Fixed VRAPP! Now i want more top speed...  By  Tripper (Read 1,517 times)

awesome

So I am guessing its a 50 , is it a 2T or 4T ? On my 2T that was stock and already upjetted to a 75 MJ I bought a Uni vent cover NOT the big red air filter , put in a MJ with stock exhaust . Wow it had more low end power and midrange pep but was louder with the increased air flow being sucked in . I rode it for 2 or 3 months without a glitch . Well I bought the proper Uni filter , my scooter dealer did not have any jets larger than nor did the local motorcycle shops . I put it on any ways just to test it . It started up fine and only had a very slight bog sound but no hesitation . Well ( CENSORED !!!!!!!) I barely went a quarter of mile , just around the block and it seized up on me . Would not restart so I pushed it home . Checked the gas and oil they were full . Pulled the plug and it melted off the prong . I have never in my life had this happen . Tried to start it after it cooled no luck . Pulled the engine and the piston and cylinder were grooved and rings looked DOA .

I bought a 47mm BBK , a HP pipe , first tested the small Uni vent cover and it did not run right . Put on the red one and it was better but I had too large of a main jet . Went with a 120 and it ran fine as a 130 and 140 would spit gas out of the Uni and 120 did not . I just put in a 105 as I want to reuse the airbox so I can ride in the rain and stock pipe as the new one is so loud it makes my ears ring @wot sounding like a lumberjack chainsaw and MX bike blend

Waaaay too lean man!
It vraaps because it needs more fuel!
Adjust A/F screw, and take out the cardboard. Problem solved.
You could also try with BP Premium fuel, they have additives that burn better than gasoline in them, so your AF ratio can be higher than with regular fuel (because the fuel is more energetic).

Funny thing is your spark plug looks like you're running rich, but the melted arm suggests that it's actually running lean somewhere.
Could be that you're running rich on idle, and lean on WOT, or reverse.

better air intake. You could upjet, but really, try the AF screw first.
Quite often the jets have enough opening to deliver fuel; only if you're demanding max speed at WOT would I upjet. But for the majority of riding, it won't harm running a bit lean when you're nearing top speed. More than likely upjetting compared to an adjusted A/F ratio will gain you only a few MPH difference at WOT.

The cardboard restricts airflow. Your airflow may be just as good as with the stock airfilter.
Upjetting will be necessary then.

I was looking at that picture and I was wondering how well the cardboard would deal with all the oil from a uni filter skuttadawg's doesn't look oiled is yours. They will run VERY lean without oil...

Well mine is not uni brand, its one of those knock off wire mesh type. I'm trying to find the right type of foam to put on it. So I figured c piece of cardboard would suffice. It seemed to work at first but its vrapping again. I'm going to cut my old air filter out of its box and wrap it inside the mesh filter. Somethings gota give.