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CL 175 Running Issues

AR_CL175

Member
Joined
Jun 21, 2021
Total Posts
16
Total likes
0
Location
Alva, Florida, USA
Hey Everyone,

So I bought a 72 CL 175 back in May. It was running alright but not great. I (no prior motorcycle/engine knowledge) decided that I would start diving in to make it run better. It was originally bogging down around 4k RPMs. It’s no longer doing that, but now it will die while accelerating. Usually, once I get up around 6k RPMs and shift into 4[SUP]th[/SUP] gear, as soon as I clutch out, the bike dies. It’s done this in lower gears too (1[SUP]st[/SUP] into 2[SUP]nd[/SUP] mostly), but normally it’s between 3[SUP]rd[/SUP] and 4[SUP]th[/SUP] or 4[SUP]th[/SUP] and 5[SUP]th[/SUP]. It’s done this since I purchased the bike, but it used to only be while riding at high speeds (cruising in 5[SUP]th[/SUP] gear) and not that frequent. It happens pretty much every time I ride now. Slowly rolling off the throttle and easing back in after shifting seems to help versus immediate stopping throttle/clutch in, but even doing that, it will still die, just not as frequent. I should mention, the bike fires up and idles fine. The issue comes once I start riding. Below is a list of everything I’ve done so far:


  • Cleaned carburetors (multiple times)
  • Set float height to 21mm
  • Replaced spark plugs and confirmed gapping
  • Replaced condenser
  • Replaced throttle cable
  • Added fuel filter
  • Cam chain and valve adjustment
  • Set the point gap and ignition timing

From talking to some motorcycle friends and family, it seems like the engine is getting starved of fuel, leading me to assume it’s a carburetor issue. I’m pretty sure I don’t have stock carbs. I looked at the jets in the carbs and couldn’t find out what sizes they are (if there’s a way to identify them that someone knows about, I’d love to know). The shop manual (thanks to this forum for having a nice library where I could download and print my bike’s manual to hang in my shop) and it looks like I need # 90 main jet and a # 38 slow jet.

TLDR; I’m looking to diagnose what may be causing the engine to suddenly die while riding. I’m thinking it’s a carb issue so I’m putting it in the carb thread. Any help is appreciated!
 
-post a picture of your carbs. if there are no markings on the jets, you may have aftermarket carbs.

-try running with the gas tank cap unscrewed and see if it improves.

-until you find the problem, i'd ditch the fuel filters as they can cause fueling problems. when you get the bike running well, you can try to add them back.
 
+1 on pictures, it will potentially help identify what you're working with. Be sure the pics show your air filter situation as well.
 
-post a picture of your carbs. if there are no markings on the jets, you may have aftermarket carbs.

-try running with the gas tank cap unscrewed and see if it improves.

-until you find the problem, i'd ditch the fuel filters as they can cause fueling problems. when you get the bike running well, you can try to add them back.

I’ve put some pictures below. Let me know if anything more specific would be helpful. Checked again and no markings on the jets. Both carbs face the right side of the bike. So adjusting the left one is a bit of a PITA.

Think I’m running the stock air filters.
95e5820225fa168a6319370c4b51a95e.jpg


1aacebf90a5b24f5c159f8ed6b75b953.jpg

70a7c0fa86d65a1db299dbb661196eb3.jpg

dd43d94cba39bfafa1881a32ab146797.jpg



Sent from my iPhone using Tapatalk
 
Well, those are not original, Honda would never have put 2 right hand carbs on a bike and they aren't marked Keihin as the originals would have been. Also, that air filter in the 3rd picture looks pretty rough. Since the jets aren't marked, who knows what you have in there. It does look like the choke linkage is connected, but are you sure both chokes are completely open when the choke lever is in the off position? When the bike starts to run poorly, have you tried lifting the choke lever a little to see if it makes things better or worse?
 
Yes, those are the same Wincycles carbs that I have fitted to my CL175, they work well when fitted with the original Keihin jets.

More info in this thread:


https://www.vintagehondatwins.com/forums/showthread.php?249-My-CL175K7/page2



In summary, needles in middle notch ( of three ), Chinese unmarked jets swapped for Keihin 38 pilots and 98 mains. Bike running DS Silver pattern CB175 pipes, CB200 air filters with RamAir foam, Charlies ignition.
 
Also make sure that all gasket surfaces (carb, intake, and spacer) on each carb are flat, like lapped on a flat surface flat, as they can warp. I get rid of the o-rings and make regular gaskets for those surfaces, I don’t trust the o-rings.
 
^^^And, don't overtighten the carbs to the manifolds or the manifolds to the engine, they can get warped if you tighten them too tight.
 
Thank for all of the quick responses. I'm going to have some free time this weekend so I'll try out/test some of the suggestions provided and let you know how it goes!
 
Is the problem the same in neutral as it is going through the gears?? Did you check the petcock screen for rust particles?? My tank was pretty rusty and would clog the screen and the screen was damaged. Fairly easy to remove petcock (after removing the tank) and not expensive to replace or rebuild. You can check the flow by removing the fuel lines at the petcock and opening the valve. Flow should be steady and even. Remove the gas cap, did the flow change?? While you're at it check the petcock in the reserve position also.
As stated above, these bikes didn't have secondary fuel filters and that may be causing added restriction to the gravity feed flow. Are the fuel lines kinked?? Also my crossover tubes were clogged with rust and had to be cleaned out. Wouldn't allow the fuel to cross over, so I was running out of gas while I still had half a tank left!
What do the plugs look like after running 5-10 miles?? Might also try a short ride without air filters, check plugs again. Without air filters should show a lean burn on plugs. Won't hurt the air filters to soak in Dawn dish soap, rinse GENTLY from inside then outside. Sit in sun a while to dry. Helped mine and postponed having to rebuild the filters.
This may sound like pretty basic stuff, but we've all throw money at a problem and overlooked the obvious.
 
Hey Everyone,

I had the day off yesterday and was able to spend some time on this. Tried riding around with the gas cap off, no improvement. Pulled the plugs and they were black black.

Black plug 1.jpg

I pulled the carb needle and moved it from the bottom position to the middle position (Thanks for your comment and linked thread Richard Pitman. I didn't know there were different notches on the needle *facepalm*). Went for a ride and it was substantially better. Rode for about an hour and a half and only had it die on me about 5 times. Still not perfect, but at least I could actually ride it outside of my neighborhood. I pulled the plugs when i got back from that ride and it's about half white and half toasted marshmallow.
Tan plug 1.jpg
Tan Plug 2.jpg

I've seen conflicting things online about what color the plugs should be. I've read that both white and tan are perfect. What color should we be going for here?
 
I wouldn't say white is perfect, it can be too lean for extended runs at high rpm but somewhere between white and malt color is where you want to be. The middle clip position for the needle adjustment is still optional, you could drop the needle one more notch (clip one notch higher, second groove from top) as long as the transition off idle isn't affected by it. You also need to find out what the WOT jetting is (on full main jet, needle fully lifted). You have to do a plug chop at WOT in say 3rd gear, pull the clutch and hit the kill switch, then coast to a stop on the side of the road to get proper color from full throttle.
 
Hey Everyone,

Wanted to give an update on this.

I ended up getting some genuine jets from JetsRus (finding the proper size), and that combined with adjusting the needle position seems to have fixed my issues! Currently chasing down a pretty bad oil leak that seems to have begun after I did a change, but at least this problem has been resolved! Thanks for your help everyone.
 
Hey Everyone,

Wanted to give an update on this.

I ended up getting some genuine jets from JetsRus (finding the proper size), and that combined with adjusting the needle position seems to have fixed my issues! Currently chasing down a pretty bad oil leak that seems to have begun after I did a change, but at least this problem has been resolved! Thanks for your help everyone.

Glad you got it running well. As to the oil leak, where is it coming from? It could simply be coincidence, but if it's coming from underneath the bike it could be related to the oil change (missing o-ring from the drain plug, lost when the plug dropped into the oil pan)
 
It's coming mostly from underneath the the right side cover, but also a little bit from behind the back end of the left side cover.
 
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