1991 Nighthawk 750 problems

[LJTurtle]

Hi,

I'm looking at buying a Nighthawk 750 that I went and test drove today. It has only 3900 miles on it and has been sitting unused for at least the last 8 years. When I rode it, everything was fine for about a half-mile, and then the gas tank started making pinging noises and the bike sputtered a bit. It died at the end of my ride, but it started right back up. What could be causing the sound/power loss? What other problems might stem from a motorcycle sitting for extended periods of time?

My father thought that the carburetor was 'varnished' by sitting with old gasoline in it. Can a mechanic just use a solvent to clean it up, or would something more drastic have to happen? How much would this cost?


And lastly, would you buy a used motorcycle with this problem? The bike is in otherwise wonderful condition for its age. The guy wants $3200, but considering this problem plus the need for new tires, a tune-up, a new brake lever and licensing it I thought $2500 was more reasonable.

Thanks!


~LJ

[Bachstrad37]

Considering it's a 91, $3200 is high for bike - even with the low mileage that it has.

Regarding the sputtering, it's probably old gas along with gummed up carbs. That will happen under even in the best of storage condition. If it's been stored in moist or in direct sunlight, its rubber (all of it) will likely be cracked or worn. That would be my number one concern...the rubber.

If you get another crack at test riding it, have him fuel it up with some fresh gas. If it runs without much sputtering and you decide to purchase the bike, I'd just add some carb cleaner with your gas and see how much it helps from there. If you're somewhat mechanically inclined, cleaning the carb is easy. You just spray the butterflies along with the metal surface surrounding it and then replace the air cleaner housing.

Would I buy such a bike with those symptoms? I would, for $2500.

[LJTurtle]

When you say rubber, do you mean gaskets and the like? The front tire on the bike is shot, cracks everywhere. The rear tire looks to be in good shape though. They are both original however, do I need to replace the rear tire simply because of age?

I could bring some gas with me the next time I go check it out, but how would I get the old gas out? Other than just running it with new gas and seeing if that helps, is there anything else I could do to check the condition of the engine?

Also, how much is reasonable for a general tune-up, and what is involved in it? I'd think that a bike that has gone 15 years without a trip to the shop should have all changeable fluids changed and the chain lubed up, but I know squat so....


~LJ

[asiantay]

Carbs are easy to clean, and yes, you should replace all gaskets/o-rings in the carb assembly.

I would buy two new tires... and if you really had the dough new chains, too.

As for tune ups... inspect all cables, check brakes, change all fluids, new filters (air/oil anything else you might need). If you buy this bike, you should start to learn to do maintenance yourself. Save yourself a pretty penny and also spend some time with your bike to "make it yours."

[NorthernPete]

you could also rip the carbs off and bring them to the shop and get them to put them in the dip tank. shouldnt cost much and if your not mechanically inclined thatd be the way to go.

tires - check them for wear and cracks on the side wall.

fluids - change them.....

cables - lube em or change them.

if its 3200 Canadian, good price....american..bad price . knock him down a bit.

[jacksonc]

I just bought a 92 750 Nighthawk from a used bike dealer that ran just fine but needed a new front tire for $2500 us. On ebay they usually bring $2300-$3500 running depending on the year (91-03) and location. $3200 is too much for a nonrunner IMO but I do love the bike, if you can talk them down on price and clean up the fuel system yourself it still could be an ok deal.

[LJTurtle]

Thanks for all the replies.

No one has really talked about the pinging noise, so I guess that's a normal/minor problem?

If any of the maitenance can be done by someone with no experience, I definitely want to learn how to do it. My dad automatically assumed that it would need to be done by a mechanic, but that's coming from the car perspective where everything is hard to get at.



~LJ

[Bachstrad37]

The pinging is typically a result of low octane gas. Buy a gallon or two of premium and pour it in there with the old stuff. This will dilute it, but will gradually flush out the old stuff. The pinging will eventually go away if it is low octane that's causing it.

Tuneups usually consist of sparkplug change, timing, and sometimes an oilchange. The timing is usually good, so changing the spark plug and oil is a good idea. Don't worry, those two items are eeeeeezzzzzy. If you know how to do that to a car, a bike is even simpler. Make sure you use motorcycle oil, too. Car oil and motorcycle oil are different. Motorcycle oil is a bit more expensive due to additional lubricants used to lubricate the transmission. A car uses separate oils for engine and tranny. Motorcycles share oil with its wet clutch system. For most bikes, it's around $20-$60 depending on the kind of oil you use. Spark plugs are cheap too. Less than $10 to do them all on this bike. Just make sure your spark plug gap is correct.

This bike is simple to work on. Its mechanical design was meant to be easy to work on. If you're interested in learning about motors and how they work, this is a great learning opportunity for you.

[Beach]

The pinging that you describe sounds like bad news. Does it sound like metal balls rattling around in a metal coffee can? If so that is likely a lean condition(carbs are gummed up and the engine is not getting enough fuel) and can do major engine damage very quickly sometimes. If its fixed soon enough after it starts happening, the engine may be OK.

I think 2500 is too much for a bike that is not running good, but it depends on your location. I bought my Hawk for $1000, in good running condition. It had 13,000 mi. and needed a new chain and tires. The front fork seals are blown, but it still rides well. These have air shocks in the front, you may want to check and see if they hold air. There is a good chance they wont, and thats another bargaining tool for you to talk him down on price.

I would try to by it cheap, and just walk away if he wont go for it. Parts are pretty expensive for bikes, and shop labor will cost you even more. I do almost all of my car and bike repair and maint. myself. I just always have since my dad was the same way, he taught me from a very early age. Thanks Dad.

Beach.

[LJTurtle]

I wouldn't say it sounds like a rattle...more like the tank is being shot with a BB gun. The guy was surprised when I showed it to him after a short ride, he clearly hasn't ridden the thing at all in a while.

I was originally planning to try and ride the bike either to a mechanic or home so I could try and fix the problem. Bad idea?



~LJ