FTZ R6 tech page: web address is: www.ftzracing.com/R6tech (sometimes case specific)
Troubleshooting your R6 600 Micro Sprint if it is not running correctly.

We made this to help you (and to hopefully help keep us off the phone saying the same thing over and over to different guys).
We will break this down into basic symptoms listed below:

*Hard to start and will not idle: Now most of us know that these motors on alcohol are "cold natured" and require some cranking to first get started and have to run a while before they will "take gas". But once warmed up the motor should restart easily and idle well. Especially after the slow mixture screws have been adjusted to fine tune the idle, and off idle response. If it extremely hard to start and does not idle at all the culprit is usually a stopped up pilot jet. This is the smallest orifice in the carb so it is often the first to clog up if alcohol is allowed to stay or dry in the carbs. Remove the pilot jets and spray brake cleaner thru them and thru all the passageways to make sure they are not stopped up. A bristle pulled from a wire brush can be used to push thru a badly clogged up jet. Replace everything and be sure the float height is set right and try it again. Don't be afraid to re-adjust the slow screws for best idle.
Also it would be a good idea to check valve clearance to make sure none are tight.

* High Rpm miss-fire or cutting-out. This sounds like symptoms of fuel starvation. This may take a lap or two to show up. Pull off the fuel line and let it pump into a container for 2 or 3 minutes. Double pumps should be checked separately. The flow should not fall off. Check fuel tank vent or check valve, fuel filter, and lines. A fuel pressure gauge on the dash that is big enough to read on the track-at wide open throttle and at the end of the straight is about the only way of knowing if you are for sure getting enough fuel. How much is enough will vary with the different motors, carbs, and jetting, but at least you will have a way to measure or compare it. Also be sure your spark plugs are gapped at .020". A high speed miss can also occur when the water temp is too low (under 190 degrees)- be sure you have our high temp thermostat in and if necessary, block part of the radiator in cool weather to get the temps up.

*Poor Idle, Poor Restarts, Poor acceleration after letting off in the corner, sometimes floods motor. These are signs that the float valve or "needle & seat" are leaking past, raising the float level allowing raw fuel to enter the motor. This can be caused by dirt or alcohol residue, the rubber tip on the float needles can be worn with a groove, or fuel pressure can be excessive.

*Poor power on track but starts and idles well. This is a sign that one of the slide diaphragms is not sealed and the slide is not raising. Take off the air filters and start the motor and warm it up. Watch all the slides as the throttle is wacked open for about a second. All slides should rise equally to nearly full open. Also make sure the throttle plates are opening together and fully.

*Poor performance on track overall. Now we all know that with dirt track racing a guy can be fast one night and a slug the next. And the motor is only a part of what makes a car fast- Driver, tires, gearing, chassis setup, and the line thru the corner are at least as important. That being said, if the motor doesn't pull hard or turn as many rpm as it did before, then here is a few things to look for:

I would check the previously mentioned things as well, just to cover all the bases. Especially the throttle and the slides opening all the way.

-Check the Clutch. Our built R6's will max out the clutch's capability- so everything needs to be 100%. Something unique to the R6 is that the clutch will slip and it doesn't rev free like most slipping clutches will do- so you may not notice it. We first saw this on the dyno.
The new racing clutch plates are .119" thick, yours should be replaced at .117". We have just seen sets of recently installed clutch springs that broke into several pieces after just a few races. They must of had a bad heat treat lot and got some of them too hard. The racing springs make the clutch tough to pull in, so if it suddenly becomes easier to pull in, you better check out the clutch springs.
-Be sure the exhaust system isn't dented, or bent up that last time Billy Bob ran over you.
-Do a leakdown test on the motor- Be sure not to get any dirt or sand down the ports or the valves will leak like crazy. Less than 5 or 6% leakdown says the motor is probably okay.
Other things to check:
-Check Ohm reading of throttle position sensor, or just unplug it.
-Check battery voltage with engine running. Under 12 volts could be a problem.
-Be sure all ground wires attach to the engine block to bare metal.
-When was the last time you drained & flushed the fuel tank? Alcohol absorbs water, especially in hot weather.
-Make sure the motor is running at least 190 degrees water temp- or it won't want all the fuel we put in it if cooler.
Other factors to consider:
-Is the car too tight - not letting you turn and get in the gas soon enough?
-Is the car too loose causing you to slow down too much for the corners?
-If the stagger is too much or too little, it will "drag" one tire along, like dragging an anchor- robbing power. This is really critical on bigger tracks where a car needs to be very "free". And try to find a line that doesn't "pinch" to corner- keep the rpms up.
-Are you sure you have the right gear on it? See if you can find out what the other guys at that track are running for sprockets. Remember tire sizes effect gearing also.

We hope this has been a help to you.
Good Luck at the races!
FTZ Crew.

Jetting Update 5/08: It appears that our Level 2 Cylinder head mods require leaner jetting than expected, due to the increased flow drawing more fuel from the carbs. Going to smaller main jets may work well for you as well to extend the higher rpms but power off the corner will suffer. Better yet, we have a new adjustable air correction modification option than we now offer, that allows you to lean or richen the mixture easily without changing main jets. This gives both proper fuel off the corner without letting it get too rich at high rpms. Most level 2 motors will require a #100 air jet, most stock motors use a #80 and this is plugged off for restrictor motors. We recommend that you gear for about 15,500 to 15,800 rpm at the end of the straights. You may consider the Mychron Data system that we offer to monitor engine vitals and air/fuel ratio perfectly and eliminates tons of guesswork.
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