My90Quadzilla
online
Suzuki ATVer
Join: about 24 hours ago
Posts: 1
Oregon
about 23 hours ago · #1
Only starts with throttle wide open.
I have a 1987 Quadzilla LT500. It has a Keihin 39mm carb (stock Pilot Jet) with V-Force 3 Reeds, upgraded to 7-bolt late model head, ported and polished, bored over one time with Wiseco Piston, FMF TurbineCore 1 exhaust, K&N filter. Running 40:1 fuel mix (Castor 927) with 110 racing fuel. I usually go through the regular routine on starting it (new Spark plug) put boots on, Turn on Gas/Choke Off, Kick over slowly 5 times, Throttle closed, Bring Piston up to TDC and go just pass TDC, return Kick starter to the top and kick hard all the way through with 1/4 throttle, Choke on if cold starting. I’ve found that if I hold the throttle wide open it starts better but I Cain’t keep it to idle by adjusting the idle/pilot screw! Since then I’ve purchased a new Mikuni 38 flat slide carb. I haven’t tried starting it yet with the new carb. I have read that I need to go up 1-2 pilot jet settings from the stock one which should help on the starting. Any other suggestions.... thank you
I see multiple problems:
Something or many things are not right. You should not have to install a new spark plug for every cold start. Your carburetor is a mile off or your riding style is not keeping the spark plug clean.
If the engine starts more quickly holding the throttle wide open.....this is usually a sign that the engine is flooded.
The choke (enriching circuit) functions best when the throttle is completely closed. As the throttle is opened the effect of the choke diminishes. By the time the throttle is 1/4 open the choke is not functioning at kick starting RPMs. A common tuning error on the Keihin carbs is having too large of a pilot jet. When the pilot jet is too large, the idle-slide-stop screw, usually requires the slide to to be open more than 2 mm, making the choke barely functional at closed throttle and choke activated.
Some brands of race fuel have poor vaporization characteristics at cold temperatures making starting at cold temperatures difficult.
Castor oil also has problems staying dissolved in some fuels at cold temperatures.
What temperature are you having starting problems?
What brand of fuel are you using?
What jets, needle and slide do you have in the carb?
What heat range spark plug are you using?
When the slide is in the idle position, what is the distance between the bottom of the slide and the floor of the airflow passageway under the slide?
95% of the starting problems is one of or a combination of the following: type of carburetor, carb jetting, and throttle positioning and knowing when to or when not to activate the choke.