CL175 carburetors problem

Talisman

Talisman

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Hello good people. I'm looking for expert advice to solve issues with my carburators on CL175 (1968). Couple of problems,
1. Idling not always the same, it could die easily or some times engine is hunting. It gets better after run, but in my view bike only really goes in forth and fifth gears. In first and second it is in my opinion lacking power.
2. I changed sparking plugs for new one and noticed a black deposit on contacts. So I did followed an idling instructions ( adjusting throttle and air mix screws together) but I wouldn't completely happy with the outcome neither.
3. Adjusting idle revs seems to be only possible with Left Carb. On the Right Carb. adjusting the throttle screw doesn't make any difference.
4. Normally after run, Right Carb. has some oily petrol smelling bleeding on front wall of float chamber( see photo). I suspect a floating chamber washer but haven't yet removed clip to open up a chamber.
Otherwise both units are looks brand new and very neat. I'm sure it can be resolved, but unfortunately I'm not a qualified mechanic )

Thank you in advance

IMG_0739 - Copy.jpg 175 carb.jpg
 
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My best guess would be a clogged idle jet. It is better to clean the OEM brass jets than replace them with ones from an aftermarket kit.
 
ballbearian said:
My best guess would be a clogged idle jet. It is better to clean the OEM brass jets than replace them with ones from an aftermarket kit.
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I have quite a few carbs spare parts ( given to me by previous owner) How to clean clogged idle jet?
 
Talisman said:
I have quite a few carbs spare parts ( given to me by previous owner) How to clean clogged idle jet?
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Very carefully. The goal is not to enlarge the precise drillings of the jets. I used to just use gas, carb cleaner spray , compressed air and very fine wire bristles, but now I also use an ultrasonic cleaner, which I can immerse the entire carb body.
Magnifying glasses and good light help as well.
As clean as those carbs look, it should be easy. Maybe just carb spray. Modern petrol (esp. with ethanol) can gum up the tiny orifices and passages in the body, if they sit for much time.
 
On the Right Carb. adjusting the throttle screw doesn't make any difference.
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I wonder which screw you mean ?

If it is the mixture screw, then yes, blocked passages would account for adjustment of this screw having no effect.

On the other hand, the throttle stop screw is simply a mechanical way of lifting the throttle slide, and screwing this inwards should definitely cause the idle speed to increase.

Unfortunately, on these 50 year old bikes we have no way of knowing what previous owners have perpetrated on them. I was lucky in that my CB175 seems to have been unmolested in a previous life, and simply cleaning the carbs in my ultrasonic bath has got them worked similar to how I remember my original CB175 running.

My other two 175's have several sets of carbs between them, but no amount of cleaning and tweaking got these working as well as I wanted, too many variables, float heights, float valves, jets, etc, which is why I gave up and fitted Chinese copies of the right side Keihin. Still not ideal, but at least the bikes work.
 
Richard Pitman said:
I wonder which screw you mean ?

If it is the mixture screw, then yes, blocked passages would account for adjustment of this screw having no effect.

On the other hand, the throttle stop screw is simply a mechanical way of lifting the throttle slide, and screwing this inwards should definitely cause the idle speed to increase.

Unfortunately, on these 50 year old bikes we have no way of knowing what previous owners have perpetrated on them. I was lucky in that my CB175 seems to have been unmolested in a previous life, and simply cleaning the carbs in my ultrasonic bath has got them worked similar to how I remember my original CB175 running.

My other two 175's have several sets of carbs between them, but no amount of cleaning and tweaking got these working as well as I wanted, too many variables, float heights, float valves, jets, etc, which is why I gave up and fitted Chinese copies of the right side Keihin. Still not ideal, but at least the bikes work.
Click to expand...

Richard, thank you. I actually decide to be on the safe side and tomorrow is sending bike for carbs fixing to a specialist. I trust this man and I know bike will revs properly after professional adjustment. Plus if something else not right it will be fixed as well :)
 
Richard Pitman said:
I'll be very interested to hear how you get on.

( I'm a cynical chap, some 'experts' are less expert than others ... )
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I keep you posted when it's done, and it will be definitely better compare with mine attempts to adjusting idling
 
Talisman said:
I keep you posted when it's done, and it will be definitely better compare with mine attempts to adjusting idling
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Please do, as well as any explanation he might have about what he found wrong. Posting final analysis and the required repairs will help another member in the future.
 
ancientdad said:
Please do, as well as any explanation he might have about what he found wrong. Posting final analysis and the required repairs will help another member in the future.
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OK, the latest news about bike, off she goes for repairs. We started bike before departure, for quick check and it seems run only on one cylinder?! I didn't spotted this before. More update after feedback from specialist.
 
Talisman said:
OK, the latest news about bike, off she goes for repairs. We started bike before departure, for quick check and it seems run only on one cylinder?! I didn't spotted this before. More update after feedback from specialist.
Click to expand...

I'm starting to wonder about battery voltage level now. It will be interesting to hear what he finds.
 
ancientdad said:
I'm starting to wonder about battery voltage level now. It will be interesting to hear what he finds.
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Battery wise, I just recently installed brand new battery. I had some problems with old battery and replaced few things, such as stop signal bulb and turn signals relay, but after placing new battery everything is working well. Last test I did I think was around 13.5 V if I remember correctly
 
Hello, reporting back. The bike is back to my garage. All problems sorted and Honda ticking nicely!
What were causes
1. Brittle fuel pipes, dislodged bits of rubber into carburetor ( both replaced with new)
2. Swollen rubber on float bowl gaskets prevented floats to move freely (both replaced with new gaskets)
3. Float valve needle is also replaced
Fuel_pipex2.jpg Floatbowl_gasketx2.jpg Float_valve_needle (1).jpg

Tip: Apart from carburators, check bike's fuel pipes regularly, as internal damage can't be so visible. Bad thing is that cracks in rubber caused small particles to clog jets.

FuelPipe-Damage.jpg
 
Excellent. It's these small things that don't get the attention and priority they should. You've got a good tech there that will quickly find the simple, fundamental issues without immediately suggesting something like a total carb swap.
 
ballbearian said:
Excellent. It's these small things that don't get the attention and priority they should. You've got a good tech there that will quickly find the simple, fundamental issues without immediately suggesting something like a total carb swap.
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That's right. Those honest people with ultimate knowledge and passion for motorcycles are indispensable.
 
Richard Pitman said:
Did they sort out this issue ?
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Yes, he is. This was a consequence of clogged jet and blocked float. Carbs went through full adjustment. It is completely different bike now. Time to enjoy the ride!
I also learnt about how modern petrol and subsequent exposure to air is damaging carb's gasket and makes it leak the fuel.
 
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