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'91 Nighthawk 750 - worth buying?


redkow97

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...pods do look cool though.

 

I'm fine with an airbox.  As someone else said, job 1 is getting the bike running well, and recording all the appropriate settings so that you have a baseline to go back to if other modifications fail in spectacular fashion.

 

Long term, I might experiment with fabricating my own airbox (of the same, or substantially identical volume) that has removable plugs to allow for less pressure and freer flowing intake in warmer temps, but can be plugged up for the winter months.

 

I'm stealing that idea from a guy on ex-500.com.  The EX benefited from a 1" (?) hole in its airbox.  It increased peak horsepower by 4-5% (which isn't much on a 50hp bike, but it's something).  But one guy had the brilliant idea to put a 1" tube coming off the airbox, which allowed him to stick a cork in the end for cold starts.  I believe he leaves it in all winter.

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Yea, I'm curious as to how the talks are going!

Btw are either the Bandit 1200 or ex-500 carbs constant velocity? I'm not trying to be a dick, but just trying to save a bunch of grief. Drilling holes in an airbox disturbs velocity equalization, which is a key airbox property in cv carb circuits. Don't take my word for it - Google yourself sick if that's what it takes.

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Bandit 1200 uses cv carbs. It's all about massaging them. Takes time and work and knowing how to read a plug and listen to a motor and let it tell you how it's running. Gotta dial in the main jet first with some full throttle plug chops, then adjust needle for midrange, then pilot circuit for idle and off idle.

It can be done, just takes time and ability.

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  • 2 weeks later...

FWIW I 100% agree with your order. I did a perfect job avoiding cosmetic work during my rebuild phase, but waited too long to replace the tires. It was easy to go from engine break-in-rides to joy rides, until I went down on a wet, silty on-ramp using those old, hard treads. I have no doubt fresh tires would have prevented my banged-up knee and a confidence set-back.

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Tires aren't even a question for me. The rear is pretty much shot on this thing. The only cosmetic mod I might consider is painting the rims while the wheels are off the bike for the tire change.

I just have to reign myself in and do the necessary work before the fun work.

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Have fun with it. I was just gonna get it in good shape and flip it this spring.

If I don't like it or find it doing more parking than riding, that is plan B. but for $500, I don't mind it taking up space and only being ridden once a week.

I commute 37.5 miles to work, so the hope is that I can use it at least 2-3 times a week for transportation. I just have to figure out how sweaty I'll get on the way in. Gotta change into a suit once I'm at work.

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I'm debating mesh, or attempting to perforate the old field sheer 2-piece leathers I have worn once.

They are ugly, heavy, and snug on me, but I got them for free... A few hours with a leather punch might be very worth the time.

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I am hoping it's not that hard to get running.  To get it running WELL is a different story, but that's how carbs are...

 

The seller reports that it ran 6 months ago before he snapped the throttle cable and started taking the bike apart.  Now he's moving to FL and doesn't have time to complete it before he leaves.

 

At least that's the story. I'm counting on replacing:

 

- throttle cables

- front wheel bearings (the wheels is currently mounted with 1 bearing!  It wasn't ridden that way, but has sat that way)

- spark plugs

- fuel hoses

- fuel filter (i'm betting this will be an addition, and there isn't one stock...)

- air filter

- tires

 

and then a really good carb clean should be about all I need to get it running.  That's the best-case scenario...

 

Worst case, I will hit you up and see what's what.  My mechanical abilities are not all that high, but I've also never failed to complete a job once I worked up the courage to take it on.

 

I need to just bite the bullet and pick up a non-running XR100 motor to take apart and tinker with.  Just learn how it all works, and then apply what I learn to bikes with 3 more cylinders :p

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For the fuel filter, I recommend replacing the one in the tank itself (it's tall and fits into the petcock assembly), and the screen in the petcock. Avoid an inline filter. Honda 4-cylinders can be thirsty at higher RPMs - you don't need more than two filters to block fuel flow and make carb tuning more complicated. You'd get a cruel chuckle out of how regularly guy's running problems are helped by cutting the inline filter out their buddies told them to add.

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what do you consider "higher RPMs?"

We're talking about an oil-cooled bike, so 8500 RPM is redline.

 

I mean at higher throttle positions, when the engine is a-drink'n.  This thread has some context.  If you must install an inline filter, at least make sure gravity is working for you, and you use a bigger one to keep up with 4 bowls refilling at once.  The idea is not to go lean in a cylinder at high speed if the filter can't supply fuel quickly enough.  Some guys experience surges and spend tons of time trying to rejet figuring out why the bike works great in lower RPMs but not at higher ones, only to remove their bling-tastic alloy filter upon the advice of other Nighthawk owners and watch the problem go away.  A few unlucky ones have scorched a jug - the one furthest down the cross-fill line (cylinder #4) has been a favorite.

 

I personally chose to order a replacement main petcock filter and gasket from Partzilla (mine was for the 700 of course).  I know it's expensive - $30 - but in the grand scheme of things, I felt it was better to splurge a little on stock fixes before second-guessing Japanese engineers who did this for a living.

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