Weird stuttering issue

[Chad Welfle]

I just got a few parts to make my bike run a little better. The bike ran ok with kit parts but I wanted to open it up a little bit so I bought the high performance carb so I have a little control on what jets I can run without having to drill the NT carb. The problem I seem to have is that when I climb hills there is no stuttering and it actually pulls pretty decent for going up a hill. When I am on flat I can sometimes find a good place to hold the throttle to not stutter but a variance either way seems to make it stutter. I thought that maybe I was leaning out but my plug is still pretty black. I hear some what I would call pinging but not sure if its clutch chatter or pre detonation. I am not sure if I am experiencing lean or rich conditions. I dont have much experience when it comes to two strokes but have rebuilt several 4 cylinder engines. Any help would be great. A little background on the parts I have installed. I have the HP carb like I stated running the 70 jet. I have a 36 tooth sprocket. I will also note that I have not touched the plug or CDI so those are still stock (ultimately might be the issue). Thanks for taking the time
Chad.

 

[gary55]

I just got a few parts to make my bike run a little better. The bike ran ok with kit parts but I wanted to open it up a little bit so I bought the high performance carb so I have a little control on what jets I can run without having to drill the NT carb. The problem I seem to have is that when I climb hills there is no stuttering and it actually pulls pretty decent for going up a hill. When I am on flat I can sometimes find a good place to hold the throttle to not stutter but a variance either way seems to make it stutter. I thought that maybe I was leaning out but my plug is still pretty black. I hear some what I would call pinging but not sure if its clutch chatter or pre detonation. I am not sure if I am experiencing lean or rich conditions. I dont have much experience when it comes to two strokes but have rebuilt several 4 cylinder engines. Any help would be great. A little background on the parts I have installed. I have the HP carb like I stated running the 70 jet. I have a 36 tooth sprocket. I will also note that I have not touched the plug or CDI so those are still stock (ultimately might be the issue). Thanks for taking the time
Chad.

It's to rich. If it's the dellorto clone they tend to run rich. Get a #68 and a #66 jet from sickbikeparts.

 

[Chad Welfle]

Alright. I have the 5 jets they sent me, but they are in increments of 5. So I have #60 #65 #70(which is installed) #75 and #80. I figured that I was running to rich. Is the knocking noise (sorry only way I can explain it since my experience is with turboed cars) the pinging I am hearing not pre detonation and instead 4 stroking. I will post an image of the carb I am currently running. Just curious how you came up with the #68 and #66.

 

[gary55]

Not sure about the noise, but the clearing up when you go up hill or under load is typ. 4 stroking from running 2 rich. You might try the 65 depending on where you live it may be to big a drop in size. I guess then you will have to get something in between. You will know if it's to lean because the engine will balk when you fully snap open the throttle, then rev quickly and take a long time to die back down when released. This might clear as the engine warms up if you are right on the edge of to lean as it will richen a bit as it gets warmer. If you are at the edge of to lean you will prob. have to go to a larger jet come winter.

 

[Thanks]

I will try the #65 and see where that gets me. Are the jets on amazon all the same thread pitch and size. I was going to get a set that goes from #66 - #70 since I have narrowed it down to somewhere in this area. I am around 750 ft above sea level near Cedar Point, in Ohio. I was worried that I was too lean as I figured the pinging was pre det but again thats coming from forced injection 4 cylinders. Now that I have some clarity I am going to lower the jet to a #65 and see where that gets me. Thanks for the input. I will check back in after I give it a spin later today.

 

[Chad Welfle]

I should mention to that I am prb still in my break in period, which makes the tuning even more difficult. I have maybe two full tanks on the motor. Maybe 50 miles or so on the motor.

 

[crassius]

either wait for end of break-in, or redo everything later

 

[Chad Welfle]

Quick question on break in then. How do you know when the motor is properly broken in. I have read a few different theories and was wondering what is the best to go by. Like I said I only have about 50 miles maybe less on the motor. Is there a way to know for sure that the rings have properly seated.. I figure more than 50 miles is what its going to need to seat them properly just curious on your guys' take as I am still new to this.

 

[gary55]

Quick question on break in then. How do you know when the motor is properly broken in. I have read a few different theories and was wondering what is the best to go by. Like I said I only have about 50 miles maybe less on the motor. Is there a way to know for sure that the rings have properly seated.. I figure more than 50 miles is what its going to need to seat them properly just curious on your guys' take as I am still new to this.

You said you ran 2 tanks through it. If so it's broke in and ready to tune.

 

[crassius]

seat of the pants on break-in - you'll notice after a while it is a few mph faster and much smoother and quieter - usually 2 or 3 hundred miles