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Post by 4950cycle on Jul 27, 2016 16:57:50 GMT -5
I was wondering if anyone knew how to get 5 or so miles per hour more top end out of a typical 257cc (260) Linhai JCL MP 250A powerplant . I know the 150cc crowd gets this kind of improvement from an aftermarket (Doctor pulley)variater. But us 250-300cc Linhai folks might not benefit much from these same mods. Maybe the engines are at their max at 63-67 mph with my 260 lbs. butt on them already ? Will a 32mm carb. with a 125 main jet plus a free flowing exhaust give me anything here ? PS I don't need better excelleration. I want a pinch of top end. Thanks for looking
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jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
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Post by jmkjr72 on Jul 27, 2016 19:01:53 GMT -5
Top end is gained by adding use able rpms ones that still make power First thing to do is take a sharpie and mark up the I side of the varatior and go for a good wot run and see if your going all the way up. If not then roller change will help. You might get a couple mph if the whole system allows better flow if you add the pipe and carb. Can the valve springs cam and head flow enough air and support more rpms
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Post by 4950cycle on Aug 1, 2016 0:16:50 GMT -5
Not even sure if I have the extra pinch of hp to pull a little bit taller gearing that maxing the pulley on the variator would need ? I think I might have it though. So first on the flow chart is check to see if belt is climbing to the top of the variator pulley ,Right ? And if it is not, do what ? By sliders that are a gram or two more than what my rollers are now ? And if it already climbing to the top try to make a bit more top end power ? I am suprized though that there is still not much knowledge about tweaking this motor trans combo with already known mods. The powertrain wasn't born yester.day. Thank you for the help
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jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
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Post by jmkjr72 on Aug 1, 2016 17:47:13 GMT -5
I adjust roller in .5 gram incriminate a while gram or even 2 is a huge adjustment. Think about it you have how many rollers in your varatior now multiple that by the amount you changed each one it's a huge jump if you add 2 grams
If you are allready at the top the next thing I would look at is to change your ratio in your trans to gain a few more mph
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Post by 4950cycle on Aug 2, 2016 22:33:09 GMT -5
If I knew where to get a taller gear set for a Linhia drivetrain I would do it. But of course after maxing my variator potential. So you say only go up a 1/2 a gram at a time Jmkjr72 ? I can't quite understand what you are trying to say in your first sentence.
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jmkjr72
contributing staff
Commander 132nd Northern Cav. Division
Posts: 2,779
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Post by jmkjr72 on Aug 3, 2016 16:24:40 GMT -5
Take a zuma 50 2 stroke varatior it has 6 rollers. If you change the weight by .5 grams it's a 3 gram increase. 1 gram is a 6 gram increase 2 grams is a 12 gram increase.
Did you look for yamaha majisty 250 gear sets Iknow there are a few of those out there I belive racing planet has them or had them
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Post by Rebel on Aug 4, 2016 23:23:44 GMT -5
I went looking for performance parts and just parts for the 250cc class, I posted some links for the Linhai-Yamaha and CN250/Honda here, I did see some 11 gram, 14 gram and 17 gram rollers/sliders for the Linhai on one of the pages. Your rollers appear to be the 20X12 size, be sure not to order them for the Honda motor, they are 24X18 scooterrebels.proboards.com/thread/2681/parts-sources
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Post by 4950cycle on Aug 4, 2016 23:49:49 GMT -5
Thanks Guys, You are a big help. Waiting for my battery so I can do that variator marker test jmkjr72 recommended. I went ahead and sprung for the 32mm Performance carburetor with a 125 main jet (stock is 30 mm with a 110 Main jet). Usually more fuel doesn't improve top end in my experience. If it improves anything it usually improves acceleration. But sometimes it does give you a little of top end. Being an easy mod I am trying it first. Wasn't cheap though. Ever pay $100 for a Chinese carburetor ! Crymany ! The thing probably cost them $ 4 to make. lol I am going to try to run my stock air cleaner and exhaust. I have gotten very little gains from air cleaner and exhaust mods in the past unless going extreme high performance. Mainly because these mods make the bike to Fing noisy for little if no real gain. If you increase flow by doing head work (porting and such) then intake and exhaust mods start helping a lot IMO. Good info though and thanks for the research tips for parts. Read more: itistheride.boards.net/thread/9619/mph-more-great-257cc-linhai#ixzz4GQZKuyBo
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Post by Rebel on Aug 5, 2016 0:02:47 GMT -5
Ah, over at IITR. JR and I set that up, long story.
The sliders seem a bit pricy for the 250 class of scooters, as does that carb, I also saw it for $99.95. I think you are right you will get more off the line with that and perhaps that 5mph you are looking for but maybe not if it does not let the motor spin faster. Going up a size in rear tire might be helpful. But yeah do the marker on the variator and see if the belt is running to the outer edge. Also getting a bigger variator will change the final drive gear ratio for the better and no low end loss.
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Post by Rebel on Aug 5, 2016 0:07:13 GMT -5
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Post by Rebel on Aug 5, 2016 0:09:02 GMT -5
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Post by 4950cycle on Aug 5, 2016 1:54:23 GMT -5
Thanks for the links. Boy, I notice Dr. Pulley sliders are slim pickens for the Linhia 257 + engines. Almost all rollers. But darn good prices on the rollers you found.
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Post by 4950cycle on Aug 8, 2016 0:54:45 GMT -5
And as far as the back tire goes I stuffed the biggest Pilot 13 I could get in there. It even rubbed just a little at first.
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Post by 4950cycle on Aug 9, 2016 1:09:54 GMT -5
I notices JR. from the old Scootdawg forum put 12 gram Dr. Pulley sliders on his wife's 250A he said. I guess that's the exact same scooter I have JCL MP 250A . They came stock with 14 gram rollers most folks say. He said the scooter worked great after the 12 gram slider install and went 75 mph . "But" He never said how tall the rider was. He never said how much the rider weighed , He never said if it was hot,cold ,head wind, tail wind. You get the picture. Does anyone know where JR. is these days so I inquire about this variator improvement he did back then. Cause hell, My scoot will do 75 mph now if it had a 140 lbs. rider, Short rider, tail wind, very cool weather and such.
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Post by Rebel on Aug 9, 2016 15:17:48 GMT -5
I can tell you that Jr doesn't weight 140 pounds. His wife I've never met. I have spoke with a fellow that said he could keep up with freeway traffic on his bt got blown around by bigger vehicles on the freeway.
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