Jonway saga still continues

Well the Jonway saga still continues.
Now the bike is bogging down. Quite bad as well. OK on start up, but as soon as you grab a handful of throttle, BLURRR stop. It is a brand new carb, and it has been running ok upto today. Of course I don't know what crap there might be in the fuel tank, and there is no fuel filter. I have all sorts of thoughts running through my brain. But first tomorrow is to clean the carb, and check jets etc. My these moped are so much fun. It also has a new cdi, but the air filter has come off the carb, so thats something else that might be the trouble. But at the moment i am betting on crap in the carb. See you all again soon, with the next installment of THE JONWAY SAGA, coming to a computer near you.

 

Air filter.
Put it on before you even bother with the carb clean

 

OK chaps, well that did not work. Cleaned out the carb and put the air filter back on. Bike still bogging.
So the Grandson was riding down the road, having just pulled away. Got to the corner and that was it, no drive or power. The bike bogs as soon as you give it a quick blip of the throttle. It will pick up if opened slowly, but never makes it to full throttle. Have got it up too reasonable revs, then stuck hand over the air intake of the carb.Hand gets wet with petrol, Engine cuts, but when restarted will be fine for a few seconds, then back to normal. The bike is not driveable as it cannot generate enough power to pull away. I have ordered a new carb, partly to establish if it is a carb issue, which I think it is. BUt if not anybody any more ideas as to what it could be. All advice welcome.
P.S. the bike starts fine, and ticks over perfectly.

 

Spray some wd40 around the carb and see if the revs pick up.
Could be an air leak

 

Water in carb? is the petrol cap outside of bodywork ?

 

That's a good point. I've seen that a lot over the years

 

Well I don't think it is an air leak. Yes the cap is outside of the bodywork, but I don't think there is any water in carb, as I have now stripped it twice. I worked on it today, and got it running ok for awhile, as long as the choke is on. When the choke comes off, it's not so good. I adjusted the accelerator pump. Thats the little lever that works the small pump when you accelerate. It was not doing nothing at all. That seems to have helped. When we fitted the new carb origionally all was ok, so did not change the jets. But it might need them changing. I must admit that when I first started it this last time, all was not good, but after a few seconds, I thought I heard a small pop, then all was fine. I thought that there was perhaps not enough fuel in the carb at first. Still it is better than it was, and it does rev through the full range. Hopefully the new carb will arrive soon, or we could try out the manky old one, if we use parts from the new one to rebuild it. I still suspect the pilot jet, as the thing is so small that it can get clogged so easily. Will have another go at it soon. Will also clean the fuel tank, just incase there is crap and water in there.

 

Make sure the hole in the fuel filler cap isn't blocked. If it's blocked by some crap it'll create a vacuum in the fuel tank and petrol won't get to the carb.

 

Another good point Milo, but this is as soon as you start, and I have had the cap off to make sure there was petrol in the damn thing.

 

No I think there is something not right with the carb.

 

You mentioned an accelerator pump?
Got a photo of the carb please?
Sounds like a Walbro carb or a copy of it.......

 

The carb I think is a jhihin or something like that, made in Japan.
See photo



The accelorator pump that I mean is the plunger covered with corrigated rubber, just to the left of the throttle cable part that the throttle cable bolts too.
I have cleaned the carb and all seems to be running OK. I have adjusted the fuel mixture as it seemed to be running a bit lean, and liked it when the choke was on. The grand son is away for the weekend so I will change the gearbox oil. I have also fitted a fuel filter, but there were no spring pipe clips with it, so it is weeping fuel. I tested with a can of wd40 for airleaks but all seemed fine. It likes to warm up for a few seconds before any wanging of the throttle, but after that all seems ok. My Grandson is a jinx with bikes, so lets see how long it lasts till it's back here again. I might also have a look at the drive belt. How easy is the rear wheel to turn by hand. Is it free like a pushbikes wheel, or is it a boit of a grunt to shift it.
Al the best Nubsey

 

Right, exactly as I thought you meant.
That plunger that sits in the float bowl is actually a type of fuel injector......sort of.......
When you open the throttle, an arm should start to depress that plunger, which in turn sends a jet of fuel up out of the float bowl and into the intake giving acceleration.
If it opens too soon or too late or is hesitant or sticky in it's operation the bike will not accelerate smoothly.
Which is probably why it liked to work on the choke but not off it, the choke was giving it the extra fuel it needed to go go go.......

 

Yes thats the thingame bob, or what ever its real name is. Anyway all seems good at the moment, till he busts it the next time. Hopefully the fuel filter will do it's job, and no more crap in the carbs.
Nubsey