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Discussion Starter · #1 ·
The project is on for a hybrid engine of CD175, CB175 and CB200 parts.

Bear with my dodgy whiteboard sketch


I grabbed peak power and torque values from tinterweb and made up some curves to discuss the point.
I assume the goal of the 200 engine was to have more torque in the lower less angry rpm range and sacrificing the peak power number?

So it comes down to torque, where it’s useable and how the engine feels compare...

I guess the question is, who’s ridden a 200, a 200 with 175 carbs (reputedly larger than the 200) and can compare with a CB175?


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Well, I'm running a CB175 engine with CB200 carbs, in a CL175 frame, and it goes the same as a CB175 with CB175 carbs.

On this side of the pond at least, the 175 and 200 both had 20mm carbs. I've had both carbs in my hands side by side, and can find no measurable difference in venture side. I have been presented with elaborate diagrams to disprove this, but I can only report what I've seen with my own eyes.

I apologise for saying this yet again, but back in the day we raced (on the road ) two CB175s against a CB200, and could detect no difference in top speed or acceleration, swapping riders for confirmation.

My impressions of the CB200. Deeper, gruffer exhaust note to the 175, larger exhaust outlets on CB200 pipes might have accounted for that. And the 200 was definitely more torquey than the 175, felt like you could short shift through the gears, generally pulled more strongly. Not a screamer like the 175, which had the needle buried well into the red without protest, not something I'm going to repeat these days.

Here's the bikes in question. Not me in the CB200 pic, Pete and Spaz adjusting the points.

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It has been a long time since i have ridden a 175 and i do have quite a bit of 160 time. When you are talking roll on power, it is more about the engine stroke than total displacement. Longer stroke equals more leverage on the crank. Back in 1972 Honda had a problem between the CB450 and CB500. The four cylinder bike was quite a bit more money than the twin, but the 450 would run away from the four.
 

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Discussion Starter · #5 ·
Thanks guys, good input so far as always.
The 175 and 200 are both 41mm stroke, but it seems like the 200 crank assembly is a bit more heavyweight than the 175 maybe that will have an influence on how the hybrid engine spins up.
It looks like I have everything to put the engine together, so we will see weather the 200 crank & top end feel good in the 175 box.

I plan on getting CB175 carbs, but as Richard said, there seems to be little difference between them and the 200 ones.



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CB200 Cam vs CB175 Cam

When I said I thought that the 200 cam might be 'better', I was basing it on these numbers, which show the 200 has an extra 5 degrees of exhaust opening, inlet has same duration as the 175. Need to go back to the manuals to see if there is any difference in lift, and of course the profiles could differ, one opening and closing more aggressively than the other.

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I know you can't really compare a low revving pushrod car engine with the above, but back in the day I fitted a 997 Cooper cam into my 998 A series engine. That was a 'mild' road cam, but had figures of 10/56 IN and 51/21 EX, way longer than the bike ones. It certainly made a noticeable performance difference, with a lovely exhaust note.
 

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I put a CB200 tank and side panels on a CB175 back in the day; and I couldn't tell the difference either! ��
 

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Seems to be working.

The age old test, shoving my finger up the venture, could detect no difference in diameter. Just looking at those pics again, might be an issue of area, as opposed to diameter / width. Minimal, though.

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I put a CB200 tank and side panels on a CB175 back in the day; and I couldn't tell the difference either! ��
Heresy !

I've always felt that the CB200 was hit with the ugly stick, while the CB176K6 was the prettiest of the range, especially in cherry red. :grin:
 
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Discussion Starter · #14 · (Edited)
Can see them in the new posts, thanks.

I’m ok with whatever carbs I can get hold of at a good price!
The tinterweb recons that the 200 is 18mm and 175 is 20mm and the 160 were 22mm.


http://www.motorcyclespecs.co.za/model/Honda/honda_cb200.htm


But I know your investigation on your UK carbs showed next no difference

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It wasn't just hit with the ugly stick! It fell out the Ugly Tree and hit every branch on the way down! I still love mine to bits though!
 

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The tinterweb recons that the 200 is 18mm and 175 is 20mm and the 160 were 22mm
Yes, but that Honda UK advertising brochure clearly states 20mm carbs, as do contemporary road tests. I'm sensing an urban myth here ...

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Discussion Starter · #17 ·
18.5 sec 1/4mile... it was never going to feature in the fast and the furious!

Maybe the US did get 18mm carbs?
either way I think the 200 will be grunty 3-6000rpm and wheezing a bit above there where the 175 and 160 would be singing and enjoying it


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My memory is that the 200 ran happily enough up to its own redline, 9500, while my 175 would go right past its 10500 redline.

I was Earnest Thrasher back in those days ...
 
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on a 175/200 cc motorcycle, I would take the horsepower over torque. Honda designed the 175 to wind out. Don't forget, it is much more fun to scream around on a smaller bike than to idle around on a 1 Litre monster.
 
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