50cc engine wont start?

Delph · L Plate Warrior Joined: 13 Apr 2015 Karma :

I have a Champ Sand Quad with a 50CC (ish) engine I bought second hand for my 5year old son about 2 months ago - the carb is a pacco p60ME from 2002. It was running well, and started without a problem, but now it's not having it. The plug sparks, and I have put a new plug in it but still nothing. It hasn't run out of petrol and the fuel tap is ok and petrol is going down the pipe to the carb. That is the sum knowledge I have - I don't want to spend money on taking it to a garage, so am looking for advice or a kind sole in the Thirsk (North Yorkshire) area who can offer help or even look it over for me.

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

You appear to have narrowed the problem down the carb or its surrounding area. Being a small quad bike I'm assuming it spends most of its time in wet mud.

I would be looking for the following problems:
1. Water in the carb. Turn the fuel off at the tap, drain the carb into a cup. You want to see clean petrol. If you see muddy stuff, you have muddy stuff to clean out. If you see beads of water in the bottom, then water has got in - probably by splashing over the filler cap, or rain.

2. Generally filthy carb. If the qud was standing for a while before you got it, then there is a reasonable chance of it being filthy inside. The main jet is probably clear - this means it will work on full throttle - but smaller jets and the idle circuit will be clogged, so it won't run slow or idle. Clean the carb.

3. Physical problem near the carb. Missing air filter, torn/split inlet rubber (between carb and engine), loose fitting on inlet rubber (jubilee clip not snug).

Of course, all that said, it can still be electrical. If it has a battery, charge it overnight and try to start the quad before pulling anything apart.

Delph · L Plate Warrior Joined: 13 Apr 2015 Karma :

I have managed to remove the carb and taken it apart, the big bottom bit had a seal (leather i think) that was broken and I have relaced it with a home made seal using gaskit paper. The air filter is empty of anything, but should I re-fit the carb using PTFEtape ?