Honda Twins banner

1 - 12 of 12 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
Hello All,

I'm looking for some assistance from people more in the know then me. I have a CB/CL175 K0 rolling frame with no engine, currently. I've been looking for some time, but to know avail. When I do find one, the sellers seem to think they've struck gold, or perhaps a better comparison is narcotics, and are pricing accordingly. I don't know how many $650 boat anchors I've seen, but it really is ridiculous.

So, what I do have access to are a bunch of bits and pieces that I can probably fabricobble an engine out of. I've got access to a set of CB160 carbs (22mm vs. 20mm on the 175 and 18mm on 200) a 1968 CD175 bottom end (The cases are a direct swap with the '68 CB175), and a CB200 complete engine (more or less) in pretty good nick. Based on some of the reading I've done most of the CB200 parts and pieces are a direct fit to the CB/CL175 engines. However, this info is seems to be on the 1969 and later, non sloper, CB/CL175.

Differences I've noted but, have limited specifics on are:

The cylinders of the 200 are apparently taller then the 175, though I don't know how much. I know the bore is 55.5mm vs the 175's 52mm.

The head of the 200 flows significantly better and though it's a direct swap on the 1969 and later cb175's, I don't know if there are exterior dimensional differences in the head itself, between the 2 models, or if the changes are primarily internal. If they are external, my concern would be height, and the compatibility of the head cover between the '68 CB/CL175 and the later 200. As mentioned the K0 CB/CL is a sloper and as a stressed member, I need the head cover of the 68 to fit in order to use the mounts on top.

Another item that has come up is that the CB175 and it's predecessor the CB160 actually had better cams then the CB200 (this is only anecdotal, I have no real confirmation of this). As I'm trying to keep this a budget build, I'm trying to avoid spending hundreds on an aftermarket cam, if I can expect moderate to good gains simply from swapping out what Honda already produced.

There are also some differences in the clutch assembly of the 200 vs it's 175 predecessor. Honda changed how it's actuated(?) as well some of the shafts are solid in the 200 vs being hollow in the 175's. Further to this I know the CD175 is a 4 speed and the CB175 and 200 are both 5 speeds. But, the sloper cases between all these models is identical so fitting a 5 speed, though a challenge, is not an impossibility. But, that's a conversation for another topic.

OK. So in a round about way I've got to my question. Has anyone installed the cylinders, pistons and heads of the 1973 to 1976 CB200 on a CB/CL175 sloper? If they have, besides the machining necessary to deal with the height differences, where there other issues?

Advice is appreciated.


Cheers!
 

·
Premium Member
Joined
·
3,006 Posts
I'm sure Simo will be along directly, but here's a few gotchas.

174 wrist pins are 14mm, 200 pins are 15mm. Might be possible to bore out 175 rod ends, or sleeve the 200 pistons, neither option really sounds viable.

175 camshaft has 30 teeth, matching 15 teeth on crank, 200 cam has 32 teeth, matching 16 teeth on crank, ie must use matching crank with cam.

Obvious answer is to fit 200 crank to 175 cases, cases bored to take 200 cylinders, piston, cam, head etc. Need to mod oilways to suit. High capacity 200 oil pump direct swap for 175 item.

175 crank has duplex primary drive gears, 200 has single gear. Late model CD175 clutch basket has single gear, matches the 200 crank to 175 gearbox.

And now for my opinions. In the real world, the CB200 makes much the same power as the CB175, but at lower rpms. So what is holding the CB200 back ? Not the cylinder head, possibly the cam, ( from memory, 5 degrees less opening on inlet side ?) NOT the allegedly smaller 18mm carb chokes. Over here at least, the CB200 has same size carbs as the CB175, 20mm.

I think its the heavier pistons in the 200, along with longer (same stroke though) conrods, just doesn't let the engine rev as freely.
 

·
Registered
Joined
·
228 Posts
Yeah why would you not just get the 200 engine running if it's complete? Honda made damn sure interchange possibilities were limited.
 

·
Registered
Joined
·
3,114 Posts
A 160 engine would bolt right in, you could bore it to 175 cc. or possibly swap in a 175 cylinder barrel.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #6 ·
Thanks Richard,

You've filled in a lot of blanks for me.

I'll take a look at Simo's thread and hopefully that will fill in the rest. Thanks for forwarding that to me.

I appreciate that the CB200 produced similar power to the CB175. This build isn't really about getting more power out of the engine though. It was more about trying to work with the bits and pieces I have available, to build a workable sloper engine for my project bike.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #7 ·
Hi markjs,

The CB200 is a vertical engine. The 1968 CB175 I am working on is a sloper frame. similar in configuration to the Superhawks or the 1965-67 CB160's
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #8 ·
Hi Mike,

Agreed a CB160 engine would be a direct bolt in and could be modified to be a 175. I'm trying to build a workable engine out of parts I already have available.
 

·
Registered
Joined
·
13 Posts
Hi

Anyone tried to ream up con rods from 14mm to 15mm to take cb200 pistons? And also using cb200 barrels in combination with 175 head? I consider trying this as an big bore set for my 175cc. Any thoughts, anyone?
 

·
Registered
Joined
·
4,770 Posts
The 200 head only flows a little better, and it stil requires work, the main advantages are they come with better guides and they have larger fins, and are designed for a larger piston.

Reaming the little ends might be possible But
They're pretty thin anyway and heat treated so youll want to treat them again to get any life out of them
You'll need a press to disassemble the crank and a couple of v blocks and a few dial gauges to reassemble. the cranks are press fitted there aren't any keys to aid re assembly

You'll find it cheaper and easier just to find some scooter pistons to fit and mill the barrels and head to fit

If you've got access to a mill,a lathe, a press, a drill press, a tig welder and plenty of time and money it will be a fun project
But none of it will be plug and play, the oil pump swap ( 200-175) won't even work on between a vert and a sloper

If you just want something to run around, I'd sell all the 200 /cd 175 parts and use the money to buy a 160 engine
 

·
Registered
Joined
·
13 Posts
Thanks for reply Simo

So maybe then using suzuki GS125(150) pistons in cb200 barrels is way to go. Afraid milling down pistons to mutch will make them explode on hi revs. Will also need liners from ex CB750 if going all the way to 250cc. Clue here is to race in the 250cc class with an very light motorcycle. CB250 racer is at least 25kg heavier. they are my target!
 

·
Registered
Joined
·
4,770 Posts
Ok
So youll want a cl175 K0 gearbox ( 5 speed) and all the associated clutch bits and oil pump
From what I've read You can bore the pump to to take a cb200 plunger
If you get a sloper base gasket lay it over a cb 200 base gasket you'll know if the stud pattern will work to fit the barrels and head
I'd mill the cb200 barrels down to the 175 height so the whole lot fits into the frame easily and at the correct angle
And that way you can use 175 studs
 
1 - 12 of 12 Posts
Top