2nd gear gone??

[Dave.B]

i went riding yesterday and all was well till after about 2 hours of riding we were going up this hill climb and i use 2nd gear for it and midway it just went neutral, but its in second, wont go in at all just like its missing completely, the motor isnt rattly or anything has a slight tingy sound to the engine but thats about it, all other gears work like a charm still, any ideas?

 

[Dave.B]

ill add again thats its a 140 atomik bigfoot
are these lifan engines?

 

[mickcr250]

same thing happened to me i have an atomic as well with a lifan 140 and i lost third i have split the cases and the pins that engage the gear are all snapped off im still trying to get the bloody selector fork off to replace the gear. but yer i would say thats your problem

 

[Dave.B]

so you have to replace the gears?, buying those gears from dhz they come with the pins? is it easy task all in all? ive never stuffed around with gear boxes but will have a crack at it, with cracking the case do you have to replace the gasket or use gasket goo once done?

 

[Dave.B]

does anyone know if the gears from a 50cc ducar would fit the 140 or not, if so would be better to rip apart my bunged out 50 so i could learn before even ripping the 140 apart

 

[Cactus Jack]

The "pins" sticking out of the gears are called dog lugs or driving dogs and they get snapped off from rough un synchronised shifting or shifting up or down without using the clutch ... ANY wide ratio transmission like chinese motors have can be easily damaged no matter who made it or what it's made from ... even kryptonite will fail from abuse ... Shifting down several gears then snapping the clutch out to use heavy engine breaking to slow the bike down will bust dogs off quicksmart ..

People get away with it with 2 strokes because they have short throw close ratio gears and bugger all engine braking or bottom end grunt so the gears and dogs don't cop anywhere NEAR the shock loading or resistance they'd cop in a 4 stroke ... try being abusive with any 4 stroke and you'll cop tranny problems in short order ...

Years ago there were a heap of Jap made bikes with horizontal 2 stroke motors in 'em ... (Kawasaki , Suzuki , Yamaha , Gemini , Hodaka etc) ... They had wide ratio gears and the boxes were absolutely atrocious JUNK ... They'd be lucky to find a gear after a few months and it was a laugh to watch the owners cursing with frustration ... Needless to say they have disappeared from history so not too many people know about them ... They were from the exact same year and era that 4 stroke horizontal engine designs are from (1965 ~1974) ... only the 4 strokes were far , far superior in every way ... The 2 strokes had to be totally scrapped and in later models they went vertical with mainshaft clutches ... then added close ratio trannies and expansion chambers giving the average knucklehead (who compared the MX built two strokes to trail bike 4 strokes) the idea that 2 strokes were somehow superior to 4 strokes ... That has all changed now that they have to be compared with MX built 4 strokes ... I laughed when everyone said 4 strokes can't be jumped and they haven't got the acceleration out of tight turns to be able to clear jumps ... Last week I watched the Aussie supercross and noted that there was not a single 2 stroke racing and also noted how smoothly the 4 strokes handled the tight track with high jumps just out of turns ...

When Yamaha was doing R&D with their first purpose built 4 stroke mx'er , the YZM400 ... They mated one cylinder off a YZF road bike to a YZ250 tranny ... Even though they both produced the exact same HP , the 4 stroke power smashed the two stroke 250's clutch , gears and rear wheel hub and spokes ... They had to beef up the gears by making them wider , strengthen the clutch so that it wouldn't fry and shatter and also had to beef up the rear wheel hub and spokes ... and on top of that ... they also had to beef up the frame as well ... In later production models , to save money , they simply used the same beefed up parts on their YZ250 2 strokes even though they never had the slightest problem with the weaker original parts ...

So when looking at pit bikes and their engines ... keep it in mind that they are a late '60's/early '70's engine design and therefore have their engineering weaknesses and limitations that can ONLY be rectified by going to a horizontal type motor like an XR or the best ... a CRF150R engine (noting the increase in expense) ... and when comparing them to Jap bikes ... compare them to the 2 stroke horizontals from the same era ...

Incidentally ... IF the Atomic 140's have a 1 down 3 up shift pattern ... then there lies the problem ... Lifan only supplies that shift pattern IF someone specifically asks for and insists on it , since it is well known to be problematic ... the engines weren't designed to suit that shift pattern ... It's not actually an engine fault ... but a RIDER fault ... The gap with neutral in between 1st and second allows the rider to shift short of second , miss 2nd , cop neutral , overrev the engine , then quickly have another frantic stab at shifting to second ... Because of the fact that they revved the engine too high , the gear shaft speeds are miles away from being anywhere near close enough so the dogs get smashed into the ends of the slots of the driven gears while they are in a vulnerable position and they can easily get snapped off as a result ... The good Lifans have an ALL 4 up shift pattern and Lifan mainly supplies their cartoned engines in that shift format ... So if you have a 1d 3up engine you can't blame busted gears on Lifan because they wouldn't recommend the 1d 3up pattern for an engine that is going to be shifted quickly or hard like in a dirt bike ... Great for use in a gently treated street ridden step thru or commuter bike where the rider is careful of doing smooth , positive shifting and synchronised clutch coordination ... but NOT good in a dirt bke that cops constant flogging and rough up and down shifting ...

Most pit bike manufacturers simply won't use 1d 3up shifting horizontal engines ... IF anyone doubts what I'm saying simply contact dirtbikesonline (Pit Pro) ... Motovert , DHZ , Pitster or any other decent seller ... IF you have a 1d 3up motor ... learn to treat it with kid gloves or get rid of it and buy a 4 up shifting motor (preferrably a newer model 150) ... and EVEN then ... don't go banging it down to use heavy engine braking or doing clutchless shifts , flat shifts etc ... which will stuff up ANY wide ratio tranny ...

I wouldn't risk using gears out of a 50 cc motor behind a 140 even IF they did fit ... unless I had metallurgical and brinell hardness testing done on 'em ... Do the maths ... they'd be copping nearly 3 times the torque so if they've skimped on the gear strength in any way whatsoever ... the impact caused by gear teeth breaking off and wedging between two gears could cause your cases to split open ...

 

[mickcr250]

my atomic came with all up for the gears but yer it still ripped the crap out of 3rd gear. i still can't get the pin out of the selector fork! its driving me insane i have been trying all morning with a magnet but its stuck on something.

 

[Dave.B]

i have the all up gear pattern aswell, what would you recommend cactus, replace the engine or would a gear swap do the trick?

 

[Cactus Jack]

Just replace the gears with proper 120 to 140 gears ... You can find 'em on ebay every now and then ... DHZ sold some complete gear sets just recently ... OR you could get a new motor then rebuild your old one in your own time to keep as a spare ... even to experiment with mod parts etc ...

 

[Dave.B]

yeh i think i might build it in spare time and just grab a new one for now, thanks champ