If it aint broke, don't fix it. Happens again ? Then we'll chase it.
________________________________ From: "[email protected]" <[email protected]> To: [email protected] Sent: Mon, February 8, 2010 12:29:49 PM Subject: [Nighthawk Lovers] Carb Issue Dennis, You asked for a ride report. On Sunday, I rode for about 5 hours, with long stretches at 75-80 mph. The bike performed just fine, no surging, no suffocating, even though I followed the same route as the time it did so. The only difference was the weather was cooler this time, about in the 50s average all day. Could cooler air lessen the problem of a clogged carb vent or do these things sometime "fix themselves"? Any suggestion for I should try or test next? Thank you, Jay S 92 NH750 South Florida Topic: Carb Issue [email protected] Feb 05 11:14AM -0500 ^ Dennis, Thanks so much for the quick reply and the good and highly detailed advice. As much as getting the steps to take, I appreciate learning the "why" behind something malfunctioning. To answer your queries, first, my bike is not a California model. Second, I tried what you suggested, leaving the bike parked overnight with gas cap open and petcock on, and in fact, it started normally the next morning, no flooding. I also noticed a slight whoosh when opening the gas cap after about a 15-20 minute ride. Both, if I read your note right, are indications of a clogged gas cap vent. If so, what is the fix? And can I do it myself? I have not yet tried a long, high-speed ride but will on Sunday and will report what happens. Thanks again. You are a fantastic asset to this board. Jay S 92 NH750 85K+ miles South Florida Dennis Hammerl <[email protected]> Feb 02 09:47PM -0800 _^_ (mip://01cdae38/default.html#digest_top) 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 Dennis Hammerl <[email protected]> Feb 05 08:00PM -0800 ^ The question of it being a California bike is because they don't vent at the cap. The venting is complex and would make us look into that system and not the cap. In your case the cap seems to be restricted. Replacing the cap is the easiest fix. They are somewhat pricey. The restriction can be many things; crud, swollen gaskets, rust, etc. They aren't meant to be disassembled and as such there are no individual parts for a cap. You can try to find and cure the problem but very often it's a swollen gasket caused by the ethanol content of today's fuels. Let us know how your long ride goes. -- 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. -- 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.
