What Did You Do With Your Nighthawk Today?

[Bob H]

I therefore strongly encourage people to check the air filter frequently, ...These carbs can be incredibly sensitive to incoming airflow.

Yep. Just went for a spirited ride (65 degrees California) and the new air filter made a big difference.

Similar to the video I just posted, I was able to hit redline in 2nd, 3rd, then when I got to the taller gears it was a lot less sluggish. I got off at the next exit, someone was getting a speeding ticket - and I remembered that is one of the reasons I love my Nighthawk rather than some of the stupid fast bikes I have had in the past.

I suppose the least restrictive air intake is a velocity stack, and this video is pretty interesting about rejetting.
The "Motorcycle MD" personally rides a late model NH 750 and is employed as a Honda mechanic. I posted one of his videos on changing the valve cover gasket on page 1 of this thread, I respect his knowledge.
So many youtube videos are of someone doing something for the first time, but this dude knows what he is doing.

[Bob H]

I'd also recommend carb removal, clean, and re-jet. Especially if you have a Cali. bike because the main in it is a 110.

OK I just ordered the same Jet kit you mentioned on previous page with the 115 main jet per their calculator. Getting the pilot jets as well. May not do the tear down until next winter, but wanted to get the parts as you never know who is going out of business. https://carbjetkits.com/honda-jet-kits/honda-750-cc-jet-kits/honda-cb750-nighthawk-1991-2004.html

[Pete in PA]

I'd also recommend carb removal, clean, and re-jet. Especially if you have a Cali. bike because the main in it is a 110.

OK I just ordered the same Jet kit you mentioned on previous page with the 115 main jet per their calculator. Getting the pilot jets as well. May not do the tear down until next winter, but wanted to get the parts as you never know who is going out of business. https://carbjetkits.com/honda-jet-kits/honda-750-cc-jet-kits/honda-cb750-nighthawk-1991-2004.html

Don't wait till next winter, that's a whole season.

I can get the carb. bank out in 1 hour now. Back in a little longer.

You will notice a BIG difference coming from a 110 main.

[Pete in PA]

Started at 3 turns out on pilot screws too rich. Haven't found a way to adjust them with carbs installed.

There may be a knock off, this is the Motion Pro tool

https://www.revzilla.com/motorcycle/motion-pro-90-degree-hex-driver-carb-tool?gclid=Cj0KCQiAorKfBhC0ARIsAHDzslv3AcTZqK5I_6Igzg1z95YgK6CUNsBUDapIkI9q7vKner9GGYwwmIcaAsFXEALw_wcB&sku_id=811334
I haven't used it, but pulling the carbs in and out of those rubber boots would make me buy it.

Have you had a chance to do the sync thing?  I got a Morgan Carbtune.

Well they're VERY proud of this tool!  $75 delivered cheapest I could find.  No knock offs found.
No dimensions given at tip so not sure if even it would work.

If the running bugs me enough I can just partially pull the carbs.

Just loosen clamps, scoot airbox back, and tilt carbs upward in front boots.

[Bob H]

Well they're VERY proud of this tool!  $75 delivered cheapest I could find.  No knock offs found. No dimensions given at tip so not sure if even it would work.

Do an Amazon search for "90 degree driver" the first image below is a $12 tool that is not as compact as the motion pro one, but would likely get the job done.



I personally own this next one, and have not used it on my carbs (they still have the factory caps on the adjusting screws). But there have been several times where it was helpful in tight spaces for various projects. Both have bad reviews for weak gears, not able to take a lot of force - but that doesn't matter for hand held work when you aren't drilling or grinding.


This thing is very "floppy" and if I was doing it again I would buy the first one because it looks like you can stabilize it better. Mine takes standard driver bits, looks like the motion pro one does as well (and the motion pro one comes with some bits anyway, if they are proprietary).

I have a bunch of extensions, and have had instances where I stick a few driver extensions - holders together if I need to reach somewhere. I do a lot of construction work on my house.

[Pete in PA]

I've got the third one in your pics.
WAY to big.

There are oil lines running under #2 and #3 carbs. If there is half an inch between them and the screws it's a lot.

[Bob H]

Gotcha. Well I will run into that as well when I do my jets (on order).
I don't suppose that "Idle drop" adjustment is too critical, if an engine idles OK, because that is the focus on the idle circuit. As long as they aren't clogged, and are consistent within the 4 carbs re: # of turns the same.

If the bike idles OK, it doesn't seem as vital as a vacuum sync.

I tend to get tools even if I don't use them often, when the time comes I may get the Motion Pro one... at least you can visualize it better in the following video. Interesting that it comes with very short bits, to assist with the small space access.

[mollusc]

I wonder if it makes sense when you have the carbs off to stick a small piece of tin plate into the slot of the mixture screws, held in with JB Weld.  That way you could push on the plate instead of trying to get a driver into the slot.

[Pete in PA]

I wonder if it makes sense when you have the carbs off to stick a small piece of tin plate into the slot of the mixture screws, held in with JB Weld.  That way you could push on the plate instead of trying to get a driver into the slot.

I've been trying to come up with a solution.  The bracket that holds the carbs together is also in the way.  If you cut too much away, you lose the rigidity.

Honda REALLY doesn't want you to mess with it.

[Bob H]

I am going to be paying a reasonable fee to watch an in depth video on rebuilding the Nighthawk carbs, which may show what tool the Honda dealer mechanic uses to do that idle drop adjustment (if he does it).

Right now I am watching the "free" course series he has, and I am very impressed with the quality of training so far. I am half way through the course videos https://www.themotorcyclemd.com/

The first of the free videos show how Cody and another guy have their tools arranged, which seemed unrelated to my scene as I don't have 1/4 the quantity of their tools - but I have picked up some tips and tricks along the way that I had not thought of. One of the things was a bent pick tool they use to assist in getting the carbs onto the rubber boots and using silicone spray, which I did not think of when I did mine about 8 years ago. It was a struggle getting 4 carbs onto the rubber boots in somewhat tight space.


Here's the carb one, it is showing a NH 750. I haven't done it yet, so don't know if it goes to the point of setting idle drop after install on bike

https://www.themotorcyclemd.com/inline-four-product-options

[Pete in PA]

https://youtu.be/_4-HdRu5Qfk

This one is great and not $40.🙄😡 Only thing I'd do different is remove choke rod and actuators first, then seperate carbs.

Don't forget JIS screw bits or drivers.

Take pics from all angles of carbs.

Wish we got the UK, AUS, etc. CB750 here.  Triple disc brakes, better shocks,  2 horns, bigger oil cooler, bigger tank, 9500 rpm redline, etc.
Same engine, carbs, HP rating though.

[Pete in PA]

Sounds good.

Pulls great from 3k rpm then harder and harder till rev limiter. I like!

Was that in gears 1-3, or does it pull well in the higher gears as well?

My 750 behaves well in lower gears, but gutless in 4th and 5th unless you wound it out in the lower gears and are at 6,000 or more in the higher gear.
I likely should do the carb mods that you did (the washers were done years ago to raise the needle a bit).

Got out riding again today 65F.  Last day for awhile.

Checked my bike against your higher gear questions.

Stock gearing, I can slow down in 5th to 2k rpm and it picks up decent. by 3k rpm its making more power and is really accelerating.

So in answer, you'll be happy with the richer jetting.

Im probably getting a 1 tooth larger front sprocket to drop rpm a bit.

[Bob H]

Stock gearing, I can slow down in 5th to 2k rpm and it picks up decent. by 3k rpm its making more power and is really accelerating.

Yeah that would be a big change from my stock setup, which "runs fine" with no hesitation anywhere, just gutless in 4th and 5th.
My new 115 jets arrived, and I got the suggested stock idle circuit jets (no change from stock per the calculator, I have stock pipes and air filter). Mine is already running the small washer under the needle, but they sent those as well. I will get to it when I wrap up some commitments around the house.

Im probably getting a 1 tooth larger front sprocket to drop rpm a bit.

Yeah I did that about 8 years ago, changed from 15 to 16 (Sprocket Center). The main reason I did it was to enable 2nd gear to work through the canyons I ride in without having to jump to 3rd unless some wide open sweeping turns.
I wouldn't bother unless you are changing old chain and sprockets anyway - but at that time the price is the same so why not.

I have had much faster bikes before - but just caught myself going 20 over the limit heading home without even thinking about it.
For riding on public roads, these bikes are really all you "need" without being stupid fast.

[Pete in PA]

I'm about to change the rear tire to a 130/90-17. I'll wait to see how much it lowers RPM.

I've had stupid fast bikes in my past also.  The kind where if you whack the throttle open in 2nd they power wheelie.

After you do the jetting your Nighthawk will be faster than it needs to be.

[Bob H]

I'm about to change the rear tire to a 130/90-17. I'll wait to see how much it lowers RPM.

Yeah it is hard to find stock size 140 tires. My last 2 rears were Avon Storm (or Avon Spirit) 150/70ZR17 69W and they work fine.

I bought some Dunlop Mutants and will be putting them on when my current tires wear a bit more.
The rear is 150/60ZR17 which is slightly lower profile. The front is stock size.  I wanted to try these 90% road, 10% dirt because we get a lot of gravel on the roads here and on the rare occasion I have to go across a bit of dirt or gravel road, my street tires are very squirrelly.

Years ago I was running Michelin Pilot Road but they stopped making our sizes - now with the Road 6 they have the exact size rear but the front is a 120 rather than 110.
I messaged Micheline, they said could not recommend that tire unless 3 ½ inch width rim and the NH is 2.75 inch in front.