Lifan 125 in CT90 carb update

Discussion in 'Lifan' started by Goob, Feb 6, 2021.

  1. Goob

    Goob Member

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    Howdy all,

    OK.. Just realized this is sort of a repeat of a couple of my previous posts, but here is some additional background/update. And, I don't see an option to delete a post...so here it is.

    Based on what I read on this site I started out my CT90 to Lifan 125 build using a VM20-273 carb. I was previously settled on a VM22-133, but it was noted that may be too big for the Lifan 125 (and it has been unavailable for a while due to production issues).

    So, I used a CT110 intake and exhaust from DRATV. Everything fit well and I was able to get the carb tuned for smooth running from idle to full throttle. Problem for me was performance was more on par with a stock 90, rather than what I expected from a 35cc increase in displacement.

    It topped out at about 45 (with a 17/45 sprocket combo) and I wanted more like 55. This is a street only bike with Michelin Pilot tires, and I want to be able to keep up with traffic on 45 posted roads; where most cars go 50 to 55.

    My thought was that the engine, which has 26mm intake and exhaust ports, was limited by the 22mm CT110 intake and 19mm exhaust. So, after a few e-mails with VInce/Tbolt for advice, I took a VM26-606 off my trail bike and installed it, along with the "Quiet" pitbike exhaust from Tbolt (26mm ID).

    The carb mounts up to the manifold that came with the Lifan 125 (from Tbolt) with frame clearance (though very close to the vent nipples). At my altitude, 5280 ft, I tuned this in with a 22.5 Pilot and 190 Main with the needle clip in the most lean, topmost, position. I am using an UNI filter (though started out with a K&N type...it fell off on a ride and was lost). The muffler is shorter than a stock, but still bolts up to the stock shock mount location.

    Runs fantastic. I can get a bit over 55 easily. Most of my riding is in the 25-35 range, and it does great there; with instant acceleration when I want it.

    Will likely go to a 185 Main to get the needle clip in a more central position, but for now I am good. Just going to enjoy for a while.

    Goob

    Carb 1-6-2021.jpg 2-6-2021 left-2.jpg 2-6-2021 right.jpg
     
    #1 Goob, Feb 6, 2021
    Last edited: Feb 6, 2021
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  3. Old Guy Too Many Bikes

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    I enjoy your CT Journey and like your method for sorting out issues and think your bike looks great and probably runs as good as it looks. I have a CT70 with a 110 in it and was getting a flat spot in the midrange. It idled fine, and had no issues at WOT. I tried raising the needle by lowering the clip and it got worse. So I tried lowering the needle by raising the clip and it got better. Finally with the needle in its lowest setting it ran the best, nearly perfect. For me, this seems like the opposite of what I would have expected. By the way, it tops out at about 52 mph. It's just a bit faster than my neighbor on his CT110. But since he outweighs be by about 40 lbs, his bike may actually be faster. I'm gonna buy a Lifan 150 with my tax refund in the hope I can keep up with my son on his new Monkey.
     
  4. Goob

    Goob Member

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    Thanks for your reply. I had a strange thing with tuning the VM26-606. I too had a flat spot...just sort of bogged down at mid-range. Though it shouldn't have made a difference off idle, I found that backing the Pilot Jet screw out...way out to almost where it was going to fall out...made things better. I needed less fuel. So, I changed the Pilot jet to one size smaller (from a 25.5 to a 22.5) and it fixed the problem. Pilot jet screw is now right at 2.5 turns out. This goes against all logic on how carbs work, but it is what it is. It had started and idled fine, and revved fine in neutral up on the center stand, with the larger pilot jet

    Make sure you do an oil cooler with that 150 and even a 140 (didn't know Lifan had a 150). I have an Orion RXB150XL trail bike, which really hauls. You will be happy with all that HP (mine has 14 and the bike only weighs 160). If you are willing to settle for a 140, or look at other brands, such as Piranha, check out Tbolt. They are really great guys (father and son team, both named Vince). I bought my engine and a ton of other stuff from them and they helped me out with all of my novice questions thru MANY e-mails. They always ship really fast too.

    The VM26-606 I used for the CT came off of the RXB150...where I had it tuned with larger Main and Pilot. I like this carb a lot, and will get a replacement for the RXB before summer riding season. It has an advantage over the NIBBI PE26 or PE28 (Keihin PE clone) in that both the idle screw and pilot screw are on the left side of the carb and easily accessible. On the NIBBI they are on the right side, so you have to try to reach thru from the right side to adjust. I love the NIBBI, but it is best on bikes that have the carb go off to the right (like my CSC TT250, that has a Honda CG250 clone engine, I have the NIBBI PE28 on it).

    My next project, when I find a cheap enough bike, is to do a Passport (or C70) with just a 90 in it. OR, do it in Electric as someone on one of the CT90/110 FB pages has done. He is doing videos of the process and list of parts to buy. He has done two of his own so far.
     
    #3 Goob, Feb 9, 2021
    Last edited: Feb 9, 2021
  5. Old Guy Too Many Bikes

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    I converted a power wheels car into a hotrod for my grandson using a mobility scooter 24 volt motor and an ebay speed controller. It's dangerously fast and I use a remote kill switch to keep him out of trouble. It would work on a small bike as well. But getting back to small Hondas, I have a CL90 with a Lifan 140 in it. It's not much faster than my CT70, but accelerates a lot harder. It's a dead heat against my boy's Monkey till about 50 mph, then he pulls me slightly. My CL is cold blooded and needs choke for the first couple of minutes, while the CT70 needs no choke, which maybe explains why lowering the needle helped in the midrange. If the 150 cc motor pulls stonger than the 140, I'll be very happy. I rarely ride faster than 40-45 mph. When the CT70 was stock, it would top out at 42 mph, but took forever to get there. The big engine should have no trouble keeping up with 4 wheel traffic when the light turns green.
     

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  6. Goob

    Goob Member

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    I'll look into that motor & conrtroller! For my 125 the change from the restricted stock type smaller (20mm) carb & intake and stock exhaust to port matching 26mm carb/intake/exhaust made a huge difference in acceleration and top speed. With a 140 or 150 I would say this is absolutely required. The Mikuni VM26-606 is the way to go in my opinion. Easy to tune, idle and pilot jet screws on left side. Sweet carb that will last a lifetime.
     
  7. OLD CT

    OLD CT Well-Known Member

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    Old guy, There is something wrong if you cant get at least mid 60's mph out of a 140cc. Sure you could buy another Chinese engine but here is the big problem, if you do not know how to tune a carburetor and fine tune the jetting/gearing you will be where you are at now.
    No china engine comes with matched or the proper jet sizes. Just because the engine comes with a carburetor with certain jets. They are far from the ''PROPER'' ideal jet sizes. There is your cold blooded problem. A air leak from the intake can also give you cold blooded issues. Most, if not ALL China engines 125cc and up supplied carbs are WAY too lean. Unless you buy a 70cc China engine kit. LOL!
     
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  8. Goob

    Goob Member

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    I agree. My dirt bike with a YX150 absolutely screams! With the "stock" cheap Chinese made "Mikuni" VM26 flange mount it is said to have 13.75 HP. I am betting the real Mikuni VM26-606 has bumped that by at least 1 HP. It didn't take that long to tune in...actually easier than the cheapo. Some folks take jetting suggestions as if there is one combination for a given engine, and don't consider that their altitude is a major factor. My tuning at a Mile High would be awful at sea level.
     
  9. Old Guy Too Many Bikes

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    I'm considering trying the Mikuni, but I still don't expect to hit 60 mph. Mainly because I purposely gear the bike too tall. As it is, it's almost as fast in 3rd as it is in 4th. I can do just about 50 in 3rd. But the bike cruises nicely in 4th at 40-45 mph without a lot of noise or vibration.
     
  10. Goob

    Goob Member

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    Mine also cruises nicely in 4th at 40-45, but I have more throttle to get to "almost" 60...from what I could tell using the sometimes working but failing stock speedo. I think the "square hole" where the cable goes in is rounded out.

    I just installed a GPS speedo and will know the real top speed as soon as the temps get higher later this week (right now -10, will be 45-50 later).

    My most normal speeds for my commute are 25-45. These are where I hope to get max MPG. But, some roads are posted 45-50 and cars go 55-60 on these regularly. I wanted to have the "room" to accelerate, even up hill, to keep up with traffic. The VM26-606 with the Tbolt 26mm exhaust lets me do this.

    Since this is a street only bike, I also swapped out the front sprocket to a 17, keeping the stock rear 45. 17 is the largest that will fit without interference. This, according to Gearing Commander, gives me the same ratio as using the stock 15 with a rear 40 (which I can't find unless I use a CT200 sprocket with the large 2nd sprocket removed).

    Check out Gearing Commander. I used the CT110 as the bike and the primary drive ration for the Lifan 125 that I found on-line of 3.35. The CT70 is a selection, but not a CT90. You can compare 15/45 stock with 17/45 or 15/40. Gearing Commander - Motorcycle Speed and Drive Train Calculator v7

    Tire size (rear circumference) is considered in the Gearing Commander, but I used this tire size guide to determine I wanted to use 80/90-17 tires (Michelin Pilot, street). It came the closest to the "stock" 76/100-17 (3" = about 76 mm) as far as circumference. 76/100-R17 vs 80/90-R17 Tire Comparison - Tire Size Calculator (tacomaworld.com)
     
  11. Old Guy Too Many Bikes

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    I'll have to check, but I run a 16 tooth in front and I think a custom 35 tooth in the rear. I run 2.75-18 tires. i used to run a 17 tooth front, which actually made the bike faster by leaving it in 3rd, but where I live there's lots of hills and I was downshifting too often. My CT70 used to be nearly as fast, but pretty scary at over 45 mph. So I moved up to 120/90-10's and dropped a couple of teeth on the countershaft to compensate, but it still cost me a few mph due to rolling resistance. However, it's so much more stable at speed.
     
  12. Goob

    Goob Member

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    Sounds like you have your gearing figured out. It is interesting the 18's fit..front & back? No clearance issues? I bumped from a 14 to 16 rear on my pit/trail bike...but massive amount of clearance. Others, for the same bike tried 19 front and it hit the skidplate. Fun stuff, huh?
     
  13. Old Guy Too Many Bikes

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    I always thought it would be neat to take a busted up CT70 and Chinese pitbike and put all its the good stuff, wheels, suspension, swingarm, motor, etc. on the CT. Anyway, my bike's a CL90 which comes with 18 inch wheels from the factory. My CT90 came with 17's. my ST90 came with 14's. My CT70 came with 10's of course, but with the 120/90-10 tires, the overall diameter is close to bikes like a Monkey which comes with 12's. When I get my 150cc motor, I'm gonna gear it for top speed in 3rd, and use 4th like an overdrive for cruising.
     
  14. Goob

    Goob Member

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    I almost used a pitbike for my conversion. I have an Orion RXB150XL that is practically new. Decided I wanted to keep it, as-is, for strictly trail riding. I did used the Mikuni VM26-606 off of it for my CT90/Lifan 125. Now have to decide if I will just put the cheap Chinese carb back on it or get a new -606. Orion RXB 150XL Street Legal MANUAL Pit Bike - On road dirt bike (orionpowersports.com)

    Orion is a pretty good company, as the Chinese bike retailers go. They actually seem to try to have good customer service and parts available. They sell the engine for my bike separatey, minus the oil cooler you must have. It is a nice YX150 engine with an oil viewing port (nice feature), and electric start (a must have with these high compression engines...very hard to kick start). Orion RXB 150XL Electric Start Dirt Bike Motor/Engine, YX150 engine (orionpowersports.com)

    Of course, the engine seller I REALLY like and trust is TboltUSA. The only 150's they carry are more expensive, but they have a Piranha 140 with electric start, includes engine, wiring harness, CDI, rectifier/regulator, coil, carb, etc. Most everything you need to install (minus exhaust) for $512 + $50 shipping. Piranha 140cc Bottom Electric Start Semi-Auto E-Start Engine - WHS-3284 - Piranha Engines - Engines - TBolt USA, LLC

    Here are Tbolts Pilster Pro's, more expensive 140-155. Only the 140 semi-auto has electric start, comes with fewer components than the Piraha Pitster Pro 140cc SEMI AUTO BLACK Engine fits Pit Bikes and other Minis - PP-11309 - Pitster Pro Engines - Engines - TBolt USA, LLC...you can prove you are a real man! Others are: Pitster Pro 140cc YX BLACK Engine fits Pit Bikes and other Minis - PP-10893 - Pitster Pro Engines - Engines - TBolt USA, LLC andb Pitster Pro 155 Z H-O BLACK Engine fits Pit Bikes and other Minis - PP-0522 - Pitster Pro Engines - Engines - TBolt USA, LLC (no lighting output from engine).
     
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  15. Old Guy Too Many Bikes

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    Thanks for all the great info. Found a guy on ebay that is selling the YX140 with all the goodies including 26 mm carb and oil cooler with lines for $539 plus shipping. So happens that he is only an hour from my house. We got to talking and he agreed to sell me one for $500 out the door. I went to his house (he's into Gorillas) and offered him $900 for two and he said ok. So I'm going to put one in my CT70 and the other in my CL90. I'll sell my existing running engines on offer up or something and get maybe half my money back.
     
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  16. Goob

    Goob Member

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    Do they have electric start? If not, hope you are skilled at kick with a strong leg!
     
  17. Old Guy Too Many Bikes

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    No, they're kickstart only. But I currently have a Lifan 140 (albiet a tired one) and never had any trouble kicking it. Can't be any worse than my Honda 650 XLR or my old 62 Harley XLCH Sportster.
     
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  18. Old Guy Too Many Bikes

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    Anyway, got the motor in today and running. It definitely takes more effort to kick start than my Lifan 140 (which is tired) . I ran it a half hour with high zinc oil, and then changed it. I plan on riding it easy for the next hundred miles, then do another oil change and valve adjustment. The motor seems to have tons of torque with my 17/31 gearing. I'm going to order an 18 tooth countershaft, and was even wondering if a 19 tooth would fit.
     
  19. Goob

    Goob Member

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    I was told by TBOLTUSA that 17 was the largest front sprocket for my Lifan 125 without cutting into the cover for clearance. So I got a 17/428 and it is pretty close.

    Not sure if this is the same for the 140, but I bet it is. You could shoot them and e-mail, I don't think they would have any issue with answering even though you didn't buy from them. They are good guys.

    You may need to swap out the rear if you can find smaller than 31.
     
  20. Old Guy Too Many Bikes

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    Thanks for the info. Even with the 17t in there right now, it looks like there's room to easily accomodate an 18, so I ordered one just in case. In fact you can even order a 19, but I don't know if it will fit. On the CT70, it looks like 31 is the smallest that will fit in the rear due to the hub size. I read about people who have gone 70+ mph on CT70's, so I imagine the primary reduction ratio I found is not correct. I ran a 15/31 with the 110 motor I pulled out and that setup maxxed out at 50+ mph, but couldn't pull redline in 4th, but could in 3rd. I've read that the YX140 makes max power at 7500 rpm and max torque at 7000. Maybe the smaller engine has a higher redline. All I know for sure is that the bigger motor has a lot more grunt and pulls at 25 mph in top gear without lugging. Can't wait to get this thing broken in.
     
  21. Goob

    Goob Member

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    Please let me know if the 18 fits. For me, 55 is about as fast as I want to go..maybe short downhill 60 if that happens...and I have Michelin Street Pilot tires, which smooths things out considerably over dual-sport tires. I start getting nervous on my 250 at 67..it just becomes too twitchy and that is with Conti GO! street tires. It's not the speed...it's the bike...I have cruised at 80 all day on a Goldwing I borrowed from a friend.
     

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