Looking for more speed.

[Le_Thon]

I have a street legal 125cc bike. Pic below, Guess which one it is ('8)') Here is the link below to where I got it. My current engine, as rated on the title sheet, is at 4.75kw.

http://www.orionpitbikesales.com/opbsxs_enduro.htm

8)

It currently tops out around 45mph depending on how it feels like driving. I use this as a daily driver around town and I live in south dakota where people love to speed. I would like to get a couple more MPH's out of my machine. I have done every "easy" (Blue CDI box, orange and black ignition coil, new rectifier [battery wouldn't charge], and exhaust) modification performance wise. My bike idles great now, I adjusted the card and its sweet but does not go as fast as I would like. The speed limit is 40mph and I do not want to burn out my engine running it at 9k rpms going 40 and 11k rpms going 45. I am putting on street tires (thanks for those who helped me pick em in another thread months ago!) this weekend in preparation for the next modifications.

The next couple of modifications I am looking at are

1. Rear sprocket
2. The sprocket inside the engine??? (i read something about this one somewhere)
3. NEW LIFAN 140cc engine(':twisted:') I see these on ebay and I was wondering how people like them or if they had experience with them.
4. New carburetor if I get the new engine -------------> I dont know which size to get. https://www.treatland.tv/carburetors...&search=%20blk

Ill probably end up doing all of these upgrades in the summer. Just let me know you experiences please.

[Frog]

Hi

You might get it to pull a larger gearbox sprocket for more top speed but it would loose out on acceleration and feel less 'nippy' which tends to be important in town. Going up one tooth is prob doable. Too large a sprocket and it will bog down and not have the torque to cope.

The 140 lifans are good engines I am told but may not be a straight swap with a 125 - you will need to change more parts.

I would also be aware of possibly ending up having more engine than chassis and brakes...

Easiest way to go faster is buy something designed to go faster - safer too.

Frog

[FastDoc]

Easiest way to go faster is buy something designed to go faster - safer too.

+1,000.

I am especially amused by the V-Max in your picture. Truth is you can already almost keep up with the Harley 8) .

Read this:



http://www.dansmc.com/hopup.htm

Speed costs money. How fast can you afford to go?

Sometimes the cheapest way is to upsize your bike.

[katoranger]

I would bump the counter shaft sprocket up 1 tooth. Not sure if a 140 will be much improvement. The 125cc is considered to be a reliable size. The 140 starts to get into race only.

[Le_Thon]

Thanks for the posts so far. I will try the cheap route counter shaft sprocket and let you guys know how it goes. Whats a good place to get one of those? Any ideas on the rear sprocket?

[Weldangrind]

I found that I could get a Suzuki RM50 rear sprocket to fit, but only in a 420 chain. I was going the other direction, where I was trying to gear the bike waaaay down. You can easily find JT sprockets to suit a 420 or a 428 chain, and they're available in several tooth counts.

Remove your rear sprocket and measure all aspects of it, then compare it with this one:Suzuki RM50

You'll need to remove your front sprocket and use the JT website to figure out which Honda sprocket is the same as yours, and then decide if you want to switch from a 428 to a 420. I think there's little risk in changing to 420, as long as you buy a quality chain, like an RK or a DID.

A 140 would be an awesome swap, but you'd require an oil cooler for it to live. Wring out the 125 first, and see what it's got. You can play with new carbs, jetting, air filters and mufflers a lot before switching to a new motor.

BTW, here's the sprocket change I did: 125 Pit Bike Wheel Upgrade

[Le_Thon]

I currently do have a 17" front and 14" rear. I am going to do the sprocket this weekend and ill keep you guys updated thanks!

[katoranger]

Is that 41st street in Sioux Falls? Can't remember the cross street, but I believe you are in the Scheel's parking lot.

[Le_Thon]

DANG KATO you are very close. I am in the dollar store parking lot hahah. Sioux Falls, SD. Know anyone from around here? Lived here?

[katoranger]

I have not been to that area in about 10 years, but I grew up in rural Iowa. We would drive to Sioux Falls for most of our shopping.

[Le_Thon]

That is pretty cool. I am from St. Paul, MN but go to college in Sioux Falls. Are there any members from these two areas that you know of? Iam always looking for fellow china riders There is a china ATV, dirt bike, and UTV dealer in town that I just found to! Its heaven... 8) Scarborough Auto Sales is the name.

[katoranger]

There is a few Minnesota members, but I can't think of any South Dakota members.

I lived on Carter Avenue by the U of M, St Paul for a summer and then with my sister in White Bear Lake. Also Richfield, Brainerd, and Mankato.

[Le_Thon]

All over the place! Thats pretty cool that you remember 41st street though.

[pete]

Yer need a bigger motor...
sure yer can gear it up 1 tooth on the engine.
( 1 on the engine = 3 on the rear )
Yer may get a few more miles per hour on the flat
but if you strike a head wind or hill..everything yer gained
in speed/time on the flat etc...you will lose, then some..
a Chinese 125 just has NOT got the power in reserve
to pull any useable higher gearing..

[katoranger]

There is no wind in South Dakota. If you want to reach 55 or so you will need more power. A 140 may do it. I have just read about more reliability issues when getting into that size.

If you are in the dollar store lot is there no longer a Scheel's store there? That is Minnesota ave. I use to come into town right there. Shopped at that Ace Hardware alot. Use to be a Kmart just past the McDonald's and a Lewis Drug on the other side of the street.