Lifan 125 into Chappy LB80

[davedynamite]

Bought the Lifan 125 and dropped it in my Chappy frame... Not as simple as I thought but with some welding and fabricating a mount on top she is where she needs to be now.
My problem is I just can't get her tuned properly. Bought a Mikuni as I thought maybe the stock carb from Lifan was crap but it didn't change. I am pretty sure my issue lies with the fuel pet****... I drill a hole in the carb manifold and attached the fuel line from the pet**** just as it was on the 80cc...but the carb sits much higher with the lifan than it did with the 80...almost even...
So my thoughts are now either lowering the pet**** a few inches... But I also just ordered a 125 fuel vacuum pump online... The ones that look like a hockey puck.
Oh... My symptoms were mega backfiring and sputtering and also slow throttle response... Lots of popping and backfiring mostly... I also replaced the exhaust gasket in case that was my back firing issue.
Any help would be appreciated... She is so ready to tour and I want to ride!!!

 

[davedynamite]

She's done

 

[my67xr]

that Chappy looks mint !!!
guess it is a mint colour too, lol

yeah the Chappy's run a vacuum operated fuel tap as you've found out.
you could get one of these and replace it-
6mm Inline Fuel Tank TAP Filter Pet**** Switch PIT PRO Quad Dirt Bike ATV Buggy | eBay


So is the Lifan 125 brand new ?
What CDI and electrics are you using ?

have you checked the valve adjustment ?
and have you adjusted the mixture screw on the carby, it's underneath at the front ?

cheers, Craig

 

[davedynamite]

Yeah it is new. I also did check the valves which were in the. 003 to. 005 range like I have read they should be. This is the second new carb with the same issue but I haven't adjusted the Mikuni mixture screw... But both carbs had same issue still. I have to remove the Mikuni to get at that screw which really sux... Do you think that would cause backfiring and sputtering though?
Cat came with the Lifan... Bought a 12 volt regulator, blinker relay and horn and all the bulbs... Also having trouble there as all lights worked at first and now none of them do except the headlight but it is about 10% of what it should be. The brake/taillight blew... Not sure why
Oh and not mint... Limesicle... Lol

 

[davedynamite]

Craig... Thanks for the reply... I ordered one of these.... http://m.ebay.com.au/itm/271553507013?txnId=1355099565017
It has the vacuum port... Should I get the one you said instead?

 

[davedynamite]

I got that one because my tank is at the same level as the carb.... Am I wrong?

 

[davedynamite]

Also Craig... I see you have some Chappy experience... I can't get the spring back on my kickstand for the life of me... Any suggestions?

 

[my67xr]

For the stand spring, use a long screwdriver though the hook end and lever it onto the post
watch your fingers too, they are a strong spring

that fuel pump should work ok, you'll need to run it between the tap outlet and the carby somewhere in the fuel line.
and the original vacuum hose will still need to go to the fuel tap as well


the fuel tap, have you had it apart ?
the 4 hole seal may have perished ?
or the fuel filter screen could be blocked up too ?
it just unscrews off the bottom of the tap, and has a 10mm head from memory.


My Chappy fuel tap had a perished vacuum diaphram in the back of it and it wouldn't let fuel through
so i replaced it with a good one off my spare Chappy, that fixed the problem.

1976 LB802AC Yamaha Motorcycle FUEL TANK Diagram and Parts

if you still cant get it working you could tee the 2x fuel lines from the bottom of the tank into 1 hose, then just use the tap that i linked above.
you wont need to vacuum line running from the manifold to the tap then either


with the spluttering, have you got filter oil on the air filter ?
i've found with the china copy Mikuni's that the Pilot jet is too small, (#15)
they hesistate off idle, and when you blip rev it.
if you have that problem try a #20 Pilot jet, it should fix it

also your carby looks like the fuel bowl could be fouling on the intake manifold, it may be causing a vacuum leak at the plastic insulator ?
start it up and spray some wd40 or even water on the join, if the idle speed changes in any way then there is your leak.

and the backfiring, does it pop on decell ?
check that your exhaust flange is tightened up on the bottom of the head.
some of the cheap fibre gaskets leak too, i use the copper ones as they last a lot longer
like these- 32mm Copper Exhaust Pipe Gasket 110cc 125cc PIT PRO Quad Dirt Bike ATV Buggy | eBay

with the lights problem, the Chappy are 6 volt, and the Lifan 125's are 12v.
you might have burnt out all your globes ?
check your headlight ground too, it's behind the headlamp in the casing.
have you run an earth from the frame/headlight down to the engine ?
you should be able to run your original horn too if you need to.
but you might need to retune it too, to suit the higher voltage, there is a small phillips head screw on the back to adjust it.
it won't need to be turned much to get it working sweet.
don't screw it in or out too far though, it can cause the horn to short out


how many volts are you getting out of the regulator/rectifier to the battery at idle, and at a few revs ?

 

[davedynamite]

The spring is way too strong to use a screwdriver to get on.
I put a new fuel tap on.
Why won't I need the vacuum line if I run both lines from the tank to the tap you suggested? My tank is almost the same height with the carb. How will the gas travel? This is where my problem lies.
The hesitation is more than a jet change.
The carb bowl is not fouling on the intake manifold.
I put in a brand new copper gasket as mentioned.
As mentioned, I changed horn, bulbs and put a 12v regulator on and tested outputs.
Yes I have a ground to engine from frame.

 

[my67xr]

the bottom of you tank in the pic looks to be higher than the entry port on the carby,
but on a steep hill it could cause problems i guess.

yeah go with the pump you have ordered.
but you will need to have the vacuum hose going to the original tap as well as another vacuum hose going to the fuel pump.

The original Chappy fuel tap will only open the on/off valve when the engine is creating a vacuum, eg being kicked over or running

the fuel tap i linked above doesn't have a vacuum operated on/off valve



so is the popping spluttering when you open the throttle ?

can you confirm that the float level is set correctly.


The problem with the stand spring, is it the side kick stand or the centre kick stand ?

being a Mikuni copy, you can check the fuel level in the bowl by lifting the drain hose upwards, have the end of it above the top of the carby and open the drain screw on the bottom of the fuel bowl.
fuel will flow out the drain hose and it will sit level in the hose approx 25mm down from the top of the fuel bowl

if fuel is sitting there in the hose approx 25mm below the top of the bowl, this means that the tap is letting fuel though.

 

[davedynamite]

As mentioned I gave tried 2 carbs. The one in the pic is lifan stock that cane with. I bought a Mikuni and have the same problems, this is why I was thinking fuel tap. The tank is above the carb but barely and the lines run below the carb then back up..
I was thinking maybe just skip the old fuel tap when I get the pump? 9
Center kick stand

 

[my67xr]

are you trying to do the kick stand spring with the stand up ? it is easier

the only problem with not having a tap in the fuel line is when you want to pull the carby off etc
then you could add an inline tap too, like the remote one i linked.
there are a lot of better ones too, like these-
1 4" 6mm Universal Inline Pet**** Fuel Valve FOR Pitbike Motorcycle ATV Moped | eBay
Fuel TAP Inline FOR Ride ON Mower Made IN USA Stationary Motor Lawnmower | eBay
6 MM Inline Fuel Petrol TAP Motorcycle | eBay
6mm GAS Petrol Fuel TAP 1 4" Inline Pet**** Valve FOR Vintage Honda Motorcycle | eBay
12 7130 SPI 1 4 " Inline Fuel Valve Petcock | eBay

or use one with an angled end-
http://www.ebay.com.au/itm/INLINE-F...t=AU_LawnmowerAccessories&hash=item27d4bc49cc

lawn mower shops would have them as well.

you could even hide the tap somewhere like under the battery tray etc, turn it off as an anti theft thing....