New carb, less speed.

[herbilious]

Hi, I just got my new carb on my bike. It's one of those dellorto knock offs. The top speed of my bike went from 34 mph to 27 mph. There is no air leak. I think the engine is running rich, because its smokier and smells more potent. But when I lower the jet it takes a long time for the engine to return to idle. And seems to run lean. What is my issue?

 

[Vikingimike01]

It's the lack of controllability on the dellorto knock offs, if you mean the HP carb. Throw it out! ew

If not then, fiddle with the pin. Get it right.

 

[herbilious]

It's the lack of controllability on the dellorto knock offs, if you mean the HP carb. Throw it out! ew

If not then, fiddle with the pin. Get it right.

It's this knockoff here: https://www.amazon.com/gp/product/B07JWFTKHN/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

Would buying a .61 - .65 jet kit help me improve my performance?

If not, which carb should I get to improve performance?

 

[JerboaJohn]

when i jetted my dellorto clone, i had an expansion pipe so I stepped up to 75 then down 1, test, down 1, test again etc,, until it was responsive and good top and ended up with a 72 but i had every jet ftom 65 to 80 to play with.
stock jet is #70. with no other mods you're probably best with 65-68 but do a plug reading and your oil ratio will have an effect too.
these carbs are pretty simple and can only tune for a certain range.

no needle bcs it's flat slide , just a jet and idle screw

 

[mark20]

Hi, I just got my new carb on my bike. It's one of those dellorto knock offs. The top speed of my bike went from 34 mph to 27 mph. There is no air leak. I think the engine is running rich, because its smokier and smells more potent. But when I lower the jet it takes a long time for the engine to return to idle. And seems to run lean. What is my issue?

that cuase those jets are spaced out a bit more, theres a 5 size diffence.
if you intalled the 70 jet and its rich, but the (im assuming) 65 is lean,
then you need a a jet thats between sizes (i think)
so try to get a 68 or a 67 jet, that should help it (also, are you sure there are no air leaks?)
what oil ratio you running? that could affect preformence as well.

 

[herbilious]

that cuase those jets are spaced out a bit more, theres a 5 size diffence.
if you intalled the 70 jet and its rich, but the (im assuming) 65 is lean,
then you need a a jet thats between sizes (i think)
so try to get a 68 or a 67 jet, that should help it (also, are you sure there are no air leaks?)
what oil ratio you running? that could affect preformence as well.

There was an air leak but I'm pretty sure I fixed it. A 65 jet is running the smoothest so far but I feel it's still a bit rich. I have a high compression head and an expansion chamber for upgrades.
Spraying degreaser doesnt lead to higher revs so I'm fairly sure the air leak is gone. I'm running 32:1. I ordered a pair of 61 through 65 jets, if none of those work then maybe there is a feint air leak. I say that because I had to dremel a bit of my intake manifold to be able to fit the new carb in the frame, so the clamp of the carb has about 4mm of space by the end of the intake where it isnt all the way on. The idle is sound, and it performs ok. Less low end and way less top speed than the stock so I think its probably just in need of smaller jets. I guess I'll update when they arrive.

 

[mark20]

There was an air leak but I'm pretty sure I fixed it. A 65 jet is running the smoothest so far but I feel it's still a bit rich. I have a high compression head and an expansion chamber for upgrades.
Spraying degreaser doesnt lead to higher revs so I'm fairly sure the air leak is gone. I'm running 32:1. I ordered a pair of 61 through 65 jets, if none of those work then maybe there is a feint air leak. I say that because I had to dremel a bit of my intake manifold to be able to fit the new carb in the frame, so the clamp of the carb has about 4mm of space by the end of the intake where it isnt all the way on. The idle is sound, and it performs ok. Less low end and way less top speed than the stock so I think its probably just in need of smaller jets. I guess I'll update when they arrive.

Hmm, well
I would just run a 63 and call it a day

 

[Freddy Snottgrass]

Spray carb cleaner around your intake manifold when it is idling. If it slows down you have an air leak. Make sure it doesn't get into your air filter or it will slow down as well. I normally park where my air filter is up wind and spray from the air filter's direction toward the engine to ensure I don't get false readings. Spray a little spurt into your air cleaner so you can see what will happen if you hit an air leak.

 

[Tyler6357]

It's this knockoff here: https://www.amazon.com/gp/product/B07JWFTKHN/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

Would buying a .61 - .65 jet kit help me improve my performance?

If not, which carb should I get to improve performance?

Yes!! I had to put a #60 in mine to get it right, but once I found the right one it flies.

 

[extremeodd]

The fun of swapping carbs is tuning them. You will be hard pressed to find carbs other than the NTs that will run right out of the box.