What size jet for 17.5mm carb

aprilia Sr 50 polini 70cc kit with 17.5m carb what size jet will I need as it’s not running right, I tried 72 and it won’t start and tried an 80 and 82 but accelerates and then bogs out

 

Dude you cant just put it out there like that , you must say at least what exhaust, filter what 70cc polini kit ............

Edit: I think we even told you in previous topic and u create another one ....

 

Sorry, I’m kinda new to this forum thing.
It’s 70cc polini sport kit
Leo Vince tt exhaust and standard airbox with malossi air filter in

 

17.5 carbs can be hard to tune and use an odd size jet compared to the other more common carbs. An 88 is probably a decent place to start out. When in doubt, go rich and tune down.

 

If it bogs out then you must have false air, there is no way with 82 that it bogs with the standard filter.

 

Malossi filter........I hate those things. The paint they use to print Malossi on it flakes off and blocks the starter and pilot jets eventually.
Buy a couple of boxes of jets, 75-100, start at the biggest, work your way down until you hit the right one.
It's tedious, but it's the only way to get it right.
No two bikes are ever the same.

 

What Steve says.
There is no magic jet size number.
Different altitude, different oil, different wear within the engine, all have a say in how the engine runs.

 

I have a set of polini jets they go from 80 to 98 shall I just start from about that and work down

 

Start with 90 try it out , the malossi sponge is totally fine it just lets little more air than a stock one.

 

What I said. Well 88 but close enough.

 

Thankyou, 86 worked. How many miles do I wear my kit in for ? And when it is worn in properly can I full throttle it on long roads and it be fine or not ?

 

Until 500kilometers you cant full throttle and max rpms must not be higher than 7000rpm.

 

Depends, is it ally or cast iron ?

Yours is Ally I think ?:the firsts few seconds will be the most important! you’ll want to heat cycle it 3 or 4 times then after this is done just make sure it’s up to temp before you hit WOT it’ll be run in under 50 miles in my opinion

 

Thats totally not true dude lmao

 

I remember running my rebuilt bikes and new cars ect ect in for 300miles back in the day.

20years later and filling my head full of useless knowledge lol i quickly learned it’s just unnecessary

I stand by my tried and tested method never had a issue

 

I'm with you on this one too.

But what the hell do I know about engines?
TFX block anyone?

 

Tfx block scuba ?? Tell us more

 

It's an all alloy big block that top fuel cars use....

 

Dude he doesnt have aluminum cylinder so he just runs it in idle 3-4 times, you dont have idea what you are talking. This is cast iron cylinder it needs more km to settle in, he can drive it like you said but it will last so much less then when you do it right, you have no clue

 

Listen, No body likes a know it all I asked him if it was cast iron or ally and he hasn’t even replied yet I was going on the assumption it was ally. No ones even mentioned the cast iron run in times expect you so calm down and take a breath lol