hole in piston. HELP

[majoman]

OK.... my first scoot.. I have built hundreds of dirtbikes; 2 and 4 stroke. and a few dozen cars. but this is a first for me.. i have a 2002 vento triton R4 i paid 80$ for. its clean has alarm and elec. start and under 2000 miles on it. i was told it was a 90 cc stock and it had a stroker crank in it... has a 12mm pin along with a 54mm bore and piston.. with a hole in the center.. the guy i got it from said he forgot to mix the fuel.. so i ordered a new piston and jug and rode it for 3 days and 40-1 mix ran great went bout 70 mph... now again another hole in the piston. has a stock pipe and filter.. the carb also seems to b stock 18.5mm, the jets have no numbers on them. im looking to order a pipe, but what do i do.. can i order bigger jets with this setup or do i need a bigger carb??

[Old School]

Is there a clearance issue between the piston and head/spark plug? That or you are getting predetonation due to timing or running too lean.

[majoman]

clearence is gotta be fine.... i broke it in for about a whole tank over 3 days and just going round town. had no issue. day 4 went for a 5 mile ride getting on it in the straights got up to 100 KMH and was still creeping slowly... so the next day i went for the same ride just cruising and started to hear what i think was deotenation.. (the knockin) so i shut it off asap and it kept running... (guessing overheated).. but once i gave it gas it died rite out.. let it sit for 30 mins. plug was white and blistered. i pulled the main pin in the carb up a click, then went on my way, as im pulling up the drive i herd the Knock and it died brffore i could shut it off. My guess would be too lean, is a 18mm carb stock? i herd of these coming in 14mm also, and between a 54mm piston and crank will i need the bigger carb or just use a huge jet. i am also getting a pipe and uni filter. wll the 18mm have enough airflow??

[Gabe502000]

Pull your sparkplug, and see what it tells you...It should be a light sandlewood color,if the fuel/air mix is correct. I'm betting that it's white, which means the mixture is waaayyy lean! You'll need to put bigger jets in your carb to get the mixture right, before you put another cylinder on it. I've sent this to one of our two stroke specialists, & perhaps he can assist you....Gabe ::usa::

[harry]

the plug could be too hot for a moded scooter.
you can't use a stock plug. a 7 will burn your piston up.
a 8 or 9 is what you need(ngk brand).

a hot plug with other conditions like slightly too lean will easily
soft seize the motor

its also said many times here on provo : do not use a open filter or
drill the stock air box!!

oilyhans

[Old School]

Definitely running too lean. Have you checked your jet sizes?(use tiny drill bits to find the hole diameters) Moving the needle pin up should lean it out as it drops the needle down.(if I am reading what you did correctly).

[Old School]

Read this article regarding spark plugs and reading them.
http://www.strappe.com/plugs.html

[majoman]

i can read a plug and it was fine during break in. but once i opened it up for a good 2 min. WOT. it started the det. (knock). plug chop and was white. wayyy too lean. like i said stock pipe, filterbox and carb. jet has no # so i guess stock. def. was to lean.. and for the plug im running is a ngk b7hs stock plug. does anyone have any opinions on other plugs.

So i ordered a pipe and uni filter along with the new 54mm piston. im porting the exhaust and doing a mild polish to the passage ways in the jug..
i
s it also time to upgrade the carb?? if so what size.???
if not what jet should i start out with??

Thanks for everyones help...

[Old School]

i can read a plug and it was fine during break in. but once i opened it up for a good 2 min. WOT. it started the det. (knock). plug chop and was white. wayyy too lean. like i said stock pipe, filterbox and carb. jet has no # so i guess stock. def. was to lean.. and for the plug im running is a ngk b7hs stock plug. does anyone have any opinions on other plugs.

So i ordered a pipe and uni filter along with the new 54mm piston. im porting the exhaust and doing a mild polish to the passage ways in the jug..
i
s it also time to upgrade the carb?? if so what size.???
if not what jet should i start out with??

Thanks for everyones help...

Right there tells me you don't know how to do a plug chop. Try reading the article I posted and then look at your plug.

[harry]

the plug im running is a ngk b7hs stock plug. does anyone have any opinions on other plugs.

dude did you read my post? about the cooler plugs???
your running a stock plug with a big cylinder , your too freaking hot !

oilyhans

[stevecameron85]

running temps in the engine are too hot, my guess too lean, too hot of a plug.. if its was a 90 cc and it was stroked it would be even larger then a 90.. depending on stroke, stock size jet in the stock carb on a 50cc vento is a 70, i am running a stock vento bore with expansion exhaust stock airbox with no snorkel, 90 main jet, needle at leanest-

got the stock airbox?

[Gabe502000]

If a spark plug is ANY Lighter than the color of sandlewood....The fuel mixture is too lean...::usa::

[veedubh20]

you dont go wot on the new bore kit!!

just go slowly on the throttle till 20- 25mph then back off the gas.

40:1 is lean premix. go 32:1 premx!!!
raise the needle up and on the low clip point on the buttom.