Topic: Highway Cruising

[vermont550]

I'm new to this forum but it seams like a great resource for a rare bread. I have a 74 cb550 with quite a few modifications, none performed by me. The most significant is the swingarm and forks which are both alledgedly from an early 80's nighthawk. The bike's near mint and has more nut than any other honda four i've ridden.

I have no complaints except for highway performance. My question deals with altering the gear ratio for better cruising. I would love to be able to cruise at 75-85 without taxing the engine so much. Could I put in a larger sprocket? Even if this is possible, it would effect every gear, lowering the torque at a given engine speed, right? A modification that would only effect the 5th gear would be great. My thoughts are that even if this is possible, installing an entirely new gear box would be more sensible given the amount of effort such a mod would probably require. So basically I'm wondering what I can do to let my bike cruise on these unpoliced VT highways a little easier, without adverse effects on acceleration through the rest of the gears. Any suggestions, corrections or information would be appriciated.

Thanks alot
Ben

[heffay]

an extra tooth or two on the sprocket in the rear or one down on the front sprocket shouldn't kill your low down torque too much... that's really your only way to go unless you wanna spend a fortune for something that's not worth the time and effort. 

[TwoTired]

The Cb550 was made to run at high RPM's.  It's red line is over 9000 RPM.  And, it will cruise all day at 5000 or higher, no sweat.
If you increase the gearing to reduce the engine RPM at a given speed, you make the engine work harder to attain the speed.  You will actually reduce performance and engine response at cruise.

If the engine sound bothers you, either get a better muffler and/or restore the air induction to the stock components.  They are much quieter than many aftermarket components.  Or, just trade for a bike that cruises at a lower RPM.

Having said that.  Does your modification list include a smaller rear tire?  Does it have a smaller rear sprocket than 37 teeth?  What is your front sprocket size?  Taller ratios here will, of course, reduce acceleration pep.

I know of no gearbox modification components available to change the internal gear ratios.  But, if you have plenty of money, I'm sure you can commission a machinist to cut new transmission components for you. $$$

Bets of luck!

[cb650]

an extra tooth or two on the sprocket in the rear or one down on the front sprocket shouldn't kill your low down torque too much... that's really your only way to go unless you wanna spend a fortune for something that's not worth the time and effort. 

You have this backwards Heffay.   Bigger in front or smaller in rear will lower rpm.



                 Terry

[vermont550]

Thanks for the responses. The 4into1 sounds sweet so I dont mind that at all. I basically just equated 6krpm+ for multiple hours with being bad for the old girl, but from what TwoTierd said she'll take it.

The rear tire is 130/80/17  (Michilin pilot activ). So it is definitely not as tall as a stock tire (right?) I guess that would cause slightly higher engine speeds at a given velocity.

Thanks for the input guys

[Vatch]

an extra tooth or two on the sprocket in the rear or one down on the front sprocket shouldn't kill your low down torque too much... that's really your only way to go unless you wanna spend a fortune for something that's not worth the time and effort. 

You have this backwards Heffay.   Bigger in front or smaller in rear will lower rpm.

                 Terry

Yeah, Terry is right.  Just like a bicycle.

[mrbreeze]

I went from stock 48 tooth rear to 42 and did what you are looking for(less RPM at highway speed) without sacrificing in town rideability.Don't go smaller on the counter sprocket as it will put a strain on the chain!!(I like that.....strain on the chain!!!) They have smaller than 42 on the rear but I don't know how they change the in-town performance. Gotta experiment!!!

[cb650]

Generally I go 1 tooth bigger in front and sometimes 1 size bigger rear tire. Slows engine down some.   



               Terry

[KB02]

Un-policed VT highways, huh? You clearly don't ride around the Burlington area during rush hour .   What part of Vermont are you  from?