[RXT]

My CB175 has had some problems for the past year or so. It gets stuck at high revs, have to downshift to get it to come down.

I thought this might be a carburation problem. I went through Steve/Spring66's advice about CB175 carburetor adjustment. I thought I'd try this before doing a full carb cleaning.

Adjustments to the left carb make no difference. Air mix screw can be all the way in or out with no noticeable change. No adjustment to the throttle stop screw makes the bike rev higher, though taking it all the way out causes it to cut off.

Hand placed behind exhaust pipe, very soft "pressure" from exhaust out of the left side. Right side is strong.

(This may be unrelated) I get a sound like a spinning free wheel after I've been accelerating for more than a few seconds. Not loud, but it's there, seems to be coming from engine/transmission. It continues even after I'm off the throttle, but eventually stops -- like it spins itself out.

Should I just begin by pulling and thoroughly cleaning carbs? If so, I welcome any good videos or photo-heavy carb cleaning guides.

 

[I-Ride-A-ホンダ]

I own a 72 CB175. The carbs are very easy to clean and rebuild. A friendly piece of advice that comes from personal experience, make sure you get OEM Honda rebuild kits and re-use any old parts that aren't damaged or worn out. I got some off brand kits and they were a total waste of money and time. Do you have a factory service manual?

 

[RXT]

I own a 72 CB175. The carbs are very easy to clean and rebuild.

That's encouraging to hear. I'm going to work on it tomorrow. Hoping I can reuse all the existing parts. I do have an old rebuild kit from a friend, though I'm not sure if it's OEM.

I have the service manual -- I think -- says SHOP MANUAL across the top of the page (it's a PDF). The date is 1974 (my bike is 1971).
Relevant pages regarding carburation seem to be 56, 143, 152, 172.

I do wish I had more resources regarding process -- those sections seem to be more about theory than how to disassemble and clean. Watching any mechanical procedure, like in a video, is always helpful for me.

 

[I-Ride-A-ホンダ]

See if this helps >>>

 

[RXT]

The video did help, I-Ride-A-ホンダ. Thanks. I cleaned both carbs several weeks ago. They were already pretty clean. No blocked jets, etc. Very little gunk or residue.

In short, left side is running badly, and I was hoping that cleaning would do the trick.

But the carb cleaning didn't change things. Right cylinder still running well, left barely running at all.

I looked at the spark plugs. The insulator around the electrode on the left side was more fouled. The right was more fouled on the threads and overall, but the insulator around the electrode was a lot cleaner. I guess the right was running richer. Someone with more expertise maybe can tell me what's going on here and if it's related.

I replaced with new ones. It didn't make any difference I could see.

The only thing I can think is maybe an air leak or bad gasket somewhere in left carb? Would that make sense?

One thing I noticed when cleaning the left carb that, in retrospect, could be a problem: the gasket next to the float seemed to have warped a bit, ever so slightly sticking out, and when the float is nudged to that side, that gasket could impede its full range of motion.

I don't have any way to test left cylinder compression, but I'm hoping that isn't the issue.

I welcome any feedback. I'd love to get the bike running before it gets cold outside.