Gear box reassembly and motor identity?

[snizzers]

Hi there my son and I have got a pit bike project on the go and we have a couple of questions. We got it cheap as the starter and/or 1st gear was stripped.

First of all we find it bloody hard to identify the thing. It has a Gongyu head/barrel with 120 cc on the side of the barrel We cant find anything on t'internet about this. The bottom end seems different altogether. The clutch housing had JL-4 on the inside (?? Jailing??), the crankcases have 156FMI and then *04102794*. Can anyone help us identify what this is and then that would help us find a good manual??

On stripping we found the culprit. 1st gear (integral to the clutch /main shaft) had been relived of all its teeth in the previous punch up... we managed to locate a replacment box with almost idetical shaft dimetion/gear teeth no, diameter etc and will be assembling it shortly. As with any job that drags on I think weve got the gears/shims mixed up and are looking for a nice diagram to tell us where they go; partculary the shims and washers.

Cheers for the help guys and also an excellent website

Neil n Eddie

 

[dirtbkr188]

Here's a generic Chinese 4-speed trans diagram, to get you started...

 

[my67xr]

+ rep points dirtbikr188, good effort !

i was going to suggest he does a search for any of sean01s posts, there is a library of links like that in his signature.

 

[my67xr]

snizzers, your engine 156FMI isnt an upright 125 is it, the 5 speed one?

 

[snizzers]

Hi, there thanks for the replies. The engine style is horizontal and has 4 gears only. It has the starter that engages inside the gearbox and not on the clutch. The main area I think we might be mixed up with is the shims/spacers at the ends of the gearbox shafts. IE the ones that are between the bearings and the last cogs on each end of the shafts. That diagram above doesnt really show this.

 

[dirtbkr188]

That diagram above is of a mainshaft-mounted clutch assembly, do you need a basic diagram of a trans from a crank-mounted clutch engine, like an OEM Honda?

 

[snizzers]

Hi again. We got the engine altogther OK and its back in the frame and we have been trying to get it started. We have no spark at the plug. I tested the coil in the way i thought sensible; primary resistance is 0.2 Ohm ie short cuircut; i would have expected a few Ohms?? The resistance on the secondary was Meg-Ohm; i would expect 20 kOhm?? If anyone has a comment on what you'd expect that would be great. I also lashed up a 12 V supply so I could energise the secondary momentarily (like a switched pulse of 12 V) and still no spark; even on the bared wire of the HT lead. Looks like the coil to me.
Cheers Neil

 

[rotn50]

start at the magneto and pickup side, unhook all the magneto wires and while someone is kicking the bike over(with plug removed) hold the black and red wire against the magneto as its being kicked, you should see a good blue spark everytime, or as its being kicked stroke the red and black wire on the engine(earth) and you should see the same thing, if its sparking good then use your multimeter(turn it on the resistence setting i think, the one that beeps when the two leads touch each other) and put one one the blue and white wire and earth the other out, turn the magneto by hand causing the raised part on the magneto to pass the pickup(do this back and forth) and you should hear it beep, this will tell you that your pickup is working, easy way to check the coil is to hook it up to a mates bike and see if it fires or a quad(if you have access to one), even having a spare cdi, coil, and plug to change and diagnose helps, also disable the killswitch in case it is faulty.

 

[rotn50]

First of all we find it bloody hard to identify the thing. It has a Gongyu head/barrel with 120 cc on the side of the barrel We cant find anything on t'internet about this. The bottom end seems different altogether. The clutch housing had JL-4 on the inside (?? Jailing??), the crankcases have 156FMI and then *04102794*.

Mate there are copies of copied engines out there also, usually a engine code in your case if it was a genuine engine would read 1p56FMI(yx140) but reading 156FMI usually means it is a copy engine from my experience, If im right the code should read 1=single cylinder(?) p56= 56mm piston and the FMI determines the engines make up as in auto or manual electric start or kickstart as such, being a 120cc(125cc) it def does not take a 56mm piston and should take a 54mm piston if it has the 120cc badge, i reckon your engine is a copied copy which isnt that bad but lacks a few small things that the others have(my opinion only)like some certain strengthening fins in the cases and distinctive case markings that all the lifans, loncins, zongshens and yx's have, the engine can still be strong and hardy but like the case numbers above the engine number reads i think good ole china has whacked a heap of these donks together with bits and pieces left unused, all the time at work we see brand new ebay quads and bikes with so called genuine lifans and other brands when its quite obvious from even looking at it we know that they are a copy of a copy, sorry to waffle on, hope this makes sense.