Runtong Dellorto clone and tuning?

Kpi890

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#1
Just received my dellorto clone in the mail from amazon. After frustratingly getting my jetting correct on my current NT carb, at a size 67-68 jet I threw the clone on the bike. Ran the bike for a hot minute down the street with the stock jet and it was 4 stroking pretty bad at WOT. I popped the bowl off and threw on a 67 jet. A little better but same four stroking at WOT. I worked my way down to my last jet in my collection, which is a 60, I knew I was on the right path going leaner because it was getting better, however it still wouldn’t get over 6000 rpms and four stroking pretty bad. With my NT I’m getting around 7,800 rpms at WOT. I’m a little confused here, why is this carb still running so rich? I pull the plug after cutting the engine at WOT and it’s dark and oily. Do they make jets smaller than a 60 I can try out or am I missing something here? Seems crazy to go below a size 60 jet. I know these carbs run a little richer than the NT but jeez! I will say my bike starts, idles, and responds a whole lot better with this Runtong “Dellorto” Clone. Any help or suggestions is much appreciated! Thanks!
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Timbone

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#2
My experience with these carbs is they are easy to go lean. 60 is small so why so rich?

Maybe the jets are drilled wrong? Maybe your air filter is impeding airflow. Since two strokes like to start and idle rich - and I have always had trouble getting good idle with these slide carbs - you have to check airflow. Do some runs without the air filter. Extend your intake. You should be lean with a 60 jet if you are anywhere close to sea level.
 

Kpi890

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#3
My experience with these carbs is they are easy to go lean. 60 is small so why so rich?

Maybe the jets are drilled wrong? Maybe your air filter is impeding airflow. Since two strokes like to start and idle rich - and I have always had trouble getting good idle with these slide carbs - you have to check airflow. Do some runs without the air filter. Extend your intake. You should be lean with a 60 jet if you are anywhere close to sea level.
I am going to be doing some test runs tomorrow without the air filter and see if that’s the issue with it being impeded by the stock filter. Thank you!
 


mybike

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#5
For most conditions those carbs run rich on top, so if your low and mid is good, your top will be rich. If you get the top to run good your low and mid will be lean. I have modified them to run good (drill an extra small hole in the tube) but still prefer the NT or Speed NT. Easy to tune and at least you have two adjustments for fuel delivery. Check out Jaguars site he has much info on the Dellorto.

Trust me the NT is all you need for even a performance build. I have all my bikes with either the NT or NT Speed carbs. I also put a o ring inside the carb for any air leaks. Here is a video with a speed NTTC which most say are no good, I don't know why, seems to run good for me. I am running a little rich which I always do. Just to be safe. Also this is a very worked engine

 

Kpi890

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#6
For most conditions those carbs run rich on top, so if your low and mid is good, your top will be rich. If you get the top to run good your low and mid will be lean. I have modified them to run good (drill an extra small hole in the tube) but still prefer the NT or Speed NT. Easy to tune and at least you have two adjustments for fuel delivery. Check out Jaguars site he has much info on the Dellorto.

Trust me the NT is all you need for even a performance build. I have all my bikes with either the NT or NT Speed carbs. I also put a o ring inside the carb for any air leaks. Here is a video with a speed NTTC which most say are no good, I don't know why, seems to run good for me. I am running a little rich which I always do. Just to be safe. Also this is a very worked engine

Man that’s a nice looking build! Do you ever burn your leg on that expansion chamber? I’m about to put an MZ 65 pipe just like that on my bike and don’t see how I won’t burn my leg on it the way it’s going to fit on the bike. I think I’m going to wrap it to prevent burning myself.
 

Kpi890

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#7
Tried running through the jets once again with the carb and it’s still four stroking a ton at WOT so I may just call it a loss with this carb not sure what’s going on but I can’t get it to run smooth.
 

mybike

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#8
Tried running through the jets once again with the carb and it’s still four stroking a ton at WOT so I may just call it a loss with this carb not sure what’s going on but I can’t get it to run smooth.
Never burned my leg. Again stick with the nt carb. Put an O-Ring in the carb, get it up to temp and then tune the carb jet. Once you get the jet close then you could play with the needle. Also don't forget, a two stroke will 4 stroke under no load conditions when tuned right. If it does not 4 stroke when under no load, you are running lean.
 


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