Yamaha LC50 Wet Spark Plug PW50 top end carb

I rebuilt the top end on my 1980 Yamaha LC50 Champ with a brand new PW50 60cc big bore top end kit and a new PW50 carb .

I used the PW50 top end to get rid of all the crazy vacuum auto choke BS.

It also has a new magneto and ignition coil and tested my CDI on a friends running Champ . . so it is not a spark issue.

It also has 120 psi compression with the new top end kit.

It seems to be wet fouling the plug after several kicks to get the fuel to the cylinder.

I reopened the top end .

Drained the small amount of fuel out of the case .

Dried it all out. Put it back together.

After many kicks I get it to start and run for about 10 seconds.

Then it dies and won't start again.

Pull the plug and its wet .

The knock off PW50 carb I bought off EBAY doesn't have any markings on the jets so hard to tell what size they are.

Any jetting/ carb tuning suggestions ?

Here is the link to the Carb I bought for it.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

I also blocked off the oil tank and i am running premix 50:1 Yamalube.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

A bad charge coil will affect spark too. Check that the needle clip is in the correct notch. I have two of those carbs and no problem with the jet they come with. prob a #70. With a 60cc kit you will need a bigger main jet and better than stock air filter.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

It was in the middle row .

We moved it up one so the needle would go down farther.

Still wont start.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb


You tube video of my progress

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

Have you bottle feed it fuel from a spray bottle? if there is a drain screw in the float bowl crack it open after it stalls and see if there is gas in the float bowl. If it were me I'd ditch both your carbs and get a good carb like a vm18 or a good pw 80 carb, not a nock off one.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

its that pesky bi valve.. i gave up on mine after many a weekend trying to get it to start.. i will say i got the same symptoms as yours after messing with the reed valve

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

Dennis Ellington /

Tim I sent you a message

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

Chris Edwards /

Did you ever get this to work? I've inherited a champ with a frozen piston and am considering the 60cc upgrade and pw 80 carb.

How did you deal with the old BVS valve? What new components did you use? Could I basically ditch the whole vacuum/choke/oil injection system and run premix through a new carb and a new cylinder head?

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

EUREKA ! ! ! !

We have found the problem .

It was a bad Charging coil the whole time.

It would read ok on the OHM meter . . until you got it hot .

Then it would fail and stop the engine.

Took forever to figure it out but my buddy Ron finally got it done !

Now it is doing 32 on the flats with the PW50 60cc top end on it.

Hope you get yours running Chris .

They are super fun to ride around on :)

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

having a very similar issue. I wonder what the charging coil was that they replaced? The ignition coil? or the source coil? there is also a lighting coil. The only coil related to charging would be in the Magneto. The ignition coil is the part with the spark plug wire. OP, if you still get notifications from this site, i have a question for you.

Re: Yamaha LC50 Wet Spark Plug PW50 top end carb

Jack Rutherford /

They replaced the charge coil on the stator.

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