Topic: Speed - Gearing change for a 1974 550

[CB4EVER]

Dear Honda faithful,
I recently changed the gearing on my 1974 550 to obtain more speed.

The stock combination was 17 x 37, went to a 18 x 34 set up.
At 65 mph the tach is reading 4200 rpm.  Yes,  I know these bikes readline at 10.

My question is, will this gearing change hurt the engine running at a lower rpm at high speed ?
This bike has approx 16K on the speedo, and I mainly use the bike for vintage rides.
Trouble is,  I cannot keep up with the faster Bonnie's, but do not want to give up the 550.

I welcome your responses !
Dave 

[mlinder]

What is it you are trying to do?

THat gearign won't give you a higher top speed. You can't redline in 5th anyway.
How fast are you trying to go? To get going to your top speed (a well tuned stock 550 should hit 105 to 107) you should gear for 10krpm at 107mph.

[mlinder]

Who has the gear ratios and primary ratio for the 550? I made a cursory search, couldn't find them easily.

[Gordon]

If you want a higher top speed you need more horsepower or less weight, not different gearing. 

[mlinder]

Well, that, too, but the peak power on the 550 is at what, 8.5 or 9 grand?
Meaning, if the bike were geared to hit theoretical top speed at 8.5 to 9 grand, he would be in the proper place for gearing and horsepower to hit his bikes top speed. 5th gear aint gonna get you there. 4th gear (on a stock geared bike) will almost certainly net you a higher top speed. Possibly 3rd. Still need to know the primary drive ratio and gear ratios to finger it out.

[mlinder]

OK, 10 grand gives a hypothetical top speed of 127 mph with stock gearing and stock wheels and tires.

Changing the front sprocket to a 16 would put you at 120 mph at 10k, which you won't hit with 50 crank HP. However, it will put you at 107mph at 9k (which you might be able to do with a well tuned 550), which is about where your engine peaks, anyway, if I remember correctly. This will also put you at 5 grand at 60 mph, which is completely acceptable.

How fast are these bonnies going, anyway?

[CB4EVER]

I was expermenting with the gearing for gas mileage and engine RPM reduction reasons
as these motors make a lot of noise at high RPM.

Based upon your replies,  sounds like it would be best to put it back close to stock, since the engine develops peak HP at the higher RPM range.

The bonnies were pulling away from me around 80 MPH, but my reasons were to go a little faster and not work the engine too hard.   

[CB4EVER]

105 mph with the stock  17 x 37 ?

[mlinder]

Yep. I've seen it a couple of times. You'd get to 105 faster and easier with 16 up front.

[TwoTired]

The stock 550 doesn't have enough HP or torque to increase top speed by simply over-gearing it.
Honda matched up the gearing pretty well for performance over the widest range.

Making the gearing as high as you have probably makes it pretty slow off the line from a stop light.  It will be pretty easy to lug the engine, which is bad for rods and main bearings.  Some engines can bend rods by doing this, but the 550 lower end is pretty stout.  And, you can expect more frequent clutch wear out issues.

This engine needs RPM to make HP.  And, you need HP for top speed when the wind resistance is the greatest.

You want to keep up with other old bikes?  Go back to stock sprocket ratios.  If you want torque and HP at a lower RPM get a different engine.  If you don't already like the sound the engine makes above 5000RPM then get the stock or near stock exhaust that is quieter than the after market types.
You want to leave them behind from a standing start, go to a 16 Front/ 37 rear, and don't be afraid of the tach needle at or near the red zone.  I've raised more than a few eyebrows with the 550 even with stock gearing (when matched with same era bikes).

 The Bonnies can twist the throttle and pull away from you at cruise.  They have low end torque and they make their best HP at a lower RPM.   But, if you down shift a gear or two on the 550 you should be able to keep up with them without much problem.  The 550 transmission is your friend and working t is essential for any kind of spirited performance.
You have 4 small cylinders and a short stoke engine. The Bonnies have 2 bigger cylinders and a much longer stroke.  They simply CANNOT hope to match the 550 in RPM that it can do routinely year after year.    You can't play their game their way.

It sounds like you don't like the nature of the 550 motor.  That's a shame, really.  Embrace what it is and what it can do, and it's a pretty fun machine, IMO.

[CB4EVER]

Lloyd,
I was hoping you were going to reply to this thread, as I respect your knowlege of this bike.  The noise is something I will get used to, no worries  just have had low reving bikes in the past, and this is my first hi rev machine. I will change it back to stock or possibly
the 18 x 37.  One tooth up on the countershaft will make too much of a difference ...right ??   I really love to riding this bike through the canyons in So. Cal
If you say it is ok to run it in the higher rpms,  then that is what I will do.
It has a four  into two custom system, where the exhaust tip curves outward 90 degrees.
It looks cool, but makes considerable more noise than stock.  I am trying to get a picture of it on this site, because of it's very unusual, but cool look.
Thank you for all your help !
Dave   

[TwoTired]

the 18 x 37.  One tooth up on the countershaft will make too much of a difference ...right ??   I really love to riding this bike through the canyons in So. Cal
If you say it is ok to run it in the higher rpms,  then that is what I will do.

I've never tried that 18t sprocket on a 550.   I still don't think it will help the top speed, unless you have a particularly powerful 550, or NOS adapted.  I have tried 16t.  And, the Buttocks dyno said it was certainly better for acceleration.  Fine around town and at general speeds below 60-ish. I didn't like it much on the freeway or cruising.   If I was doing mostly drag racing, I'd certainly want that 16.  For general street, I think the 17 is better, IMO.

The shorter stroke keeps the piston speed down with RPMs (compared to a long stroke engine).   The engine was designed for these higher RPMs, and that is why the red line is so high (compared to the Brit twins).  I've never been shy of using the RPM band whenever the whim hit me.  My 74 has over 40000 miles on it since I got it 1975. The valve guide seals are now worn and it makes some oil smoke now after deceleration.  But, they are the original seals from 1974, so I'm not complaining.  I'm not riding as much these days.  But, I see no reason why it still can't be wound to red line when needed, and cruise at 80 all day long.  If it doesn't, then it's broken and needs to be fixed.

I had a 4 into 2 for many years on my 74.  It was put on when I got it, as the originals were smashed along with many other bits on the bike.  I always assumed they were louder than stock, until I finally sprung for a new set of originals.  The originals are only a tiny bit quieter.  

Funny your bike does 4200 @ 65.   If it were me, I'd downshift 3 gears just to pass!  Gotta have more than 5K on the clock to scoot, or get any reasonable throttle response.

FYI: I had a 650 BSA many years ago.  So, I have some idea of the difference in how the brit bikes are operated vs the 550 Honda.  You have to drive the Honda a bit differently.  Do the canyons with 5000 and up on the clock.  The brit bike rider better be pretty good to stay with you.  They can use torque out of the turns.  But, your HP will already be there and it will climb faster.  Expect a lot of left foot and clutch action with the trans.  I gets to be second nature after a while.  And, the engine just won't feel right unless it is making RPM noise.  Even in town I keep it at or above 3500 through traffic.  Power can be an escape.  And with only one gear down, you can get going quickly.

Cheers,

[chippyfive50]

TwoTired said it: "Embrace what it is and what it can do".   I have a 550 and a 750~which was under restoration for the last 1.5 years~ and have done long trips on both.
I had a 35T(from my 500)  on the back for a while then switched to a 37T(stock) which I prefer.
Needless to say, the 550 is primarily my local bike now, and much more "fun". The trips were OK on the 550, just a bit BUZZY as it cruises (as you found out) @ around 4-5K, and all day long if you would like..  (My friends had 750's and 900cc BMW'S)
The 750 is like a Cadillac on the highway, just git you one, and problem solved!

[BobbyR]

TT has given you sage advice. The thing you must learn is understanding and managing your engine for whatever situation you are in. Attempt have Harleys to race me from stoplights and getting onto roads. Their motors as TT said have very good low rpm torque, my 750 has it's torque above 4500 and it gets feroicious at 7K  So, a HD will get a hole shot with those two big pistons, he will need to shift at around 4500, My 750 on the other hand will go to 8K before I shift and walk away from him.
With our overdrive cars we get used to engines turing very slowly at high speeds. It's just a matter pf practice. With practice you will learn your bike.   

[CB4EVER]

I want to thank everybody that contributed to this thread.  My 550 has been converted back to the stock gearing.  I had no idea that these motors could rev so high, and stay together as per their design.  I ride a TLS Suzuki 1000 sport bike w/ a 6 speed, and at 100mph + the engine is not even breathing hard.  That is why I wanted to lower the engine speed on the 550.  I was wrong to say the least.  I will learn how to drive this little beast properly, and enjoy the noise ! 

[tygrant]

im running a 15/37 on my 550 and i love it, i never realy go over 65 around town though so its pretty dam fun when it winds out so quik and you bang through the gears, cept my clutch is still slipin damn it.

[L.A. Nomad........]

A CB550 can keep up with New Bonnies all day. New ones are slow!

Things I would suggest for the Cb550 for a quicker ride:

-UNI replacement foam airbox! Better than the stock paper filter box! Easy drop in swap! Check Ebay!   Gives better flow of air!

-Suspension, new rear shocks and front fork springs(progressive springs)! Sloppy suspension makes you go slow. How can you go fast if your bouncing all over the place?

-New clutch and good tires! Responsive controls and good traction = better take off.!

-New throttle cables, make responsive acceleration easier. Old cables are hard to pull, makes throttle response poor.

-New Brakes: front and rear. The better you can stop the faster you'll be willing to go.

There's lots of guys in the L.A. area with CB550s, Come down to the Motorcycle Swap Meet June 28th. I'm sure you'll meet a few.

P.S. I ride my 550 everyday and agree the stock gearing is the best setup.

[TwoTired]

Uni makes foam pods, and the NU-4055 drop in replacement filter in the stock air box.  I've not had to do any jet changes for the Drop in type.

There is a chart in the FAQ that shows the stock jetting.  They were all #100 main, except the F models which was #98, and the PD style type that were #90.

I bought the Uni cleaner and oiler "kit" many years ago and haven't use it all up yet.