Topic: Sucks gas and bogs out at 5500rpm.

[cb550forbes]

It's a little hard on gas. The bike is a 1978 CB550K and i'm only getting 130km to a $17 tank of gas (rounds out to about 16 mile to the gallon). Is this normal? One more question. What would cause my bike to run great at 1/4 throttle up to about 5500 rpm but then bog out horribly and when applying full throttle the same bogging comes around?

- It can't be the carbs because i just had them professionaly redone.
- I was told it was my points and i was told it was my stator.

[Gordon]

- It can't be the carbs because i just had them professionaly redone.

This statement is where I see the biggest problem.  The ONLY way to know they were cleaned and rebuilt correctly is to do it yourself.  This would be far from the first time I've heard of a bike shop screwing up a set of 30 year old carbs.  They just don't have the time or patience required to rebuild and readjust them properly.

[cb550forbes]

Thanks for the input.

My problem about carbs is that i have no clue what I am doing. I know the basics of how carbs work and what everything is and where everyhting is, but i just dont know the specs for synchronizing them and i don't know how to thouroughly clean all the "inards" if you will.

[putnaja1]

Didn't you just say in another post that you were running an aftermarket 4:1 pipe with the baffle removed?  With stock jetting, my guess is that your bike is jetted too lean with that pipe(and no baffle).  Do you have the baffle still?  Try putting it back in, and see if your performance/milage improves..

I have a '77550K, with a Mac 4:1, with stock carb jetting, and baffle installed.  My bike runs good, and I would guess it gets at least 3X 16mpg.

[cb550forbes]

thanks alot. Just Curious what's the top speed of your 77' 550K?

-Yes I have the baffle and i'll try er out and see what happens. Thanks

[putnaja1]

No problem- hopefully that will solve your issue.

So far, I've only been able to man-up for 85mph, but I still have work to do:  I recently bought the bike, and I still need to redo the fork seals, and install the new tires I bought for it.  The back tire is an offbrand Cheng Shin copy (!) that is getting close to bald in the middle, and the front tire is a Dunlap, but both tires are at least 10 years old, and they don't feel 100% balanced either- like they have flat spots on them from sitting.

Anyway- I got up to 85 before I chickened out, but it still had plenty of throttle left.  This is just from cruising around at like 65mph in 5th gear, and just opening the throttle a little more.  I'm positive if I wound out all the gears a bit before shifting, I'd go over 100 is my guess. 

[cb550forbes]

nice...i had my 550 wound out at 185 km/h last summer. but over the winter i bought the Mac 4:1 pipe, Pod airfilters, went down 5 teeth on the back sprocket (34 now) and up 1 tooth on the front (18 now)...so i'm hoping to pull off 210 - 220 km/h hopefully once i get my problem dealt with.

Forbes.

[Gordon]

but over the winter i bought the Mac 4:1 pipe, Pod airfilters, went down 5 teeth on the back sprocket (34 now) and up 1 tooth on the front (18 now)

Generally helps to put that kind of info in the first post when asking questions about a problem. 

[putnaja1]

but over the winter i bought the Mac 4:1 pipe, Pod airfilters, went down 5 teeth on the back sprocket (34 now) and up 1 tooth on the front (18 now)

Generally helps to put that kind of info in the first post when asking questions about a problem.

Oh, definately like Gordon says- now that we know you have pod filters on instead of the airbox, and a 4:1 with no baffle- I gotta say your bike is certainly running too lean!  Best case scenario with lean running is that the motor just doesn't run very well, performance problems, and bad fuel mileage.  Worst case scenario with lean running is burned exhaust valves, holes burned through the pistons, etc.

If you are commited to running the pod filters and want no baffle in your muffler, you're gonna have to have the carbs re-jetted.  In a nutshell, since your engine breathes air easier now, the fuel/air mixture is too lean- too much air.  So, you'll need to re-jet the carbs to provide more fuel, to take you to the proper mixture given the mods you've done.

If it were me, I'd put the stock airbox & filter back on, put the baffle back in, and see how the bike runs/rides with the sprocket change you did.  It might be perfect and you can do a lot of riding- or the sprocket change might make your bike not too comfy in town riding.  My guess is it will be okay, but you'll have to see.  I'd get the sprockets decided on before doing any more tuning of your motor, but that's because I'm impatient, and I just want to ride.  Re-jetting might take a while, and if it's gonna be done professionally it might be expensive too.

But, that's just me- others here (more experienced than me) will probably be able to give you a quick jet recipe to get you in the ballpark with those pod filters and that pipe, and maybe it won't be too difficult or too long to get your machine running right with the upgraded stuff.  It's all up to you.

[TwoTired]

- It can't be the carbs because i just had them professionaly redone.
- I was told it was my points and i was told it was my stator.

The carbs are the fuel delivery vehicle for the engine.  Why, exactly can't it be carb related?

Are your choke plates opening completely?
Is your air filter new or as clean as new?  
Do you have any fuel leaks?
Have you found gas in your oil sump?

Do check your points setting and engine timing.  But, the bike should get 40-50 MPG, assuming your using 5th gear sometimes.
Ignition foibles shouldn't take off more the 10 MPG, provided it still works at all.

Stator issues?  I will tell you not to listen anymore to the person who suggested that.  Advice like that is not worth the saliva to spit on.

How will you learn more about your carbs if you don't get in and poke around a bit?

Your sprocket changes will definately have an impact on fuel mileage.  Stock was 2.17 final ratio, your set up is 1.89.
The taller ratio should give you better mileage.  But, it may not give you better top end speed as the drag at that speed goes up exponentially with speed.  You may not have enough HP to increase top speed.  In fact, you may lose top end due to lost mechanical advantage.

What brand pods?  Did your shop rejet your carbs for the pipe and filters?

Cheers,