NRG bogs and cuts out after about 5 mins

[lukash616]

Hi Guys, new here but spent a lot of time with Scoots.

Got an issue with my Piaggio NRG project that's driving me crazy. It'll start up on the button almost immediately and tick over perfectly. I can ride it around the block for about 5 mins and it feels perfect until suddenly it bogs out (can keep it alive for a little bit by feathering the throttle) but zero power and then it just cuts out.

I can start it right back up again but usually have to put the choke on for some reason (manual choke lever) then it will do the same thing, but usually cut out even quicker.

This weekend I replaced the fuel lines and inspected the vaccum lines, all seems to be operating correctly. Carb inspected and cleaned out. Checked reeds, all fine.

I was concerned about a soft seize so I took the head off and there's no signs of scoring. I did notice some odd scorch marks on the piston head though - maybe there's a clue there? It's a Malossi Sport 70 with probably only about 30miles on it, been fighting issues ever since it went on.

Any ideas would be much appreciated

[pinkscoot]

Did you up jet the carb when you did the 70cc kit?

[lukash616]

Yeah played with jets for a fair while it's on a 78 currently with standard airbox and Yasuni R. Runs good while it runs

[lukash616]

Just remembered I have a video of the first time it happened!

[pinkscoot]

Thats a nice scoot, I like the color. 78 sounds like it might a little small. What does your plug look like?

[aeroxbud]

Sounds like it might be jettting. What was the original size jet in the carb? I would start with at least 10% bigger.
I would get a jet pack. Start bigger than you think. Then work down in size.

[190mech]

Sounds like fuel starvation,,Do a fuel flow check by applying vacuum to the petcock and watching fuel flow into a canister,should be ample..Clogged fuel cap vent could cause this too...

[lukash616]

Thanks guys

Jetting is on the rich side as is, its a 53 as standard.

I've checked the fuel flow by sucking on the vaccum line and letting fuel flow into a bottle. If I put the end of fuel line lower than the petcock after applying vaccum it will just drain all day - not sure if that's supposed to happen, might have to try changing the fuel pump next.

This is the first bike I've had with a fuel tank lower than the carb, much easier to troubleshoot when the tank is up by the seat!

[190mech]

OH!Thought tank was under seat,,Yes,swap out that pump..Small engine shop has them; P/N 491922 .Also ebay etc..

[lukash616]

Alrighty, Fuel pump ordered. Also chucked a new spark plug cap in the basket as noticed the plastic is a little cracked on mine. Figure it must be one of those ¯\_(ツ)_/¯

Will keep y'all updated

[christopher]

Not sure what your choke lever does, if it adds fuel and doesn't block incoming air can you leave the choke partially on to create a richer condition to see if it helps?

[lukash616]

hmm no dice... changed out the fuel pump, changed the vaccum line, changed the spark plug cap, changed fuel line from tank to pump - exactly the same.

Could it be the rings already?

[lukash616]

Hmm just dropped a couple of jet sizes and there's a big improvement... maybe it was the opposite all along, too much fuel not starvation.

Will experiment more tomorrow!

[lukash616]

Nope - gone from jet so low it wont move to jet so high it wont move, always the same. So definitely ruled out jetting I guess. Completely at a loss now.

[aeroxbud]

Looks like you need to do a compression test. Probably a leak down test would be a good idea too.