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Author Topic: How fast should it go?  (Read 1896 times)

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montana550

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How fast should it go?
« on: July 21, 2008, 05:28:46 PM »
OK

I've read a lot of posts here and have heeded much advice.  I have a '77 CB550K.  It has 17,470 miles on it.  I bought it a couple of months ago.  I have replaced the plugs, points condenser, fixed a broken wire from the coil, thoroughly cleaned the carbs, set the dwell, set the timing, and adjusted the valves.  The only thing I'm not sure about in the work I've done so far is setting the adjusting chain.  I loosened the set nut when the bike was at top dead center on cylinder number 1 and the screw did not move.

The bike sounds terrific, and drives like a gem, but it is slow.  I am able to get a top speed of about 70 mph.  This will slow down a little when in fifth gear.

The only problems I can see now are there is an oil leak somewhere on cylinder number one (I will try to get picture tonight) and the idle will sometimes go up or down 400 to 600 rpm  when at idle.

This is the first 4 cylinder bike I have owned.  I'm just not sure how much I can get out of this bike.  I have not checked for carb synch yet or compression.  I know my question is probably premature without compression numbers, but I'm curious as to acceleration and top speed expected.

Thanks to all for the great advice thus far.

Pete
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Offline mlinder

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Re: How fast should it go?
« Reply #1 on: July 21, 2008, 05:31:34 PM »
I've seen a number of 550's do a bit over 100.

Sounds like you have some issues.
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Offline NickC

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Re: How fast should it go?
« Reply #2 on: July 21, 2008, 05:35:15 PM »
I'm trying to figure out why mine isnt going over 40
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Offline TwoTired

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Re: How fast should it go?
« Reply #3 on: July 21, 2008, 05:38:00 PM »
Your speedometer, if stock, should nudge the 100MPH mark in top gear.

Your air filter (if stock) and your Exhaust (if stock) can have some impact on achieving this speed.

A note about all the head pipes being of equal heat might shed light on your speed limit.

You should also count your sprocket teeth as some people are phobic about RPM and gear their bikes up.  This can make the bike lug and not make enough power to reach designed top speed.
Is your chain lubed?

I might also ask if you are holding the brakes on whenever you go faster than 60mph.  ;D

Cheers,



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Lloyd... (SOHC4 #11 Original Mail List)
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montana550

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Re: How fast should it go?
« Reply #4 on: July 21, 2008, 05:46:39 PM »
Well I guess 70 is better than 40.  Maybe I'll quit complaining.

Two Tired,  The exauhst is Kerker 4 into one.  It has a stock air box and filter.  I blew the filter out.  It looks clean, but it is not new (since I've purchased).  I have not lubed the chain.  I will do this tonight.  BTW, thanks for the earlier advice on putting the air box back on to stop the lean condition when I was testing. 

I am also going to pull the plugs again tonight to check condition, will advise in the morning.

Thanks,

Pete

p.s.  What brakes?
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Offline TwoTired

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Re: How fast should it go?
« Reply #5 on: July 21, 2008, 07:43:59 PM »
As a test, you could pull the air filter out and recheck top speed.  The paper filters are only good for one year or so.  Being paper the fibers collapse, trap dirt, and then it begins to behave like partial choke.  Can't really clean them to "as new" performance.


Another thing you can do is a "plug chop" when you reach your top speed.  Then plug deposits will tell you what kind of mixture issues you might have that is limiting you top end.

The Kerker just might need a larger main jet size.  A plug chop should give you info about that.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
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Offline gc8andy

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Re: How fast should it go?
« Reply #6 on: July 21, 2008, 08:50:02 PM »
what is a plug chop?
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martino1972

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Re: How fast should it go?
« Reply #7 on: July 21, 2008, 09:06:25 PM »
plug chop is take out the bike and go full trottle under load,so in your case go 70 mph with the trottle full open.........then while going top speed,pull in the clutch,and right away kill the engine with the kill switch..
then roll to a stop,preferably near your shop,and push the bike to where you want to take the sparkplugs out..
with this method you can see on the plugs how your bike is doing on full trottle..
keep track out of what cylinder the sparkplugs come,and compare the color of the tip with pictures of plugs on this site>>http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
that way you can see if she is lean or rich,if cylinders run equal etc..
then you can post your findings here,include the numbers that match your plugs from the above site,and/or include pictures from each plug,and you will get more detailed advise of what to do..
please be safe when doing the plug chop..
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Offline GammaFlat

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Re: How fast should it go?
« Reply #8 on: July 21, 2008, 09:06:45 PM »
Quote from: montana550 on July 21, 2008, 05:28:46 PM
OK

I am able to get a top speed of about 70 mph. 



Pete,

If you want more than a ton, get a 750 :) 

Ok, that was cheap.  My apologies.

I'm sure that the expertise on this forum will get you some good speed.  For me, a great deal of the enjoyment is working on the ole girl.... so, enjoy yourself.  I will, however, admit that it's hard not to smile when I twist the throttle - I'm glad I have a tinted face shield so people don't have to wonder why I'm grinning so much and I don't have to clean the bugs off my pearlies ;)

But heck, if you're getting good mpg's, you believe it's running well, a hundred or more might not be such a good idear since any mishap at that speed will make you very unhappy (at the least). 

Again, Enjoy!,

John
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Offline CBGhia

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Re: How fast should it go?
« Reply #9 on: July 21, 2008, 09:40:41 PM »
My 550 hasn't been running long, but it will do 100mph haulin' my 220# ass without a problem. 
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Offline neil10

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Re: How fast should it go?
« Reply #10 on: July 22, 2008, 02:07:29 AM »
Test top speed with a friend on car or bike if ok check exhaust heat on alll pipes to seee if hot
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Offline Hush

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Re: How fast should it go?
« Reply #11 on: July 22, 2008, 03:10:32 AM »
It's called the "OUCH" test, touch each pipe near the head after running for a while, you'll understand the ouch part pretty easily. ;D
I did it on my non performing 650 the other day and was surprised to find one cylinder was stone cold dead (plug cap was off) and I thought she was running quite well so it's an easy free check.
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Offline ieism

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Re: How fast should it go?
« Reply #12 on: July 22, 2008, 10:52:24 AM »
Put the bike on the centrestand and check if the wheels rotate easily without much force. You may have a sticky frontbrake (very common on these bikes). Check the rearwheel too.

If it's a K with a chokecable.....make sure the choke closes completely. Check the cable too. A slightly open choke can make the bike lose power in the topgear at full trottle, but you might not notice it so much while driving normally. This happened to me once too.

I have a 550F that is stock exept for the ignition. It does well over 100 miles/hour. This is on the speedo of course....
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Offline cleveland

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Re: How fast should it go?
« Reply #13 on: July 22, 2008, 12:13:15 PM »
Mine has almost hit 100 MPH a bunch of times, but seems to top out at 95 MPH - 98 MPH.  Of course if I was less the 240lbs I think it would do a fine job of hitting 100 MPH.
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montana550

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Re: How fast should it go?
« Reply #14 on: July 22, 2008, 12:14:17 PM »
Well for lunch I did the heat on the pipes test.  Number four has no fire.  I checked for spark.  It is nice and juicy.  I opened the petcock on the bowl, no fuel.  Perhaps the tube running between carbs is plugged.  Yet another piece of the puzzle.  Will I have to remove the connecting tube?  What else might be wrong here?

On another note.  This bike sure runs good on 3 cylinders.  I would have never suspected a down cylinder by the way it runs.  I've been riding this thing to my shop every day.  My big V-Twins have been home lonely in the garage.  What an awesome machine!

Pete
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Offline SKTP

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Re: How fast should it go?
« Reply #15 on: July 22, 2008, 12:23:02 PM »
mt 1978 cb750k hits 85-90mph easily...then feels wobbley....I bet it could go at least 100...but those speed wobbles scare the hell out of me...also, I think my speedo is off...I might be going faster...my Harley friend told me we hit 100...I'm still not sure?

I can hit 60 in 2nd...
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montana550

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Re: How fast should it go?
« Reply #16 on: July 22, 2008, 01:41:07 PM »
WOW!

I pulled the bowl.  The bowl had fuel in it so I was bummed.  Just for kicks I pulled the jet again.  The bottom hole was plugged.  Cleaned it out, reinstalled, it is like a new bike.  It smoked like crazy for a little bit then ran great.  Sounds like a different machine and has plenty of power.  Hit 97 before I got into some traffic.  It doesn't feel too stable and I won't drive it that fast anyway, but I sure appreciate the acceleration.

I just can't say enough about this engine!

Thanks to all who posted.

Now I can work on seeing where the oil is coming from on cylinder no. 1.  It is on the top of the fins and down the front side of the cylinder.

Pete
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martino1972

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Re: How fast should it go?
« Reply #17 on: July 22, 2008, 01:46:19 PM »
probably the float needle is stuck in carb #4..
or the float itself rubs against something there,but thats unlikely..
take #4 carb apart,i woulds say and clean float/needle etc..
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Offline bistromath

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Re: How fast should it go?
« Reply #18 on: July 22, 2008, 01:47:01 PM »
Well I'll answer that one for you. It's coming out of the rocker shaft cover on the left side there, under that big Philips screw. There's a couple of plugs underneath with O-rings on them, and those O-rings are shot. You can replace them pretty cheap. While you're in there, though, take a look and see if the rocker shafts have eaten into the valve cover and ovalled the holes; on the older 550s it is a common problem, fixed by mid-76. Plenty of threads here on that problem.
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