86 200SX cold start issues - Honda TRX Forum
 
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post #1 of 7 Old 03-25-2019, 11:02 PM Thread Starter
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86 200SX cold start issues

I have an 86 trx 200sx all original. I'm having problems with it starting and idling after sitting over night or longer. I did a rebuild kit on the carb with essentially no change. The choke seems to have zero affect on how it runs, and yes it is working mechanically. Once it is warmed up it will start and idle fine. I've only run 90oct ethanol free in it since I've owned it.
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post #2 of 7 Old 03-27-2019, 01:06 PM
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Hard starting and idling issues may be caused by valves that do not have enough clearance or a faulty spark plug - install a new spark plug and if that doesn't help, check the valve clearance and see if that helps.
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post #3 of 7 Old 03-27-2019, 09:00 PM Thread Starter
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the first ride after I did the rebuild kit I pulled the plug and it was white. I tried adjusting the screw on the side and it did not help. I then picked the needle up one notch and after a short ride the plug color looked much better but it didn't help the initial problem. should I put the needle back to where it was? Also, is it a air screw or a fuel screw on the carb? I assumed it was a fuel screw since it has an O ring to seal it. I will try a new plug but it is not very old.
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post #4 of 7 Old 03-27-2019, 10:32 PM
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With unleaded fuel, you have to run the engine for about an hour to get a good plug reading and then you want to run it at the speed you want to take the reading at.

The screw on the side is just to adjust the idle speed - the fuel screw is the one on the bottom parallel to the float bowl - if the carb has never been worked on before, the fuel screw may be capped preventing you from seeing it and adjusting it.

The slide needle adjusts the fuel mixture between 1/8 and 3/4 throttle openings - it has nothing to do with idle - if it runs clean at partial throttle openings raised one notch, you can leave it there.

The only thing that affects the fuel mixture at idle is the pilot jet and the fuel screw - the fuel screw should be adjusted when the engine is at full operating temp - run for 15 minutes or more.

The only thing that enriches the mixture for cold starts is the choke - if the choke butterfly is closing, then only the float level, quality of fuel (age, octane and blend), amount of compression pressure and spark affect starting. When then choke butterfly is closed an abnormally high vacuum pulls on the fuel in the float bowl and sucks more than normal through all the jets - the rich mixture ignites more easily, but produces a cold burn - the engine starts, but is low on power until it gets hot enough to run without choke.
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post #5 of 7 Old 03-28-2019, 01:51 AM Thread Starter
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Mine has no screw on the bottom. It has the idle screw on the ride right and what I'm calling the fuel screw on the left side.
The choke functions mechanically but doesn't seem to help as far as running is concerned.
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post #6 of 7 Old 03-28-2019, 01:10 PM
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I stand corrected - the idle speed screw is on the right and the air screw is on the left

The o-ring for the air screw is supposed to go in a groove on the end of the screw nearest the outside of the carb - the o-ring only seals dirt and water from corroding the screw or the threads in the carb making adjustment easier after years of use. If the o-ring is not there, it will not affect the function of the carb. Run the air screw in thill it seats lightly and back it out 1 1/2 turns. Start the engine and run (not idle) about about 15 minutes - with the engine idling, adjust the screw for the smoothest idle - that's all there is to it - the air screw serves no other function other than to adjust idle.

If the engine bogs when the throttle is opened, it's either getting too much fuel or not enough fuel - to help determine which it is, if you open the throttle and the fire goes out and stays out till the machine comes to a stop, but restarts easily, it's probably too lean - if you are holding the throttle open and losing speed but close the choke and it runs normally again while the choke is closed or partially closed, then it's definitely too lean.

If it bogs but continues to run while losing speed and closing the throttle slowly finds a spot where it starts to run normally again, then it's too rich.

You will need to jet up or down as required.
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post #7 of 7 Old 03-29-2019, 12:54 AM Thread Starter
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thanks for all the help I will try to work on it this weekend
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