PZ30 carb parts? ...and odd fork behaviour

[tenthousandfeet]

Hello everybody.
I recently picked up a Viva250/db31-style (different brand) bike, and have been quite pleased with it with a couple of exceptions.

Firstly, the carb was running way too lean, so I did the adjustments recommended here to enrich the mixture - those being to adjust the needle and to turn out the idle mixture screw. With a little bit of fiddling, it was starting and running like a champ.

...for about fifteen minutes. At that point, it starting bogging down and stalling, and finally wouldn't start at all. Upon examination, the idle mixture screw had completely fallen out!

Now I find myself in a bit of a problem. I'd rather not replace the whole carb for a $2 part, but I'm really not sure where to find a suitable replacement.

Does anyone have any ideas for a fix?

The other quirk of the bike is that upon compression, the front left fork shoots out a blast of air from the top screw. This doesn't seem exactly right - in fact it suggests to me that the cap isn't sealed properly. A friend of mine has the same bike and his doesn't exhibit this behaviour. I haven't yet had the opportunity to really test the suspension performance, however, so I can't rightly say whether this affects the functionality.

I think I'll probably try tightening it and inspecting the seals - but has anyone else had a similar experience?

For clarification, here's the bike in question:

http://www.giovannibikes.com/pictures/_5/4599/4598761.jpg

Thanks!

[red2003]

That's a nice looking bike. As for the fuel screw, most all of these Chinabikes use a copy of a Keihin carb. I bet if you can find a motorcycle boneyard, or repair shop around, they would have a fuel screw for a keihin carb and it'll fit right in there. Make sure when you replace it you turn it 2 turns out from FULLY CLOSED. If you turned it out 2 MORE turns, that's why it fell out. Next time, put a little locktite on it (the threads) before you screw it in, and make sure the spring is on it too.

[fatboy250]

+1 loctite

[bronevaya]

I would love to make a bike like that into a dual sport

as a matter of fact, that will be my next task


how fast can that thing go?

[tenthousandfeet]

I would love to make a bike like that into a dual sport

as a matter of fact, that will be my next task


how fast can that thing go?

Without getting too off-topic...
if you believe the sales text it does 90kph. The gearing is quite low, so a sprocket change would definitely be in order for road use. The lack of an alternator might be an issue for d/s use, though it does have a battery and starter.

There are a few threads about the Viva 250 in the dirt section.
(sneakily I posted in here anyway just to get more views)

[usmc-mustang]

PM me your address, I have one, and will drop it in an envelope monday..