Topic: CB650 ultimate performance list

[Cafe650]

I am looking to compile the CB650 ultimate performance index as i know it is incredibly frustrating as it stands. any input would be welcome as i am in my infancy of owning a 650 and have very few places to turn for upgrades

Carbs.

77/'78 cb750 carbs on a 79 head (my current setup)

Keihan CR's from http://www.dynoman.net/carb/keiCR.html


Pistons.

http://www.dynoman.net/engine/pistons/dp-CB550.html#cb650


Clutch.

Barnett and EBC offer clutches so no too bad, also EBC has a "stiffer" spring


Cams.

Can be reground at Web Cams  ( i am currently looking into this)


Exhaust.

Mac 4-1

Marving out of Italy

Hindle from Ripple Rock Racer



Headwork

[scunny]

you might find this interesting.
http://forums.sohc4.net/index.php?topic=40414.0

http://the1moto.com/bikes/2013/4/17/1976-honda-cb550-now-735cc

[Cafe650]

quite interesting indeed. im looking for more of a 650 mod list. i know it was overlooked. everything below it quite a following and the 750 and above obviously paved the way for the supersports we see today. i want to create a list of bolt on goodies with minimal to no mods

[Camrector]

You can read DaveBarbiers and my own 650 in the project section. Both are bored to 672 with stage 2.5 porting from Mike Reick. Both have the c5 ignition. Dave is using the megacycle 126-20 cam,
I’m using the Yoshimura TT special 122-00.  You need extensive valve work to fit either of these cams. Dave is using CR carbs, I’m using 77 cb750 carbs. Both motors are in CB550 frames.

[Cafe650]

ill have to take a boo. looking for minimal mod somewhat bolt on. just so people have a starting point on where to start

[calj737]

I am looking to compile the CB650 ultimate performance index as i know it is incredibly frustrating as it stands.

i want to create a list of bolt on goodies with minimal to no mods

These 2 statements are polar opposites to each other. "Ultimate performance" is never going to be "bolt on". If you want bolt on performance, by a small block Chevy.

These motors are 40 year old, carbureted air pumps with 40 year old electrical systems and early style ignitions. You don't have a computer running VVT, multiple cams, and EFI.

Swapping carbs, exhaust and the like will yield a mild butt dyno change, but real performance comes from major machine work to extract the limits from the platform. Even a cam change will only do so much without machining the valve train and a piston change. Bolt on performance adds for the 650 are far fewer than the 750/550 due to their limited years of production. Plopping a 650 motor into a 500/550 frame is a bump in performance, and any upgrades to that 650 will make that hybrid 5xx/6xx bike better than it was, a la Dave or Cam's bikes.

[Cafe650]

i should clarify the ultimate more, i meant the ultimate list of performance upgrades for the average guy. while i would love to to a complete tear down and rebuild with high dollar performance goodies, the dollars aren't there. i know there have to have been some little tricks used by guys that have owned these bikes in the past. 

[calj737]

Yup, a full and proper 3k Mile Service does wonder for your bike's performance. Shed unnecessary weight from the bike and rider. Ride in the upper RPM band and enjoy the darn thing. Its a 50HP motor. What do you really expect? Any modern 500cc bike will lay waste to it in handling, braking, and reliability. Welcome to vintage bikes.

[Cafe650]

new bikes for the most part are missing the soul of older bikes, i've done all you've mentioned, mine is a full restomod with all handling and braking of a new bike, just looking to optimize the motor without being too close to the limits of the motor. More setting this up as a go to for guys as lost as I was when i first embarked on this mission with the red headed stepchild of the Honda family

[CBGhia]

... Shed unnecessary weight from the bike and rider. ...

Did you just call me fat?  Damnit, I need to get back on the Keto diet.   

[DaveBarbier]

You can read DaveBarbiers and my own 650 in the project section. Both are bored to 672 with stage 2.5 porting from Mike Reick. Both have the c5 ignition. Dave is using the megacycle 126-20 cam,
I’m using the Yoshimura TT special 122-00.  You need extensive valve work to fit either of these cams. Dave is using CR carbs, I’m using 77 cb750 carbs. Both motors are in CB550 frames.

674*

Honestly, the simple bolt on upgrades are exhaust, intake and cam. And as Cal says, that can only get you so far, but it will be a nice improvement. Weight savings doesn't count because that's unbolting

Switching sprocket ratios will give better acceleration but sacrifice top speed, or vice versa of course.

I have a RRR stainless exhaust and love it, but a custom exhaust (titanium?) with equal length headers built for performance would surely give you a hair more power. But obviously that's super expensive. Even so, with these mods you'll need to go to a proper dyno to extract all the horsepower possible.

[RAFster122s]

Just do not go chasing more and more power from these motors unless you are willing and able to open your wallet wide to spend 3K or more on doing things right and doing a proper rebuild. Heck, 3K might not cover the headwork and engine boring much less the gaskets, seals, bearings, paint, and other things that go into just a motor rebuild.

Better to be satisfied with what it can do.  Enhance the suspension with a cartridge emulator and new fork springs from the folks at RaceTech. Put a good set of Hagons or Ikons or more expensive and good shocks on the bike. Put a good set of tires on the bike. Do the 3k tune up and change your oil regularly. Take an Advanced riders course or two...  Maybe consider a track school to learn how to corner properly and efficient use of braking and proper braking techniques.  You do not want to use racing maneuvers like pushing into a corner a very high speed on public roads. You may not have the visibility on the track and it is not a safe place to be doing this. You never know if some kid, or bicyclist, or car or truck is going to be around a corner and if you are coming blazing into a corner where you can't see the road ahead you might hurt someone or hurt yourself.  Stuff on the roadway, be it leaves, or gravel, etc. can really ruin your day/week/year.

Have fun with the bike and learn to enjoy it for what it is...take a ride in un-populated areas so you can ride slower and look around.  That's my unsolicited $0.05
So many great guys with far more knowledge than me have weighed in and given you good advice to follow.

[SOHC4 Cafe Racer Fan]

I went the 674cc route with a ported head and 126-20 cam because it was the best bang for the buck while still remaining a middleweight platform.  I don't expect mine to be some sort of ultimate street beast -- just a peppy fun bike that is lightweight, can turn and stop decently, and pull out of corners -- better than a similarly modded 550 engine.  Losing weight off the bike (and the rider) is the goal, too.

[MRieck]

I went the 674cc route with a ported head and 126-20 cam because it was the best bang for the buck while still remaining a middleweight platform.  I don't expect mine to be some sort of ultimate street beast -- just a peppy fun bike that is lightweight, can turn and stop decently, and pull out of corners -- better than a similarly modded 550 engine.  Losing weight off the bike (and the rider) is the goal, too.

The increased torque of that 674cc over the 550 will make it more fun. I really like riding my RC51 simply because of the torque. Oh yeah....it does handle nicely.

[GI_MECHANIC]

Not to sound like a noob but I currently have a 79 Honda CB650 with 24,xxx miles and started getting ready to refresh the upper end and since I am currently overseas in Ukraine on a mission I had to put the top end rebuild on hold for the time being, I have been thinking and doing research (since I have been in country) on big bore conversion looking at going with the 836cc. So from what I gather from the thread is since I have a 650 I can do the machine work to the jugs drop in some 750 sleeves, and get some 750 pistons with "stock" connecting rods and achieve 836cc? of course a nice stage 2 cam to help free up with the displacement increase and some 750 carbs which I have that need to rebuild, I want something that gets more ass because I am not a small guy at 6'3" 275lbs granted I have my Yamaha Stryker 1300 that moves me pretty good even when riding two up. I know Paulge has done a lot of this so I want to be one of those guys that has a sleeper.     

[gschuld]

I’m FAR from an expert on cb650s (or any other Cb for that matter) but the largest displacement I recall seeing is Paul Ages at 735cc.

http://the1moto.com/bikes/2013/4/17/1976-honda-cb550-now-735cc

64.75mm bore using factory cb750 sleeves
55.8mm stroke factory cb650 crank

I’m certain one could go to extremes and squeeze a little more out of a cb650 engine, but I have a feeling that it starts getting riskier to push the limits much further.

If you really felt inclined to go bigger(as a fellow card carrying member of the Sasquatch club I get it) I’d put serious thought into picking up a cb750 as a base.  An 836 is simply a bore and hone job (using the factory cylinders) and fresh pistons.  Performance parts are PLENTIFUL.

George