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87 ninja 750 problems

12K views 13 replies 5 participants last post by  killerpooch 
#1 · (Edited)
I've had this bike for 4 years now, and since the day I've owned it, every time i go for a ride longer than 30-40 minutes, the thing sounds as if its choking or its clogged. it first becomes noticeable when i'm taking off in 1st gear, if i lightly roll on it, the thing feels like its hesitating, but if i half throttle it or more, the thing will scream, but eventually after that, every rpm will sound the same, clogged to all hell. This bike has been piped, and the previous owner put on 4 K&N air filters. So, 3 years ago i got 2 new floats do to liquid being inside them.the bike ran good for longer now but still same problem. I realized the gas line from the tank to the carbs (i think. the bikes at the shop and i forget :X) was really short and was getting kinked. so i lengthend it and put a fuel filter in their in case of dirt or rust coming from the gas tank. Then i took the carbs completely apart and made sure all of the little holes in my jets were clean as a whistle, and to make sure my floats are working properly. I did notice that on carbs 1 and 2 on the left side of the bike are spitting a wee bit of gas into the filters.

Does anyone have any clues or ideas as to what might be happening?

Currently my bikes carbs are being synchronized and my uncle is looking it over very carefully for any other issues. AND i replaced those K&N's with some UNI air filters.
Also this bike used to have 2 exhausts , but one of the previous owners converted it to a single yoshi exhaust.

Your help is greatly appreciated :smilebig:
 
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#8 ·
The PowerCommander is for FI bikes.

Get a Factory Pro kit, better than the DJ kits.

If the pump wasn't working, it would take a lot less time that 45 minutes beofre it overheated. The way you described the symptoms, it would be a cooling issue.
ya, go to factory pros web site and youll find alot of info on carb tuning there. i like your bike im into those 80's bikes. post some pics id like to see it.
 
#6 ·
So all the places i checked locally and online dont have the water pump or cant get it because its been discontinued. On top if that, while my mechanic was working on a chainsaw, he smelt a funny smoke smell coming from my bike. The key was off and all of my lights were on. Some wire was shorting out and my battery was still connected. so now theres a frickin hole in my electric junction case or fuse box. Luckily he was there to witness the event and stop it before it burnt down his garage. SOOO Im going to try and order a new junction box and find a used water pump at a salvage yard or somethin. Possibly sell the bike before i have to put any more cash into it. TIME to Bite the bullet and buy a new bike with a warranty.
 
#9 ·
also check some specific forums that discuss those bikes. they are becoming collecters bikes. dont sell it, fix it up and be proud to ride a bike that is not not on every corner. ive got an 86 gsxr 1100 and more people talk to me about that bike than my 929 or harley thats for sure. google your bike and youll find lots of info and parts. also try ebay if you havent already and keep current as the auctions change daily. if you rebuild that bike in your spare time as finances allow youll have a sweet ride and no payments or insurance. i may be biased but the first generation sport bikes rock.
 
#11 ·
A thermostat is a crude device and when it fails it fails in the open position; spring wears out. The spring keeps it shut and as the temp rises it opens up. The bike is fully capable of warming up in a matter of minutes and 30 to 45 minutes is way too long; so IMO the thermostat is not the issue.

The pump is a possibilty in that it is not circulating enough coolant, but wouldn't produce the choking issue. It is either way too hot or it's not.

You mention that half throttle and it is better for a little while; that sounds like a fueling issue. Half throttle would use a different jet compraed to low speeds.
 
#12 ·
So I am back, I replaced all of the spark plug caps, which 3 of them were toast. my coils were ok, but i have an extra set with wires hanging around that came with my caps in case i need it. I got the carbs synced and replaced the water pump, which was leaking a little before.

So none of this changed the bogging down at low RPM's problem once its gets a little warm. i did not even get 10 minutes down the road before it started hesitating in FIRST gear, and then once it got a little warmer it kinda started doing it in sencond, but not as much. So all and all its running a little bit worse than before in regards to the hesitation/bogging aspect.

this friggen machine is depressing me.

As for the good news, The response from the throttle is much better . thats about it for good news. It runs great in the higher rpms in all gears, i can feel the difference from the carb sync.

We discovered that it is the alternator making a ticking squeeking noise when i initially twist the throttle ( most obvious when in neutral). So i will go ahead and get a decent used one from the guy i've been getting all of my other parts from.

Could this cause the problem i am having?
Should i just go ahead and replace those coils? My mechanic never tested them when the bike was warm, because we didnt have the plug caps in yet.

Im at my wits end here, im really about ready to sell it as is, and get a new bike with no problems..... thanks again
 
#14 ·
you can put the carbs back on they're fine. the problem is that the air box has been removed and 4 K&N air filters have been installed in its place. you see i own this same bike and it has crank case ventilation that feeds into the airbox to burn unspent gases in the crank case helping fuel economy blah blah blah you get the point. so by removing the airbox the previous owner created a giant vacuum leak. your repair is simple, replace the airbox and buy the correct K&N filter that fits into the stock airbox. i dont know why people always think they're smarter than the team of engineers that design these bike. best of luck
 
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