CL175 Idles like its on crack

So, I have a 1972 CL175 I picked up a couple of months ago and originally idled ok for the test ride and then started getting weird. I opened up the carbs and the floats were full of gas and bad solder. Ordered new floats, installed them and put the air boxes back on ( PO had them off, no pods, no air box, nothing) and when I started it back up it idled so high it was scary. Wasnt sure how high since I didnt have a tach cable. So I bought and installed the tach cable and did some research to see what it might be and talked to a mechanic friend since I dont know anything about motorbikes other than what Ive absorbed lurking here.

Thought it might be a vaccuum leak so made sure everything was snug and sprayed WD-40 on carb boots and manifolds to see if that helped and it didnt seem to. also some smoke was coming out of somewhere, I think from where the headers attatch to the bike but I didnt want to keep running it like that so it was hard to tell.

Its idling at 7,000 !!! What do I do?? Im afraid the things gonna kill itself!

The one thing that comes to my feeble mind is the float height. I didnt adjust it or measure it assuming the new part was made for the stock setup and I'd be OK. Should I go ahead and measure it?

Air screws are set to spec 1 1/4 turn out and the throttle screws are 2 turns out.

I dont want to mess with it till I have a solid lead on the problem.

Thanks!!!

You'll definitely have to set the float height, it could be the culprit. Also, when you started it did you have the choke closed or open. Did you try turning the idle screw to lower the rpm's?

Set carbs to factory specs (as per your manual), sync carbs, set timing and points to factory spec (again... manual), and go from there. No point in trouble shooting until you know you're working from a solid foundation.

Also... Lube your throttle cable and make sure its not pinched or kinked anywhere.

thanks for the quick response guys!

The throttle cable is a little chewed and really wants to sit in an extremely dangerous place where it gets pinched by the steering lock since the clubmans sit so much lower than stock. ALL of the cables are routed like garbage actually. Ive looked for good examples but havent found any. I'd love to see some good examples to follow rather than doing everything 2 or three times.

So float height - in the manual thats fuel level I assume? It says 21 mm, is that measured from the flat of the carb (when the bowl is off) to the top (exposed part) of the float?

Ill start with your suggestions and let you know how it goes.

Also will the clymer manual be better than honda at telling me HOW to do thing as opposed to just listing specs?

When I said top of float I meant bottom, I was thinking about how they look open and in my hands. also When i said 'flat' of the carb im talking about the gasket surface.

Sorry, Im learning!

Clymer books kind of suck, but for what you're after it'll work fine. Look for an actual Honda service book. There are digital copies online for free.

As for the floats... Search YouTube. There are several really great how to vids that will explain what you need to do way better than I could (I'd link some but my dumbass smart phone wont let me). Good luck, and keep us posted

You can download the Honda manual here: http://www.manualedereparatie.info/en/download/honda-cb-125-cb-175-cl-125-cl-175-1971-Service-manual.html

Click the small 'Download' below the three preview pics.

Also, I have the carb section of the Clymer manual scanned that actually documents setting the float height pretty good, along with a nice picture. PM me your email address if you'd like it.

Here is the section for the float height

HotPotato said:

So float height - in the manual thats fuel level I assume?

Click to expand...

Good question. Actually float level is more or less the corollary of Fuel level. The "higher" a float is, the further it is from the gasket surface and the LOWER the fuel will be in the bowl.

What we are trying to do is to change fuel level but on most carbs, it's hard to do because it requires a modified float bowl with a clear tube attached. Most riders don't have a spare float bowl to modify, so carb manufacturers came up with a way for us simple folks to adjust the floats instead. What we want is for the fuel level to be around 3mm below the gasket surface in most cases.

The key to doing a float level check is to carefully and slowly tilt the carb as described above.

In your case it sounds like the slides are hung up or a cable is holding the throttles open. I'd start by checking teh slides. They should be more or less closed.

Sounds like the slide may be installed backwards? I have done that before...

i have fabbed an adapter to the drain screw port to verify float height with a clear hose
your float level should be set correctly of course

however it is not your float making it idle at 7000 rpm's,it just does not work that way your slides are not all the way down or throttle valves are not closing depending on the type of carbs
if your advancer sticks it can mess with your idle as well

So much good advice, thank you guys!

Im gonna start with installing the new throttle cable, making sure the slides move freely and arent installed backwards and check the float height. I get how to set the float height and measure it now, but what should the float height be?

And how to I know if the slides are closed all the way, can I see them through the air intake when I take the air boxes off? Is the cut away in the slide supposed to face the rear of the bike?

And what are the throttle valves and advancer?

I'll sync the carbs too, I watched a good video on youtube a while ago about this Ill try to find it again.

OK, this seems like a good start, I'll do the points and timing later as this seems like a big obvious problem and less of a fine tuning one. Hopefully I can get to the bike in the next few days (I dont have regular access to my buddies garage). I'll let you knwo how it goes and get prepared to do the work in the meantime.

You guys are awesome.

Throttle valves are the slides. The advancer is the ignition auto advance-retard unit that sits on the end of the cam under the points plate. They consist of two weights that are moved under centrifugal force as the revs rise and that rotates the points cam to advance the ignition timing. Over time the springs wear out and things rust up and if that sticks at teh wrong point, teh timing could be sitting at 35 degrees at idle instead of at 5 or so degrees BTDC. That will cause it to rev high.

Yes, the cutaway is supposed to face the intake side (rear).

Thanks for clearing that up Teazer, I'll check the advancer when I get to the points.

Today I checked the carbs and installed a new throttle cable. The slides werent facing the right way, though when I changed the cable, I had put the slides back on wrong, left on the right, right on the left. Thought I had kept track of which was which, but maybe not. If I did, then they were on wrong and keeping the slides would have been wide open.

I didnt get a chance to turn the bike on since I ran out of time, but it woulda been nice if it is such a stupid problem.

the old throttle cable seemed to move smoothly even though the cable housing was all chewed up (the inner steel housing was fine). I replaced it all the same and rerouted so it wouldnt get bit up again. Not sure if I did it right, how much play should there be? and do I need to do anything to make sure each cable is adjusted right or do they just work in unison?

I checked the float height and theres no way that it could be 21mm which is the height im finding everywhere – or at least if im supposed to measure the way the clymer manual says (see p.1 of this thread). I didnt have a guage or ruler but A = 18mm +/- as set. I made a jerry rigged guage that sat on the gasket surface and capped at 21mm and brought it with me to the garage to set the height, If A = 21 they would be all the way down. which I assume is incorrect. what am I doing wrong here?

Also one thing I forgot to mention is Im missing the right airbox cover. Im sure I'll need one to get tuning right, but could missing it be making it run like this?

What me and my buddy whos helping me cant figure out is why it ran fine when we picked her up but now this...?

Next I'll adjust the points and check advacer for corrosion and spring wear? would worn springs be obvious?

of course 'ran fine' is subjective, but it certaintly idled in the right range and rode ok minus the brakes being garbage

correction: subjective to a dude who doesnt know anything!
Obviously objective to someone who knows....

Pretty much. You would be able to see/feel the free play.

If it ran when you picked it up and won't run right now, it's a pretty safe bet that something you did was the cause of the problem and it sounds like the slides are hanging up. The slides may be in back to front and in the wrong carbs or both. Either would cause that problem. Make sure that they both close properly as a first step.

There should be a couple of mm of free play at the throttle housing and both carbs have cable adjusters on the top so that you can adjust them so that they open together at the same time.

If one lifts before the other, adjust the first opening one to have a little more slack or tighten the slower lifting cable so that they both have a little slack in the cables and both rise together.