Pa50 problem, AGAIN, going fast UPHILL only...

Hi, everyone.

Joew might be the one i need to talk to, but anyone's welcome to answer me.

Once again, my pa50 has problems. It's SLOW.

I ordered weight for the variator, but that doesnt seem to do the difference.

When i test ride the moped, i go around 13mph (20kmh), the speed is constant and it's not bogging. It's a PA50-II.

The funny thing, is that when i go uphill (small slope, nothing really big) I hear the moped rev higher, and i can reach 25kmh (16mph). YES, UPHILL, not DOWNHILL.

So my guess is that the variator has a problem or something, so when under load, the variator start doing it's job (partly).

Do you think that it's the variator which has a problem, or the rear pulley on the wheel?

I'm having so much problem with this variator, and the moped overall, i'm starting to hate those japnese peds!

someone help!


Re: Pa50 problem, AGAIN, going fast UPHILL only...

jeeze.. that's a weird one.. lets see..

Take the left side belt cover off so you can watch the variator. On the center stand, rev the engine up.

Does the front variator unit close as engine speed increases?

Does it close all the way so the belt is riding near the pulley's edge? (maybe 1/2 inch (10 -12mm) from the top edge)

Go for a test ride on a flat road .. look down at the front pulley while driving.. Don't hit any cars or people or trees..

Does the same thing that happens on the center stand also happen on the road?

Re: Pa50 problem, AGAIN, going fast UPHILL only...

ya know.. for some reason my brain tells me this could be due to a loose belt.

I know it's hard to adjust the belt. You have to pull that rear wheel back hard and tighten a few of the bolts at the same time.

Under a large load (like when it hits the hill) the belt pulls harder and there's more belt-pulley friction. Under a load, the front and rear variator units act properly.. the rear spring and front weights find the proper resistance and stress is balanced.. So the bike can go faster. That rear spring won't allow the rear pulley sides to open (raising gear ratio) unless the belt pulls hard.

If the belt is loose or slipping the variator just acts srange.

So, also check for a slipping belt.. a bit of grease or oil on the pulleys or the belt can do it.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

Guillaume Bergeron /

Humm, thanks for the fast help joew!

i've already tryed to rev the engine on the centerstand, the variator faces doesnt close a lot, the belt stays down, it only raise a little. Same thing happens on a flat road.

The belt is not slipping, i'm sure of that, i checked well. And i think that the belt is tight enough, to tighten the belt, i sit behind the moped on the ground, i hold the rim with my hand, and i put my foot on the pedals. then i tighten it with my other hand.

Next step is to try to start the ped without the belt, and see if the variator faces close together. Do you think i can start the ped with a drill on the variator center nut?

Also, could the problem be that the rear pulley is stuck? It opens a little, but it's kind of hard to open by hands. I dont think that the little weights in the variator can pull enough strenght to open my rear pulley.

thanks for the help!

you are THE pa50 guy on this site! At least we have one!


Re: Pa50 problem, AGAIN, going fast UPHILL only...

Guillaume Bergeron /

also joew, should the weight in the variator be lubricated with something?

If i recall, my shop manual asks to grease them, is that right?


Re: Pa50 problem, AGAIN, going fast UPHILL only...

fast help? well.. i took my bike out yesterday and it was dying at idle..(?? wtf!) i was sittin here taking a break after dropping the engine and pulling the carb right when your message popped up.. runs ok now.

i never tried starting the engine with anything but the pedals.. doesn't seem like there's any really good way to do it. Try it and lemme know what happens :)

So, the belt is ok .. and i think the rear unit is Ok too.. But:

_rev the engine on the centerstand, the variator faces doesnt close a lot_

As the weights are thrown outward the pulley is forced to close. It's a powerful force. If something is preventing the pulley from closing, it should be obvious.

With the belt removed the pulley face should easily slide all the way in by hand. If not, find out why not and fix it.

If the weights inside cannot slide outward until they touch the wall in the variator, the pulley won't close all the way. Fix that if you can.

But sometimes the variator casting is damaged. The ramps the weights slide on could be damaged or worn down. Fixing that will be difficult bordering on impossible.

If i know some things about the PA50s it's only because i'm always working on this freakin bike for some reason :/

Re: Pa50 problem, AGAIN, going fast UPHILL only...

a touch of grease on the weight's ends and on the plastic rollers and on the ramps is a good idea. The outer steel plate might last but the inner casting is a much softer metal.

I have one variator here who's little ramps are worn down.. so it's useless. The weights push with enormous force. The metal ramps will wear down without lubrication.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

Guillaume Bergeron /

thanks joew.

I'll try everything i can, and let you know.

i'll check everything, but my feeling is that the rear pulley is bad


Re: Pa50 problem, AGAIN, going fast UPHILL only...

This is an odd one for sure.

It almost sounds like the variator is acting too quickly, not too slowly. From my understanding, two things control the state of the variator - RPM and load.

If the variator was acting too quickly, it would hobble the engine with too high of a gear ratio. The engine might not be able to get into the powerband. Simply not making enough horsepower to overcome the ever-increasing gear ratio.

When under load (on the uphill) the load is enough to keep the variator at a lower ratio for the same RPM - so now the engine can get further into the powerband, and make a little more speed.

Does the PA50 variator have return springs for the weights? Possible that the spring(s) are sacked? Otherwise, it seems that the engine is just not making enough power at the RPM the variator system is designed for.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

no return springs other than a very strong spring inside the rear pulley.. it forces the rear pully to stay closed.

on my bike, using stock weights on a flat road from a dead stop, the variator almost immediately goes to top gear. I'd estimate RPM to be about 2,500 to 3,000. This RPM would depend on acceleration rate and wind resistance, etc. So, RPM is even lower with a tail wind.

Of course, if i hit a headwind or go up a hill, RPM drops. The variator then shifts to a lower gear. And road speed can remain the unchanged.

Thepoint is that RPM and road speed are practically unrelated. I once mounted a tach for some tuning feedback and it was useless.

The effect of load as an independent force is hard for me to picture..

But i know that increased load causes RPM to drop..

And when RPM drops the weights have less outward force.

The rear pulley/spring is then able to pull the belt and so closes the front pulley.. which lowers the gear ratio.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

i hate not being able to edit posts..

_The rear pulley/spring is then able to pull the belt and so OPENS the front pulley.. which lowers the gear ratio_

Re: Pa50 problem, AGAIN, going fast UPHILL only...

that rear pulley's spring is very strong. You should be able to open it just a bit with your bare hands.. I would be more concerned if it opened easily than if it were difficult to open.

Springs loose strength with age. they might take a "set" and lose their springiness, or the metal can fatigue.. In either case a spring will never (i hate saying "never") get stronger.. it'll get weaker.

But if you're curious about it, you could make sure that rear pulley is mechanically able to open all the way. I've opened the pulley with a couple of strong prybars wedged between the sides.

Don't let anything slip or the doctors might be prying a prybar out of your skull.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

The only thing I did not read about is whether the belt is the stock one. The thread about the gear ratio and rpms changing is a possibility. Have you cleaned out your exhaust pipe? It might be so plugged that at lower rpm there is not enough force to let the exhaust out. There is a plug under the right side muffler protector. Remove it and poke a long screwdriver in there to see if it is plugged.

Re: Pa50 problem, AGAIN, going fast UPHILL only...

Guillaume Bergeron /

i have burned the exhaust in a fire before to repaint it, so it should be good. But the belt point is probably the problem, or a part of it. The one i have is a little dry rotted, and when i remove it, it's a little hard to move. It keeps taking back it's original shape of when it was stored outside for like 10 years.

Where can i get a new original belt?



Re: Pa50 problem, AGAIN, going fast UPHILL only...

New Honda belts are $$$$$$.

You can try or one of the european sites like or

There was a Hobbit for sale on ebay that had a different belt on it. I emailed the owner and he said that it was a#5L420W

and that he go it from Napa Auto. He said that it worked good but I have no proof of that. Check the price. If it is cheap enough it might be worth a try.

Fuel problem?

Hey G.B.,

I don't know much about mopeds, but I read through this thread and it doesn't look like anyone's mentioned fuel flow as a potential source of trouble. That's what I'd suspect if it runs better when it's tilted. Maybe your float sticks at a certain angle, or there's an obstruction in your tank/hoses/carb passages. If you could tilt it up while it's running on the stand (without letting the rear wheel touch, maybe with the stand on some cinder blocks?) and it reved higher, you would know it was a problem like that. If it didn't rev higher, you'd know that it was a problem relating to running under load.

Re: Fuel problem?

Guillaume Bergeron /

i checked that, but everything seem perfect. the engine runs without any problem on the stand for long minutes.

i dont think that it'S the issue.

thanks a lot everyone for helping.

i'll make tests soon and i'll let you know.

i'm busy for the next couple weeks, but after that, i'll have all my time to play with the peds



Re: Fuel problem?

Guillaume Bergeron /


i checked EVERYTHING

the engine isnt the problem' the variator neither"

i started the bike and then removed the belt

the variator was closing completly so i guess that it's okay,

I've changed sparkplug, i've tryed a less restrictive air filter, i've removed the exhaust bolt to see if the exhaust could cause too much back presure.

the engine seems to run as strong as it could.

Also, it starts REALLY easily.

last thing i can check is the driven pulley. It's the only thing that can be wrong, i THINK!

After playing with the ped a little and taking it out for a test drive(2-3 mins), i've touched the rear pulley, and it was HOT, really HOT! The front pulley was hot too, but i can understand it becoming hot because of the heat transfer from the engine, but the rear pulley... humm, i think that's really weird...

The pulley case wasn't hot... only the pulley itself...

there is oil in the case, that's not the problem, i checked many times.

Is it normal for the rear pulley to get hot, i mean, not a little hot... REALLY HOT???... i could almost get burned if i touched it too long.

maybe it's normal?

anywa, thanks in advance, once again.


Re: Fuel problem?

As I see it, the only reason a driven (rear) pulley would get that hot, is from belt slippage. Might also be bad bearings, but if they are making that kind of heat, the noise and roughness would be totally obvious. Or, maybe it's just a case of simple posession...

Had you considered exorcism? Light a couple pieces of charcoal in a metal or stone bowl. When they are glowing, place the bowl under the bike and thow on sage, tobacco and sweetgrass. Knickinick is good too, if you can find it. Try to blow the smoke into the exhaust, intake, gas tank and crankcase(s). Pray for intervention from friendly spirits.

Couldn't hurt at this point. If I were in your shoes, I might also consider an offering of hemp, if you know what I mean,

Re: Fuel problem?

Guillaume Bergeron /

haha legendre, i'll try that as soon as i can find all the ingredients...

i'm kind of frustrated about this moped, but you made me smile... TY.

i think i will simply buy a new rear pulley, i'm pissed.

the belt isnt slipping... i should see it if it slipped right?

the bearing thing is possible, but i dont think so, it seems to turn freely when i use my hands.

anyone knows where i can get a new pulley?


Re: Fuel problem?

_i’ve removed the exhaust bolt to see if the exhaust could cause too much back presure_

You mean the big bolt in the side of the muffler? That bolt only allows you to go in and clear a small tube. If that tube is clogged, removing the bolt will do nothing... the bolt is on the outer, clogged-side of that tube. Stick a screwdriver in there and clear the tube.

All that heat means friction .. you were asking about new belts earlier too.

My guess is the belt is slipping for some reason, or that the pulleys are not operating correctly. When the front and rear variator units do not work together, but fight against eachother, lots of friction can be developed.

For instance, if the rear unit's inner face were rusted on it's shaft (not really a shaft) it would not open wide easily.. that could cause belt slipping and cause the belt to pull a lot harder than it needs to pull.

And if it wasn't mechanically able to open all the way the front pulley would be keeping the belt extremely tight at high speeds... more friction.

Mine get nice and warm but nothing like hot.. no sense that it would burn me .. Sometimes i notice it's quite cool after a ride. I think it depends on how you're riding.. steady speed or lots of speed changes.. someday i'll check it out.

Re: Fuel problem?

it does make sense that if the rear pulley is jammed and can't open all the way, lots of belt friction will be developed and, also, top speed would be restricted.

take the rear unit off the bike..(got a puller?) Remove the big nut in back of the unit.

(Unless you have the special puller) Get a big hammer and a big round piece of steel bar. Pound on that threaded part sticking out the end. Don't damage the threads.

If you're lucky, after a sharp whack or two that center piece will pop in (it's a tapered fit).

Immediately, the strong internal spring will pop the thing open..

Now you can examine the internals for damage or something... it's pretty simple.. only 5 pieces total..

The manual shows the exploded view for reassembly. Reassembly might require a couple clamps to compress the spring while putting the nut back on. I can do it with my bare hands..

Before assembly lube it with grease as the manual instructs.

Re: Fuel problem?

Guillaume Bergeron /

i think we are getting to the point !

that's good news!

i think i need a new belt. The best would be to find a stock one, so that way i know i'm allright with the belt...

if the belt was slipping, should i be able to see it?

i think i should see the belt turning and the variator staying is place.... am i wrong?

also, i think the problem is situated at the rear pulley, so i'll try to open it... is seems a little hard to do, but i'll try what i can.

If i have any problems, do you know where i can get a new complete pulley/assembly?

Also, what type of oil are you using for the variator?

i know i'm asking a lot, and often... but THIS moped is giving me so much problems that i can't solve myself...

i can fix a puch moped completly myself... but the honda... ARGHH.... it's completly different, and it makes me feel stupid...

at least the site with you folks is there, and i'm thanking you for giving me some of your time.

thanks a lot!!


Re: Fuel problem?

The variator does not take any oil at all. Just a slight smear of grease on the face of the rollers and a small smear of grease on the shaft where the moveable pully half of the variator slides back and forth.

You can get the belts from Honda but they are very expensive. Mitsuboshi is located in Ohio but they will not sell the belt as it is an OEM item for Honda. Theu are a little cheaper in Europe but then you have to put up with shipping, etc.

I scored a good one on ebay but they do not come around very often.

When you run the bike with the left side cover off, does the belt climb up on the front pully? At the same time does the belt ride down into the rear pully?

Re: Fuel problem?

You may not see the belt slipping.. all it takes is a slight difference in speed between the belt and pulley.

The front unit is supposedly run dry.. no lube. But i dont see how lube will hurt .. i see severe wear on these parts.. i've got some steel rollers that are all chewed up... ramp plate with deep grooves worn into them and ramps on the other side worn down. (Even slight wear on the ramps has a big effect.. lowers the gear ratio dramatically.)

The rear unit uses has a "Grease Capacity : 5 - 7 grams" according to the manual.

Check out that rear unit.. i get a strong feeling it cannot open up as wide as it must. And that's causing the lower top-gear ratio and lower top speed as well as the belt wear and heat build up.

Re: Fuel problem?

Guillaume Bergeron /


when i asked for the oil of the variator, i made a mistake, i was asking the oil for the rear pulley.

also, my drive faces are kind of worn by the weights with the time... but i dont think that would make the difference between 20 and 50 KPH

i'll check everything.

thanks everyone.


Re: Fuel problem?

Guillaume Bergeron /

what type of oil are using in the rear pulley gearbox?

Re: Fuel problem?

you wanna put some sae 80/90w gear oil up in there per the honda manual; you should be able to find it at any hardware store..

Re: Fuel problem?

Valvoline SAE 80W90 gear oil

Re: Fuel problem?

Guillaume Bergeron /


i removed the rear pulley, removed the big bolt at the rear, but i couldn't get the thing out with the hammer.

all i managed to do is to bend the pulley faces.

when i hit on the center threaded piece, it doesnt do anything, the pulley faces only separate from each other, that's the only thing my hit does.

Also, after playing with the pulley for a while, i managed to realize than the pulley could separate more from each other when i made a 90degree turn from each other.

this enable the 2 plates to separate completly when using screwdrivers.

the opposite also happened. If i turned the 2 plates from each other on the opposite side, i couldn't open the faces anymore, even with screwdrivers. They were kind of locked together.

so i decided to place the 2 plates in the position where they could open, and i made a mark on each plate to remember to align those 2 mark.

re-assemble the moped, and tryed it...

each time i pedal to start the moped, the faces moves from each other and taking the position where they cannot open, and they lock together.

The positive fact: Now i know what's the real problem... THE REAR PULLEY.

The negative fact: I don't know what to do, this is stupid, and i feel completly numb.... and noob.

Usually, some explanations are allright and i can do pretty much everything... but not now.

I must have played 2 hours with the pulley, trying to open it.

Honda made so much pullers and special tools for this moped...if i had all these, it would be a lot easier...


The only thing i really want to know is how you managed to separate the 2 pulleys faces completly from each other.

like i told, when i hit the threaded part, it only separate the 2 faces, but they pop back together.


g.b. (AGAIN)

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