I have a friends quad that he brought to me with a couple of issues. The carb was full of sediment and needed cleaned and the starter only engaged while flipping the headlights on and off. The start button made no difference. I replaced the rear brake/taillight bulb which had the brake filament burnt out. Now as soon as either brake is applied the starter begins cranking until the brakes are released. I looked all of the wiring over and everything appears to be properly connected and all in good condition. Where do I need to start to solve this problem?
Thanks in advance

 

There is a safety interlock in the quad start wiring that requires that the brakes be applied before the starter motor will engage. This is to keep the quad from starting in gear and lurching into to someone or something unexpectedly. This is the same idea as in your car, where you can't start up the car unless the the transmission is in neutral or park.

So you need three things together to get the starter motor to turn:

1) Ignition switch on
2) Brake switch closed (brake light lit up)
3) Start button pushed.

So it sounds like your start button is shorted on all the time.

Probably your start button is part of a multiswitch aray on the left handle bar which includes headlights and kill switches. Follow the wires from this array to the connector into the main harness (may be under plastic). Disconnect this connector. Turn on the ignition and apply the brake. Does the starter turn or not? If it doesn't then your left handlebar switch is bad or miswired.

I don't yet know why headlights have anything to do with starter motor operation, except that headlights wire into that same left handlebar switch assembly.

When digging into the left handlebar switch look for any signs of wiring tampering (solder joints, electrical tape, etc.)

 

I took the left handle bar switch apart right off the bat. The starter switch is open and all the wiring looks correct in regards to attaching to the headlght, dimmer, kill/run, and start switch. But here is what I did find just a few minutes ago the yellow and red wire on the bottom of the start switch had a large blob of solder on it and it was making contact with the metal base of the switch. Causing it to act if it was stuck on. Thanks for your help it's greatly appreciated

 

I got another question on this bike. After cleaning the carb and reinstalling it I can only get it to run with the choke on. I took the breather off and feel very little vacuum pulling through the carb so I'm thinking the valves are out of adjustment. What are the specs on the valves?

 

Good troubleshooting... You figured it out .

 

I looked at one 110cc light service manual. The clearances were listed as

Intake: 0.05 to 0.09mm (0.002 to 0.004 inches)
Exhaust: 0.11 to 0.15mm (0.004 to 0.006 inches)

Valves are adjusted with the engine cold.

I did the conversion from mm to inches myself using pencil and paper while drinking a beer (since I can't find my calculator). So please double check my math.

But I don't think your problem sounds like valve adjustment at all. The symptoms of tight valves are hard starting (or no starting) when cold, but once the quad fires up it starts running fine within 10 or 20 seconds. And if you were to shut the quad off and restart it would start back up fine.

Valves get tighter when the engine is cold, and they get tighter with normal wear. This is why valves need to be periodically adjusted. Marginally tight valves exhibit problems when trying to start up cold, but once it fires and the valves warm up (very quickly) the problem goes away until the engine cools again. If you ignore the periodic valve maintenance, then hard starting when cold gets progressively worse over time, eventually leading to no starting.

Loose valves make noise. Clackety Clackety. No mistaking that.

But that isn't anything like you described. You need the choke on to run, and that indicates that the mixture is way too lean. Do you have an air leak? Spray carburetor cleaner around the outside of your carb and intake manifold while the engine is running. Any change in speed or sound indicates an air leak.

Else its back to cleaning the carburetor. Did you *completely* disassemble it? Every jet removed? Do you look to see if light gets through every orifice in the jets?

 

mine did the same thing. Clean the jets again. I had to clean mine four times before I got it right.

use compressed air to blow out the jets dont try to do it with a foriegn object.

 

Both times I took the carb completely apart. I used compressed air to blow through every passage and checked all of them with a good led light. I checked compression it has 115psi. I checked the valves intake was at .004 exhaust was at .001 so I set it. It actually started to idle for a few seconds so I took the sparkplug out to see if it was fouled and noticed the ceramic was damaged around the center electrode so I'm heading to the parts store. What is the plug gap supposed to be set at?

 

I think I'm figuring this one out. Put the new plug in and still wouldn't run without the choke on. Anytime it will run only on the choke tells me there's not enough fuel going through the carb to keep a good mix (exactly like Lynn said) so I was going to take it apart one more time. Instead I read the sticky on the carb and realized I could adjust the needle height with the e clip. I took the slide out removed the needle and the clip was at the top setting. I tried out the next four lower settings and at the fourth one it now starts runs and idles!!! Now I gotta get the back brake bleed and it's heading out the door. Thanks for a great site and all of your help!!!

 

Did a search on bleeding the brakes used the technique that BigAir49 suggested and now I have back brakes. I took it for a test drive and it makes a horrible noise when you drop it in reverse so back to the searches!