My ZX50 barely gets to 30

[shroomigator]

Hi all,

Newbie to bikes in general... got a 2005 zx50 with 16000 KM on it about 2 months ago... when I first got it, it would give me 43 mph and it was great...

then one day, I had to go about 10 miles away for an employee training session... another girl from my job was there, and her ride didn't show up... i jokingly offered to let her ride on the back of the scooter, and well, open mouth insert foot, she took me up on it...

i weigh 230, she was about 150...

So after this epic ride, maybe a day later, i hit a bump and suddenly it won't go more than 10 MPH... I got to work, worked my shift, and afterward the bike was normal again, like it fixed itself...

So this happens every time I hit a bump for a few days, til I do some research and get the idea that my CDI is going bonkers...

Took the panels off the bike, found the CDI checked all the connections, found nothing obviously wrong, and put it back together.

The problem where it slowed down after hitting a bump was gone, but now the bike won't go above 25mph until I've been riding about 10 or 15 minutes, and after that I can get 30, but no more...

Not sure what to do at this point.

Sorry for the long post.  Any advice would be greatly appreciated.

[naughty lee]

Take your front variator apart and check the rollers for wear flats

[shroomigator]

Take your front variator apart and check the rollers for wear flats

Yes, there are flat spots on a few of the roller weights... I'll be replacing those, hopefully tomorrow if I can get some from my local dealer, and hopefully that will be the end of it.

Thanks for the response.  I'll post an update once the roller weights are replaced.

[naughty lee]

Skim your boss down a little whilst it's in bits, you'll squeeze a bit more out if it

[shroomigator]

ok, so here's the update:
Took a few weeks for parts to arrive.  I got a new boss from scooter assasins, and roller weights from my local dealer.  Put both in (the old roller weights were worn down about 1mm)

the result: no change...

at this point i'm thinking that the problem may be clogged carb jets...

thoughts?

[naughty lee]

Remove, clean and gap your plug. If you lift the bike on wooden chocks on the centre stand will it rev up nice and high ?

[LoveMyKymco]

I would guess plug or needing a main jet cleaning on the carb. You can do that by removing the top to the carb and removing the slide. Then take your can of carb cleaner down the middle of the slide tube and stick the nozzle into the recess and spray a while into it with the carb cleaner. After your done just release the bowl screw and it will clear out. You dont even have to take the carb off the bike to do this. Since you have no issue with starting, the pilot is fine.

[shroomigator]

another update:cleaned the carb thoroughly... wasn't blocked at all... now it's squeaky clean... but I did find the problem... cylinder head gasket was busted, oil leaking out the front.

so...

I ordered new gasket from my local dealer, but in the meantime I tried making a silicone gasket... it worked, but I still wasn't getting any compression, and my bike wouldn't do more than 5 mph...

got tired of waiting for the damn gasket to arrive, so I ordered an upgrade kit (been wanting to do this anyway)... got the ruima 75 cc kit from provoscooters, it arrived in two days (still waiting for the gasket from my local dealer...

so, I take everything apart, and I find that there is no bottom gasket on the cylinder!

beats me how the thing ran at all, but now I knew why the silicone gasket didn't have any effect...

so, upgrade kit comess with gaskets, I put it all together, and...

bike won't start at first, then i hold gas at full throttle, and it will idle...

what now?

[naughty lee]

It wants re jetting now to compensate for the bigger top end

[shroomigator]

would you happen to know which jets I should buy with a stock carb?  do I need a bigger carb than the stock?

[TLRam1]

I would call the people you bought the kit from or the mfg of the kit, they may have some info or a starting point.

[naughty lee]

I would call the people you bought the kit from or the mfg of the kit, they may have some info or a starting point.

Good advice. Swapping jets isn't difficult, you'll need two or three new spark plugs too.
Once you've fitted the jet, replace the plug and go for a five mile run, when you get home remove the plug and check the colour of the insulator at the sparking tip, it should be a gingery greyish colour.. If it's still white, the mixture is still too lean and you'll need to go up another jet size, mine went up eight or ten sizes just by fitting an exhaust !

[shroomigator]

Are carb jets a standard thing or are they unique to each carburator? I mean, can I just go buy a jet kit with a bunch of different sizes and try em out, or do I need something made special for my carb?  And how do I find out the make/model of my carb if it's a stock kymco carb?

[TLRam1]

There are Round jets and Hex shape, you have to get the proper ones or your flow will be different.

[LoveMyKymco]

You need jets for a Honda PA series keihin carb. Theyre hard to find and I would just go to the Honda dealer to get them.
Heres some part numbers:

JET, MAIN (#80) (99101-187-0800) $7.93

JET, MAIN (#82) (99101-187-0820) $7.22

JET, MAIN (#85) (99101-187-0850) $7.93

JET, MAIN (#88) (99101-187-0880) $7.22