PLEASE HELP SOMEONE, DEAD AT 7,560 rpms

Steve I experimented with that exhaust port "step" by making a ramp of JBWeld.
To my surprise I got more low RPM power without any loss of high RPM power. But of course the high heat there meant it wouldn't stay in place. A well designed engine doesn't have that step.
 
Steve I experimented with that exhaust port "step" by making a ramp of JBWeld.
To my surprise I got more low RPM power without any loss of high RPM power. But of course the high heat there meant it wouldn't stay in place. A well designed engine doesn't have that step.

Interesting.
On a 4 stroke car engine, a 351C Ford V8, I made exhaust port inserts on the header pipes to fill the bottom area on the pipe. Exact same effect as you mention. 3/8" x 3"steel insert on the bottom of the port and the engine worked better. I've learned to not take any metal off the bottom of most 2 stroke exhaust ports because it gives up low end torque for no top end gain.
On the intake side, I've filled the intake reedbox on several engines with several ounces of JB Weld (it will survive there) to gain power everywhere. Minimal volume in the ports is very important.
I've never looked at radiusing the window into the cylinder. Good idea Jag. It is very important in the valve seat area on 4 strokes.

Steve
 
Gary tell me if your cylinder has stock exhaust port height and max speed on level ground with your pipe.
All I do to the exhaust port at the top is clean it up. I oval it out on the sides to come out square to the pipe mounting surface or close to square and take some material off the bottom of the port. So hight is stock. lots of hills up here so I like the low end torque. My daily rider is jack shafted to a 4 speed rear hub and toped at 46 mph. I went to a smaller drive gear at the crank, and now it is 41. With this set up I have more than enough speed, and I can idle slowly through the grocery store parking lot. I will test my other bike with similar engine but no jack shaft and 44 t sprocket and get back to you.
 
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I've used ramped pistons to gauge where to cut expensive cylinders (on other engines, sleds and CR250).
The cut cylinder always worked better than the ramped piston.
I think the reason is because of the effect on squish turbulence.

I noted and like the idea of the ramp helping to smooth flow into the cylinder, but my personal results differed.
I too have been decking the jugs. First about 0.010" to get them flat, but recently did one almost 0.030" to see effect on powerband when lifted with base gaskets and teflon headgasket. Even that little made a difference but I do like the low rpm torque of a low exhaust port. There is a problem with the exhaust port not being completely uncovered. Your ramps may help that, but so will lifting the cylinder.
If the intake and exhaust ports are wide enough as they open, there is no need to change port timing unduly to get rpm.

I have a couple of the Delorto "RT" clones. Sad to hear they are poor copies. How do they differ from the real thing?

Steve
I am still on the 2 stroke learning curve. By ramping I get a larger opening and smoother transition for the exhaust and transfer ports without changing their relationship as to when the rings go by the top of them allowing me to keep my low end torque. Removing the casting lip at the top of the transfer port, cleaning up the intake side of the trans. port, and knifing the lower portion of the trans. port in the cyl. making sure not to remove enough to create a hot spot seems to make my motors pretty snappy and responsive. As to the decking I have two new jugs in front of me right now. One mics 2.744 the other is 2.778. I shoot for 2.710 2.705 is pushing your luck with chinese quality tolerances anything under 2.700 the piston's bouncing with standard gasket set up. Ok Delorto's clones surely you have heard that lots of folks have good luck with them. It just wasn't the case with me. I might have given up on them to early. The ones I've gotten claiming 15\15 were all 14\14 and were no improvement over the stock nt. The 16\16 Italian was a true 16\16, and even with the larger openings runs well with the #68 jet that I use on the smaller nt's. I'm not sure why maybe it atomizes the fuel better. It is smooth thru all the throttle positions so I'm just really pleased with it's over all performance. The only glitch is a slightly temperamental low idle so I just adjust it up a little.
 
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I want to put a Walbro on mine, too. One thing I can tell you from doing it on a Huasheng is that there is no need for a crank case pulse if the tank is mounted higher than the carburetor. That's for the fuel pump that line trimmers have to have since they sling the tank lower than the carburetor. I saw someone on youtube who went to all the trouble of drilling into their crank case to get a line for a crank case pulse, you don't really have to do that. My Huasheng still relied on a goped gas tank, that had the lines fed into it at the top, so I usually had to squish the bulb to get a siphon started, but only when I started it up. If you are keeping secrets, you are missing the point of a support forum. The only thing a "kit" for that should involve is something to adapt the fuel line sizes together, and maybe a manifold, if I can't find a way to get the Walbro one to fit like I did before.
 
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