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Hot Start Woes


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HI All,

 

I think this one has been discussed but I am fresh back from a long ride and need some wisdom on this malady. I just returned from a 5 day 2200 km trip thru Montana and the Kootney Mountains. During the ride it was hot out (85 plus) during which I had severe fuel boiling issues (vapour lock type) after a decent run. The bike would not restart after a hot drive unless I refilled the tank completely. Very little burp when the tank was opened at any time. However, while stranded nowhere near a gas pump I determined that if I undid the fuel return line (it runs from the fuel filtre past the injectors and back to the tank thru a valve on the passenger rear side of the tank) that line would sputter like mad and vent fuel and air for about 10 seconds and then stop. The bike would then start fine. My bike is a 2002 V-11 Le Mans and has an external fuel pump. I am wondering if this valve is some type of one way vent that may not be venting the fuel lines after shut off allowing the system to pressurize and as such is defective. There are two spigots on this valve. The large one takes the fuel return line and the small one has nothing attached to it ? A buddy at the event I attended recommended the wrapping of the fuel lines in aviation type insulation which I will do but is there more going on here than simple heat soaking? Any advice is appreciated. Nicholr

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It may not be "one" thing, but let's start somewhere: groom the fuel line away from the left cylinder. Some shielding material is helpful. If your pump (or even the filter) is mounted there (above the left cylinder), be sure it's pushed as far forward as possible in the clamp.

 

The electric petcocks are rather flinky, and the manual replacement is more reliable.

 

The basic Tune-up with valve adjustment, TPS setting and throttle body balance are also good medicine!

 

Keep us posted, eh?

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The valve you see is the pressure regulator, it sets the injector pressure, about 45 psi I think.

My bike had a section of large hose slipped loosely over the fuel line from petcock to the pump, I suspect this was to shield it from the heat coming off the cylinder head, perhaps to solve a similar issue.

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As mentioned, that "valve" is the fuel pressure regulator. It is not likely the cause of your issue. Heat soak boiling the fuel in the hose and in the pump is more likely. A tune up is always a good thing. When you have trouble starting the bike when hot it is a good idea to make sure your valve clearances are not too tight. But if I was to guess, I would say that the issue would be solved with insulating the fuel pump and line from heat. But I would check the valve clearances, that is easy to do on a Guzzi.

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I recently posted about this same problem. Totally solved it by relocating the pump. I had to delete the air box, go to velocity stacks with K&N filters, and a couple of other mods, but am very happy with the outcome. No amount of heat shield tape will keep you from barbequeing your pump when it is mounted right above the left hand cylinder. What were they thinking! Then the fuel filter is right above that. I am curious about the small vacuum spigot on the pressure limiting device. If vacuum is applied, will it open and let fuel flow? This could solve the air lock after parking a hot bike. Just wondering.

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I recently posted about this same problem. Totally solved it by relocating the pump. I had to delete the air box, go to velocity stacks with K&N filters, and a couple of other mods, but am very happy with the outcome. No amount of heat shield tape will keep you from barbequeing your pump when it is mounted right above the left hand cylinder. What were they thinking! Then the fuel filter is right above that. I am curious about the small vacuum spigot on the pressure limiting device. If vacuum is applied, will it open and let fuel flow? This could solve the air lock after parking a hot bike. Just wondering.

 

 

It would be in your best interest to forget that thing exists...............

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If vacuum is applied, will it open and let fuel flow? This could solve the air lock after parking a hot bike. Just wondering.

I work with pressure regulators all the time. Applying a vacuum will lower the pressure but only by the equivalent of atmospheric pressure say from 45 - 30 psi. Interestingly there are guzzi documents that show the spiggot connected to the inlet manifolds which would lower the fuel (pressure) flow under low throttle not by much though. I think that must have been dropped early on. and if you tried it would throw the map out.

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...If vacuum is applied, will it open and let fuel flow? This could solve the air lock after parking a hot bike....

 

It probably would. The thing is, normaly you don't carry around a piece of vacuum in your pocket, and if you had it then how would you connect the hose to it ;)

 

On my bike the bubbles go out when I turn the key or kill switch on and off for a few times. In most cases they then find their way back into the tank through the left side, the petcock. Anyway, if you hear the pump whine instead of the usual noise it makes it makes no sense to start the engine. Swich on and off until the pump sounds normal and only then go on.

 

Another hint: start the engine WOT when it's so hot that you suffer from vapour lock. It helps to keep the throttle bodies attached to the cylinders ;)

 

Hubert

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I disconnect the line from the petcock to burp it. Then I have no problem. Even if I idle at a traffic light too long in 80 degree plus temps it will start to spit and stumble. I think it may be too lean to begin with. But it;s real sensitive to temperature.

 

I have a manual petcock to install ( one of these days) which should help. If you have the electric petcock there is a good chance it isn't working , but the pump sucks it open anyways, unless you have vapor in the lines.

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I recently posted about this same problem. Totally solved it by relocating the pump. ... No amount of heat shield tape will keep you from barbequeing your pump when it is mounted right above the left hand cylinder. What were they thinking!..

 

Obviously, they had a bit of a rethink on that since on a couple of the "specials" made prior to the move to an in-tank pump, the pump was relocated to under the steering head [Tenni, & iirc, MR? Centauro?] where it could get some cooling air flow... :luigi:

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Obviously, they had a bit of a rethink on that since on a couple of the "specials" made prior to the move to an in-tank pump, the pump was relocated to under the steering head [Tenni, & iirc, MR? Centauro?] where it could get some cooling air flow... :luigi:

can anyone direct me to photos/diagrams of the Tenni set up ?

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On the V11/24/7 list, look up my post "Dreaded vapor lock", and there is a photo of the front mounted pump.

 

anyone have a link to a parts schematic for that model ? i have one for my 2000 V11, not sure what year Tenni that is. would be pretty easy to buy the bracket and hoses , I assume- the pump is probably the same

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  • 3 weeks later...

I lined my fuel lines a month or so back with heat tape in anticipation of the heat this August but today the temps are in the 90's and the lock is there yet again. Burping the line works but I'd like to solve this annoyance.

 

Any idea who carries the manual petcock?

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