Hitting a rpm wall at 7,560, please help getting upset

[LandSpeedRecord]

As for wrist pin bearings I like the newer stock GT-5 style piston and Japanese bearings. I think it gives us room to safely modify the pistons, cylinders, etc and get pretty amazing power out of these things when they are right.
Best thing from here is I usually try to make sure everything is functioning properly and running strong with stock parts when there was a problem then move on to making big power if wanted. Just have to be sure yournot covering a problem before moving ahead or it will impede performance oor cause big problems once you really get the motor screaming.
Keep us updated.

 

[salorr33cc]

hey LSR thank you for your good replies,,, keep them coming..!!!

how does your bike run with 3oz to 1 gallon i think thats 48:1,, is it safe ??

my bike still runs rich and its not the jetting cause it want more gas at WOT when i was running a .065 main jet,, had to up drill to .069 to cure starving dead spot at WOT,,, might even need a .070 but have to find away to lean out mid range,, this is where i want to put the WALBRO carb kit i made on,,, it has the idle, high, and low screws,,,, was amazing on my 50cc scooter.. when i get some problems ironed out i will..

want to get the NT figured out first,,, almost there,, that way i can see a difference and what performs better over all

do you get noticeable more power with the 48:1 leaner mixture and does it help eliminate 4-stroking,,, what type oil,,, regular or synthetic

 

[sbest]

Oils:
Mineral - distilled from crude oil (petroleum) tends to generate a lot of carbon, quality depends on additive package and base stock.
Castor - made from castor beans, builds a lot of sticky varnish, messy but very good oil.
Synthetic - "created" molecules from esters, petroleum or natural gas. Designed for purpose.
Injector oil - low viscosity to flow thru pump and lines regardless of temperature
Marine oil - for water cooled marine engines, might not handle high temperatures. Bio considerations over performance.
Premix oil - purpose made for mixing, not injecting. Tends to be (but not always) more viscous.
I would avoid buying oil at Walmart. Go to a motorcycle shop and get good oil.

My GT5A is on same wristpin, at least 1000 kms. Pin and bearing look great.

You cannot run thin rings in a wide groove. Ring HAS TO fit the groove.
I run 1 ring on some engine but it is typically an overlapped ring, not a butt type like these. Like LSR said, these have to be plain cast rings. Thin rings give the advantage of rpm, but might shred the chrome faster.

LSR's trouble shooting technique is well worth listening to.
It is the standard method used in industry.

Steve

 

[salorr33cc]

WOW....Steve..what can i say your AWESOME man !!! you always answer so good and thou row .. your so experienced and smart...i didnt think about groove size and ring width,,, and the softer rings then the cylinder makes sense for seating wear down purpose..

Thats why I always ask you, I learn new stuff everyday and that how you do it to get a good final result,,and I have learned to do one mod at a time so you can see what works and doesn't and if you have a problem and just move on or mask it,,, it will come back to bite you and you will get future false results and data corruption...

Steve you never answered my Silencer question from another thread,, you said you got a Canadian one for $19 bucks,,, i am installing a 2004 Suzuki RM 85 pipe tomorrow,,, can you help me find a low cost, stubby silencer...please help me with this,,,i have now luck searching

and one day I want to see a picture and info on your bike,, I know its simple but runs perfect,, I am learning that it doesn't cost a thousand in parts to get an unreliable motor with only a few gains,,,, you can use the stock stuff if you learn how to adjust and tweak it better so all parts run in favor of each other

its like having a matched set of something, other then a real expensive unbalanced nothing...

TTYL,,,, thanks buddy, always look forward to your replies the most...JAMES

 

[sbest]

Ummm, I don't know that it runs perfect...

I hope this pict shows up. It is from weeks ago.
I blew the ported cylinder a few weeks ago when the wristpin circlip broke.
Running a stock cylinder at the moment, playing with the factors that interact with it. Today it was shaving 2mm off the piston skirt. Killed some low end torque and I might have gained 1-2 kph. Not a raving success.

The 48cc bike is just a cheap generic 10spd with a SBP jackshaft kit and no jackshaft in it now. Running it as a single speed, bigger back sprocket, skinnier tires (2.10?).

Just play with stuff and let the bike teach you what works and what doesn't.
Head swap in less than 10min, complete cylinder and piston in 20, unlike a Banshee.
These are the engines to tinker with!

Steve

 

[LandSpeedRecord]

Steve is for sure right on the oil. I build to sell and what I need in 2 cycle oil is the ability for me to get the rings seating properly in a short amount if time so I can try to get the bikes initially tuned for new operators. I actually want an oil that is safe but allows the rings to cut in for lack of a better description extremely quickly. I haven't actually broken in a motor in a long time but I just got the first shipment of my own motors and will be keeping a 4 stroke and a 2 stroke personally for a long time and breaking them in and developing them.
I bet that RM pipe is going to make awesome power, let us know how you like it.
Is the bike you are working on the one in your avatar? That's a great looking bike.

 

[LandSpeedRecord]

Steve it's interesting what you experienced with the piston skirt mod. I used to open them for full duration but I no longer do that. I used to actually lower the intake floor slightly and shape the skirt for full opening at top dead center. What I do now is just try to shape the skirt and port for flow without changing the timing at all. The port timing on these motors seems so conservative I think we assume to get more aggressive with all of it. I think the intake floor is about as low as it should be though so unless we are going reed valve I think the biggest gain there is just shaping.
When I get my new 2 stroke broken in do you have any super slippery synthetic or other oil that you have had good experience with? I am thinking with these motors we could run something very thin but I haven't pushed this area with these and wonder your thoughts.