low speeds/low RPM’s, in addition to high speed/high RPM’s.

However, when it completely dies it feels like it might be fuel related, because it bogs down to the point of stalling. The only way to keep it running is to give it massive amounts of throttle, which doesn’t always work. When this happens, it will usually start right up after sitting for a few minutes.

Something I have noticed is that the fuel tank seems to be building up a lot of pressure. When I take off the gas cap, it makes a loud sucking noise and emits a light spray of gas. I haven’t tried running it without the check valve which is fairly new. I have had stalling issues on more modern Ducati’s directly related to faulty check valves. However, this is the second check valve in place.

I also experienced a strange incident last weekend while stopping at a gas station. I was about to leave and noticed a loud, high pitch whining noise, which sounded like it was coming from the gas tank area. Oddly enough it sounded like what a modern fuel pump sounds like when it’s failing. It lasted for about 15 seconds and was loud enough for my friend to hear who was standing 10 feet away with his helmet on. I know these aren’t fitted with a fuel pumps but the sound was similar to what I’ve heard on modern bikes with pumps on their way out. At that point, it started up fine and didn’t cause me any grief until I got closer to home. I wondered if the noise was the gas tank straining under excess pressure. That made me begin to think that maybe the vent on the top of the tank might be clogged. I’m also not sure if the stock gas caps have a vent like more modern rubberband bikes.

Lastly, the shop who works on it (who I trust implicity) had gotten feedback that fuel can sometimes vaporize in the rear fuel line because of its proximity to the exhaust. That was rerouted a bit with heat shielding wrapped around it.

That’s all I can think of right at the moment. Any help is greatly appreciated and I apologize to those board member’s who I might have reached out to directly.

Thanks in advance-
Gary Herman
Nyack, NY
Brandx52@optonline.net


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 1:16 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1122
My experience is that the noise when you open the cap is a great clue. You are probably not getting fuel depending on how fast you are riding. So, first, put a simple long tube on the vent and go for another ride. If the problem does no recur you have an answer. I removed the funky plumbing under the tank and used two simple fuel taps (which you must always remember to turn off overnight, or it may drain into the front carb and into the case) and a tube with a check valve. Good luck. MikeV


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 1:37 pm 
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Joined: Fri Oct 15, 2010 12:20 pm
Posts: 1209
Location: Vermont, USA
Hi Gary,
I'm wondering about your fuel tank venting. The sound you described at the gas station, reminds me of the sound my 748 makes when relieving built up tank pressure, which is normal, but never heard that on my F1. You're 100% sure the new vent check valve is pointed the correct way? I would definitely try checking without it. Are you sure there is no crud that got pulled into the tank part of the vent that's blocking it? The fuel lines from the tank to the carbs - do you have a balance cross over tube from one to the other?

Some other thoughts off the top of my head:
Are the new petcocks flowing plenty of fuel (holes big enough)?
Did you install new carb o-rings and gaskets when they were apart?
Carb floats set properly?
And, I've heard the alcohol in our gas can impede flow thru the little round screens at the carb fuel inlets.
Bill


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 3:30 pm 
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Joined: Sun Oct 17, 2010 3:26 am
Posts: 82
Images: 3
My TT does not run well with a SS type tank vent, it runs to lean on it.
Maybe because the SS has a pump and does not mind the underpressure in the tank.
So that could be an issue with your bike,

Jarno


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 4:16 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Same as Jarno said, my TT was starving for fuel with the valve in the vent line.


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 4:23 pm 
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Joined: Wed Jul 06, 2011 3:35 pm
Posts: 3
Gents- I sincerely appreciate the responses.


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 4:51 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1122
When I bought my first F1, in 1996, it would suddenly just stop running after a decent time at a good speed. It acted like it was starving for fuel, or had some electrical gremlin, and then it would shut down. I would sit by the road in consternation, and then it would start up in a few minutes. One time I opened the cap (kinda like looking at a tennis racket when I miss) and heard that rushing sound.

That is when I removed the plumbing under the tank, which was starting to leak anyway. I used the 900SS valve and never had a problem. On my current F1 I have a gaudy dirt bike (yikes) tube with a built-in vent and it works.

Still, this problem could be many things. MikeV


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Wed Jul 11, 2012 10:55 pm 
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Joined: Fri Apr 29, 2011 5:20 pm
Posts: 90
Location: McKenzie, TN
618F1 wrote:
On my current F1 I have a gaudy dirt bike (yikes) tube with a built-in vent and it works.

Still, this problem could be many things. MikeV



Yep, mines racin' red... :lol:

(If I were you, I would try a plain tube on the top tank vent, draped over the front, just to see if it would run normal for a few miles. ;) .)

.


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Thu Jul 12, 2012 2:05 pm 
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Joined: Tue Feb 21, 2012 2:18 pm
Posts: 22
Hi - hope you found a solution but if not you might try one other thing. A couple of years ago my F1 starting dropping the rear cylinder and I suspected fuel starvation straight away. Removed carb drain plug and found very little fuel in the bowl caused by the float needle sticking shut. Float needle appeared OK but was definitely sticking shut (and had been doing so intermittently) even with all that vibration when running. As a cure I carefully bent down a LITTLE the slotted tag on the float (which is captive on the spring loaded pin in the needle) so that when the float was in its bottom position i.e. resting on the float chamber casting, the slotted tag on the float just pulled the needle off its seat. This cured the problem but in the longer term I fitted new needle assemblies. I think my problems may have been down to modern fuel and, hopefully, modern replacement needles are more resistant to ethanol! Hope it helps,
Richie. ;)


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 Post subject: Re: 1986 F1B intermittent one-cylinder and sometimes both
PostPosted: Thu Jul 12, 2012 10:41 pm 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 139
Do what the racers do, use a long piece of hose loop it twice and secure it to the inside of the fairing or to the upper brace for the fairing. The loops will hold fuel that surges out the vent and the tank will breathe so it doesn't pull a vacuum and starve the carbs for fuel.


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