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Thread: Most effective mods - Lifan 140
30-01-2008, 09:42 AM #1
Most effective mods - Lifan 140
Okay an old topic, but I'm looking for a summary.
I am keen to learn more ... What I want is a moderate power (acceleration) increase (like 10 to 15%) over a reasonably broad RPM range, from my new Lifan 140 with the engine still being able to last for 50 to 70 hrs of riding (mostly full throttle or full brakes) using 98 fuel, clean unifilters, fresh good oil every 4 to 6 hrs, and my magnetic oil drain plug. I don't mind spending on good results. After 70 hrs of serious fun, I'd happily get a new engine.
With no case split (limit on time investment in the mods), key variables appear to be:
* Good jetting, air filter and decent carb.
* Hour meter for maintenance timing.
* lightened flywheel (IRK) and/or slinger. Balancing issues??
* Coil and CDI. Quality.
* Polish ports and intake.
* plug type? Better than the NGK-CR7HSA.
* Camshaft+springs (I need to ride my bike more before picking a cam). Akunar?
* Compression ratio increase (Akunar domed piston).
So what's the priority ordering of these mods plus anything I've missed?
Re cam and compression/piston: I am not sure of the type of cam I'll need (lift, duration and curve). Ideally I'd have a "top end" cam so the mid pulls thru into a good top end, but that means using sustained RPM a lot (it'll never be too powerful but shorter engine life). I could instead go for a bottom end cam, since the mid RPMs already pull good, and the bottom feels weak and boost the compression ratio with a new piston.
Re IRK. I'd like to conservatively play with ignition timing. I believe I can hear pinging and reasonably early. I always use 98 fuel. But the crank vibration and fatigue issue due to the crank ends weight loss does concern me. I believe I want less spinning engine mass since I am after bike acceleration and not just fixed RPM HP.
Last edited by numroe; 30-01-2008 at 01:33 PM. Reason: mag oil plugMSO SR
30-01-2008, 02:12 PM #2
I got an email from Runuka at Akunar.com. Very helpful guy! Based on his input I am currently thinking of going for:
Either the A1 or A2 bottom/mid 6.7mm lift cam. Plus springs.
Better coil and plug.
Probably keep both crank weights installed.
The 8.5mm dome hi-comp piston (with thinner alum gaskets to match deck height).
Polish my ports and intake.
My goal would be to have a motor which is very snappy/torquey anywhere in the bottom to mid revs. Of course not a high revving high peak HP engine, but a good torque spread of usable power. Avoiding the issues with high RPMs. I just need to ride my bike more and be sure on jetting before picking a cam curve.MSO SR
30-01-2008, 02:34 PM #3
I'd start by getting a decent sized exhaust pipe to allow the 140 to breathe the best that it can ....... THEN a bigger carb (26 mm for the best all around power) .
Read what Mick Mackeral engine Tuna ... ....... says in this thread .... it's brilliant advice .... he knows what he's talking about ....... I've found precisely the same thing from years of experience modifying XR75's . TT500's and XL 350's ... Get that exhaust gas flowing as well as the intake flowing ... and any engine will come to life ..... even with a bone stock cam ......
Also , doing a high velocity port job and 3 angle valve job as described in the porting thread will further help you achieve what you want ... The modifications are designed to increase bottom end power and pull right throughout the rev range ........ If you don't rev your engine higher than stock it will last as long as any stocker since they are set up to live that way ......
I lighten my rocker arms to further reduce the possibility of valve float ...... it's an age old mod that was done to race XR's and has proven to be 100 % effective and reliable .......
As to the IRK and lightened slinger ........ you'd have to ask someone who has been running one on a 140 for an extended period of time to see if they can honestly tell you that they've been super reliable ........ but they ALSO have to tell you of every other mod they've done and how they've used the motor to get a reasonably accurate idea ........
Last edited by Cactus Jack; 30-01-2008 at 02:44 PM.
30-01-2008, 02:47 PM #4
Did you quiz Akunar on his views as far as IRK's are concerned ???? The A-2 .. 6.7 mm lift cam sounds good ..... but they have no anti kick back mech ......
30-01-2008, 03:41 PM #5
Durant has been running this cam it's the goods...in fact all our trickery has come Akuna
They are on the GAS ...ask him about thier 180 scooter lol.
But yeah you are already on the money ...this is close to the build me and Durant did to the MSO Elite they are giving away in the hood .
Cam , dome piston ,cdi,and a bit of porting trickery ....and yeah make sure ya header is big enough to let it breath....
oh yeah the oko 26mm d slide carb with the clear bowl is also worth askin Akuna about.
But yeah tough ,torquey ,RIDEABLE motor ..... you won't be dissapointed and sound like you'll have no trouble makin the mods .... let us know how ya go." I don't mean to sound bitter, cold, or cruel, but I am, so that's how it comes out. " Bill Hicks
Brotherhood 88limo ...
Fast 50's- Seat cover,swinger , rev box, jelly bean rims, fork legs and springs, full bar kit incthrottle and tripple clamp,fuel cap ,foot pegs,Gear leaver, ignition cover,Takegawa 88 kit (full kit) Super Head, TCS back shock,SRH/Brotherhood graphics kit, AHP over the top back break leaver plus more.
Leaked Media .... Brought to you by the man that brought you the 50sbrotherhood.
30-01-2008, 03:48 PM #6
currently I am working on my 140cc. I have ordered a z40 cam, new springs rockers, etc. Using the stock piston I will put the assembled head on and check clearences. Afterwards, if its all good (should be) I will get the head ported out by AHP, I wanted to get it done by mack but shipping is alot of money. I also might get the flywheel lightened a bit, and if I figure out a way to install an akunar piston w/o clearence issues or timming issues, then I will buy a hc piston. These friggin 140's are a pain in the ass to mod. If you use that piston from akunar, ur valves will probably hit, and you cant lower the cylinder to match the deck height on the akunar piston by much. The base gasket is .5mm thick, remove that and use glue, your piston will now be about 1.3mm down in the cylinder, and the head valves might not clear the piston. If you can run the piston lower in the cylinder (what im trying to figure out) then you could install a bigger head gasket, if clearence is an issue, or even use a dremel to the piston dome where the vlaves make contact. There is a lot of **** u needa look into, everyday I am doing reaserch to find out exactly what to do. I think I may just get the head ported, using the normal size valves, and use the stock piston, just to get things done quicker and then wait for the BBK to come out.
30-01-2008, 04:06 PM #7
Thanks Cactus. I read Mack's posting too.
32mm exhaust is std. 41mm muffler exit is std. Same pipe as on the pitster pro 08 I presume. A 26mm OKO carb (flat slide round I believe) on the way.
Been riding with a 24mm Mikuni round as an interim solution. Stock main jet is marked 97.5 (keihin numbers?). Got a 95.5 in there at present. Stock 97.5 probably better. Pilot = 17.5, screw (air?) seems best at 1.75 turns (if I remember right), fiddled with screw in 1/8th increments and sure makes a diff. Needle clip in stock posn = one up (leaner) from middle. Runs terrible with the needle in any other position. Raised float level a tiny bit because is was bogging on heavy flat jump landings which seemed to fix it - impressed myself . Basically all stock in the Mikuni 24mm seems best apart from the float level. First day out I had too much oil on my filter.
Now prefer wait for the OKO26 and fiddle with that with good air (uni)filter. Also put a new rear tyre on today for next weekend. A Pirelli Scorpion MX 12-80/100 which looks like a little meat hook.
Valves adjusted after about 5 minutes of running. Intake manifold hand sanded with 120 to 400 and I verified inlet ends line up. Done about 3 hrs total now. I've also dropped a Fuelstar TM-VC $35 thingy in the 140 fuel tank (does magic on my KX450F) and I'll remove the TM-VC later to see what diff it makes - after it has coated my valve seats with tin.
My Lifan 140 runs pretty good considering this hot+humid weather. I just want it to be a bit more intimidating without killing it too soon. The lightened oil slinger sure helps the top end wind out faster. I'd love to keep that spinning weight off, but if I go for the A1 (bottom end) cam then I am sure I'll need the spinning mass to prevent stalling with the HC piston. I use a 15:39 final gearing, since it easily pulls 2nd gear in the slowest of turns (maybe a click flick at times) and does not run out of legs so early in 4th. 15:41 was a joke in 1st gear - blip and shut the throttle and I almost got whip-lash. If the engine feels great, I might hunt around for a new 1st gear cog, split the case, and make the final gearing taller again.
So my plan in summary: The OKO26 and good air filter is next. Then jetting. Inclined to try get a nice fat low+mid torque curve via the A1 or A2 Akunar 6.7mm lift cam, hi comp piston and probably keep the crank weights installed. If I check valve/rocker and valve/piston clearance then I hope she'll pump out the action for many hours. It's a hobby for me, and I'd like to be able to race it against big bikes at club meetings in winter.
Re IRK and Akunar, he just implied that I run the risk. Just like you said!
Dreadful: Really - the Akunar A2 6.7 lift cam and the 8.5mm dome piston is the norm for you guys? Cool! You tried the A1 cam? As mentioned I need to ride my machine more before I work out where I want to patch up the torque curve the most. With only 3 effectively useful gears and riding on large mini and small MX tracks I need some rev range. You use Akunar's CDI too - what's the diff and price?
btw: Where is Mack's workshop?
Last edited by numroe; 30-01-2008 at 09:28 PM. Reason: new 1st gearMSO SR
31-01-2008, 12:34 AM #8
Re the 8.5mm dome HC piston from Akunar: I am not sure what probs your z40 cam creates, but what I think Akunar told me is that:
a) we can remove the 0.5mm base gasket entirely and use a glue.
b) put in a thinner (0.5mm alum) head gasket ($5) to get more compression back.
I assume it does not matter much (or at all) where the head/cylinder join is relative to the top of the piston. The join is up in the chamber, no more detonation risk surely. According to Akunar's advice, I assume the Akunar 6.7mm lift series of cams wont push the std Lifan valves into the 8.5mm dome HC piston (but I'll have to check that and adjust via gaskets).
Time and patience permitting I think I might do mine in stages. eg.
1) OKO26 + unifilter.
1b) New coil + CDI.
2) Akunar A1 (bottom) or A2 (mid) cam + springs. Port polishing.
3) then lastly an Akunar HC piston.
Before step 3, I suppose I could thin out the head gasket with the stock piston still in there for a mild compression increase and try that. I can also try with and without the flywheel weights - but with the A1 cam plus a higher compression I cannot see myself going without the stock flywheel and slinger weights, since I'd be stall too much I think. I don't mind difficult starting and kick back. I wear real boots and know how to kick it. But stalling aint ever fun.
Last edited by numroe; 31-01-2008 at 12:42 AM.MSO SR
31-01-2008, 03:13 AM #9
I think you are spot on....OKO26+Uni filter..good way to do...
BUT: Donīt buy akunar cams!!!
I like Rakuna ...he`s a hell of a guy and their other stuff is decend ,but the cams suck BIG TIME!! ...its the material and the bearings !!
Get a racecam from AHP!!...some here will say that this ones are from akunar too, but thats not true...I spoke about this with mark(the owner) and he said they got a lot of stuff from Akunar, but no cams, because they had issues!!
31-01-2008, 11:05 AM #10
Dependent on the outcome (torque spread) with the carb, I am very tempted to give an A1 or A2 cam a go in any case. I assume an AHP "race cam" is a top end cam. I want to keep the revs below stock design limits. At AUD55 per cam, and being a quick job to replace, and not over revving valves etc, I'm not panicking.
Appreciate your feedback! Keen to hear more details.MSO SR
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