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Discussion Starter · #1 ·
I got another twin today.
(Sold the DOHC750 I was working on to a guy that wanted the engine for a single seat dunebuggy.)
It is a 1972 CB175.
No title junk bike.
Hoping to get it running, throw some dirtbike tires on it and ride it around the trails with by buddies that own atv's.
I got it torn down to the frame today.
I'll post photos soon.

I will eventually need to know how to wire this thing up for kick start only with no lights and a single on/off switch for an ignition. I'm pretty sure I will still need the battery uless I buy a cdi ignition, right?

I know I will need a new kickstart lever, a shifter lever, and maybe a seat. so if anyone has something they would be willing to sell let me know and we'll work something out.

Thanks in advance guys, Looks like I'll be hanging around alot more often from now on.
 

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About time Dustin.... I have ALL kinds of 175 parts and stuff.....
Yes, you will need the battery..... Ground the negative as always..... Hot lead to toggle switch to coil black/white....other coil wire to points.... done..... Steve
 

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Discussion Starter · #3 ·
thanks steve! I think I am just going to build a new wiring harness. How do i need to wire up the rectifier and regulator?
though this info is wonderful, I am focusing on the engine first.
So, I will be spending money there before buying parts. When the time comes I will hit you up.
here's kind where I wanna go with this bike with a 72 tank and stock seat.

[attachment=0:2q5x2wc9]0023.JPG[/attachment:2q5x2wc9]
 

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Sensei
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Dustin..... Good photoshop work!....LOL....
Here's an easy wiring diagram....



On your's, the black wire (pointing left) will only go to the coil.....

Does that give you the info you need?

Steve
 

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Dustin, BTW, the 175 stock frame is very close in design to the pictured 350 frame, so your results should/can be really close.....
Here's mine with a "knee-pad" tank.....





:D Steve
 

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Discussion Starter · #7 ·
question: (given that I could make new intakes) would my stock cb350 carbs work on the 175 or are they entirely too large?

Also, what are the MM sizes of both stock 175 and 350 carbs. I think the 350's are 28mm. correct?

Thanks, dustin.
 

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Dustin....Believe it or not, carb size depends on "K".(serial number determines this)... 20 mm was most common on the CB, and most CL's had 22mm's...... We run Mikuni PV 22's or the 24mm Kei Hin's from either a 305 or an SL 350) on the RACING 160's (which are roughly equivalent to the needs of a well tuned cafe' 175)....... The 350CV's would likely overload the 175.....
 

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Discussion Starter · #9 ·
ok. great. what modifications are required to run these larger carbs? does someone make intakes for this upgrade?
I'm just curious and trying to get a feel for what is available for these bikes.
 

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Dustin, Nothing (I know of) is specifically available as finished parts, there are too many variables... However, some intake parts are available as "kits" you modify to fit your carbs... Any decent machinist can fab you up some once you have the specific measurements required, but a lot of factors are involved: Tract length can be varied to affect the torque curve, and angle is determined by the specific carbs float bowl design, and the mounted angle of the engine within the frame...(port angles) as well as port size, stud placement, and others......


I could be more helpful IF I had some idea of your intentions.... BUT, be realistic! ...altering a CB175 to run a 100MPH is probably possible, but NOT without adding a TON of money, whereas an 80MPH dependable runner is relatively easy (by comparison).
Manufacturers (optimistic) listed top speed was 72 on these bikes.....Actually it's more like 67/68.....

What carbs did you WANT to use?..... And what's wrong with the stock 175 carbs?
 

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Discussion Starter · #12 ·
steve, nothing is wrong with the stock 175 carbs. I just have to 350 carbs lying around and wondered if they were too big. Remember, More Power is always a good thing.

I am not looking for a top speed of 100 or anything close. looking at more like 45 or 50.
I will be finding or modifying a larger sprocket for the rear. this bike will be strictly ridden in the woods on trails and in/or around a creek bed.

If It pulls hard enough I may take it out in the sand. but not really looking for that to happen.

-dustin
 

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Dustin.... Most of YOUR power increase will probably come from stripping the excess weight off the bike (unless you BUILD the engine appreciably)..... Unfortunately, the 175 doesn't have much excess once you yank the lighting, fenders and stock exhaust...... Lighter components will be the key..... (aluminum bars, aluminum wheel rims, smaller battery, plastic fenders and tank, small seat, etc.....).... I'm sure you will end up with a fun toy!........ Steve
 

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Discussion Starter · #14 ·
got the engine tore down today. looks like the cam is toast. going to take it to work and mic it to be for sure though.
Where can I get a new cam. NOS would be fine but I can't seem to find one.

I know these are used for vintage road racing alot. does someone make an aftermarket cam?

-Dustin
 

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dustinlwood said:
got the engine tore down today. looks like the cam is toast. going to take it to work and mic it to be for sure though.
Where can I get a new cam. NOS would be fine but I can't seem to find one.

I know these are used for vintage road racing alot. does someone make an aftermarket cam?

-Dustin
There is a NOS cam on ebay right now with a reasonable price.
http://cgi.ebay.com/ebaymotors/Genuine- ... ccessories
 

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Dustin,
The ebay NOS one is a LOT cheaper than having yours hardfaced and reground.... (about $275)..... I like the Megacycle 122-20 grind, but the valve "pockets" in the pistons need "adjusted" for clearance....
Another option is to put a "wanted" ad on Craigslist...You may find an entire "parts bike" for $100 or so......(same as the NOS cam + shipping)
Steve
 

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Dustin..... Which way did you decide to go?.........There are some steps you SHOULD take to insure adequate oiling to the top end.....But these are easy to do and don't require an investment other than time....We'll get to those when you're ready..... Steve
 

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Discussion Starter · #18 ·
I have decided to take the "run her till she dies" approach.

I put a good cross hatch back in the cylinders and cleaned everything up real good.
Did the gas test on the valves in the head.
Everything seems to be wore like a engine with 13k on it, but I didn't check tolerances.
After all, It is really just going to be a dirt toy.

Going to spend the least amount of money I can and then rebuild the engine later.

I would appreciate any tips you have Steve.
Don't feel like you can't tell me my idea is a bad idea if it really is.
I would rather spend the money now than have a bike the will only last a few months.
Buy if i can get a year or two out of it that would be fine with me.

Thanks Again, Dustin.
 

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Dustin, I'd need pics and specs on the "worn" areas, particularly the cam, journals and rockers....Then maybe I can Guesstimate its life span.....
In about two weeks I'll be starting back on my 175 engine rebuild....It's a sloper, so there are a couple of very minor differences, but it is so close to yours, we could go step-by-step together on the rebuilds....I'm starting with bare cases....
If I were you, I'd go ahead and rebuild now..... Steve
 

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Discussion Starter · #20 ·
I have run into problems with my project money lately. Seems like every time I go to order parts something comes up and I have to spend my Motorcycle money on life!

Anyhow, I have tax refund money and my CL350 is getting new tires - PERIOD.
I kinda like the looks of having the same size tires front and back, but the CL's have a 19" front.
I cannot seem to find wheel size specs for my CL350 or CB175.
Does anyone know these specs?

I would like to maybe do a little swapping with the CB175. is the drum on the 175 the same size as the 350?
 
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