Gilera runner 50 strange speed issues

I did some work on my clutch/rollers/belt the other week due to my moped just acting a tiny bit strange. I ended up replacing rollers and the belt due to them being worn. But after doing that I've had some weird problems. Sometimes when I set off the bike will be really slow. Like I'm setting off struggling to hit 15mph. Like the engine is going, but not smooth. And I worked a way around the problem for when it actually happens and I have cars piling up behind me. I shake the bike around a bit with the handle bars, then usually the engine sort of dies down to idle speed, slows down basically, then suddenly kicks back in and I zoom back off again. I know it sounds weird but it fixes the problem. I had an idea that the carb bowl had water in It so I opened it up and it was just fuel and it was all nice and clean. I gave it another clean to be sure though. One strange thing I noticed is that the breather line had a plug in it. Just straight up a bolt in the line. So I took out and started the engine. There was a noise though, there was lots of air being sucked through the breather line and the engine would take a long time to drop down to idle after revving it up, which I presume are the conditions of a lean engine due to the extra air being dragged in. So this problem could be something to do with the slow setting off sometimes, but why would shaking the bike fix this? So then I'm thinking some thing electronic?? Bad earth, bad connections?

I'm just super confused and still cannot work out what's going on but it's such a pain!

Any help would be much appreciated, thanks

 

Double check every thing you replaced is in the correct order and tight, use thread lock!

Did you replace like for like rollers ?

 

Yeah, everything is all tight and same weight rollers. Because it's not broken all the time, I'm starting to lean away from any of the stuff I did their to be honest. I even put it all back to how it was before and it didn' help. But yeah it's all tight and everything, I've had it all taken apart 5 times aswell, just in case some thing hasn't clicked into place properly or something. But I really I'm trying to work out a problem that links to the shaking the bike thing. I think I might try and record the issue, but like I said it doesn' happen all the time and also you need to be able to hear it clearly. As the engine revs up and down

 

Carb manifold leaking? Maybe?
Someone else had this problem too I recall.
But put that bung back in the vacuum tube.

 

I had the carb off yesterday. Looks like its all nice and tight so I doubt its that. Also. Why is there a bung in the vacuum line? Like surely it's not supposed to be there???

 

Which vac line ? what’s the other end connected to ?

 

Yeah thats what I was wondering.

 

im not sure what it is to be honest. there is just a clear line connected to the carb about 10cm long, with a random bolt in the end. like its not supposed to be there, its just a cap head bolt. but when i remove it makes a pop pop pop noise as it sucks air in and the engine runs wierd when i take the bolt out.

 

That gos to the fuel tap under the tank as it’s vacum operated or at least it’s meant to be! Yours is either broken and doesn't need the vac as it’s free flowing, or it’s been replaced with a Petcock?

 

ok, not to familiar with what your saying. but are you just saying whatever it is just leave it? is it not a problem

 

Well....it’s not how it’s meant to be,that could well be your problem... look under the tank where the fuel line comes out there should be a port where that vac line is meant to connect?

 

ok, might be a pain to get to but ill try and have a look. so its to designed to put a vacuum in the fuel tank? which then drags the fuel through the actual fuel line? thanks again

 

It’s not a pain it’s near the shock if I remember rightly...there’s two lines one is fuel the other is the vac line (the one with a bung in it in your situation), when you go to start the bike a vacuum is created on the vac line and that vacuum is what opens the fuel tap that’s why I said yours must be broken and free flowing or it’s been modified because it needs the vac to open the tap to let the fuel flow.........

Investigate!

 

Lower port is for your bunged up vac line

 

ok, i dont think were looking at the right thing here. the tube im talking about just goes straight into the carb. like its literally i 10cm tube that goes direct to the carb just dangling in mid air. ill get a pic, one second

 

Yes it’s meant to go to carb! the carb creates the vacuum

 

That’s goes to the bottom port in the pic I sent and shouldn’t be plugged

 

ah yes. i just dont see this fuel tap anywhere...