I want about 5 MPH more top speed on my JCL MP250A By 4950cycle (Read 3,801 times)

[4950cycle]

I went to put on my old carb on today to get ready to do the variator test. What a bitch working through that hole underneath the seat. Especially when I'm not using pod air filter (K&N style). When I finally get it in there and all hooked up I try to start it. Gas started coming out of the overflow tube as fast as the fuel pump would pump it. I guess all that wresting with the carb somehow got the float stuck inside the float bowl is all I could figure. Tomorrow's another day

[4950cycle]

Finally got my old carb back together and got it back in my JCL 257cc. "THEN" I leave the driveway on a test run and something gets sucked up in the main jet I figure . Blasted up the small hill from my driveway entrance. Ran great for 200 + yards got to the top of the hill and started starving and sputtering. All I can figure is the WOT up the hill sucked a piece of debris right up against the bottom of the main jet I guess. I'm starting to get a complex here. Someone doesn't want me to ride I'm starting to think ? I can't get a block down the road without something lousing up on this otherwise good running scoot.

Read more: scooterrebels.proboards.com/thread/2676/miles-hour-257-linhai-jcl#ixzz4IPGhinjD

[jct842]

How is the fuel filter? Your last 2 posts seem to indicate same under lying cause. Hoses from china been known to disintegrate on inside from crapahol gas too.

[4950cycle]

Thanks for the info, Actually I'm very lucky in that department. Whole fuel system seems do be totally debris free ! Not a darn crumb of anything in tank, Carb, hoses, anywhere. But my first problem was my main jet fell out in the bottom of the float bowl, Holy crap I feel like a total YO Yo. I guess in all the junk I was screwing with that day I forgot to torque the 115 main jet I moved from the new 32 mm carb (trying to get it working) back to the old 30mm carb where the 115 came from. Anyway, I got it running good again except for my float bowl running empty often. Seems this fuel pump I bought off Ebay just isn't enough. I will return it. I don't want to go electric fuel pump like a lot of 250 and up guys do. I got another Vacuum Jin Bo Chinese fuel pump on the way. Hey, The last Jin Bo exactly like it lasted almost 8 years before it quit. That's good enough for me. It is somewhat equivalent to a Mikuni DF 52-21-D fuel pump. But under half the price. I'd like to adjust my valves and pull my cover and mark my variator while I'm waiting for this new Fuel pump.

Read more: scooterrebels.proboards.com/thread/2676/miles-hour-257-linhai-jcl#ixzz4IgvWXpdw

[4950cycle]

While I'm waiting for my fuel pump I'm making a trap door to get to my intake valve easy. I made one years ago to get to the exhaust valve. These Linhia's with receding valve seats (exhaust valve mainly) need valve adjustments often. And since the engine lays down the exhaust valve is accessible from the belly and the intake has to be accessible from under the seat. If you don't make these access doors or holes you would have to take off all the body work just to get to the top and bottom of the cylinder head to adjust the valves. The trick is to make these mods as invisible as possible. We wouldn't want to louse up the beautiful lines of a Reflex clone would we .

[4950cycle]

Aug 9, 2016 16:10:50 GMT -6 jct842 said:

First thing I would look at is the rpm at the top speed you get now. Depending on if it is wound out or not to decide on what weights you have and what you need to go to. If you don't have a tach get one on there. If you are a whole lot under red line you need to go lighter in weights which is what I would suspect.

Doubt if you will be happy with a larger carb with out doing other mods to go with it. Jetting is usually all that is needed.

JCL MP250A Lihai 257cc powered / This is how it all ended up here. This info is not for a 50cc-150cc scooter. They are a different animal in some ways to the Yamaha 250 / Linhia powered scoots. I have come to the conclusion that my 257cc Linhia will not go any faster on the top end without a meaningful power upgrade. Like a "real" 295 cc (300) cylinder / piston change plus maybe a little upjetting ? It just dosn't have the torque in its present form to go any faster than 68 mph with my 270 lbs , head right up in the wind resistance situation. I don't care what I do to my variator it just can not change this fact. But I have learned a lot about what works and what is a waste of time. #1 Forget about a bigger or a performance carburator if you don't improve your flow in some meaningful way ie: porting your head and exchange some torque for HP , And get an open / noisy exhaust and and lets not forget a performance pod style airfilter, also more noise. Yes , your intake makes noticable noise with no airbox. " It will sound faster " with just a pod airfilter and a more free flowing exhaust, But in reallity the numberes will change no more than slieghtly if at all. But if you are young and like to be noticed this may have some value. #2 Variator changes gave" ME " (big and heavy) no more top speed. But if a rider is much lighter than 270 lbs. this is what you want to do. #1 On the variator improvment, Shorten your variator boss by 1 1/2 mm do not exeed 2 1/2 mm shorter than stock or your belt will almost climb off your variator at top speed. This will allow your variator to reach its full out high gear. In stock form they stop short of this. #2 on the variator improvement, Exchange your 14 gram rollers for 11 gram "sliders" This will give you everything this motor can offer (with the boss mod too) IMO. I have four 12 gram sliders and four 11 gram sliders. This is what I personally want because I am going to get more power in this engine in the near future. But number 2 will keep you in the higher RPM for maximum excelleration and number 1 will give you full top end capibillities. You CAN have the best of both worlds this way.

Read more: itistheride.boards.net/thread/9619/mph-more-great-257cc-linhai?page=5#ixzz4PQde3hJC