5 mph more top end would be great on my 257cc (260) Linhai  By  4950cycle (Read 7,144 times)

quote author="tortoise" source="/post/117072/thread" timestamp="1470382814"]
. . . which should be compatible with more displacement.
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Yes, But if my motors max potential has been reached already. I can't find anybody who has worked with the 257cc Linhia to see if we are already getting all it has to offer and still be reliable. Anybody can just go buy a bigger scooter. I'd like to know if what I have already has what I need first. It's so close to what I want and need already.

The 20 Something HP 4 Valve Engine, EFI, Sport Fairing and Large Wheels with Motorcycle Tires do help as does the relatively high compression ration. I inadvertently buried it once just flowing with traffic late one night. Can't see the speedo very clearly without my reading glasses and the chin bar on my full face helmet blocks the view of the speedo but it was a true 100 mph according to the GPS that one time flowing with traffic which was quite a realization since everyone knows a 250 taps out at 80 mph. Won't knowingly do that again but now I know its there.

How come I can't find this thread in the mainstream 250 and up section of this forum ? I always have to go to my user name and access my user names participation to get here.

4950cycle,

FINALLY... Someone with the exact same problem as me... LOL!

I have an old 2007 Kymco Grandvista 250 which I absolutely LOVE... except I too could use 5 more mph top end... Or more accurately, 5-mph more CRUISING speed.

Apparently the old Grandvistas are fairly "frisky" for single-cam, carbureted 250's (even though the factory specs show only 67-mph top-speed). The GV sites relate that most will top 70 with a 200 pound rider.

"Minnie Mouse" as I call her has had a one-tooth up change to the final drive, done by the previous owner back in 2008. She currently tops out at an honest 80-mph on level ground. However, "real world" CRUISING performance, including hills, wind, etc. limit her to a realistic cruise of 68-70-mph, leaving just a tiny bit of throttle left.

On local freeways here, you absolutely MUST be able to cruise 75-mph minimum to be safe ( would be much better, but not realistic for a 250 except maybe ITALIAN ones...).  If you need near -cruise, you need a bigger bike... LOL!  And, like you, I'm five short...

I experimented with my original Chinese 150 and found the variator IS the main secret to improved performance. I installed a performance variator (which by itself did little or nothing...). Then, I played with roller weights. THAT did the trick. 11 gram rollers gave me terrific acceleration, but a useless top-speed of 45 at a screaming 10K rpm.

12 gram rollers gave me a great 65-mph top-speed, but ZERO acceleration and hill climbing.

A mix of 3 ea. 11, and 3 ea. 12 gram rollers was perfect, giving me decent acceleration and a top-speed of 62-mph.

I'm sure a 250 will respond in like manner, only more forgiving due to double the horsepower and torque of a 150.

Upping your final drive is not the easiest thing to do, and I'm not sure how much more top-end you'll get. I'm told my Kymco seems to have gained around 5-mph, but that may or may not be the case. I wouldn't mod the engine. They put out good power for their size already.

I would try changing the rollers to Dr. Pulley SLIDERS for sure! I am going to do that myself, but health issues may keep me from doing it this season.

The sliders allow the variator to FULLY close for highest top speed, and FULLY open for fastest acceleration. I've heard nothing but RAVE revues of the sliders in all displacement sizes.

Several site members have upgraded to Dr. Pulley sliders in their 150 and 250 scoots, with AMAZING improvement. Getting the proper weight is the secret. As recommended in previous replies, I'd check with Dr. Pulley for advice. Most think 1 gram lighter than factory rollers.  My "gut" feeling is to use the same weight sliders as factory rollers since the sliders ALSO increase acceleration, but I'm no expert.

My old 250 drives just about "perfect" as-is, since I don't run freeways too often.  It's just that even at 70-mph I'm a "rolling road-block" incurring the common honking, "getting the bird" and the occasional beer can tossed at me by passing traffic.  Seventy-five seems to be the magic speed to be "accepted".  And to cruise 75, I'm going to have to try sliders...

SURELY sliders are THE easiest and most affordable way to upgrade your performance.

Please keep us posted, and best wishes. I'm betting the right weight SLIDERS will give you that elusive extra-five!

Ride safe,

Leo in Texas

The bigger carb can also hurt you if you do not have an electric fuel pump. The stock air cleaner usually has a tuned port feed tube going into the carb to maintain vacuum and intake pulse to keep the diaphragm in the fuel pump fluttering and pumping fuel. The slide in the carb mitigates this to a degree but not past a certain point.