Author Topic: 550 vs. 750 What was considered faster? (Read 3132 times)

zoo mob · « **on:** July 17, 2007, 08:46:51 PM »

I've got a 73 750 K3 and my buddy just picked up a 74 550 KO, his bike seems way faster than mine and I was surprised by this. What have been you guy's experiences in regards to this?

MrZxp · « **Reply #1 on:** July 17, 2007, 11:29:13 PM »

Quote from: zoo mob on July 17, 2007, 08:46:51 PM

I've got a 73 750 K3 and my buddy just picked up a 74 550 KO, his bike seems way faster than mine and I was surprised by this.

Is this a joke? I would have to say that your 750 is need of a tune up!!

I have both, and my 750 has it all over my 550... there is only around a 25kg weight difference (in favour of the 550)..

Cheers, Phil

zoo mob · « **Reply #2 on:** July 18, 2007, 10:25:44 AM »

No joke, I was shocked as well. It seems to run well, and its my first bike, I was only troubled once I rode the 550. I guess its going in for a tune.

Chris Liston · « **Reply #3 on:** July 18, 2007, 12:19:06 PM »

550 is lighter and lower which could make it feel faster especially through turns,etc..

ieism · « **Reply #4 on:** July 18, 2007, 01:42:17 PM »

My 550F is in running pretty good, but I can't keep up with a 750.

[/quote]"I have both, and my 750 has it all over my 550... there is only around a 25kg weight difference (in favour of the 550).."
[/quote]

I think it's a fair bit more more than 25 kg. Probably more like 50 kg more than my 550f.

snyquist53 · « **Reply #5 on:** July 18, 2007, 01:47:18 PM »

you got spanked

, check or clutch or something.

kuyarico · « **Reply #6 on:** July 18, 2007, 01:54:51 PM »

I have both (78 550K and a 76 750 F). My 550 felt faster until I rejetted and tuned the 750. The PO did not have it properly jetted. Now there's no question about it. The 750 is faster. But my 550 is prettier

Mountainman · « **Reply #7 on:** July 18, 2007, 05:13:36 PM »

I have faith that my 550 would eat up a stock 750. My 550 however is NOT stock

. Now a 750 with the same mods as my 550? THAT, would eat my 550s lunch.

dustyc · « **Reply #8 on:** July 18, 2007, 05:46:06 PM »

Quote from: Mountainman on July 18, 2007, 05:13:36 PM

I have faith that my 550 would eat up a stock 750. My 550 however is NOT stock . Now a 750 with the same mods as my 550? THAT, would eat my 550s lunch.

I was wondering if his buddy's 550 was modified. What have you done to yours Mountainman?

zoo mob · « **Reply #9 on:** July 18, 2007, 06:19:08 PM »

I don't think the 550 is modified, the last owner did not mention it, but the engine has clearly been out of the bike and painted, so who knows, but then again, my other friend witha 550 is faster too. I'm going to have to do some investigating. I've got the feeling mine might have been re-jetted improperly or something, because it runs well, just not fast.

BobbyR · « **Reply #10 on:** July 18, 2007, 06:30:39 PM »

You also may be discounting the gearing someone may have made yours taller or theirs shorter. You knock off a tooth you get fast acceleration but lower top end.

edbikerii · « **Reply #11 on:** July 18, 2007, 06:32:51 PM »

OK, so you mentioned that this is your first bike. Perhaps you aren't riding it right? How high do you rev the engine on the tach? I find that new riders tend to rev bikes too low, because they are used to driving cars.

BobbyR · « **Reply #12 on:** July 18, 2007, 06:56:25 PM »

Quote from: edbikerii on July 18, 2007, 06:32:51 PM

OK, so you mentioned that this is your first bike. Perhaps you aren't riding it right? How high do you rev the engine on the tach? I find that new riders tend to rev bikes too low, because they are used to driving cars.

Ed is right, get some good oil in her and open her up. They like to be ridden hard to run well. Ridden hard is not being silly and running it to the redline at every shift.

HondaMan · « **Reply #13 on:** July 18, 2007, 07:54:20 PM »

Boy, I never heard of this one before, unless the 750 was sick....

The lowest HP 750K, stock I ever tested was about 41 HP, and the highest 550 I ever saw stock was 34 HP, at the rear wheel. Most 750K bikes were in the mid-50s at the rear and 550K series were normally around 30.

That said, the 500 in roadrace trim was a solid 61 HP and the 750 almost 92 HP, rear wheel numbers...

Kile · « **Reply #14 on:** July 18, 2007, 10:32:49 PM »

I'm in agreement with the other comments regarding the 550 either being heavily modified, or the 750 needing a tune-up. I'm guessing more likely the tune-up is the culprit.

My dad bought my current K8 brand new almost 30 years ago. (I was lucky enough to talk him out of it when he decided he needed newer cruiser type a couple of years ago...) He is constantly talking about how hot the bike was when he got it, with relatively few mods (EI, new headers/pipes). He claims to have had the spedo pegged a few times (140+ MPH!) I'm not sure if this was going down hill, tailwind, etc., but I have yet to have the bike up over 100, (believe me, I've tried...) It feels strong and relatively quick when I ride it, but certainly not capable of getting to and beyond the century mark. I know these bikes are capable of it, which is making me lean real hard on the idea of my bike really needing a tune-up. The bike is running on points now, and has a pretty inexpesive exhaust, so it could well be that the bike is still jetted for whatever mods my dad had on the bike previously. I'd love to get ahold of the Jardine headers he had, if that's what gave the bike its spunk!

However, even having said that, my dad and I went on a weekend ride to the coast last summer. At one point we opened them up, and the K8 was dead even with his Vulcan 1500 (even pulling ahead a bit) up to about 90-95, whereupon I had nothing left and he pulled away like I was standing still. He later told me he was a bit dissapointed in all his new 1500 cc's when he couldn't shake me under 90. Mind you this was on a flat straightaway... He most certainly had problems keeping up with me when we got on it in the twisties.

- Kile

neil young · « **Reply #15 on:** July 18, 2007, 11:41:42 PM »

when i drove my 77 550 home after buying it last year i could not get it above 60 mph.i immediatly adjusted the valves.the points,cam chain,new plugs,did the timing which was way off.now 100 mph no problem

MrZxp · « **Reply #16 on:** July 19, 2007, 02:10:44 AM »

Quote from: ieism on July 18, 2007, 01:42:17 PM

My 550F is in running pretty good, but I can't keep up with a 750.

"I have both, and my 750 has it all over my 550... there is only around a 25kg weight difference (in favour of the 550).."

I think it's a fair bit more more than 25 kg. Probably more like 50 kg more than my 550f.

I've personally not weighed them, but, from the specifications published on this site, a '74 550 is 192kg (wet) and a '72-'74 750 is listed at 218kg (dry). I guess that is actually a 26kg difference with a bit more factored in for the 750 if it was to be full of oil/gas?

Cheers, Phil

ieism · « **Reply #17 on:** July 19, 2007, 10:03:28 AM »

So a dry 550 will be 174kg. That's still a 44kg difference then. And a 550F is lighter than a K, so I wasn't too far off guessing 50 kg.

Of course a 550 without oil and gas will be much faster than a dry 750 (pushing it). Unless it's going downhill.

HondaMan · « **Reply #18 on:** July 19, 2007, 08:42:06 PM »

Quote from: Kile on July 18, 2007, 10:32:49 PM

I'm in agreement with the other comments regarding the 550 either being heavily modified, or the 750 needing a tune-up. I'm guessing more likely the tune-up is the culprit.

My dad bought my current K8 brand new almost 30 years ago. (I was lucky enough to talk him out of it when he decided he needed newer cruiser type a couple of years ago...) He is constantly talking about how hot the bike was when he got it, with relatively few mods (EI, new headers/pipes). He claims to have had the spedo pegged a few times (140+ MPH!) I'm not sure if this was going down hill, tailwind, etc., but I have yet to have the bike up over 100, (believe me, I've tried...) It feels strong and relatively quick when I ride it, but certainly not capable of getting to and beyond the century mark. I know these bikes are capable of it, which is making me lean real hard on the idea of my bike really needing a tune-up. The bike is running on points now, and has a pretty inexpesive exhaust, so it could well be that the bike is still jetted for whatever mods my dad had on the bike previously. I'd love to get ahold of the Jardine headers he had, if that's what gave the bike its spunk!

However, even having said that, my dad and I went on a weekend ride to the coast last summer. At one point we opened them up, and the K8 was dead even with his Vulcan 1500 (even pulling ahead a bit) up to about 90-95, whereupon I had nothing left and he pulled away like I was standing still. He later told me he was a bit dissapointed in all his new 1500 cc's when he couldn't shake me under 90. Mind you this was on a flat straightaway... He most certainly had problems keeping up with me when we got on it in the twisties.

- Kile

When I worked on these a lot, a tuneup for street racing only lasted about 1000 miles, then it started "falling off". This was typical: the points and plugs, in particular, are short-lived from a performance sense. But, we could also get the D8ES-L sparkplug then, which made a noticeable difference. Likewise the X24es-U series, and the Champion R6 (I think it was), all gone today. Too bad, really. The difference between a sharp tuneup or a 5000-mile old one on a fresh CB750K was the difference between taking down a Kawasaki 900 (the early ones) or a BMW R90S in stoplight racing or the drags, or having them take you. The difference on mine would be like this: I could start a 5000-mile tour of the US West with a fresh tune, 2-up, full tenting gear, running 105 MPH while pushing a Vetter fairing, no problem. By the end of the tour, 95 was pushing things hard, all else being equal. Unloading the bike would put it back above 110 MPH out-of-tune, but fresh points, plugs, valve setups (chain, too, don't overlook that) would put it into the 130 MPH range again, just like that.

Yep, they like those points.....that's why I switched to transistors....

Adding Dyna sort of helped, but they use more current than stock ones, and the HP loss is approximatley 1/4 HP as a result.

bwaller · « **Reply #19 on:** July 20, 2007, 04:52:22 AM »

I just finished a 550 project with a larger bore and a cam plus peeled lots of weight off it and it will embarrass all but the best 750's, but in stock trim no bloody way!

This weight thing sparks my interest though, if you don't mind the sidetrack.

Can anyone weigh their stock 550 to check? Don't believe Hondas numbers... (174kg) 383lbs dry??? I always thought they were more like 425lbs dry.

Jay B · « **Reply #20 on:** July 20, 2007, 05:23:49 AM »

I'll weigh mine later today.

TwoTired · « **Reply #21 on:** July 20, 2007, 10:15:53 AM »

Honda CB500 owners manual 1972 (k2):
Dry Weight 403.5 lbs. (183 kg)

Honda CB550 owners manual 1974 (k0):
Dry Weight 423 lbs. (192 kg)

Honda CB550F owners manual 1977 (F2):
Dry Weight 421 lbs. (191 kg)

Honda CB750F owners manual 1977 (F2):
Dry Weight 512.6 lbs. (232.5 kg)

BobbyR · « **Reply #22 on:** July 20, 2007, 10:45:12 AM »

1978 CB750K with my fat butt on the seat 712Lbs

mlinder · « **Reply #23 on:** July 20, 2007, 12:09:28 PM »

The K0 750 was (supposedly) quite a bit less than 500 lbs.
They got heavier, for some reason, over the years.
I haven't weighed mine, just going off sources.

/edit 480lb's according to honda

bwaller · « **Reply #24 on:** July 20, 2007, 12:10:27 PM »

Ah thanks TT that seems a bit more realistic.

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Author Topic: 550 vs. 750 What was considered faster? (Read 3132 times)

Mountainman

Kile