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Discussion Starter · #1 ·
CB 175

Last year I decided to buy my first Motorcycle after growing up riding dirt bikes and always having a passion for two wheel vehicles. I ended up finding an old 1973 CB175 on Craigslist and was immediately attracted to the bike. Something about vintage simplistic looking bikes are beautiful to me, but I assume so for many of you as well.
Anyways, I decided to meet up with the man and look at the bike. The bike looked fairly clean IMO besides a rust spot in the back right exhaust, but I could look over that. I rode the bike and it ran, but it didn’t like to idle, it would die if you weren’t giving it gas. This should have been an immediate warning sign, but I guess I was so naïve and excited by the bike that I assumed that I could just do minor repairs and throw a few more bucks into it.

I just recently took the bike into a local shop and they came back saying that the bike has no compression in the right cylinder. The estimated cost was $1000 for repair which is more than what I paid for the bike so I decided against it. I also assume at this point that won’t be the only problem I’ll run into with this bike and I’m not looking to spend more money on this bike than its worth. When I went to go pick up the bike from them, the owner of the shop said it may be worth taking it apart on my own time and tinkering with it, that being that these bikes are great for learning how to take apart and put back together. I decided I’ll look into it. W hen I got home I checked out a few threads about this bike and they seemed to have echoed what the owner had said.
I thought about it and I am saying f*%k it why not. I am young (18) and in my humble opinion, fairly competent. I know it’s A LOT easier said than done, but I am up for the challenge and instead of piecing out this beautiful bike or pawn it off on someone else I thought I at least get a life lesson or some skills/knowledge out of it. Even if it's a lost cause or I fail, I think its worth trying.

The Bike still does run, it's just constantly wants to die on me if not given gas but when it goes it goes (on a good day). This makes me believe that it's not a lost cause but I could just be giving myself false hope and could be wrong.

Anyways, this is my starting point. I am going to search other forums and threads to help better wrap my head around this bike, but if any of you have any idea or advice to help point me in the right direction, it would be much appreciated! I'll try to answer any questions the best I can but again I am new to this!

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I do have the filter covers, they are just off.
 

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Most shops these days don't have the expertise to handle vintage bikes, if they do work on them it will cost a fortune. You're going to have to do most of the work yourself to afford ownership. Pull the valve adjustment caps off and look for a broken valve spring or a bent valve(stays part way down, w/a whole lot of valve clearance). No obvious signs of damage? then adjust all four valves, run it a while and retest the compression. The idle problem could be any of several things, bad plug, carb out of adjustment or a plugged carb jet.
 

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Hi and welcome
First off change the oil if you plan on running it again, even for 5 Min. oil is cheap, parts not so much.
Get a FSM
If there's no obvious broken top end parts
Charge the battey set the timing,change the plugs, check the compression.
Running on one side could be mechanical, electrical or fuel related, all of which are easy to fix on a 175
 

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Discussion Starter · #4 ·
Most shops these days don't have the expertise to handle vintage bikes, if they do work on them it will cost a fortune. You're going to have to do most of the work yourself to afford ownership. Pull the valve adjustment caps off and look for a broken valve spring or a bent valve(stays part way down, w/a whole lot of valve clearance). No obvious signs of damage? then adjust all four valves, run it a while and retest the compression. The idle problem could be any of several things, bad plug, carb out of adjustment or a plugged carb jet.
I have at least already cleaned out jets so I am good there, but I'll check off the other possible problems and get back to you about the idling! I'll also check the valves, thanks again for the advice!
 

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Discussion Starter · #5 ·
Hi and welcome
First off change the oil if you plan on running it again, even for 5 Min. oil is cheap, parts not so much.
Get a FSM
If there's no obvious broken top end parts
Charge the battey set the timing,change the plugs, check the compression.
Running on one side could be mechanical, electrical or fuel related, all of which are easy to fix on a 175
I have already changed the oil and bought a new battery so I am good there, I will need to pick up some new plugs though. As for the service manual, luckily someone has put the PDF for the FSM online! Thanks again for the advice!
 

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Discussion Starter · #6 ·
I opened the side of my bike to adjust my valves and right when I popped it open oil came spilling out.
Is this normal, i haven't seen or heard about this in any other valve adjustment videos or threads?

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Yes, oil will come out there. Tip the bike a bit. To keep the oil spill down, get an old cover and cut out a window so you can see the pointer and rotor. Make it much better when you check the timing with a strob while it is running.

Get a compression gauge and double check the compression--chokes open, throttle wide open, kick until reading no longer changes. Don't trust what the shop told you.
 

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I want to second what jacksvintage said. This is not a non compression situation if what you say is true. If it runs well at speed with decent power and response, then the engine is running on both cylinders sometimes, and if there was no compression it would never do that. What you have is an maintenance problem, and in my experience, if poor idle and hard starting like you describe is still there after the usual maintenance things like valve adjustment and setting the timing and point gap are done, then it's time to clean the offending carburetor again. The pilot jet circuit is very narrow and can plug up easily. The jet can be clean, but check the adjusting screw and be sure the passages inside are clear. Use a parts blow-up like the ones at www.cmsnl.com https://www.cmsnl.com/honda-cb175k7-super-sport-1973-usa_model423/partslist/E20.html#results to see what I mean. If that's seems OK, then it's likely a vacuum leak. They can drive you nuts. Make sure the gasket between the carb and the intake pipe is good, and between the intake and the engine.

More than one person has sold a very nice old Honda like yours because of a vacuum leak that they could not find. If it's there it can be fixed for a few dollars, but finding it can be tough.
 
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