Topic: 75' cb550 top end questions/potential issues. newbie need help.

[COOKIESandBEER]

I've had my 550 for a year now and its been way too much fun. My only issue aside form a couple minor issues is the bikes top speed. On the highway in the flats she will do 70 mph at 7krpm, and 75mph at 8k and thats about it. And when the road starts to go up(i live in SF) even a little bit, forget about it. what id really like is to be able to hit the 100 mph mark, something that from what I've read isn't unattainable. While i have done some searching on the forums i dont really know what im looking for so I've kind of been shooting in the dark. i Recently had her tuned up and replaced the clutch, so theres that. If theres anything else i should be aware of i would love to learn what it is i should be looking at and what i can do to address the problem, this is my first project and first bike.

oh i almost forgot she's stock except for the 4 into 1 exhaust and a couple of cosmetic changes by the PO.

Id like to appeal to the collective conscious of the forums and hear what the greater minds out there have to say. If you could please help or point me in the right direction it would be much appreciated.

[xsmooth69x]

well take down the back sprocket to like 33 teeth.

the stock gearing is 17/37.

so if you start taking teeth off the back or adding teeth in the front you will achieve a higher top end at the expense of low end speed.

[dave500]

negative,,33 will let the chain foul the carrier and would need to be custom made i would think,running the 34 will be too tall,have a count of the front and rear sprockets and see what you have first,it should do 100 mph.

[xsmooth69x]

negative,,33 will let the chain foul the carrier and would need to be custom made i would think,running the 34 will be too tall,have a count of the front and rear sprockets and see what you have first,it should do 100 mph.

the only reason i said that was maybe i thought it was common

when i bought my bike it came with a 33 tooth sprocket. the whole hub was off another honda motorcycle since the bolt pattern wasent even close to the 37 tooth one

[TwoTired]

List the tune up items you've performed.
How old is the air filter?  (stock type?)

Do all the head pipes get warm/hot, both at idle and with the throttle opened?

Pull all the spark plugs and examine the combustion deposits.  Post pics or describe.

Have you verified spark on all cylinders?

Doe all the carb float bowls fill with gas?  Have you collected the drainage from each one to look for debris?
Does the gas tank have rust/sediment?  Fuel filter clear/clean?

The stock bike does 100 with the stock 17/37 gearing.  It doesn't have enough HP to go faster with taller gearing, unless you are drafting a lead vehicle and riding in the air pocket behind it.

Cheers,

[Greggo]

List the tune up items you've performed.
How old is the air filter?  (stock type?)

Do all the head pipes get warm/hot, both at idle and with the throttle opened?

Pull all the spark plugs and examine the combustion deposits.  Post pics or describe.

Have you verified spark on all cylinders?

Doe all the carb float bowls fill with gas?  Have you collected the drainage from each one to look for debris?
Does the gas tank have rust/sediment?  Fuel filter clear/clean?

The stock bike does 100 with the stock 17/37 gearing.  It doesn't have enough HP to go faster with taller gearing, unless you are drafting a lead vehicle and riding in the air pocket behind it.

Cheers,

+1.  And where the hell in San Francisco do you plan on going 100mph     

[cameron]

+1. I dont know if I ever had the balls to hit 100.. but I break 75 any day of the week.
I only mentally top out.  Too much wind.. death too close..


PS: if TT is being too subtle... you should be doing better than that with a well-tuned stocker. No modification needed.
First bring her up to factory spec, as outlined in the shop manual.. THEN talk mods.

[fastbroshi]

You said 75 @8k and that's about it.  So will it not rev any higher?

[Danno]

 8000 rpm for 75 is not right something else is going on 75 mph on the 550 should be 5500 rpm so  what is the front and rear sprocket it sounds like someone put a 48 tooth rear on your bike with an 17 front the 48 tooth hub off a cb750 will fit right in the trailing arm of the 550 but you need a 37 tooth or 38 tooth rear not 48 which if someone put a rim off a 750 on it... it would be impossible to put the 37 tooth sprocket on

[TwoTired]

I gotta wonder if the clutch is slipping.    Computed top speed for stock sprockets  @ 8000 RPM is over 90 MPH in 5th gear.

[Danno]

I also agree with twotired we need to know more about the general condition of the bike
as it sounds like you have more than one issue going on
 and guys don't goad him into silly things the lowest gear the bike can use without running out of horse is 37 and the biggest to stay in honda spec is 38
 also the bike valves start to float at 9200 rpm in 5th gear but by that rpm low riding it should be about 100mph
check those sprockets sir and check the other things that twotired asked also and then get back with us

[COOKIESandBEER]

WOW! its great to get such an awesome response from you guys, im sory its taken me sooooo long to get back at you. between work and school ive been slammed. ill take a look at some of the things you suggested today and get back to you guys with that info. I did find a 17 tooth front sprocket in my parts box so ill have to see what the PO replaced it with.

Greggo this is why: DRZ 400 SM supermoto super moto jump   , in reality i just want that extra power on highway driving. i go up to petaluma and theres plenty of opportunities on the 101. but i just like knowing i can pass and get out of trouble and frankly, sometimes just keep up with traffic. theres nothing scarier then having the bike redlined and trying to merge when everyone is doing 10-20mph faster than you are. i almost got rear ended just trying to merge off the highway into oakland due to that exact situation.

Fastbroshi: she will redline just fine, she just doesn't want to go any faster. I just dont like to run her up at 9 grand unless i have to.

Danno: i think theres definitely more than one issue going on. i just need to get down to the bottom of what it is, i have electrical issues as well. i just replaced the stator and regulator due to the battery not holding a charge, it now lasts for five days on a charge instead of three, unacceptable. what was next on the list of things to do was replace the coils, they are old and starting to rot. could this be contributing to my power issue perhaps?


TwoTired: last but not least, im going to have to agree with you on the clutch slippage. i did replace the clutch recently but just the friction disks. i still think theres something wrong, would replacing the springs help? Or should i go back in there replace the disks, plates, and springs just to be sure?
the air filter is new i had that replaced when i took her in for a tuneup 3 months ago.  the rest i will have to look into and report back later this afternoon.


thanks again for your awesome replies and patience.

P.S. if any of you are in the bay area and are willing to work for beer and show a new guy the ropes, id be willing to bring a case, tinker, and most importantly learn.

[Greggo]

That video is INSANE!

[TwoTired]

TwoTired: last but not least, im going to have to agree with you on the clutch slippage. i did replace the clutch recently but just the friction disks. i still think theres something wrong, would replacing the springs help? Or should i go back in there replace the disks, plates, and springs just to be sure?

I don't like replacing parts on a guess.
Clutch springs have measurement height. Standard is 36.8mm and the service limit is 35.4mm.
The friction disc service limit is 2.3mm.

Clutches can slip if "energy conserving oil" has been introduced. (or STP)
They can also slip due to poor adjustment.

If the clutch limits the power transferred to the rear wheel, the top end speed will certainly suffer.

Think the bike can make it to Milpitas?

[Duanob]

I think your gearing must be changed from stock. at 75mph I'm humming along @ 6500 rpms.

[COOKIESandBEER]

TwoTired: last but not least, im going to have to agree with you on the clutch slippage. i did replace the clutch recently but just the friction disks. i still think theres something wrong, would replacing the springs help? Or should i go back in there replace the disks, plates, and springs just to be sure?

I don't like replacing parts on a guess.
Clutch springs have measurement height. Standard is 36.8mm and the service limit is 35.4mm.
The friction disc service limit is 2.3mm.

Clutches can slip if "energy conserving oil" has been introduced. (or STP)
They can also slip due to poor adjustment.

If the clutch limits the power transferred to the rear wheel, the top end speed will certainly suffer.

Think the bike can make it to Milpitas?

i got called in for production meeting  yesterday, so i unfortunately didn't have a chance to take a look at the bike. Lame i know, but such is life. i did check the pipes at the head and they all get hot , so theres that.

when i pulled the clutch, i didnt even think to measure the springs. dumb. live an learn, i guess.

as far as oil goes, i put in sae20w-50 castrol 4t motorcycle oil. this decision was made after reading through the oil threads.........

Anyway, i dont see why she couldn't make it down to milpitas. Its more a matter of me strapping on my man pants and braving the highway + california drivers. haha

[TwoTired]

Your present oil should not present a problem.  But, previous oil presence can.
When I got my 74 CB550 in 75 with 1500 miles on it, the PO put STP in the engine.
The clutch slipped. On each oil change it slipped less.  It took about 5 oil changes and 5000 miles of use for it grab and lock as it should.
Still couldn't do wheelies, but it would no longer break sync with the trans using a simple whack of the throttle in the higher gears.

So, here is a test.  Have the engine in the power band 4000-7000 in a higher gear, and whack the throttle suddenly.  Does the engine RPM zoom up noticeably higher than the bike accelerates?  If so, you have a slipping clutch.

It is possible to adjust a good clutch pack poorly, causing it to slip.  Do you have any free play at the clutch lever where there is no tension on the clutch cable?

Don't worry about 9000 RPM operation (under load).  The engine is happy there.  Just keep it below the 9200 Red line.  If I want to scoot, I'll use 9000 RPM as my up shift point...routinely.

I have one CB550 that gets all the pipes hot at idle throttle.  But, above 50-60, a cylinder cuts out and then 70-80 is about as fast as it will go. if I give is plenty of time.  This was due to a failed repair attempt at corroded carbs where the main jet sits.  The JB weld build up, just didn't seal.  I did a shut off, clutch pull in, and coast to stop, finding #3 pipe cooler than the rest on the cylinder which had the corroded carb.

Pipe heat can be related to throttle position.  It is easier to diagnose if a pilot jet isn't working, 'cause then the cool pipe occurs at idle and you can check it without even riding.

Have you done a compression check yet?  Have you drained each carb to see if there are contaminants and all the carbs are getting about he same amount of fuel?

PM me about what day you'd like to make a trip.

Cheers,