Low end trouble

[SHeva4ever]

I finally assembled my engine few days ago. I've changed a lot of parts during the process. It works strange now. It has normal idle, but when I give it WOT I have a lag.
When I’m trying to open throttle slowly it decreases revs and then suddenly revs it up. This lag is on first 1-2mm of throttle. I can't test it on high rpm because I have a lot of new parts in my engine including new pistons. I have all in stock including air filter, jets and exhaust.

P.S. Carbs are cleaned and synchronized.

 

[one2dmax]

Still sounds like a jetting issue. You didn't say what you changed but it's obviously got different demands on the circuits. You may want to check out the "engine break in secrets" that is easily found when using google.

That's the break in we use. 25 miles and you're ready to go.

Sean

 

[SHeva4ever]

I have changed pistons, rings, valves, connection rods, bearings, CARBURETOR JOINT, AIR CLEANER JOINT, air filter. All pars are original from local Yamaha dealership.


I've ridden 170 miles after this repair. No changes.

 

[one2dmax]

I would still put my money on the carbs. It could be electrical but not likely the engine if it's got decent compression, good valve adjustment, and correct cam installation.

Sean

 

[jfeagins]

Are all your rubber boots on correctly and snug? Are you doing this with the air box back in place with the lid on? Sounds like an air leak to me.

 

[SHeva4ever]

Boots are installed correctly. Airbox is on it's place with lid and Y on.

I agree that it's carbs or a leak.
I am trying to close one side of Y and it works better. So it's too lean.

I have rised the float level on 0,5 mm but it has became worse. It works same on idle, but the engine stops when I am trying to give it some throttle.

 

[jfeagins]

With some choke applied, does it perform any differently? Did you have all the carbs completely torn down and cleaned during this process too, or are you simple reinstalling them on a motor rebuild, and they worked OK before?

 

[SHeva4ever]

With more chocke I have more rpm on idle so difficult to say is it better or not. I think it's better with choke. Yes I completely disassembled my carbs and cleaned all channels and jets with ABRO carb cleaner. I have installed new gaskets and o-rings to the jet block. And they were working OK last year.

 

[SHeva4ever]

I have found vacuum leak. I had a small hole in the air box lid. It was because I used to have long screw to hold carb ventilation hoses. I have fixed it with super glue and my bike works much better now.

Thank you guys

 

[SpecOps13]

Wow.:ummm: