50cc issues By div (Read 2,462 times)

[div]

Background:

I have a 50cc 4-stroke roketa. Had it for about 8 months now. Has ran fine up until a few weeks ago - but has always ran pig rich. A/F screw turned all the way in, washer in the top slot of the needle - plug is just black. UNI pod filter, scrapped the stock airbox. Scoot would still do 43-45mph all day. Up until about a week or so ago - loss of power and now likes to die at idle. Hard to restart.

Adjusted the valves to .004
Found that a hose from the PAIR/EGR setup that connected to the valve cover had broken off - fixed.

Now when it ran, it's smoother than ever. but he idle hunts from 900-2k rpm, and it still likes to die every now and then. Still fouling plugs.

check for vacuum leaks, replace the fuel line and filter.
when i'm tugging on the vacuum line from the intake manifold, the fitting pulls out of the manifold still attached to the hose. manifold rubber is split - need a new manifold.

Since i have the manifold off, i dig into the carb to see how it's jetted. Number on the top of the main jet is H17. Number on the pilot is H37.

Everyone always talks about 75-95 for the sizing on the main. Does anyone know what I have? The main is smaller in diameter than the pilot - is this normal?

[kr10k50]

That is very curious. Under no circumstances I can imagine should the main jet be anywhere close to the size of the pilot, let alone smaller.

This may sound silly, but does the "jet" itself appear to be smaller, or are you referring to the hole in the jet? You should just barely be able to see light through the pilot jet when held up to a bright source, and a couple strands of copper wire should be the only thing that you can get in there for cleaning purposes.

Were that actually the case, then it would be nearly impossible to run as rich as you are describing, if it would start and run at all.

It's hard to say what jets you have in there. If you haven't done any jetting work after installing the Uni-filter, you should be running lean.

Enviromoto has a nice Naraku jet kit, that should be able to take care of any up or down jetting you might feel you need. I've got an itching suspicion, it could be something else.

You'll need to straighten that manifold problem up before it sounds like you can stabilize the idle enough to tune the A/F mix properly. I'd replace that then get back to us for sure. Pic's and Vid's will sound help bunches.

[div]

Yeah - it's baffling me, too. The scooter was purchased new - no one has been into it but me, and this is the first time I've cracked open the carb.

My camera battery is dead at home, and i didn't bring the parts in to work - which i may end up having to do to measure them with real calibrated equipment.

Eyeballing it - the hole in the pilot jet is noticably larger than the hole in the main. The pilot looks to be almost 1mm in diameter, and the main is closer to half that. But those are eyeball guesses.

The carb I have is almost identical to the one in the big guy carb cleaning video - the fuel enricher mount is cast into the carb (not removable and able to be blocked off with a plate), the jets, float assembly all look the same. The only difference I see is that my cap for the diaphragm and slide is brass instead of black plastic.

I know I'm going to have to fix the manifold issue first - I'm hoping someone can identify and/or explain the jetting to me so i can order all the parts i need at once (the scoot needs a new belt, and i want to upgrade the variator and rollers/sliders as well).

[kr10k50]

This thing ran fine for 8 months.

If the orifice in the main appears smaller than the pilot, then it has to be clogged. Just to make me happy. Soak it over night in carb cleaner and run a wire or something through there and see if that doesn't open it up. Heck, soak and clean them both for that matter, and since your there take another good look at the needle and float assembly, and the diaphragm.

At that point you'll almost have run through carb cleaning 101, if you haven't already, go ahead. Whats to be lost. There are a lot of ports and holes that have to open in the carb and the only way to know they are open is to get some cleaner or air or both physically through them.

You said you have the A/F screw turned all the way in clockwise, and your still running rich. Did you ever turn that screw more than three turns counter clockwise? You might also have turned it too far clockwise or to the lean side and bent or broken the needle, if you cranked on it too hard.

[div]

Air/Fuel needle is fine. I've never had it out more than 2.5 turns, and never tried to tighten it past where it stops. It came from the manufacturer set out at 2 turns.

Brought the pilot and main up to work where i could measure them in my lab. Main is .76mm, pilot is 1.01mm. Here's a pic - pilot is on the left, Main is on the right.


After an ultrasonic cleaning, i can tell now that the main is indeed labeled as a 77 - you can even make it out in the pic. The pilot, however, is in no way shape or form a 35. I'm surprised it ran - but it's not surprising at all that it ran rich. Can anyone offer a suggestion on a pilot size to start with?

[Alleyoop]

WOW!! that is strange as heck, the Pilot being much bigger than the main. No wonder your running rich at Idle and low speeds.
Alleyoop

[erictheviking666]

True, but the question remains. Why has run so well up until now? Doesn't make any sense to me.

[Alleyoop]

The only thing I can think of is that your Main Jet got or is clogged and or the Diapghram is leaking causing bogging in mid to upper range. It also could be that your enricher(choke) is not extended out and shutting off the Extra Fuel after it warms up. Now you could check if the Enricher is working, take it out mark the Plunger right by the Rubber Part and start it up and let it warm up. Then check if the Plunger and Needle extended out about 3/16 of an inch. If you ride it around in the low end and then take the plug out I will guess that the Plug will be Sooty looking due to the Large Pilot Jet and or your Enricher not working.
Alleyoop

[div]

I tested the enricher before i pulled the carb - it works - but i'm going to end up replacing it with a manual choke and handlebar mount lever.
It's possible all manner of things were clogged in the carb. When i pulled it apart, everything was coated in a yellow gummy film. If you're from the south - imagine a car parked outside for several days with no rain in the spring - a nice thick pollen coat. now, pollen shouldn't have been in the gas, and the scooter has never sat more than a couple of days since i bought it, but... i think i'm going to blame the ethanol in the gas combined with the sealant coating in the tank plus the fact that i only just now swapped out the stock fuel line.

I'm going to see if i can find a local source for the pilot jet. I''d already ordered a new 90 main from monstergy6, along with a new manifold and variator setup. i guess i'll try a true 35 pilot, and go from there.

[Alleyoop]

Div,
Sounds like you found the problem, carb all gummed up. I think you are on the right track with the 35 pilot although unless you have a free flow filter I think the 90 main might be to big. Since you said you have a #77 or so in there now I think you may need something in the 80 range. But you will now right away if the sucker bogs on you in mid-range and WOT.
Alleyoop

[div]

finally got all my parts in.

carb cleaned, new 35 pilot in. stock 76 main in. new manifold.

now i can't get this thing to idle below 6k. and if i let it, it'll run out past 8k. idle speed screw is all the way out - the throttle spring won't even return that far. A/F screw is out 8 turns - plug still looks lean. I've got a 90 main i can swap in, but is the high idle because it's too lean, or is something else going on here?

[Bashan]

The standard setting for the A/F screw is out about 2 1/2 turns. It supplies more gas to the low speed circuit as you turn it out. Mine would fall out at 8 turns but if you have it way out past 2 1/2 it'll make it idle fast. Try turning it in all the way until it stops, gently. Then back it out 2 1/2 and see what happens. Don't worry about the plug appearance yet, let's get it idling. Rich

[div]

Ok, did a lot more tweaking last night.

High idle was caused by a mis-adjusted throttle cable. My own dumb fault. That's what i get for working on the scooter while not drinking.

Took it out for a spin after getting the cable sorted and it ran pretty well, up until it died at a stop sign. Wouldn't start back up. Poke around and find that the A/F screw fell out. I guess 8 turns is too much. Fortunately, it landed on the CVT case. Put it back in, adjusted it out to 3 turns out and the scoot just ran like crap. It's way too lean with the 75 main and the UNI filter. Swapped in the 90 main, set the needle shim to the middle position, set the A/F screw to 2.5 turns.

Scoot ran pretty well. About where it was before when i was hitting 45mph on it. Idle at 2k rpm. Didn't speed test it to confirm top speed, and it would still run up to about 5500rpm, then back down to 3500 before slowly working it's way back up and to 8k.

Installed the new performance variator, 5g rollers, and a new belt. On a full throttle launch, the scoot bogs hard for a second, then spins up to 6500 rpm, and stays there. it was getting late, and i had some errands i had to take care of, so i didn't take it outside of my neighborhood - don't know how it'll run above 30mph.

So I figure the bog is probably a combination of roller weight and tuning. I haven't checked the plug since the 90 main went in. Any advice here would be great.

New problem... this morning, it was really hard to start. It would start to catch and then die. Had to give it throttle to get it to finally catch and run, and then it idled at 600rpm. At this point, if i gave it any gas, it would die again. Let it run at idle for a bit, and the rpm slowly came up to 1200. Then I could give it a little gas, and get it going okay. When I hit the stop sign at the end of the street - it died, and i gave up.

So, it started and ran great last night when it was fully warmed up. this morning, cold, it was a PITA. The fuel enricher worked fine when i tested it last week. Is this a choke or tuning problem? I'm seriously considering ordering the parts to convert this to a manual choke.

[sprocket]

Sounds like your auto enricher on the carb is not working. Check the power at the harness. These things are flakey and a manual choke conversion is far better IMHO...

[div]

Does anyone know of a US-based supplier for the parts? The thread in the FAQ has a Canadian and a German supplier, and I'm not having much luck with the google.

With as many people hating on and having issues with the auto enricher, you'd think some of the vendors would sell complete kits - handlebar mount lever, choke converter, and cable.