Need Gearing Advice

If it's broken or just needs tweaked

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bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Wed Aug 13, 2014 6:12 am

MiGhost wrote:
cb650 wrote:Just bought on off ebay DK has them also. they need to be narrowed down a little. And for you gearing chart isnt there diff gears for the custom/nitehawk vs the standards? Seems to me the standards always had the 16 and the customs had the 17. All my customs have. You can find a 37 rear also.


I stand corrected! Thats what I get for looking at the wrong notes!
79-81 Standard 16\40
82 Standard 17\39
80-81 Custom 16\39
82 SC Nighthawk 17\38

The 17T front was a common upgrade.

37T rear available in aluminum through either JT Sprockets, or Sprocket Specialist

Another tidbit of info.
18T Front: Will need to be narrowed to fit.
23801-300-620 SPROCKET (18T)
71-76 CB750K (K1-K6)

18\37 70.1mph @ 4650rpm
I knew that 6th gear was hiding there somewhere!



This 18/37 sounds like my perfect option, and I happen to have a brake lathe at work. I suppose it is possible to turn it like I turn a rotor, no??

Do I have to get a different chain based upon the tooth counts, as per the chain length or link count, etc.??

What happens to low speed riding with this sort of change from the stock 81 Custom setup?

cb650
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Location: Denver CO USA
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Re: Need Gearing Advice

Postby cb650 » Wed Aug 13, 2014 8:19 am

Your low speed will suffer but not really noticeable. For the first time you might try a 17/38 and see if you like it. you can always keep them for spares if you want to go more. for the street i wouldnt use the alum. will wear to fast. I posted the part num from DK in another thread not to long ago.
The gearing calculator is a bit optimistic. Probably dont account any for parasitic loss.
I'm running a 18/37 with a 79 17" rear and do 5k at 70. 80 custom.
It goes pretty good unless im two up and we are both older and fatter now. Or up in the mts. Love it out on the plains. Engine is getting tired to.
Did you clean the tank out?!?!?!?!

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Wed Aug 13, 2014 2:11 pm

CB650, of note is the heaviness issue you mention. I am about 280, wife is a shade under or at 300. I did take her with me on one trip back a few months ago, about 15 miles each way and she had a ball. Insists we should get a bigger bike too (nice!).

If I go with the higher ratio, do I need to change the chain, or can I get a new chain that mimics the old, and just get taller gears?

Also, as I understand there is no such thing as a free lunch, would going to higher gearing like this increase engine strain significantly?

cb650
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Location: Denver CO USA
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Re: Need Gearing Advice

Postby cb650 » Wed Aug 13, 2014 4:57 pm

Sprockets and chain should be replaced together. Most new chains you get will be 110 links and u just cut to what you need. If you want to experiment before u buy new. I'll send you a old 18 if I can find one.
Good thing she likes to ride. Might look into a old wing. I might be getting one soon.
Did you clean the tank out?!?!?!?!

MiGhost
Posts: 379
Joined: Tue Jun 07, 2011 2:30 am
Location: South Central Mitten

Re: Need Gearing Advice

Postby MiGhost » Wed Aug 13, 2014 5:48 pm

Lets start off with the chain. You will stay with the same style chain as what you already have. Which is 530-104 link.

On the sprockets. I agree that the aluminum 37 tooth sprocket will wear significantly faster than a steel 38 tooth sprocket. There is such minimal change in the rpm (125 rpm) between the two that the extra maintenance, and wear does not justify running the aluminum sprocket on the street.

What you will be doing by changing the gear ratio is effectively changing where the power band gets used. By reducing the cruise rpm. You are increasing the overall top speed (mph) which will move the power band higher overall. The power band of the motor will still start comming in around 6500-7000, but to be in that range you will change from approx 70mph to 80mph or higher.

You will give up a little bit of bottom end, but the bike has enough of take off that you will barely notice it. You may not want to do stop light racing. You will also lose a little bit of pull on the hills. Just drop a gear, get the rpms back up, and go. You probably won't have to though. Unless you live in CO, and make a habit of running Pikes peak, or the devils backbone.

The place where it really makes a difference is on the flats during steady speed cruise. With the right riding technique you could possibly gain 2-3mpg. Your 40-41 mpg is not bad. I was running that average also.

The 17\38 gearing was stock for the 82 650SC, and other than a couple gears in the transmission the engine was pretty much the same. That gearing would deffiantely be safe for the rest. Changing the front to the 18 tooth will not casue any problems as far as strain on the engine.

As I have noted before. The 650 is a great run around bike for just me, but it gets a wee bit snug when riding two up. The step up to the 750 made all the difference, and is a very comfortable two up rider.

I got bored, and did some rummaging on ebay to give you and idea what you are looking for.

18\38
70.1@4775
JT Sprockets
JTF338.18 (if you can find one), JTF338.17 CB650SC 82
JTR284.38-650

Sprocket Lock Plate & Bolts
HONDA CB750 CB650 CB550 NOS Sprocket Lock Plate & Bolts

Complete Sprocket & Chain set
1982 Honda CB650 SC NightHawk Chain and Sprocket Set - Heavy Duty

17 Tooth Front Sprocket
JT Sprockets Steel Front Sprocket - 17T Street Natural JTF338.17
JT Sprockets Steel Front Sprocket 17T Honda CB650 CB650C CB650SC

18 Tooth Front Sprocket (These are the 550\750 sprockets, and are aprrox 2mm wider than the 650 sprocket)
JT 530 Front Sprocket 18T Honda CB 550 K 1974 1975 1976 1977 1978
FRONT SPROCKET 18 TOOTH CB500K1 CB500T FT500 CB550 CB650C CB750 CB750K CB750S
Parts Unlimited - 23801-300-620 - Steel Front Sprocket, 18T

38 Tooth Rear Sprocket
JT 38T Rear Sprocket 530 for Honda CB650C 1980-1981

530-104 Link Chain Heavy duty
Honda CB650 CB 650 1979, 1982 Heavy Duty Chain
530-104 Link Chain OEM
530 STD Standard Series Non O-Ring Chain D.I.D Natural D18-531-104
~ Ghost

PD50 Carb Info
82 CB650SC Brake Caliper Info

Stable
Wayward Son:1980 CB650C, RestoMod Period Custom Touring
Bad Moon: 1983 XJ750MK Midnight Maxim, Full Dress Tour Deluxe w/ X-1 Fairing
Nemesis: 1983 XJ750K Maxim, Old School style chopper

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

still waiting on my goodies from BikeBandit

Postby bubbachicken » Wed Aug 27, 2014 12:30 am

They were out of the O-ring chain I ordered, but supposedly shipped them Monday. I can't wait!! :P

When installing the chain, do I have to make it up before I put it on, or place that pin AFTER installation? I have never changed a motorcycle chain, but have done a few bicycle ones, and the links on the bicycle were usually assembled on the bike.

I have been told to grind the head off the pin for the master-link on the old chain to remove it, and to peen the shroud around the pin on the new one, so I want to be positive I get this right. Assumedly I only get one shot at it, and don't want to goober it up. The chain they are sending is the plate with pin version, not the clip.

Got new sprockets too, 17/38 IIRC..

The power band change you describe is precisely what I am looking for, MiGhost. It should make the commute over mixed light traffic 4-lane/light traffic town pretty decent. The majority of the trip is 4 lane highway, and I occasionally do have to take a short run on the freeway, but I attempt to keep to surface roads any possible way I can as a general rule. The freeways here are pretty open though, so not nearly so busy as in major cities or near those places that tons of people live. We are pretty rural here.

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Fri Aug 29, 2014 7:09 pm

OK, o-ring chain and 2 sprockets arrived. 17/38. Interestingly, there was a 17 on the bike already as it turned out. Back was not a 38. Not sure precisely what it was yet, still clearing grease off it.. pretty grubby..


Regardless, I have this wonderful bullet swaging press, and thought I would make great time if I riveted and swaged the new chain on it. Worked like a champ with no effort whatever. Went out and took a look at the old chain, and it turned out to be a clip chain that had a snapped link plate along its length. I was lucky not to have lost it. The front sprocket was hooked a little, as was the rear. Both obviously needed replacement so I made a good call there. Now, however is the rub.

The old chain can be removed using a dremel tool, but the new one is fully riveted nicely into a single chain. Which means the swing arm is now EXACTLY in the wrong place! AAARRGGGHH!!! :x I was so concerned that I did not have the chain riveting tool (not enough cash left after chain and sprockets) that it never occurred to me to verify if the swing arm went THROUGH the completed chain loop (and it DOES!! :evil: ).

I have 1/2" drive ratchets and breaker bars, and they are one by one doing just that, BREAKING, as I attempt to loosen the nut for the sway arm. It is this slotted beast that grabs onto the bolt exceptionally well, as it turned out. Tomorrow I am bringing home an electric impact wrench from work, with the hope that I can break this sucker apart, drop the swing arm a few inches to loop the new chain around it, and lift it back into place.

Now, before I go and REALLY FUBAR this process up, are there any wise words that anyone has (other than "Don't do it this way, break the new chain and buy another plate and pin," because I don't have the tools to rivet it together on the bike yet) that can save me even more tremendously bad events in replacing this chain? Also local shops don't lend tools, and will charge me Harley prices (that is the ONLY semi-local option I have, the other option is to spend more on fuel in my 3/4 ton pickup to drive an hour to a Honda dealership (assuming they will take pity on me) and before Honda's shop cost I could buy the tool with the gas money :cry: ..).

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Fri Aug 29, 2014 7:11 pm

Oh, my God... I ordered a 104, and they said they sent it. I did NOT count the links to verify.... :shock:

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Sun Aug 31, 2014 11:21 pm

The electric impact did the trick, the swingarm locknut came off after a few seconds of hammering.

Ok, now I have to count and verify the links I guess. Then I can actually just slip the old chain out and lift the new one in, then assemble the sprockets (I hope) with chain in place on them. The front sprocket is on already.

As a side note, the front sprocket (a JT Sprockets unit) has a shoulder on one side, where the old sprocket had shoulders on both sides. This makes the thing a hair loose on the shaft. Is that normal? The lockplate locks it in place I suppose, but there is a minor amount of play where the original was tightly secure (requiring a very straight pulling action to remove from the shaft). The play is not front to back, but more side to side, so I suppose the chain could technically move laterally left or right a hair. We are talking less than 1/16" here, but it is concerning. Should I insert a washer or just flip the thing around? For now I flipped it around, but it still seems to not be as tightly locked side to side as the original was. Supposedly these are both 530 sprockets, and it is a 530 chain.

Ideas?

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Chicken soup from chicken poop...

Postby bubbachicken » Wed Sep 03, 2014 10:31 pm

I reset the shocks while I was at it and had the bike up on stand, hoping to soften the ride a bit. The rear sprocket is on, the front one is on, and in the morning, I am putting the chain on (tons of rain last several days...). Wish me luck!

As far as stretch goes, should I expect there to be a slight adjustment period while the new chain gets accustomed to the strain? I am assuming I should soak the new chain with o-ring compatible chain lube, and letting the goo fly as I go down the road! Don't follow too close! :P

bubbachicken
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Re: Need Gearing Advice

Postby bubbachicken » Fri Sep 05, 2014 12:15 pm

ok, new chain is on. Swing-arm was a pita, but it is on as well. No spare parts and bike is road-test ready. I checked the rivets I installed, just to be sure, and BikeBandit did a correct job of counting links (unless we both screwed up, which I doubt because I counted em twice yesterday).

Note to other new folks:

When removing the chain, take the other one off with the clip, put the new one on with a clip. If you get an O-Ring chain that does not have a clip, spend the money for the tool or stop riding until you have the money. Harbor Freight sells a POS semi-disposable one for 8-10 bucks, I hear. The one I found everyplace else was upward of 5-10 times that cost or MORE. The bullet swaging press works exceptionally well if you can get your bike lifted to the bench... sideways... :lol:

For those who want an opportunity for an undercarriage cleaning like I decided to do after I was "in there", just remove the front sprocket, rear wheel, swingarm (have an impact tool available for that danged swingarm locknut), and while you are at it, probably a set of rear wheel bearings and brake shoes/hardware. Have two cotter keys, one for the rear axle and a tiny one of the bar that holds your brake drum stable, 12 mm sockets, 8 mm sockets, 14 mm sockets, a 12 mm wrench, a new 3/4" ratchet you want to break and throw across the yard, foamy engine degreaser, 4 or 5 shop towels, a few Band-aids, chain lube, access to air conditioning on rest breaks, Guinness Stout (I left this one out, sadly), and lots of patience (to keep lifting the swing arm into location while the seals keep falling off of it, one side then the other as it bangs into crap under the bike). Oh, and set aside two days to do it (though if you have a very well lit garage and shelter from nearly incessant rain you can probably do it in four hours with only the above tools if skilled in their use).

Trust me.. Get and use the chain assembly tool and do it in ten minutes with only that tool, chain lube, a 12 mm socket, and a 12 mm wrench (those are for adjusting the wheel forward).. Save your sanity. Just part the original chain on ANY link (masterlink preferred, but does not have to be), hook new chain masterlink to old one at that link temporarily (no clips or masterlink lock installation yet), feed over rear sprocket to the front one with bike in neutral by spinning rear wheel, and when the new chain covers the rear sprocket again, unhook the old one, and link the new one's master together. Adjust the newly installed chain with the 12 mm bolt and nuts at the rear axle, watching for alignment (you MIGHT have to remove the chain guard, so you may have two small bolts to remove there, I think they were 10 or 8 mm). Once the chain is on and tracking correctly after your side to side adjustments on those adjusters, reinstall the chain guard if you removed it, and Viola, you are there. Check your tension one last time, take a short ride to work it a bit, go home, check it again to remove any slop that may have been there, and resume normal 300 mile checks plus your (hopefully) pre-ride safety checks that you should be doing anyway. :evil:

bubbachicken
Posts: 368
Joined: Tue Nov 13, 2012 2:19 pm

Re: Need Gearing Advice

Postby bubbachicken » Mon Sep 08, 2014 2:10 am

MiGhost, you were smack on. She rides like a different bike entirely. I have to pay attention very carefully, or she runs about 15 mph faster than she sounds like she should be, in 4th gear she is going like she is in fifth at the same rpm. It is like getting a 6th gear. Nice!

No loss of low end that I can determine, but she creeps a little faster than normal. Not a lot, but it is noticeable. I just have to get used to it.

All in all, I think this is an excellent change, and I don't think I will need the 18 front sprocket. The 17/38 is an excellent solution to my problem, and I have the feeling my mpg is going to go up noticeably. I have not checked yet, but will in the next several days. I have seen no chain stretch in the first 30 miles.

jsmith800
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Joined: Wed Jul 13, 2022 9:43 pm

Re: Need Gearing Advice

Postby jsmith800 » Tue Jun 20, 2023 8:41 am

The 79-81 CB650 are the same from what i can tell, why is 38T 530 sprockets not listed as working on 79 year. I've got a 79 and interested on getting a 17/38 530 but unsure.

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Volker_P
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Re: Need Gearing Advice

Postby Volker_P » Wed Jun 21, 2023 1:30 am

Listed where?
The 1979 has the RC03 frame while the 1980+1981 US models have the RC05 frame. I think RC03 vs. RC05 swing arms are different. So this might be an issue of chain length.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

jsmith800
Posts: 20
Joined: Wed Jul 13, 2022 9:43 pm

Re: Need Gearing Advice

Postby jsmith800 » Wed Jun 21, 2023 11:06 am

Thank you, didn't realize the frame was different. I've got a 79 and 81 CB so I'll compare. Heres an 81 i'm building and noticed the passenger peg brackets...so this is an R05 frame, these are NOT on the R03 frame. i'll measure the swingarm later. thanks again for the info!
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