It will only start by pulling behind a vehicle when its cold. Wat could be the problem I'm thinkn it needs a valve adjustment

What year is the vehicle? Most modern cars often don't need the valve clearances adjusted. They are fitted with Hydraulic 'Tappets' that automatically adjust to suit the valve clearances as the engine warms up. You can usually tell by looking at the valve rockers. Hydraulic set ups don't have adjustment screws fitted to the ends of the rocker.

Could be failing ignition module or needs valve lash adjustment... periodic requirement for BS OHV engines.

Throttle valve cable adjustment:Place throttle body in idle position. Press cable lock button to release cable. Pull cable conduit toward rear of vehicle until wiper is completely retracted into end of conduit fitting. Release cable lock button. Raise vehicle for access to trans throttle valve lever. Rotate throttle valve lever toward front of vehicle until ratcheting sound (from cable) stops. CAUTION " Do not rotate throttle valve beyond the idle stop. The lever, valve and manual lever shaft will be damaged if rotated too far." Check cable adjustment. Throttle valve lever should begin to move at same time lever on MPI throttle body moves off idle position. Lower vehicle. 1991/1992 Rear Wheel Drive Truck There is also an adjustment procedure for front and rear band adjustments at engine if you need them.

cold start make sure choke valve closes all the way then start, close plate by adjusting it until it just starts running rough then adjust it open until it smooths out.

What year? If it is an older vehicle, remove and clean the IAC valve without turning the pintle...remove as much carbon as possible....use MAF cleaner only...replace IAC valve. If the engine is shaking, it can be bad coil packs or plugs?? Test these properly... cheers

May b u have put valve wrong way round.....the other possibalty needs adjusting

really need a little more info. but at first thought sounds like either a cold start sensor if equipped. or a coolant temperature sensor. the cold start sensor squirts fuel directly into the intake upon startup wen the vehicle is cold. the coolant temperature sensor adjust fuel air mixtures based on the temp. of the vehicle. when they go bad they go to default which is usually about 175 degrees. so when the car is cold and the faulty sensor tell the computer that the car is 175 degrees when its not then the computer delivers the wrong fuel air mixture, the mixture as needed when its warm when the car is actually cold and needs a different mixture in order to start more easily.

Engine is difficult to start when cold

1. Check the battery condition, battery state of charge and starter motor current draw. Replace the battery if marginal and the starter motor if the current draw is beyond specification.
2. Check the battery cable condition. Clean the battery terminals and replace corroded or damaged cables.
3. Check the fuel system for proper operation. A fuel pump with insufficient fuel pressure or clogged injectors should be replaced.
4. Check the engine's tune-up status. Note the tune-up specifications and check for items such as severely worn spark plugs; adjust or replace as needed. On vehicles with manually adjusted valve clearances, check for tight valves and adjust to specification.
5. Check for a failed coolant temperature sensor, and replace if out of specification.
6. heck the operation of the engine management systems for fuel and ignition; repair or replace failed components as necessary.

Engine is difficult to start when hot

1. Check the air filter and air intake system. Replace the air filter if it is dirty or contaminated. Check the fresh air intake system for restrictions or blockage.
2. Check for loose or deteriorated engine grounds and clean, tighten or replace as needed.
3. Check for needed maintenance. Inspect tune-up and service related items such as spark plugs and engine oil condition, and check the operation of the engine fuel and ignition management system.

check the mas air flow sensor(is this the 6 cyl) the sensor has a problem with the nose piece inside not moving enough to tell the ecm the propper air flow for the cold start,also check throttle valve for dirt build up around it-if its a four cyl repost

doulbe check the grounds, & you might need to add and extra ground wire to the bike, closer to the starter. This should help. There is a valve that release the compression when you kick it off.You might see if you can pull this release the compression valve while pushing the start button????