Topic: Chro-Moly frame?

[mlinder]

More info, how about John Wyatt's book, the  "Original Honda 750"  he quotes some specs from Motorcycle Sport magazine when the 69 was first ridden . . ."The Honda is a heavy bike - 517lb (wet)"  My guess is that the motorcycle press actually weighed the bikes rather than believing Honda's specs although I can't find an official Honda spec.  Figure at the end of the SOHC 750 run the F model had gained (from the 69) about 30lbs and that the K had gained about 20.  Not to burn your Sandcast nostalgia buzz but I think your bike is heavier than you think.  And if you believe the period mag reviews, it is actually slower (acceleration wise) than the porky "end of the run bikes" as well.  . . . .

I don't have a sandcast...

I also dont have turn signals or any of the electronics required for them. Tell ya what, I'll go weigh it at its current weight, which is only slightly less than stock would be.

[mlinder]

a lot of that weight difference can be attributed to gasoline. Honda listed the bike's spec wet weight as with all other fluids but gas.

A ha! this makes a lot fo sense! I did not know that. A full tank of gas is about 24lbs. This is a large difference.

Most magazines will weight the bike with a full tank of gas, and at 6lbs per gallon that is a good 20 lbs right there. Plus the magazine will use truck scales while honda has it's own calibrated bike scale and it is possible to get some variation.

Like I said, ima go weight my bike, see what it says.

What is heavier on a K8? well for starters the frame is heavier. Exhaust, seat, Tank, carbs, countershaft - you name it. even negligable weights can add up to lbs (as my father used to say nickles and dimes add up to dollars). The fact it has a longer wheel base and more trail indicates it is a more stable ride in a straight line but has less cornering ability. The bike is less flickable (roll side to side) because of the added weight.

And again, it has parts that my 69 didnt even come with.

I have two 78 Fs, one stripped down and one stocker. The stripped down one is easily more flickable (maneurvable) than the stocker because I have 100+ less lbs to fight  in changing direction. However overall cornering prowess it is probably only marginally better than my stocker.

This is why I think a 430lb wet K0 is easily obtainable.

I'd have to ask about your setup to understand why the cornering ability isn't much better. You've said it's more flickable. You have 150 less lbs @ .75g in a turn for frame, tires and suspension to deal with. Let me know what you are doing so I can improve upon it for my own bike.

[Geeto67]

a lot of that weight difference can be attributed to gasoline. Honda listed the bike's spec wet weight as with all other fluids but gas.

A ha! this makes a lot fo sense! I did not know that. A full tank of gas is about 24lbs. This is a large difference.

Most magazines will weight the bike with a full tank of gas, and at 6lbs per gallon that is a good 20 lbs right there. Plus the magazine will use truck scales while honda has it's own calibrated bike scale and it is possible to get some variation.

Like I said, ima go weight my bike, see what it says.

What is heavier on a K8? well for starters the frame is heavier. Exhaust, seat, Tank, carbs, countershaft - you name it. even negligable weights can add up to lbs (as my father used to say nickles and dimes add up to dollars). The fact it has a longer wheel base and more trail indicates it is a more stable ride in a straight line but has less cornering ability. The bike is less flickable (roll side to side) because of the added weight.

And again, it has parts that my 69 didnt even come with.

I have two 78 Fs, one stripped down and one stocker. The stripped down one is easily more flickable (maneurvable) than the stocker because I have 100+ less lbs to fight  in changing direction. However overall cornering prowess it is probably only marginally better than my stocker.

This is why I think a 430lb wet K0 is easily obtainable.

I'd have to ask about your setup to understand why the cornering ability isn't much better. You've said it's more flickable. You have 150 less lbs @ .75g in a turn for frame, tires and suspension to deal with. Let me know what you are doing so I can improve upon it for my own bike.

Flickability is the ability to rapidly change direction, this is the area of handeling that weight has the most effect on. The bike's supension and trail have little to do with it's ability to transition side to side. This is also the area that most street riders will feel because you rarely are knee down but you are constantly changing direction (like when you are threading the needle between cars in light traffic). This will make the bike feel more precise. Your tires will have an effect on this as well. A thinner tire means a quicke turn in and transition but a smaller contact patch (and is thus less forgiving), a wider tire means slower turn in and a bigger contact patch. Since the contact patch is a crucial part of braking finding the happy medium is good. I find that our heavy bikes like rear tires in the 120-150 range. I personally prefer 130-140.

Cornering is the other component of handeling and largely affected by rake and trail. This is how tight your turn is when you are at the limit of banking. It is affected by how much lean you can get before your hard parts drag, how much rake, how much trail, tire contact patch, and to a lesser degree weight. The less your bike ways the faster it can take the same line but you are not altering the line. The best way to affect cornering is to adjust your suspension and the rake and trail. This is very dangerous however and should only be expirmented with in small increments. The fastest way to adjust rake and trail is to adjust suspenion height. A nose low rear high setup decreases rake and trail and will increase how fast you turn in and to some degrees your line but will make the bike twitchy and unstable in a straight line at high speed. A tail low nose high attitude will increase the rake and make the bike stable at high speed in a straight line but will decrease cornering prowess.

Race teams usually adjust rake in the form of tenths (.1) degrees. I suggest the penny method which is you slide the forks up through the trees using the thickness of a penny as a gauge. The DOHC guys have mentioned a good setup on their bikes are 2-3 pennies. you can also raise the rear and this will make small changes on the front - the 900f shocks are an 1" longer and this was an old time trick to improving the handeling.

 

[eldar]

How is the exhaust heavier? Other than the mating, the pipes are virtually the same. I do have lighter mufflers though than the stock ones.
I can see the frame heavier to decrease flex and maybe that is why i dont feel much. As for the seat, other than being thicker and stepped, should not add much though, yes it is weight. But it sure is comfy on long trips.  Are you sure the carbs are heavier though? I mean, they are different but do not seem to be any bigger overall. As for engine, well there were a number of refinements made and the k8 has all these improvements to increase durability at least in the K engine. So that is acceptable weight unless you like flirting with disaster or have wads of cash to get lighter parts, Hi-po parts.

Have you actually weighed these parts though to see if they are heavier?

[mlinder]

a lot of that weight difference can be attributed to gasoline. Honda listed the bike's spec wet weight as with all other fluids but gas.

A ha! this makes a lot fo sense! I did not know that. A full tank of gas is about 24lbs. This is a large difference.

Most magazines will weight the bike with a full tank of gas, and at 6lbs per gallon that is a good 20 lbs right there. Plus the magazine will use truck scales while honda has it's own calibrated bike scale and it is possible to get some variation.

Like I said, ima go weight my bike, see what it says.

What is heavier on a K8? well for starters the frame is heavier. Exhaust, seat, Tank, carbs, countershaft - you name it. even negligable weights can add up to lbs (as my father used to say nickles and dimes add up to dollars). The fact it has a longer wheel base and more trail indicates it is a more stable ride in a straight line but has less cornering ability. The bike is less flickable (roll side to side) because of the added weight.

And again, it has parts that my 69 didnt even come with.

I have two 78 Fs, one stripped down and one stocker. The stripped down one is easily more flickable (maneurvable) than the stocker because I have 100+ less lbs to fight  in changing direction. However overall cornering prowess it is probably only marginally better than my stocker.

This is why I think a 430lb wet K0 is easily obtainable.

I'd have to ask about your setup to understand why the cornering ability isn't much better. You've said it's more flickable. You have 150 less lbs @ .75g in a turn for frame, tires and suspension to deal with. Let me know what you are doing so I can improve upon it for my own bike.

Flickability is the ability to rapidly change direction, this is the area of handeling that weight has the most effect on. The bike's supension and trail have little to do with it's ability to transition side to side. This is also the area that most street riders will feel because you rarely are knee down but you are constantly changing direction (like when you are threading the needle between cars in light traffic). This will make the bike feel more precise. Your tires will have an effect on this as well. A thinner tire means a quicke turn in and transition but a smaller contact patch (and is thus less forgiving), a wider tire means slower turn in and a bigger contact patch. Since the contact patch is a crucial part of braking finding the happy medium is good. I find that our heavy bikes like rear tires in the 120-150 range. I personally prefer 130-140.

Flickability is also a product of rake. A steeper rake makes turn in MUCH faster. It also contributes to tank slap under heavy acceleration. :/

Cornering is the other component of handeling and largely affected by rake and trail. This is how tight your turn is when you are at the limit of banking. It is affected by how much lean you can get before your hard parts drag, how much rake, how much trail, tire contact patch, and to a lesser degree weight. The less your bike ways the faster it can take the same line but you are not altering the line. The best way to affect cornering is to adjust your suspension and the rake and trail. This is very dangerous however and should only be expirmented with in small increments. The fastest way to adjust rake and trail is to adjust suspenion height. A nose low rear high setup decreases rake and trail and will increase how fast you turn in and to some degrees your line but will make the bike twitchy and unstable in a straight line at high speed. A tail low nose high attitude will increase the rake and make the bike stable at high speed in a straight line but will decrease cornering prowess.

Yes. I know this too.

Race teams usually adjust rake in the form of tenths (.1) degrees. I suggest the penny method which is you slide the forks up through the trees using the thickness of a penny as a gauge. The DOHC guys have mentioned a good setup on their bikes are 2-3 pennies. you can also raise the rear and this will make small changes on the front - the 900f shocks are an 1" longer and this was an old time trick to improving the handeling

I will be doing this to some degree.

I's the suspension setup different on your stripped f, or the same as your fully loaded one?
Again, at .75g, a load of 150 lbs less should make a pretty large impact on corner speed. 900lbs vs 750lbs on all those parts is pretty huge. It's almost a 20% decrease in load.

[Geeto67]

The last time I rode the stripped down F it had hagon shocks and stock forks with 10w oil, drag bar, and cut down seat. I have not measured if the hagons are longer or not but I think they might be 1/2 an inch longer. I have since replaced the hagons with 900f shocks which are a full inch longer and I have dropped the front down an inch so I could bolt clip ons on top of the trees. I have not ridden it yet like this since it has been snowing and also I need to do a fork seal in the left fork.

[eurban]

Even more info. . .  . . . .this site under the specs for the K0 has 517lbs listed for the Curb Weight.  Obviously the amount of gas that you put in the tank will effect the weight measurement, the K7s and K8s have honking huge gas tanks so if you fill them up and compare them to a full up K0 there will be an exaggeration of their weight increase.  . . . .Geeto, Honda (and just about every other bike manufacturer) tend to exagerate many of performance specs of their machines including for instance: horsepower, 1/4 mile times, top speed,  and weight.   In an advertisement in a 69 magazine, Honda claims 445lbs (doesn't specify wet or dry), and 1/4 mile times of 12.6 seconds.  Cycle Worlds 1969 review of the 750 speced the curb weight with 1/2 tank of fuel at 499lbs and 1/4 mile times of 13.58 seconds.  Cycle's 1969 test specs a curb weight of 485lbs (no mention of gas but I would suspect none) as and a 1/4 mile speed of 13.5 secs.  What's real and whats exageration? Well either both the mags scales are off or thats at least 40lbs (for Cycles'  specs assuming they included gas which they probably didn't)) pounds of oil and gas, and a whopping 54lbs (based on Cycle Worlds specs) for 1/2 tank of gas and oil.  Do the math on the weight for those fluids and things don't add up.  Truck scales for weighing?? I doubt it and the manufacturer certainly has the incentive to fudge specs to increase hype.  Hype is why they include the bikes weight in their ad.  Speaking of hype, how about the exageration of the 1/4 mile times?? 

[mlinder]

I do believe more than one sub 13 second 1/4 mile on a K0 were recorded by reliable parties.

I'll look em up after a few.

[Geeto67]

How is the exhaust heavier? Other than the mating, the pipes are virtually the same. I do have lighter mufflers though than the stock ones.
I can see the frame heavier to decrease flex and maybe that is why i dont feel much. As for the seat, other than being thicker and stepped, should not add much though, yes it is weight. But it sure is comfy on long trips.  Are you sure the carbs are heavier though? I mean, they are different but do not seem to be any bigger overall. As for engine, well there were a number of refinements made and the k8 has all these improvements to increase durability at least in the K engine. So that is acceptable weight unless you like flirting with disaster or have wads of cash to get lighter parts, Hi-po parts.

Have you actually weighed these parts though to see if they are heavier?

I don't have many k8 parts to weigh but if you send them to me I'll gladly weigh them.

The exhaust is longer and definatley not the same as the earlier models. The pipes are also fatter. And while I have not seen the baffels out I am willing to bet they are wider and longer too. Just because they look the same does not mean they are the same. Honda is fond of making parts that look identical to others but are actually not (honda even does this with tanks!).

The seat pan is longer, much longer. I have one (my K5 has mounts welded to take a K8 seat)  and off hand I would say it is probably a couple of pounds heavier. It certainly feels heavier when I have one in each hand.

The carbs have more parts and are physically larger. Sure it may be heavier by a few ounces but other parts that are heavier by a few ounces are the sidecovers (which the K8 covers are slightly larger and a little thicker). So is the larger countershaft. If the carbs of the K8 are the same as the F2/3 I'll weigh the set I have and get back to you.

all this stuff adds up. Most of it doesn't look any different until you are physically holding it in your hands on the workbench, part of honda's idea of establishing a brand identity (all their bikes of the same era have the same or similar styling).

by the time the k8's came around honda's cb750 was already pleny durable and most changes were done to accomidate an increase in hp to try and make them competetive in the marketplace. The expanded wheelbase of the K8 was to switch the marketing of the bike to the crusier/touring set and to make the bike as stable as possible on loaded down at 65mph+ on highways. The F was more of the sporty bike which it why it got the bigger valves and more of an hp jump.

[eldar]

For the pipes, do you mean larger diameter or thicker? The pipes do not have a large diameter, about 1 3/8 inches or so. Again, I have aftermarket slash megaphones, not as long or as heavy as even earlier models but then that is after market too.  I think the f3 though, had the same frame and swingarm as from what I remember, all their parts are interchangeable, main diff of course is engine and wheels/brakes.

I am not doubting you but I just dont see how the k8 is so much heavier than everything else, I really doubt the difference is very little if one were to put a stock k8 and stock k1-6 on the same scale.  I really have a hard time believing that there is a 29 pound difference between dry weights.  however, I will never be able to check it out as I probably wont ever have anything earlier than my 78 and most people with k1-6 will never have a k8.  So it ends up being all speculation based on the numbers put up by honda which may or may not be accurate.

[Geeto67]

For the pipes, do you mean larger diameter or thicker? The pipes do not have a large diameter, about 1 3/8 inches or so. Again, I have aftermarket slash megaphones, not as long or as heavy as even earlier models but then that is after market too.  I think the f3 though, had the same frame and swingarm as from what I remember, all their parts are interchangeable, main diff of course is engine and wheels/brakes.

I am not doubting you but I just dont see how the k8 is so much heavier than everything else, I really doubt the difference is very little if one were to put a stock k8 and stock k1-6 on the same scale.  I really have a hard time believing that there is a 29 pound difference between dry weights.  however, I will never be able to check it out as I probably wont ever have anything earlier than my 78 and most people with k1-6 will never have a k8.  So it ends up being all speculation based on the numbers put up by honda which may or may not be accurate.

It isn't just honda that shows the K7-K8 being heavier, the cycle mags showed it too.

If you don't have your stock exhaust then it is going to be hard to get a weighing on it to find out if it is really heavier. Aftermarket exhausts are much much lighter than anything the factory put out and don't work for this comparison, my whole kerker is probably about a heavy as my stock f3 muffler without the headpipe. I wasn't talking about the inside diameter of the exhaust being bigger on the K8, but the cone shaped mufflers are larger overall and they are longer.

The F3 does not have the same frame and swingarm as the K8, the f3 frame is closest in relation to the f2/f1/f0 frame than anything else. The only thing that ties it to the K bikes is that the side covers are interchangible (and maybe a fe other parts you can use that are not exactly the same). The f3 has a disc rear which right away makes it heavier than the k8 arm because of the caliper support mounting lugs.

Scale inaccuracies be damned, take whatever STOCK k8 parts you have lying around and weigh them and I'll come up with the stock 69-76 counterpart. If you want to weigh your whole bike at a truck scale (with you off of it) I'll do the same with me stock K5. Just keep track of how much gas is in it.

[eldar]

There is the problem. I dont have the parts laying around. I am a poor boy and cant afford it!   But like I said, it probably is heavier but I would like a side by side comparison. something with complete bikes and not just parts. More accurate that way. maybe once spring actually arrives here, I will do that. No one may care but at least I will know.

 As eurban said, even the mags listed different weights and so may not be completely accurate. not trying to argue, I would just like to have more accurate numbers.