1993 Nighthawk CB750

[Scott Jones]

Does anyone recommend something to put in the fuel tank to help clean the carbs? In stead of pulling the carbs and cleaning them that way. I don't think these carbs have ever been off the bike. I have heard of seafoam but have never tried it. Thanks, Scott Jones.

[Bob H]

It depends how bad the carbs are. No tank-additive will bring back the dead.

I used Seafoam with some success on my NH 750 when I first got it, and it smoothed out a somewhat rough engine that had previously been cleaned by Prior Owner's dealer then stored again for about a year.

[mollusc]

I regularly run Seafoam or B12 Chemtool through all my bikes and yard equipment to keep things clean and help stabilise the fuel.  They will help remove some gunk but as said above, they won't revive carbs that are gummed up or full of lacquer.

[ExTex]

I regularly run Seafoam or B12 Chemtool through all my bikes and yard equipment to keep things clean and help stabilise the fuel.  They will help remove some gunk but as said above, they won't revive carbs that are gummed up or full of lacquer.

I also use Seafoam & B12.  They do help

[Scott Jones]

Thanks guys. The bike runs well but has a little hesitation when the throttle is snapped. Otherwise no problems. I was just thinking I could add something as a preventive maintenance thing. Thanks again.

[mollusc]

How long since the carbs have been syncronised?  How about new plugs and wires?

[Scott Jones]

I put new plugs in last weekend. The wires looked ok. I have not ridden the bike since I put the plugs in. The bike has 26,000 miles on it & they looked like the original plugs. The carbs have never been syncronised that I know of.

[mollusc]

Wires can look okay but replacing them can still give huge benefits.  I was astonished at how much difference it made to mine, and I thought it was running fine.
Maybe see if you can find yourself an old-school bike mechanic who will sync your carbs, or get yourself a gauge/manometer set and try to do it yourself.

[Scott Jones]

I have a gauge set. I might look into replacing the wires. I do have another question. Has anyone had any success removing the baffles in the exhaust? I saw a U-Tube video where this guy drilled out the 4 rivets & pulled out the baffles. Does this change anything with how the engine runs? Does it affect the carbs? Thanks. Scott

[mollusc]

Most Nighthawk exhaust mods don't tend to affect the carbs that much, but removing the baffles completely is probably going to need rejetting to make things run right.  Plus it will be stupidly loud.

[Scott Jones]

Sounded pretty good on U-Tube. LOL  I won't mess with it then.

[McG99]

I bought my 1991 750 from a guy who chopped a bit off the pipes.  I don't know how many baffles were removed with the chopped off portion but I think it sounds good, not too loud but definitely louder than stock(from what I've hear online of stock pipes in videos).  I could measure my pipes if you like and tell you how long they are and how much was cut off(I have two bikes, one is a parts bike(ish) that has stock pipes so I can compare length).
Let me know if you want that info and I can get it to you and possibly  a video so you can hear what mine sound like.  I don't know if chopping the pipes or removing baffles is best.  Like I said mine came chopped.  Removing baffles may be best since technically you could replace the baffles at some point if needed?

[Bob H]

The old forum had an exhaust mod known as the "Tim Hodge" mod, you can see a video of the result here

My exhaust is stock. I have had loud bikes before. In 1976 I had a Kawi Z1 with a kerker that sounded amazing, but I no longer want to wake up the world.

Anyway, I have PDF's of the mod but it seems to have disapeared from the internet, the various other sites that had the mod appear to have gone down.

The old mod started out with this:
This modification was pioneered by mail list member Tim Hodge. Tim became
somewhat of a legend because of his simple modification that opens the exhaust up,
allowing a more mellow sound and some midrange performance improvement. I did the "Hodge mod" on my own Nighthawk several times - experimenting
with different size holes and settled on five 3/8" holes per side (note that on my
funnel though, my innermost hole is partially covered by the baffleplate--I should
have moved this hole away from the end a little more). The beauty of this mod is that
it's nearly invisible from the outside, thus preserving the good looks of the stock
exhaust system.

Basically you drill out rivets visible at the back end of late model 750, pull out a rear plate with vice grips, drill holes in the baffle that you pulled out, and reinstall the back plate.

Personally I would recommend leave it stock, you could butcher a perfectly good exhaust.

[mollusc]

My dump of the old NH forum only includes a link to a defunct 750 forum in regards to the Hodge mod.  I think Hodge dates from the earliest Nighthawk Forum days before the Great Server Crash.
So yeah, I have no precise details but all info points to drilling out the end rivets and removing the cones, then drilling several holes in the central outlet pipe.
I also remember that someone further developed the Hodge mod because a previous owner had completely removed his baffles and the end plates were rusted through.  Apparently standard water pipe flanges can be used instead of the end plates, with water pipe in place of the central outlet pipes.  Drill as desired, and wrap the central pipe with fibreglass insulation in place of baffles.