Lowering Crusing RPM

CBR Forum Classifieds News Photo Gallery Search Member List Timeslips Contact Sponsors Register Login

Lowering Crusing RPM

Printable Version

CBR Forum >> Past CBR Models >> CBR 1000F "Hurricane" >> Lowering Crusing RPM

Page: [1]

Message

<< Older Topic Newer Topic >>

Lowering Crusing RPM - 9/11/2005 11:19:36 AM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

I want to lower the RPM's, at crusing speed of around 75 mph.
Three reasons for it:

1) Vibration is less on handle bars at my cruising speed.
2) Sometimes I'm shifting, because I think/feels I'm on 5th.gear, when in fact I'm already in 6 gear.
2)When off the throttle, the bike nose dives as it was in 5th gear and slows down fairly quick (very little off throtle rolling distance).

I know solution is: Bigger front sprocket (adding 1 or 2 teeth) or smaller on the rear (1 or 2 teeth less) .
Which one is easier/better/cost less to do????
I know low end will suffer a little, but I don't care.
Thanks for any info.

< Message edited by Red Baron -- 9/11/2005 11:21:32 AM >

Post #: 1

RE: Lowering Crusing RPM - 9/11/2005 12:14:52 PM

rEdLyNeR

Posts: 244
Joined: 1/9/2005
From: Decatur,IL
Status: offline

Rear would be easier to do IMHO. Tha way you dont have to remove any covers to get the job done. You will spend a little more on the sprocket maybe, but it beats tearing down fairings, covers, etc. Just my $.02

_____________________________

STEP UP OR STEP OUT!!!!!!

1993 CBR 1000F

Shane Workman

www.onedownfiveup.com

(in reply to Red Baron)

Post #: 2

RE: Lowering Crusing RPM - 9/11/2005 12:51:51 PM

Logan

Posts: 77
Joined: 4/16/2005
Status: offline

I would go bigger on the front, makes the chain have less stress going around the smaller sprocket. Besides what's the difference between taking off the rear wheel and moving a litle fairing around?

(in reply to rEdLyNeR)

Post #: 3

RE: Lowering Crusing RPM - 9/11/2005 1:07:28 PM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

Thanks for the input.
Now I need a tie breaker.
Last question, would I need to replace the chain or the chain adjustment bolts are enough???

(in reply to Logan)

Post #: 4

RE: Lowering Crusing RPM - 9/11/2005 2:17:22 PM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

I did a search and found, that it would be better to do the front sprocket.
The reasons are:
1) Less stress and wear on the chain
2) Eliminates the need of a new chain, since the rear circumference by being bigger would most likely require a new chain
3) The rear sprocket has a factory damper, that might not fit or be compatible with the "new" none OEM. (This might not be true, since I checked the service manual and don't see why not)
Thanks for the input anyways

Great web site for chains and sprockets.

http://www.sprocketspecialists2.com/Products.aspx

< Message edited by Red Baron -- 9/11/2005 5:52:39 PM >

(in reply to Red Baron)

Post #: 5

RE: Lowering Crusing RPM - 9/11/2005 11:21:03 PM

Logan

Posts: 77
Joined: 4/16/2005
Status: offline

Well... I'm one down in the front, and three up in the rear. My chain is stock 114 links. I do however go through chains in a little under 15000 miles. I am very good at oiling and cleaning my chain. When I replace my chain and sprokets next I will go with the stock size in the front even if it means a extra link. I feel I should get at least 20000 out of a chain since I'm so anal about them.

(in reply to Red Baron)

Post #: 6

RE: Lowering Crusing RPM - 9/11/2005 11:53:24 PM

DRam

Posts: 396
Joined: 7/21/2005
Status: offline

You might want to consider the effect of lowering rpm at 75. You could drop far enough down on the torque curve to adversely affect your bike. Admittedly my only experience with this was on a CB650, but lowering the rpm by two teeth turned it into a dog. The CBR1000's have gobs more torque and it might not be a problem.

Too, you might check your sprockets and see if a previous owner has fiddled with sizes already. You might be running higher than normal RPM now. For comparison, my '91 CBR1000 turns about 4,700 rpm at 70, 5,000 rpm at 75. Vibration is minimal.

Actually, if you are finding objectionable vibration at any rpm with this bike I'd check the engine out. It should run nearly glass smooth at all rpm. After working my CCT over and replacing the cams mine would cause numb hands in just a few miles of riding. The vibration was finally traced to the balancer shaft. After adjusting that as directed by the Haynes and Honda Service Manuals nearly all vibration is gone. How it got out of adjustment is a total mystery, but may have something to do with accidentaly turning the engine backwards for a couple revolutions while adjusting the cams. Be sure you turn the engine counter-clockwise as you face the left side. That pulls the cam chain down the front of the engine, and may also be necessary to keep the balancer shaft properly aligned. I don't know that for sure, I'm just guessing.

(in reply to Red Baron)

Post #: 7

RE: Lowering Crusing RPM - 9/12/2005 11:34:40 AM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

quote:

ORIGINAL: Logan

Well... I'm one down in the front, and three up in the rear. My chain is stock 114 links. I do however go through chains in a little under 15000 miles. I am very good at oiling and cleaning my chain. When I replace my chain and sprokets next I will go with the stock size in the front even if it means a extra link. I feel I should get at least 20000 out of a chain since I'm so anal about them.

Thanks for the input, but your solution will increase the RPM's at 75 mph, not lower them for me.
Think of a ten speed bike, the front sprocket being smaller and the rear being bigger, your legs will spin like crazy.
This would increase engine RPM's and vibration.

< Message edited by Red Baron -- 9/12/2005 4:36:44 PM >

(in reply to Logan)

Post #: 8

RE: Lowering Crusing RPM - 9/12/2005 5:28:40 PM

Logan

Posts: 77
Joined: 4/16/2005
Status: offline

It wasn't a solution, it's just what I have. I was telling you the average miles I get with a smaller sprocket. I believe the smaller sprocket shortens chain life, which is why I suggested you go one up in the front to get your desired results.

(in reply to Red Baron)

Post #: 9

RE: Lowering Crusing RPM - 9/12/2005 7:07:01 PM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

Logan, you are correct.
Sorry I miss read your post.

I talked to "The Expert" from Sprocket Specialist today and he said:
Add 1 tooth on the front and RPM's should go down between 400-500 revolutions.
Go down 2-3 teeth on the rear sprocket and the RPM's will go down about 500-600 revolutions.
Front sprocket 18 teeth ordered today, I will report on results.
OEM sprocket specs 17F/43R, 530 chain with 114 links

< Message edited by Red Baron -- 9/12/2005 7:12:17 PM >

(in reply to Logan)

Post #: 10

RE: Lowering Crusing RPM - 9/13/2005 6:44:44 AM

Trips

Posts: 801
Joined: 3/31/2005
From: Perth (Western Australia)
Status: offline

Hey Red Baron I have an Excel spreadsheet tht clcultes everythin you need.

Just give me your snail mail and I will send it.

Cheers
Rob

BTW 16F & 42R is std!

< Message edited by Trips -- 9/13/2005 6:45:33 AM >

_____________________________

Remember the light at the end of the tunnel may be an oncoming train!

(in reply to Red Baron)

Post #: 11

RE: Lowering Crusing RPM - 9/13/2005 1:11:38 PM

Red Baron

Posts: 127
Joined: 3/6/2005
From: Prosper, Texas
Status: offline

Thanks Trip, this is the info I found, plus what my manual has listed.
The factory is highlighted in bold numbers.
Questions, do you have the bike from new, maybe previous owner changed your set up or is it a different year model or Country???
Check this web page link.

http://www.jtsprockets.com/52.0.html?&L=0&sel_uid=3855&p=

< Message edited by Red Baron -- 9/13/2005 1:27:37 PM >

(in reply to Trips)

Post #: 12