150 vs 150 which way to go

[tricky33au]

hi guys and gals im in the market to upgrade my old pro x 125 to a 150, but im unsure which engine to go with, Can any one tell me which of these will be preferable ; the gpx oil cooled 150 from dhz, the lifan oil cooled 150 from kdf sport, or the dirtmax avenger....... my old pro x has a 17" 14" rim combo for a beter ride over the bigger rocks on some of the fire trails i ride thru so it now is a little longer thru the gears and ive found that this seems to be much beter on gearbox wear and has given he a much beter ground clearence to....... any input will be very welcome

 

[lvn]

have u thought about loncin 150's, they make some pretty quick 5 speed water cooled/oil cooled with vertical piston

 

[lvn]

nvm just realised they wouldnt fit your frame

 

[Cactus Jack]

The Lifan 150 has better bottom end torque/lugging power than the YX150's due to it's longer stroked crank ... (59 mm vs 53 mm) ... The YX has more modification parts available but the cost adds up ... IF you buy the YX you'll also need a KLX type exhaust pipe to fit it ...

The Lifan 150 is great out of the box ... some YX150's have reliability issues when modified (BBK ... higher compression piston) unless you buy the very latest model which has the newer/stronger needle bearing crank case , gear shaft and thicker kick starter shaft ... You'd have to ask Ken if they still have the old IRK , OR the newer ORK with non adjustable advance ... The YX ORK's had problems with the timing tabs on the flywheels being out of whack with the keyway and varying the timing from engine to engine ... bad ones kick back from excessive advance and cause problems ... The yanks grind the leading part of the tab off and slot the pickup mount holes in an attempt to back the advance off and fix the f'ck up ... LOL ...

They also had ignition and kick back problems , oil slinger problems and clutch problems ... DHZ sells Lifan 150's as well as GPX150's ...

 

[tricky33au]

thanks cactus it is dhz who im looking at sourcing my bits thru . so it looks like im going the way of lifan..... im also big boring a few 125' a 110 auto if its possible (will all depend on gudgeon pin size there) and doin a couple of 140s to 150's using there upgrade kits.... any thoughts about them

 

[Cactus Jack]

Yeah I've got a 125 and one of their 57 mm ceramic BBK's plus two 140's and two of their 150 BBK's , cams , springs etc but I haven't fitted them or ran them yet ... I bought Lifan 150 ORK's for them all to help avoid kick back and other associated problems ... The 146 kit has a shiny chrome looking bore but the 150 BBK's look like bare alloy stained by acid or something ... plus they have a 13 mm gudgeon pin and a brass bush that goes into the 140's conrod ... I hope they last a fair while ... The main thing to check is the piston weight of the BBK compared to the weight of the stock piston ... if the 57 mm piston assembly is heavier ... either it will need to be lightened OR the crank will need to be rebalanced ...

You can't bore 110's out much ... their stock bore is 52.4 mm and boring to 54 mm leaves the bottom of the cylinder sleeve as thin as paper ... The main problem is that the stud spacings are closer together than it is on BVH motors ... so the stud threads are too close to the edges to bore the cases for a bigger sleeve ... Maybe there's an S-Cut BBK for 'em ... but it'd be better to fit a high compression stock bore piston or 53 mm piston instead and be happy with that ... 110's can gain a lot from a good port job , carb , manifold and pipe ... Read up on a few of Fiddy@Norways older threads ...

 

[tormentandglory]

I was lucky enough to find a 110cc cylinder that would bore out to 56mm, yx140 piston, but they're not common. I don't like to see the spigot wall thickness go under 0.75mm.

 

[Cactus Jack]

The ones I checked were 56 mm O/D at the base of the sleeve ... (Loncin 110 w/iron cylinder) ... Thin cast iron is likely to crack off ... Some 110's have a wider stud spacing and 8 mm studs ... but Loncins have the stock CRF50 Honda spacing and 6 mm studs so I suppose you could bore as big as a CRF50 can go if you use an alloy cylinder with nickel iron sleeve ...