8,000 rpm limitation

[skuttadawg]

Well I put on an unlimited cdi and it made not diff at all . Removed and weighed my rollers they were 6 gram and tried 4 gram and had a top end loss due to rpm limit . Went from 65 stock to 75 jet and its a perfect caramel color on the plug . Replaced the NGK with an iridium . It has an expansion chambered pipe like those advertised but it has a hose and reed valve just before the expansion chamber . My dealer showed me the EPA tag where it has a catalytic convertor which he thinks its in the expansion chamber instead of muffler . They mostly sell and service 4Ts . I have hit 8,500 on level road and 9,000 downhill but it will stall and I let up off of the throttle and it returns to normal in half a second . It runs perfect and mostly hits 45 mph but has hit 50 at times but still limited . No washer limiter in the variator . I was happy as I though tit already had a decent pipe as I have seen some that was just a tube and no expansion chamber . I have a Japan 19mm carb with stock air box . So it looks like I need a HP exhaust to get high rpms then put on a Uni and upjet . Its a blast to ride and I enjoy passing cars and 4T 40s but know it has more to offer with out pushing it beyond its limits . I have talked to others with 2T and they can hit 10,500 max rpm but unsure how many the stock crank can handle . A racing forged crank I am looking at can go up to 18,000 wow www.mhr-usa.com/racing-crankshafts/std-10mm/jasil-10mm-racing-crankshaft-for-yamaha.html .

My intake seems longer than the HP ones like from Hoca so maybe a shorter one with a Uni and unrestricted exhaust will let me get higher rpms . Yes I know I need to upjet to avoid being too lean . Its 2 months old with 1,600 miles . I have not removed the intake or pipe to see if I need to smooth out the ports with a dremel like imperfections from casting .

I know a 49cc will only do so much but I would like to get past the 8,000 limitation to get up speed for the hills here . My area is called " Foothills " since its below a mountain range .

I was thinking about a 90cc crate engine but read those who got one were not impressed and they are almost gone so it looks like a 72 BBK maybe my answer for more power . I had a hotrod Spree that I could ride a wheelie .

I do have huge 130/60/13 tires which do have more drag than small tires but the ride and comfort are worth some loss .

Manual says I have 10.5 to 1 compression and only run nonethanol premium gas

Any ideas or tips will be appreciated . I have been a small engine tuner starting 26 years ago but have been out of the scene and have been catching up on current products and trends

[reveeen]

Physics.... you are fighting physics.

As you posted elsewhere: with my 200 lb self on my 2011 Jonway Magnum

You simply are not making enough power to pull that.

So let's analyze what is going on:

With an unrestricted exhaust, and the snorkel removed from the air box, most of us are running, or are having to run an 80 main jet. So my best guess is: you should be buying an exhaust, a "name brand" pipe, that has a reputation to defend, and that offers a "known" result. In keeping with your rpm goal, a LV ZX, or a Stage6 Pro.

[90GTVert]

If your expansion chamber has emisssions accessories attached, it's prob just a stock pipe disguised as a tuned pipe. Since you say it has a cat, pretty sure that's all it is. The stock pipe and cylinder porting limits them to around 8,500RPM for any decent power. Pipe especially. Even with a ported cylinder on my 90cc project, it really doesn't wanna make much power above 8500RPM with a standard pipe. Just falls off.

If you have the rear facing intake you may not be able to use shorter intakes for clearance issues.

The 90ccs impress me to the point that I greatly prefer them and converted every scoot to over 90cc. Just depends how they're tuned. A good 70cc kit can be a strong runner too though. A sport level kit and a good pipe would probably make you quite happy with it. Of course along with adjusting the CVT to work with the powerband and tuning the carb as needed. Should be fine with the stock crank for a sport kit and pipe. Polini Sport is about as torquey as they come. If you prefer revs a little more than max torque you might consider something like the Top Performance Trophy. Never used one of those, but a few of our members seem very pleased with theirs. I've used the Polini Sport kits for myself and customers in the past and everyone was pleased. With just a Polini Sport kit and a carb and CVT tune a customer scoot would pull the front tire an inch or two off the ground with power off the line. None of my scoots did that, but they are a little bigger and heavier than the Beamer that was on.

[skuttadawg]

Thanks what I figured . I did let it hit 10,000 for 1/4 of a second on the center stand as I did not think the cdi was unlimited

[jmkjr72]

yeah you are reving to the max for a stock pipe and stock bore

i love the tp trophy its proably the best bang for your buck out there

with the right pipe it will rev to the moon and still make good power

[skuttadawg]

I planning on going with a 72 BBK to get more power but as is it still does very well but I know it more potential