Honda C50 not starting

[xww10]

Hi all,

I'm new to this forum. Just joined today. I'm having some trouble with my Honda C50 I bought a couple days ago (my first bike!). I've just fixed a vacuum leak from the carb to the intake manifold and the idle was really erratic so I fiddled with the pilot and throttle stop screws according to some instructions from the manual with no results. After that, it can't start anymore! I've checked the spark plug and there's a spark and I can smell fuel (checked the tank just in case too) but nothing happens when I kick start it. Can anyone help with some basic settings for those screws because I may have mucked it up. Please help! Thank you all in advance.

[F5 Dave]

Welcome to the site.

First off you have clearly admitted that it might have been what you have done which is a first. But perhaps it is as simple as the spark plug has fouled, try replacing it with a new one for a start. Sometimes they spark when out of the cylinder but not inside which can trap you for a while.

Otherwise try cleaning out the carb particularly the pilot jet (smallest hole, but don't poke wire through).

[xww10]

Welcome to the site.

First off you have clearly admitted that it might have been what you have done which is a first. But perhaps it is as simple as the spark plug has fouled, try replacing it with a new one for a start. Sometimes they spark when out of the cylinder but not inside which can trap you for a while.

Otherwise try cleaning out the carb particularly the pilot jet (smallest hole, but don't poke wire through).

Hi Dave,

Thanks for the support. I pulled the spark plug and its so worn the electrode is barely poking out of the ceramic but it was still sparking! Remarkable it was running before. Anyways, I changed it for a new one (I thought it was expensive at $7). Installed it, kickstarted it, 2nd kick and it runs! Amazing little engine this.

[F5 Dave]

15million asians can't be wrong (or how many zillion there are running around in some form or another).

Right now you can go out & practice wheelies (hint: stand on the lever & rev it up then let go).

[xww10]

Cheers, Dave hmnn not sure I'm competent enough for wheelies yet. What sort of maintenance should I be doing on the c50? I probably need to lube the chain and change the oil but not sure what products work in my case. How about chain adjustment do I need to do that too? Thanks for your help!

[F5 Dave]

In general there is a cap under the seat that needs petrol put in it every two or so weeks.

Do a google search & you will find any amount of info. These bikes will run on virtually any sort of 4 stroke oil, car or bike oil take your pick. oil the chain with the same if it still has the cover on it, else chain lube from a bike shop.

However:
Pay attn to brakes & tyres. Get checked if intending to ride on the road.

[xww10]

Hi again Dave, my C50 stranded me at the side of the road today!
I slowed for a roundabout, put it in neutral while waiting in line, and the engine died. Tried restarting to no avail. I'm trying both screws on the carb to make it run better but the idle is weird, it doesn't seem to be constant. If I get it running OK, then go for another ride and stop, the idle is a little different again.

There are two screws on the carb, one has a spring around it and the other is recessed into the carb housing and needs a screwdriver to turn (the other doesn't). Do u have any tips on how I should set these two up so that I can get a decent idle going. Full throttle running is beautiful but it seems that the low speed and idle is a bit tricky on this bike. It also has difficulty starting even with the new plug. I think this maybe due to the improper set up and may be flooding the cylinder and wetting the spark plug. Please help!

[F5 Dave]

Hmm. Airleak is my guess. These probably have the carb bolted on to the engine with a block of something resembling rubber or phenolic in between. when the bolts get overtightened the faces warp. Some sort of gasket may be in order, but try to check for flatness & dress up carb & block with A good oilstone or sandpaper on a piece of something flat. May need to remove the studs with 2 nuts tightened against each other. These won't have come out in a million years so this might not be so easy.

he one with the external spring is the idle speed adjuster. It just lifts the slide a little. The recessed one is the idle mixture which adjusts the mixture at closed to just off closed throttle. Start with say 1.5 turns out & adjust for best idle when bike warmed up. As for other problems I'd check there are no other blockages in the carb around the pilot jet (smallest jet) & it's passage into the throat. I'd check the floats aren't leaking (shake & listen) & that the float needle is sealing properly.

So when it stops & refuses to start there is still a spark? Worth checking.

Also thinking back. . these will be points which are a bit before me, but plainly simple. check the gap is sufficient, erm guesses 24 thou. Not too critical but if they close up they are a bitch.

[Motu]

One of the best bikes I've ever owned was the lime green C50 I was given.The previous owner had cleaned the carb and couldn't get it running again.I removed the slide and fitted it the correct way round and had 8 years trouble free running out of it.

I also have a TF100 that the previous own spent $800 on a complete engine overhaul - but he couldn't get it running when he put it back in the bike.He cleaned the carb and everything y'know.So I removed the slide and fitted it the correct way round and she's a real sweet runner.

As Dave says,you've done something to something that you know nothing about....I'd get someone who does to have a look at your work.

[F5 Dave]

Haha, not a bad couple of stories, sort of thing you take for granted. I wonder if our chap with the Dellorto'd Pampera has a similar impediment? Just trying to remember the slide.

An old friend once told me, Listen to what people say, but don't listen to what they say. I might have spouted this before but the amusing bit was he who whilst working through a list of multiple 'this'll be it' faults on his ancient B120 when he embarrassingly had to admit he'd put the float needle jet into the valve upside down so it was flooding, surprisingly only a little.

[xww10]

Thanks for all the replies F5 Dave and Motu. I have to admit I messed up. I'll be trying F5 Dave's method to get the settings right. Now at least I know which screws do what. My C50 Haynes manual has also arrived which is a plus. I've just been pulling the screws out, making sure they're all clean and using some carb cleaner. When I pulled the throttle slider out, the return spring came out all mangled, so I went to the wreckers for a new one. That explains why the throttle is quite sluggish to return. The needles look very clean and with no scratches so I think they're OK. I also got a new air filter from Casbolts which I think will help things. Will let u know how my tuning gets on the weekend! Have a good Christmas and New Year everyone!

[F5 Dave]

Cool, take out & blow through all the jets & passages in the carb (sometimes some tube helps if you don't have compressed air), but don't poke anything through them.

[xwhatsit]

I removed the slide and fitted it the correct way round

You may recall my (rather panicked) thread on this matter, which was resolved in the same way

I believe the C50 moved to CDI some time around 1974-6, so I'm pretty sure this bike won't have points. Definitely do the points, though, if it's got them; I know a guy with an original XL250 (the early 70s model). After doing the points on that it was a completely different bike -- the C50 hasn't exactly got horsepower to spare, either

Good luck! Love those bikes.

[Motu]

My 1981 C50 had points,I've got half a dozen C50 motors and all have points.

[xwhatsit]

Hmm, maybe that was just USA and Japan that got CDIs, and they used up their remaining stock in the rest of the world.

EDIT: One or two sites mention they changed to CDIs because of USA emissions regs. So maybe the rest of the world stuck with ankle-breaking points