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Km baja 29cc 1st run. Boggy then fast


Fg-Mart

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Just taken it out for its first run on flat grass. 25:1 mix. Cracked up first pull. Let it sit for 20 mins. The drove it about for awhile. When i hit full throttle it was fast. Then 5 mins later it was boggy. The it picked up then boggy. You get were im goin. Any suggestions as ive only just come back to petrol and its miles different to the marder

Thankyou

Mart

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Sounds like a tuning issue to me, reset to factory and go from there.  If it's boggy pulling off then more than likely the low end.

 

Also, you shouldn't really let the engine just idle on petrol cars, the oil build up will cause the plug issues..

 

It may need a good blow out or a new plug and tune!..

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Did you buy it brand new? If so then it'll be a genuine 668. Can't remember stock settings off hand, but when my 002a was brand new the tune was way out, so as said above, reset to stock settings and try again.

Just remember when tuning to move the needles 1/16th of a turn at a time in either direction.

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As said above ...idling is murder on 2 stroke engines.

 

Check exactly what carb you have, and set the base settings up carefully. Tuning the engine will be exactly the same as your Marder...just with the carb at the front not at the back!

 

The carb will either have Walbro cast in it ( good ) or Ruixing ( bad.... )

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Should be the 668 then with the choke?  IF so then usually - L = 1 and 1/4 turns out, H = 1 and 1/2 out.

 

Close the needles until they are all the way in BUT don't tighten too much when closing as this can damage the needles, keep light fingered!

 

Then adjust the idle to suit and go from there in very small increments.

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Set it up as per Hyper-Boy's post...and then take it for a good run. If you have any build up of unburnt mix or a soggy plug...you want to clear all that out.

 

There is no 'break in' procedure for these motors, they have proper piston rings etc. You just take it easy on the first couple of tanks as the motor beds in. Then you hammer it. No idling fuel through, no heat cycling. Watch for things like exhaust bolts loosening as the motor settles ..... and tighten up anything that comes loose.

 

Should only need very small tweaks to set it up, then leave it unless you change something on the motor.

 

Also....don;t confuse with nitros about when you richen or lean it. Nitros make more power when they are leaner .... petrols don't.

 

To lean...turn the screw clockwise ( screw it in )

To richen...turn the screw anti-clockwise ( screw it out )

Make tiny adjustments and allow the car to run for a few minutes to show a change. Messing about with big changes to needles will cause issues ( screw it up! )

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That's the manual idle adjustment, the low speed needle also effects the idle, so once the low speed tune is set you can then set the idle, you're looking for a nice gentle popping sound from the exhaust.

As with the other two needles, this requires minimal movement as it's pretty sensitive, and when you do adjust it do it slowly so you can stop when it sounds just right.

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