Help mid throttle sputtering

[Stomp rider]

I bought a second hand brand new bike it was sputtering 1/3 two 1/4 throttle so I changed plug didn't work clean carb it gave it more power improved it a wee bit so I clean it again just incase then it was bad again so no av bought a new carb and the bike way mor power full but still does it its only wen the bike heats up eny ideas baring in mind it's brand new and it only does it for a second then opens up thanks

[Mississippi Bullfrog]

I don't understand brand new and second hand - if it has a carb then it's not brand new. Do you know the service history - eg when were the valve clearances last checked?

What bike is it? Mileage?

Have you checked the air filter?

If it only does it when hot is that because you've pushed the choke in? Or if you're not using choke from cold then weak sparks when hot point to an ignition weakness.

[Guest Richzx6r]

Hi an introduction would be good before asking for advice so hi and welcome to the forum..

I'm going to hazard a guess that theres a slight air leak between carb and head

[WD-40]

Try putting the choke on a bit. Does the splutter go away or get worse?

[Stomp rider]

Hi sorry for not introduction it was a second hand bike because I bought it of a 3rd party but it's brand new the stickers still on it nipples on tyres not a mark yea it's dome about 1 hour I changed the carb I changed the spark plug I haven't cheked the pipe from carb to engin so will check that it's a bout 1 second delay of sputtering but wen I pull the throttle future back it opens up its a z3 160 stomp dirt bike it's fine wen cold soon as it heats up it sputters

[Stomp rider]

It's not chock doesn't run with chock bike starts first kik it's a 2020 bike

[Stomp rider]

I hope Iam okay on this forum as I don't have a real bike lol

[Stomp rider]

I hope Iam okay on this forum as I don't have a real bike lol

[dynax]

I hope Iam okay on this forum as I don't have a real bike lol

 

If it has two wheels and engine

[Mississippi Bullfrog]

From what you've said it sounds like either the mix is a bit weak when you first open the throttle. I know nothing about that bike or what kind of carb it's running but the suggestion to check for an air leak is good. If it's starting from cold without choke then the mix itself can't be far out. Which suggests something is opening up slightly as the engine gets warm. Or if it's a very basic carb it may just not have any system to richen the mix on partial load. You could try richening it a wee bit - just remember your base setting before adjusting.

Since it runs better on full throttle it's probably not an ignition issue, a weak spark would do worse under full throttle load.

[Stomp rider]

Thanks I will defo check that I put a new carb on it as it was the same with the old one I put it in to garage and it's not the valves so all it can be must be air leek I no its not carb air fule as the carb came from reliable bike shop the garage was no very helpful as I put it in to get my valves looked at and thay coned me in to fixing a wee oil leek get the bike home and the oil leek isny even fixt and thay went a head and sed thay cheked my carb and done a oil leek and the sputter is 10 times worse am raging

[Stomp rider]

Sorry done a oil change

[Stomp rider]

Wats the best and easy way to see if thares a air leak I hope it is that thanks for your reply mate

[Stomp rider]

It's a molkt 26mm race carb

[Mickly]

To check for an air leak, spray WD-40 around the carb to cylinder interface & see if the rev’s rise.

[Bender]

https://www.howtomotorcyclerepair.com/how-to-diagnose-motorcycle-vaccum-leaks/

Don't set fire to it in the process.

[onesea]

https://www.howtomotorcyclerepair.com/how-to-diagnose-motorcycle-vaccum-leaks/

Don't set fire to it in the process.

 

Thanks [mention]Bender[/mention] and [mention]Mickly[/mention] thats a new trick on me..

[Mississippi Bullfrog]

In the days when more people smoked blowing smoke around the area worked quite well. I prefer easy start to WD40 for anything with a catalyst, WD40 can affect the lambda sensors.

[onesea]

In the days when more people smoked blowing smoke around the area worked quite well. I prefer easy start to WD40 for anything with a catalyst, WD40 can affect the lambda sensors.

Sounds like a perfect job for a Vape, big clouds.

[Copycat73]

it's fine when cold soon as it heats up it sputters

 

i keep a 65cc mini stomp .. similar sort of problem .. i dropped the needle one grove .. this helped .. also i cleaned the air filter .. using petrol .. and re-oiled .. again this helped .... i fitted a NGK suppressor cap.. again this helped somewhat .. i also made sure the connection from the HT. lead was good..