Loss of power on my 50cc after repair By jdhammer (Read 14,007 times)

[jdhammer]

So here's my issue......

I had a problem with my 50cc scooter - It was dying when going up even a slight incline with the throttle wide open. I then had an incident where the fuel hose broke in half, so I took it in and they put a new fuel hose on, and also replaced my belt.

I got my bike back, it doesn't die anymore, but now I swear I've lost about 25% power, more like 50% uphill. I can feel the bike trying to accelerate normally, then I can feel something is holding it back. Sometimes I'll speed up, and I'll feel a kind of on and off drag.

I can sometimes hear a bit of a higher pitched whining noise when I get up a bit in speed, I'm guessed it was some kind of abnormal friction in the belt but I took a look at it yesterday and it seems fine......

The shop I originally had it repaired at ripped me off, and I don't really want to take it back there. I'm hoping someone recognizes the symptoms and can point me in the right direction so I can fix it myself. I picked up that Chinese Scooters Haynes Manual and it's been a godsend so far.

I just need my power back. Riding a 50cc, you can't afford a 50% loss let alone 5%!

Thanks for the help!

[Bashan]

I've had problems just like that and it was a different cause each time. The first was a leaky intake manifold, it can cause surging and lack of power. Spray some cab cleaner around your intake while it's idling on the centerstand and see if the RPM's go up, if they do, bad manifold...replace it. Second, I had a coil that would act normal at certain speeds and fall flat at others, swap it out with another and see how it does, your CDI might be a little hinky too but that's not as likely, I bet it's your coil. Let us know what happens, this is a learning process for us all. I'm going to move this to the tech section so more wrenches will see it. Just follow the link. Rich

[docmackinnon]

Check your exhaust manifold/pipe fitting. I can't diagnose this properly as you didn't tell the admitting nurse at triage if you have a 2-stroker or a 4-stroker.

Bit if your's is 2 good old 2-stroke smoker...then this should be the fix! Take a proper size wrench (amazing how many people bollocks up this bit) and check the fitting(s) for tightness.

On the DiBlasi, it is a large male retention nut that encircles the exhaust pipe direct from the cylinder. If it's loose, remove it and check for the copper ring gasket. Sometimes these will vibrate loose, and the ring falls out- and sometimes it is assumed it it still there. The bike I had to fix tonight had that problem- the guy it was assigned to had put the exhaust pipe back, yet failed to stick his finger inside to check for the ring. It was gone--as was his horsepower.

So..a quick rummage thru the "Bike In A Box" bits and I had the ring I took off mine when I replaced the entire header & muffler unit- stuck it in and wrenched the nut back into the jug.

Purrs like a big hungry kitty..but has some serious improvement in the "OOmph"- vital to a small scoot like a DiBlasi R7!

BTW- Some tools to carry: Trust me...you might find them handy!
- Big crescent wrench (it also doubles as a hammer)
- Vise-grips
- LED flashlight (the 3 AAA ones are great, with extra batteries)
- a multibit screwdriver (the 6-way ones are perfect! Get 2!)
- some nitrile gloves and carry them in a ziplock bag
- Needle-nose and slip-joint pliers


Doc MacKinnon MD
Mopedium Doctorus

[Bashan]

Thanks Doc Mac for a great reply! That was a mini-tutorial for us all. I hadn't thought about 2T or 4T, I might need to move this again! Thanks for the tool tip, I'm getting an article together about that and forgot about the vise grips, the gloves are a good idea too. Hey, I just read something by Alleyoop, is the throttle cable tight? If it's loose the butterfly won't open all the way. Rich

[jdhammer]

Hey all,

It's a four stroke.....and I swear it's getting moodier. Sometimes it gives me good power right up to 55-60 kph on level ground, and sometimes it take forever to hit 45 on the same stretch......

Another symptom that has become more apparent is at startup.....when I get it going and open up the throttle......nothing. The engine kind of putts along, just ignoring the fact that I've opened the throttle wide.....and within 5-15 seconds, voooom, I'm going just like normal.

I'm definitely starting to suspect electrical as opposed to mechanical, but I'm but a humble amateur. Maybe this new symptom will ring a bell with someone.....I'm planning on ordering a new coil off Ebay this week, I figure 25 bucks isn't such a bad investment at potentially solving the problem.

[Alleyoop]

Bashan,
"Hey, I just read something by Alleyoop, is the throttle cable tight? If it's loose the butterfly won't open all the way. Rich"

That was one of the first things I checked out. I manually twisted the throttle at the carb and then reached over and cranked on the throttle to see if it opened all the way. But good thought because thats what it feels like, the last 1/2 inch twist does NADA
But here is another thought I will take the carb off at the intake and see if the BUTTERFLY ITSELF is SET RIGHT the Screw that holds it in place is under the GOLDEN BIG BUTTON right above the Air/Fuel Mixture screw. I will kill myself if that is it, but I don't believe that is it because I put on a brand new carb thinking it might help
Alleyoop

[james03x]

A normal 50cc scooter maximum speed is 50 Km/h and power is 2.5 kw per 7500 rpm you are saying that you have lost 50 % then of course it's become much slower. Well it's much difficult to diagnose the problem without watching i think you should contact with mechanic in your own town.

[lostforawhile]

check the diaphragm in the carb, I just discovered mine had a tear in it. this is a very common easy to fix issue . This was after being passed by a handicapped scooter, I couldn't find the diaphragm so i just ordered a new carb (cheap)

[seanstr]

Jun 30, 2017 22:39:12 GMT -6 lostforawhile said:

check the diaphragm in the carb, I just discovered mine had a tear in it. this is a very common easy to fix issue . This was after being passed by a handicapped scooter, I couldn't find the diaphragm so i just ordered a new carb (cheap)

Seems possible that this is indeed something to check

Do one change and check results.

[lostforawhile]

I'm waiting on a carb, with a hole in that diaphram the main meeting needle can't lift out, and you will have almost no power, very common issue  

[seanstr]

You can order diaphragms but they don't always fit. I had to order 3 different ones. 2 worked 2, the other didn't. I also replaced whole carb thinking it was something else. I had 2 issues. My choke stopped working, even when newly replaced and the hole in the diaphragm. I ended up blocking off the choke. runs great was only getting 60 to 70 mpg. After the change I am getting 92 to 94 mpg. Hugh difference. Had to decrease my main jet also.

Do one change and check results.

[lostforawhile]

I have a legitimate Keihin,  I just can't find parts, it's only got 700 miles on it, I took off the top cover and  it had a hole in the diaphram, probaby from someone running corn gas from before I bought it