Author Topic: CB750 tank mileage (Read 16199 times)

jdubb1977 · « **Reply #25 on:** June 12, 2014, 09:53:27 AM »

Sheesh! Subscribing to this one. I've got a '76 750SS. Stock airbox, with a Kerker pipe (unwrapped baffle inside). I'll have to double check my carb specifics and review the thread. I'm getting 30mpg for mostly around town riding. I do ride it a bit hard (bad habit from my sportbike days), but that seems low in comparison to what most people are getting.

run-tmc · « **Reply #26 on:** June 12, 2014, 10:54:34 AM »

Lucky, it's the OEM tank for the K6, should be about 5 ga. I'm going to attempt to adjust the needle position to the middle setting tonight or tomorrow as Jerry suggested, see if that helps clear things up.

run-tmc · « **Reply #27 on:** June 12, 2014, 10:56:59 AM »

And Jerry, the carb sync was only completed two weeks ago with a vac gauge by an actual mechanic while I hovered nearby and promised not to touch anything. Hopefully, it was a good sync! I'll pull the plugs tonight too and see how they look. I've been told a cardboard color is ideal...

jdubb1977 · « **Reply #28 on:** June 12, 2014, 11:08:12 AM »

On a related note, what are other resistance factors that could affect mpg? i rebuilt my brakes and replaced my drive chain recently, but the bike is still a beast to move around when sitting on it. i know it's heavy, but it's always felt like there's something else that's adding resistance. any thoughts?

Schnell · « **Reply #29 on:** June 12, 2014, 11:13:21 AM »

Quote from: jdubb1977 on June 12, 2014, 11:08:12 AM

On a related note, what are other resistance factors that could affect mpg? i rebuilt my brakes and replaced my drive chain recently, but the bike is still a beast to move around when sitting on it. i know it's heavy, but it's always felt like there's something else that's adding resistance. any thoughts?

On its center stand, do the wheels spin freely when off the ground?

Puntas13 · « **Reply #30 on:** June 12, 2014, 03:20:00 PM »

I'm getting close to 45mpg with mine

That's with:

Cyclex 4-1 with megaphone
Uni pods
Dyna ignition and 5 ohm coils
160 main/42 pilot needle clipped in second to last spot.

jdubb1977 · « **Reply #31 on:** June 12, 2014, 04:00:23 PM »

Good question. The front end does fine. Theres a little resistance from the dual disc setup, but nothing major. The rear seems to be the problem. Definite resistance there. When I had the brake and chain off, the rear wheel spun just fine. With the brake on it was slower, but not bad. Hooked up the chain, and even w/ it having a proper amnt of slack, the wheel probably won't make a full revolution when it's spun. Any ideas on that? I'm guessing it's affecting my mpg, and my ability to go fast.

Schnell · « **Reply #32 on:** June 12, 2014, 05:42:34 PM »

I don't think that the rear wheel not freely rotating a complete turn after being given a spin, is a problem. I don't think mine would either.

BobbyR · « **Reply #33 on:** June 12, 2014, 08:22:04 PM »

I have a K8 with a 5 gallon tank. I have an enlarged prostate so my gas tank empties slower than my internal tank fills. When I have to take a piss I pull into a gas station. I top off one tank and empty the other. Works fine.

Actually, I get below 40 mpg with my habit of accelerating too fast for no reason, being over jetted and the hilly terrain around here. I did use reserve a few times and you can easily do over 15 miles, if you take it easy. If you really have to know how far on reserve you can go. Fill a 2 liter soda bottle with gas and run yourself on reserve till she quits. Pour the gas in and get to a gas station.

Switching to reserve around Town if she starts to sputter is quick. At 75 mph it takes a while to catch. Pull in the clutch, close the throttle for a couple of seconds and she motors on nicely.

evanphi · « **Reply #34 on:** June 13, 2014, 05:39:02 AM »

I was having a similar issue... I think I have it solved, but haven't been able to test yet.

My hard brake pipe was acting like a spring and pushing the piston-pad into the disc. After undoing this, though, I found the pipe was leaking... so I had to order a new one (which two weeks later still has not arrived yet!). Leaky front brake = no riding for me. I hope my pipe comes soon so I can see if this was the issue.

jdubb1977 · « **Reply #35 on:** June 13, 2014, 09:50:38 AM »

Quote from: BobbyR on June 12, 2014, 08:22:04 PM

I have a K8 with a 5 gallon tank. I have an enlarged prostate so my gas tank empties slower than my internal tank fills. When I have to take a piss I pull into a gas station. I top off one tank and empty the other. Works fine.

Ha! Keeps the overall weight regulated, too.

Hon3ybadger · « **Reply #36 on:** July 03, 2014, 01:26:07 PM »

So yesterday I did 100 miles on 3.1 gallons. I can't complain about 32 mpg. Far better than what my car does!

1976 750F SS
Third clip, 105, 40
17 and 48 gearing
1 3/4 turns out

BobbyR · « **Reply #37 on:** July 03, 2014, 01:32:01 PM »

Quote from: Hon3ybadger on July 03, 2014, 01:26:07 PM

So yesterday I did 100 miles on 3.1 gallons. I can't complain about 32 mpg. Far better than what my car does!

1976 750F SS
Third clip, 105, 40
17 and 48 gearing
1 3/4 turns out

I think that is a more realsistic mialge than some that have been claimed on this site.

jdubb1977 · « **Reply #38 on:** July 03, 2014, 01:36:46 PM »

Quote from: Hon3ybadger on July 03, 2014, 01:26:07 PM

So yesterday I did 100 miles on 3.1 gallons. I can't complain about 32 mpg. Far better than what my car does!

1976 750F SS
Third clip, 105, 40
17 and 48 gearing
1 3/4 turns out

exactly the same situation here! same bike, same carb setup, same mileage. glad to know i'm not only one getting low 30's.

flybox1 · « **Reply #39 on:** July 03, 2014, 02:06:26 PM »

On the majority of my fills last summer, I was in the 36-37mpg range
120/40's and a stock airbox. the rest is the same as in my sig.

Don R · « **Reply #40 on:** July 03, 2014, 02:16:38 PM »

I think the F bikes go on reserve sooner than the K's and trap more fuel on the wrong side of the tank when close to empty.
My Sandcast just got 98 miles on 2.1 gallons, that should get me 125-130 before reserve at 3 gallons. 46.7 mpg with 120 jets.

Steve_K · « **Reply #41 on:** July 03, 2014, 02:36:04 PM »

My 73 CB750K gets around 40 + mpg. Don't rev much over 6000 rpms, tho. I refill at around 100 miles and try not to use reserve.
Stock jetting, stock air box with K&N filter. Has stock gearing, but has a 16" rear wheel.
Steve

Hon3ybadger · « **Reply #42 on:** July 04, 2014, 10:22:37 AM »

Quote from: Don R on July 03, 2014, 02:16:38 PM

I think the F bikes go on reserve sooner than the K's and trap more fuel on the wrong side of the tank when close to empty.

This is true. Like what HM said the filter in the petcock on the F bikes blocks the fuel to a certain degree when you get close to reserve causing the bike to stumble. I tried leaning the bike over to the left when it did this and got enough from the right side of the tank to the left to keep riding above reserve.

Schnell · « **Reply #43 on:** July 04, 2014, 11:22:47 AM »

Quote from: Steve_K on July 03, 2014, 02:36:04 PM

My 73 CB750K gets around 40 + mpg.
Steve

Me too. Average 39mpg

run-tmc · « **Reply #44 on:** July 04, 2014, 11:25:55 AM »

I am happy to report that I just finished a 2300 mile trip on my K6 over 10 days with no breakdowns whatsoever. Bike ran beautifully. Mileage was horrible though, averaged 23 mpg! Great times, great roads in BC and WA state, but some further tweaking obviously necessary.

Sent from my iPhone using Tapatalk

PeWe · « **Reply #45 on:** July 04, 2014, 11:54:28 AM »

I remember 0.6L/10km in speeds up to 120km/h driving nice and easy with std engine.
Miles and gallons is not my way of expressing it. US 'wet' gallon is 3.785L
This will give 3.785/0.6=no's of 10km= 63km
63km/1.6093=39.14 Miles/gallon

I noticed less consumption AFTER engine modification, IF I was able to NOT twist the throttle harder....

Tanks are different too if comparing when to switch to reserve. My tank I use now with older petcock runs out of fuel very quick, need to switch on the reserve much earlier than I remeber my K6 tank with different petock on the left side.

AJK · « **Reply #46 on:** July 05, 2014, 03:39:12 AM »

I'm getting an average of 45 mpg (US) on my 750K2. This is a mixture of city and back roads, with probably about 70% of that riding being backroads. My setup is 110 mains with the clip in the 2nd position from the top & stock air box & filter. I have a pamco electronic ignition with my plug gaps set to 0.035". So with more city riding, it would probably drop to about 40 mpg or so i'm guessing, but that would be about its minimum.

Actually on one run, i recorded 51 mpg which was the most i've seen.

On thing that can affect MPG is ignition timing, so make sure that you are firing on the || at full advance. Overly retarded timing drops power substantially and you need to open the throttle more to compensate for lost power (also generating more heat).

Steve_K · « **Reply #47 on:** July 05, 2014, 06:26:19 AM »

A couple a years age I had two 550s. They both pushed the same in the garage with same tires and age. I replace the wheel bearings on one and I was surprised at the ease the new bearings made. I had a friend come over to see if I was full of ####. He was able to tell with in 6 foot of pushing each one. I replaced the bearings in the other one soon after.
These bearings are 40 years old and possible that the grease is worn.
Could help with mileage.
Steve

hman0217 · « **Reply #48 on:** December 03, 2016, 02:56:33 PM »

20 mpg. Yes I wrote that correctly. I ride hard in Nyc but still...20? Rejetted to 1115s with pods and 4-2 mac exhaust. But even then...lets even say I'm a wee bit rich. What gives?

hman0217 · « **Reply #49 on:** December 03, 2016, 03:02:28 PM »

I do have a faulty pin in my front tire that I need to fix and the tire pressure was in the mid 20s (psi) when I checked it today. So maybe that's a tiny bit of it. But even then...

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Author Topic: CB750 tank mileage (Read 16199 times)

AJK