Topic: 550 rpms at speed?

[chadbenson]

So I've recently been able to get my 550 up and running and finally put some miles on her. So to all the 550 guys out there, what's the rpm/powerband like on your bikes? I'm hitting 4800-5000 rpm's running 55-58 and it just feels like the motor is working harder than it should. I'm pretty sure I'm hitting on all 4 cylinders. Maybe I'm just not used to a higher rpm powerband? I let me my dad ride it also and he feels like its winding out too and sorta lacks power (granted he is used to a Honda 1300 twin) Anywho, what's your thoughts fellas?

[bollingball]

Are you sure you are in top gear

[bender01]

My 75 550k rides along about 60 at 5K. Im sure the tach and speedo are off a little though. Can you twist the throtlle and hop to 80 fairly quick? They like to work hard at high rpms! I think.

[Frostyboy]

What sprockets are you running front & rear? I think you'll find the standard gearing is 17/37.
There's a link I've pasted below that started about a 400, but somehow it sorta got hijacked to talk about 550's that maybe of interest to you.

http://forums.sohc4.net/index.php?topic=71098.0
Also
http://forums.sohc4.net/index.php?topic=72962.0

[chadbenson]

i'm running the stock sprockets and yes that's in 5th gear. Again i'm fairly sure it's hitting on all 4 cylinders. I'm going to go on a short ride today, i'll check to see if it's still got it's getty up past 5k! Thanks for the advice guys

[chadbenson]

So I did a short 50 mile ride earlier today and found that i'm hitting around 5,000 rpm at 55 mph and 6,000-6,200 rpm at 65 mph. I asked another 550 guy what he usually hits and he says he is doing 70 mph at 5,000-5,500 rpm's. Could there be a tach/speedo problem between different years or am i really losing that much power somewhere? I'm running stock sprockets (to the best of my knowledge, they are factory set still when i changed the tires) new tires at stock sizes, and stock chain. Could I be losing alot of power from the old sprockets and chain possibly? 

[underachiever]

As far as running high rpms goes, it's all tied to gearing. 55-58mph at 5000 rpms is a product of whatever sprockets you're running. Whether or not you're firing on all cylinders has nothing to do with it.

My bike feels right at home at 5k rpms, which for me is an indicated 70mph in top gear, or about 65-66 actual, running 16/34 gearing and a 110/90-18 tyre. And above 5000rpms right to ((and into)and through ) red is where it really comes alive.

Alas I have no experience as to how it runs or accelerates relative to other bikes, as this is my first. However its get up and go gets up and goes just plenty well for me.

tony

[Stev-o]

You need to confirm the size of both sprockets, pop off your L engine cover and get a visual, count the teeth.

It really sounds like someone changed 'em at some point. [you are not the original owner, right?]

[apex_seeking]

Not sure how much help this is but my stock 550k1 would do 55mph at about 5k. It was explained to me that the reason for this was because the speed limit at this time was 55 and that's not to high of an rpm for the average user and still left plenty of giddy-up if you wanted to mash on it.

I felt like the bike wanted another gear when I was cruising at highway speeds. The PO gave me a set of sprockets(not sure what size) that he never got around to installing and they really changed the way it acted on the road. Now my revs are a bit lower when cruising and I have less power out of the box but again, I don't have the feeling that I need to up shift all the time I'm driving on the highway.

[Gordon]

You need to confirm the size of both sprockets, pop off your L engine cover and get a visual, count the teeth.

It really sounds like someone changed 'em at some point. [you are not the original owner, right?]

+1

Assuming or guessing won't do you any good.

Stock sprockets for the 550 are 17 front 37 rear.  

[Stev-o]

It was explained to me that the reason for this was because the speed limit at this time was 55 and that's not to high of an rpm for the average user and still left plenty of giddy-up if you wanted to mash on it.

Someone is feeding you a line of BS!

If Honda built bikes to speed limits, why do sport bikes top out at 150+ MPH?!!?

[crazypj]

It's not really pulling at 5,000rpm.
Redline is 9,300 but it should easily hit 10,500~11,000rpm, depending on condition of points. (points 'bounce' at lower rpm when they need changing, act as a rev limiter)
It will easily hit 13,500rpm with a cam, exhaust and with electronic ignition
 It aint a Harley, you won't break it, run it up to at least 8,500rpm, much nicer bike
 

[chadbenson]

LOL! "It's not a harley" I guess maybe having to rev high is a perception thing i'm not used to yet. So far i've heard of dudes that say it will go 70mph at 5k rpms. And yet another who says his goes 55mph at 5k rpms. The bike seems to run fine other than a perceived "high revs" to go 55 on country highways. Btw, i have a 76 550k. I still need to check and make sure that it's running the 17/37 sprocket setup. Thanks again for all the advice! 550 guys feel free to chip in your observations/opinions/experiences.

[TwoTired]

Stock bike
MPH/1000, top gear = 12.24

70/12.24 = 5.7  (x1000 = 5700 RPM)
60/12.24 = 4.9  (x1000 = 4900 RPM)
55/12.24 = 4.5 (x1000 = 4500 RPM)

Harley's and diesels have a pretty low red line on the tach (if they have a tach).
The SOHC4 does not have a low red line, which is why they need a tach.

The 550 doesn't work hard until over 5000 RPM.  That's why the transmission is your friend.  If you want to scoot don't just twist the throttle, downshift a gear or three and twist the throttle.  It'll do 40-50mph in first gear, and 0-50mph in 4.5 sec.  0-90 in 13.9 sec.

Any RPM below the red zone is normal operating range.  The fun zone is just below the red zone.

Cheers,

[apex_seeking]

It was explained to me that the reason for this was because the speed limit at this time was 55 and that's not to high of an rpm for the average user and still left plenty of giddy-up if you wanted to mash on it.

Someone is feeding you a line of BS!

If Honda built bikes to speed limits, why do sport bikes top out at 150+ MPH?!!?

You need to look at the purpose of the bike. Honda knows that the person buying a sport bike is buying it to drive fast. They also figured that a 550 sold in 76' was probably going to to be driven at road speeds by commuters, not race built machines. Its not an uncommon practice by car manufacturers to gear a car to have its shift points at 60mph so it limits the time the car shifts and makes the 0-60 time look better. Doing this sometimes sacrifices gearing on the top end, but if the numbers look good for the media and the consumers, then that's fine with the manufacturer.

[crazypj]

Stock bike
MPH/1000, top gear = 12.24

70/12.24 = 5.7  (x1000 = 5700 RPM)
60/12.24 = 4.9  (x1000 = 4900 RPM)
55/12.24 = 4.5 (x1000 = 4500 RPM)

Any RPM below the red zone is normal operating range.  The fun zone is just below the red zone.

Cheers,

 Mine was a bit modded, geared for 70mph @ 5,400rpm.
 Wouldn't go over 127mph, bad aerodynamics 

[chadbenson]

So i've verified that I am running the stock sprockets 17/37. I'm going to replace the chain and everything but first have to take care of the common left side leaks. I'm thinking of going down to a 35t in the rear. I definitely want the bike to have lower revs at highway speeds. The bike always felt frantic at 65 because it was pushing the rpm's really hard. I've come to understand that yes that these motors like to rev but my 550 feels like it's working far to hard to maintain 55-65. I've read that other 550 guys can run 70mph at 5200 rpms. My bike doesn't even get close to that! It does 55-58 mph at 5200 rpms. I'm sorta clueless as to what's up with my bike. I've done all the basic stuff, new plugs, stock airbox with new filter, valve clearances, chain adjustment.....however my old mufflers are definitely internallly in rough shape. Could a lack of back pressure really be causing performance problems? What about the carb needles? I've got the carbs set to factory. The bike starts and runs fairly well it just doesn't have any top end. It struggles to keep up with my other biker friends and cars alike.

Sorta clueless at this point.

[crazypj]

Run it up to redline through the gears.
 Cruising at 5,200 rpm means you will have to change down twice to accelerate when passing.
 My 550 would do 82mph in second gear, (at 13,500rpm  )
 If you really can't live with 'high' rpm, you really would be better off selling it and buying a twin

[dave500]

tuning isnt your problem as far as your question goes,your not losing power somewhere in this respect,even if the engine ran on one cylinder the rpm at that speed would be the same,i think both speedo and tacho speak with forked tonque?have you got a buddy you can pace and check road speed with?,id try that first,my 500 seems to be revving on the highway,thats what they do,its an early 70s engine and they are/were quick off the mark in the day,itll feel more revvy at those speeds if the carb sync is off.,do a full tune from the ignition up,sync or get the carbs synced,or just get used to it.,just out of interest i tried a 37 spocket on my 500,it should be a 34,,it was like i lost 5th gear,truly,,it went well but lost any high speed cruise mode.

[Stev-o]

Your speedo is not accurate, it is off by approx 10%.

[underachiever]

So i've verified that I am running the stock sprockets 17/37. I'm going to replace the chain and everything but first have to take care of the common left side leaks. I'm thinking of going down to a 35t in the rear. I definitely want the bike to have lower revs at highway speeds. The bike always felt frantic at 65 because it was pushing the rpm's really hard. I've come to understand that yes that these motors like to rev but my 550 feels like it's working far to hard to maintain 55-65. I've read that other 550 guys can run 70mph at 5200 rpms. My bike doesn't even get close to that! It does 55-58 mph at 5200 rpms. I'm sorta clueless as to what's up with my bike. I've done all the basic stuff, new plugs, stock airbox with new filter, valve clearances, chain adjustment.....however my old mufflers are definitely internallly in rough shape. Could a lack of back pressure really be causing performance problems? What about the carb needles? I've got the carbs set to factory. The bike starts and runs fairly well it just doesn't have any top end. It struggles to keep up with my other biker friends and cars alike.

Sorta clueless at this point.

Stock 550 gearing equals stock 550 rpm levels at a given speed.

Running 55mph or 70mph at a given RPM level will ONLY be affected by gearing - smaller rear (34,35) = going faster at the same rpm's, bigger rear(37,38)= going slower at the same rpm's. NOTHING else will affect this.

If you're using the stock airbox with a clean stock air filter and your carbs are CLEAN, then there's no reason to think you need to adjust the needles.

If it's not running well then it may not want to rev high (how are points, condensers and timing? is your advancer working properly?). If it won't rev high, changing sprockets to lower the rpm's will likely make riding it worse, as the engine will have less leverage over the wheel.

Try this, find some quiet open space(be sensible) and from your usual second gear shift give that throttle a good twist and hold it right to redline before shifting into third. It should accelerate smartly, evenly and reasonably quickly. If it doesn't, there's something wrong with how it's running.

Otherwise enjoy it, it rides like a 550. Change the gearing if you wish. I run 16/34 because I got them new and cheap at a swap meet. 4500-6500 rpm's on the highway depending on traffic speed.

If you want 3000 rpm's on the highway, you need a different bike.

tony

[tango911]

good luck bro

[OldSchool_IsCool]

Your crank is mechanically connected to the rear wheel via chains and sprockets and gears and the clutch.  This means that there is a fixed ratio between engine speed and tire speed.  If your sprockets and tire are indeed stock, then the gear ratio that TwoTired posted should hold true.  A 550 engine turning at 5700 RPM in 5th gear will turn the rear wheel at 70MPH.  It doesn't matter if the engine is tuned or rough, its a function of RPM, not power.

That being said, there are a few points where a divergence from the fixed ratio may occur.  As discussed, the 17/35 sprocket setup is one variable, but you have already verified it is stock.  Tire size and pressure can make a difference.  What size tire do you have on the back and is it at proper pressure?  Next, there is the possibility that your clutch is slipping.  If it were slipping this badly though, you clutch would have burned up long ago.  

I suspect you may have an inaccurate speedo or tach.  Some higher-end timing lights or dwell meters will display your engine RPM.  You can use this to check the accuracy of your tach.  

As for speed, the police department will measure your speed for you, even write it down on a slip of paper.  They tend to hide though, so you have to find where they have their speed checking service set up and blow by them well above posted speeds.  There is a fee for this service, however  

Another method would be to find a measured stretch of road, hold you speed constant and time yourself.  You could also set up a GPS that can display speed and see how it compares to your speedo.

[chadbenson]

Your crank is mechanically connected to the rear wheel via chains and sprockets and gears and the clutch.  This means that there is a fixed ratio between engine speed and tire speed.  If your sprockets and tire are indeed stock, then the gear ratio that TwoTired posted should hold true.  A 550 engine turning at 5700 RPM in 5th gear will turn the rear wheel at 70MPH. IT doesn't matter if the engine is tuned or rough, its a function of RPM, not power.

Thing is mine doesn't run 70mph at 5700 rpms, according to the speedo and tach mine does about 60-62mph at 5700 rpms? I'll definitely try and do the gps speed thing to check what i'm actually running.

Your speedo is not accurate, it is off by approx 10%.

inaccurate down or up? Because I run a indicated 55mph at 5k rpms. If it is off down then I'm actually going 49.5 at 5k rpms, or off up 60.5 at 5k rpms.
I did the math and with a top gearing of 12.24 like TT said, that means ... 12.24 x 5.0 (x1000 rpms) = 61.2 mph 
which is pretty darn close to the 10% error margin.

[Stev-o]

Yes, slower than indicated.