Hello, Dennis & Jay, First of all, thanks for responding, Dennis - even if we're not the one with the engine problem, the solution can help all of us. I'm just an amateur and my bad ideas reflect that.
I'd concur that the vent is probably an issue. I have read about, but never tried, using a washer as a shim to let more air into the tank. It may not be sufficient but it's probably easier than opening things up at highway speed. :) Related to the flooding when stopped, what about the float inlet needle? A high-mileage Nighthawk would probably have a little varnish here and there. A little (lot) of Seafoam, plus an italian tune-up, might work. Cheers, Marco Philadelphia, PA On Feb 3, 12:47 am, Dennis Hammerl <[email protected]> wrote: > Ok, OK... now slowly, very slowly, let's look at your problem. Or rather two > problems. And yes, they both can be related. (we'll see that later) First > off, is this a California bike ? The answer makes for a different approach. > The highway deal can be a function of thermal failure of the ignition (it > gets hot..duh) That one is harder to trace out so let's go with a more common > problem (there really are no "common" problems with the late model 750's) I > would suspect that there can be a fuel starvation problem at highway speeds. > Normally it doesn't take very long for a fuel starvation problem to show up > (just a mile or so) if it has a restricted fuel supply. (kinked hose, etc) > Yes, opening the throttle more makes it worse. Now if the tank vent is > obstructed it can take longer to starve the engine. (here's where California > bikes are different) If the fuel supply is inadequate, it can run well at low > speeds and "run out" at higher ones. An inadequate vent > would just make it work longer than if it was blocked completely. So much > for deep thinking. (hey, you have to sometimes) What do you do ? For > starters, leave the tank cap open overnight with the petcock "on" and see if > it starts OK. (I always turn mine off... ) Then report back. In south Florida > it gets hot (whew) and a bike in a garage or shed (I won't do it again) will > cause the tank vapor to expand and force the fuel past the needle valves. See > the relation now ? A blocked / obstructed vent can cause carb flooding and > fuel starvation.(different times, different causes) Opening the cap at > highway speeds is not a great idea but try it and see if it clears up the > running. If you go out for a ride and open the cap before you start it and it > goes whoosh... TaDa ! > This is just a place I'd start to look for your problem. 85K is a ton of > miles and there may something other happening, we'll see. I go with simple > stuff before I dive into the complex. Get back to me with what you find. > Remember that if this isn't "it", that's just something to cross off the list > of possibilities. > > ________________________________ > From: "[email protected]" <[email protected]> > To: [email protected] > Sent: Tue, February 2, 2010 7:37:44 AM > Subject: [Nighthawk Lovers] Carb Issue? > > I'm hoping the experts on this board (and hopefully Dennis H) can give me > some guidance on a problem with my '92 NH750, with over 85K miles. > > On one hand, the engine floods when the bike is parked, leading to hard > starts. Turning off the petcock between rides makes this manageable. > However, now there's another issue. On highway rides, after an hour or so at > 75 > MPH, the bike suddenly starts to lose power as if it's starving for fuel, > surging and suffocating. The more I open the throttle, the worse it gets. But > if > I slow up to 60-65, it recovers and then is fine. Don't know if the problems > are > interrelated, but the local tech doesn't want to do a carb teardown to check > it > out. Says it would be expensive and there's no guarantee he'll find what's > wrong. I love this bike and think it has many more miles to give. > Any help would be appreciated. > > Thanks so much in advance. > > Jay S > South Florida > -- > You received this message because you are subscribed to the Google Groups > "Nighthawk Motorcycle Lovers!" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group > athttp://groups.google.com/group/nighthawk_lovers?hl=en. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
