Mentally priced bikes

[AceOfHearts]

Not sure if there is a thread running like this already, but saw this on eBay and couldn't believe the asking price

£9500 for a CX500, and not even a particularly nicely modded one

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2...

Any chancers that you have seen online?

[trickywoo]

Any of the new CCM bikes people are falling over themselves to buy.

[yellowstreak]

I think we may have already passed "peak cafe".. that would be over priced at half that.

[crusty]

Any knackered old 90’s trial bike

[tdm34]

The CB900F from the late '70's is one of my favourite ever bikes, i've owned two think they're great, and they haven't yet got to the
prices of CBX's or Z1's etc but you then see this apparition and the balloon that's selling it thinks it's worth £13k

https://www.ebay.co.uk/itm/Honda-CB-900-F-cafe-rac...



To Balance the force, here's a proper modded CB900F, this missile has over 195bhp and weighs under 190kgs.........
and yes i'm fairly certain that it cost more than £13k, but just look at it!

[dibblecorse]

yellowstreak said:

I think we may have already passed "peak cafe".. that would be over priced at half that.

Yep, I think the whole scene is (thankfully) on its tweed waistcoated knees ....

[Chipchap]

Not even sure that a CX500 would make a good drag anchor for a boat, let alone a £9500 road bike. They were st in 1981 and now they are just old st.

[yellowstreak]

tdm34 said:

The CB900F from the late '70's is one of my favourite ever bikes, i've owned two think they're great, and they haven't yet got to the
prices of CBX's or Z1's etc but you then see this apparition and the balloon that's selling it thinks it's worth £13k

https://www.ebay.co.uk/itm/Honda-CB-900-F-cafe-rac...



To Balance the force, here's a proper modded CB900F, this missile has over 195bhp and weighs under 190kgs.........
and yes i'm fairly certain that it cost more than £13k, but just look at it!

The bottom bike looks great. The top one is terrible. I just can't see why someone would make their bike less capable on the road (this thing is never going off road) though a voluntary tyre choice like that. Its a bit like "stanced" cars, style over substance.

I have been following some of the builds on the bikeshed youtube channel. Some of them are just plain dangerous!

[OverSteery]

AceOfHearts said:

Not sure if there is a thread running like this already, but saw this on eBay and couldn't believe the asking price

£9500 for a CX500, and not even a particularly nicely modded one

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2...

Any chancers that you have seen online?

If I were buying a CX at that price, I would at least expect it all to be there - about 40% of that one is missing!

[crofty1984]

I like the stripped back looks of a lot of the new café style. Trouble is it's so easy to do it badly. Seat lines on the wonk, obviously cheap accessories, and those 80's Honda tanks. They're supposed to flow into the side panel, without it they just look naff.
Still, when the proportions are right they can look great.
And with my "don't be a miserable fker EVERY day" hat on - if it gets people interested in fiddling about with motorbikes, good on them.

[Steve Bass]

tdm34 said:

this missile has over 195 bhp.....

In fact, that's soooooo hilarious have another..



(It's a lovely thing but seriously.... )

[Rubin215]

Chipchap said:

They were st in 1981...

I think you will find they were shirt for a good few years before then too...

[crofty1984]

Rubin215 said:

Chipchap said:

They were st in 1981...

I think you will find they were shirt for a good few years before then too...

I had a CX500 eurosport in 2005. I really liked it!

[tdm34]

Steve Bass said:

tdm34 said:

this missile has over 195 bhp.....

In fact, that's soooooo hilarious have another..



(It's a lovely thing but seriously.... )

Well I expected someone to bite, I suggest you look at the following facebook pages " Vince and Hyde racing" and "Brent Hyde" or better still subscribe to cb1100f.net, and look up "captains" posts as that is Brent, everyone has the same reaction when I mention this bike, but i've followed this guys work for years, some would say obsession in sorting the issues everyone seems to have with the CB-F engines, some of the fixes have been very hi-tech but some like his revised tensioners and primary gear drive conversions are inspired, infact after talking to him recently the power figure has improved again, in classic bike racing down under the usual engine is the 4V 1100cc Suzuki motors which are capable of 175-180bhp. before they get unreliable, strangely with his mods the bike becomes bomb proof and is now 1220cc and revs to over 12k, he also has sold over 500 sets of the tensioners to happy CB-Fers with out a single failure and is now transferring the the tech to the mighty CBX.

Edited by tdm34 on Tuesday 12th November 20:28

Edited by tdm34 on Tuesday 12th November 20:29

[Steve Bass]

tdm34 said:

Well I expected someone to bite.......

To take a 1980's 900cc normally aspirated engine at an original power output of 89bhp @ 9000 rpm to 1220/12000 rpm would not produce 195bhp. Any engine is a pump and it's capacity to make power is simply based on how much air (and by extension fuel) can be ingested in a single stroke.
Without forced induction the increase would be roughly in line with the increase in capacity especially when the fundamentals of the engine layout haven't been changed. Remember air pressure is pretty consistent and therefore that's all there is pushing the air into the low pressure area caused by the descending piston. Anything above
100bhp/litre normally aspirated is a big achievement.
Then look at the line between the carbs and the exhaust. The barrels are 90 deg to them meaning the fuel air mix needs to turn 90 degrees to get in and 90 degrees to get out. Highly inefficient and by comparison look at the layout of a modern superbike motor where the inlet stacks are almost vertical to the piston.
Next.... it's on carbs apparently. Rather small diameter inlet carbs by the looks of it. Carbs are a huge compromise as the air velocity is required to suck the fuel from the bowls... Bernoulli effect. Bigger the diameter and the more power you make at the expense of low/mid performance. Also, the actual diameter of the inlet is a function of the power as too small and you choke the air able to enter the cylinder. And those in the picture will never support over 45 BHP per cylinder of 305cc.
The head itself won't support the kind of power you're mentioning for many reasons but the valve included angle is a start. Air cooling is another... aibox capacity and design is another limitation to air ingestion, lack of ram air to positively charge the airbox is another.....it goes on and on.
And for what it's worth, great engineering that doesn't provide significantly more air into the cylinder is not going to make much difference.
Bottom line is tuning a normally aspirated engine in a game of small increases due to the fundamental limitations of air pressure (which fills the cylinder) and frictional losses/engine efficiencies. Forced induction is another thing however but in such N/A conversions you're doing well if you maintain the original cc/bhp ratio.
So unless Down Under uses a wholly different box of physics fundamentals I'm sorry but I call custard.... Facebook don't make it really real
Lovely thing mind but more than 195bhp @1220cc N/A ?? Have some more

Edited by Steve Bass on Wednesday 13th November 04:10

[Steve Bass]

tdm34 said:

........... strangely with his mods the bike becomes bomb proof and is now 1220cc and revs to over 12k, he also has sold over 500 sets of the tensioners to happy CB-Fers....

These claims are truly astounding especially when you consider he has a financial interest in the matter....

I'll raise you what some Aussie bloke is telling you with the basic laws of physics and engineering....
It's t'internet.....not real life

[tdm34]

Actually he’s from New Zealand, and obviously you’ve not looked at the work that he’s done, in 1980 for the US AMA series Honda where getting 150bhp out of 1025cc at around 10250rpm, so his claims are reasonable.

But hey what would I know..

[Krikkit]

tdm34 said:

Actually he’s from New Zealand, and obviously you’ve not looked at the work that he’s done, in 1980 for the US AMA series Honda where getting 150bhp out of 1025cc at around 10250rpm, so his claims are reasonable.

But hey what would I know..

If they're so potent he must have some videos of them on reputable dynos pulling these spectacular figures?

Steve is right, you can't just double the power without doing ridiculous amounts of work to it.

[Steve Bass]

tdm34 said:

Actually he’s from New Zealand, and obviously you’ve not looked at the work that he’s done, in 1980 for the US AMA series Honda where getting 150bhp out of 1025cc at around 10250rpm, so his claims are reasonable.

Of But hey what would I know..

Irrespective, physics doesn't lie.
Based on the original stroke of 69mm and rpm of 12k you arrive at a piston speed of over 27m/s which is equivalent to F1 engines of a few years ago.
To add 80cc to each cylinder to achieve 305 (1220/4) requires more than a simple overbore so the stroke is likely increased resulting in even higher piston speed.
Then you have the fuel volume required to support 49bhp per cylinder.... which at a ratio of 12:1 AFR the cylinder head will not flow that volume given the 80's layout.
Also consider the thermal loads of burning sufficient air and fuel to make over 195bhp. In simple terms the energy released is expended in 1/3 power, 1/3 heat and 1/3 noise. Is it possible for an air cooled head and barrels to be able to dissipate the resultant heat??? Water cooling arrived in the late 80's because of the engine performance increase and the need to remove the additional heat generated.
So regardless of who he is or claims to be, simple maths rules.
As a simple comparison, a 2015 RSV4 engine makes 175 bhp at over 14k. Is it really feasible for a 1980's motor to be as efficient as a modern motor? The maths simply says not.
I'm not calling you a liar but the individuals claims don't stand up to basic mathematics and known engine science.
And what really gets the bell ringing is the claimed weight of sub 190kgs from a manufacturers claimed weight of 250 kg.
I have a project CB400 which is very similar in terms of architecture and I'd struggle to see where I could pull 20kgs out let alone 60!!
And FWIW I've spent many years building a radical Ducati and I've got the weight to under 170kgs with EVERYTHING being carbon and magnesium.
Oh, and the motor? 1198S/R with RS parts, crank, rods Ti valves, RS cams makes 200 at 11500. Standard 1198S makes 168.
So 195 from the same capacity in a 40 year old engine??

Edited by Steve Bass on Wednesday 13th November 08:29

[tdm34]

Steve Bass said:

tdm34 said:

Actually he’s from New Zealand, and obviously you’ve not looked at the work that he’s done, in 1980 for the US AMA series Honda where getting 150bhp out of 1025cc at around 10250rpm, so his claims are reasonable.

Of But hey what would I know..

Irrespective, physics doesn't lie.
Based on the original stroke of 69mm and rpm of 12k you arrive at a piston speed of over 27m/s which is equivalent to F1 engines of a few years ago.
To add 80cc to each cylinder to achieve 305 (1220/4) requires more than a simple overbore so the stroke is likely increased resulting in even higher piston speed.
Then you have the fuel volume required to support 49bhp per cylinder.... which at a ratio of 12:1 AFR the cylinder head will not flow that volume given the 80's layout.
Also consider the thermal loads of burning sufficient air and fuel to make over 195bhp. In simple terms the energy released is expended in 1/3 power, 1/3 heat and 1/3 noise. Is it possible for an air cooled head and barrels to be able to dissipate the resultant heat??? Water cooling arrived in the late 80's because of the engine performance increase and the need to remove the additional heat generated.
So regardless of who he is or claims to be, simple maths rules.
As a simple comparison, a 2015 RSV4 engine makes 175 bhp. Is it really feasible for a 1980's motor to be as efficient as a modern motor?
I'm not calling you a liar but the individuals claims don't stand up to basic mathematics and known engine science.

Edited by Steve Bass on Wednesday 13th November 08:12

Whilst I get everything you say, your comparison with a 2015 RSV4 is invalid as it a pure roadbike that has to meet all emission and noise regulations, where as Brents is a pure race bike, it terms of the mods the only original parts are the Crankcases, Cylinder block and gearbox everything else is bespoke, as i've said please register on cb1100f.net and look up his build threads, he uses some very exotic components
has a total titanium fixation, the cylinder head work is some of the best i've ever seen. Now current competitor bikes are generally the TSCC 16v Suzuki's and they're pushing out around 180bhp, so why the doubts?


https://www.facebook.com/Vince-Hyde-Racing-2057333...

A couple of interesting photos, if you "know" the early aircooled Honda 4 valve engines, what's different about this one, and the second one shows the flow chart of the Cylinder head...

Edited by tdm34 on Wednesday 13th November 08:40