XR70 won't idle?

4 replies to this topic
  • Flynall

Posted May 27, 2002 - 04:10 AM


Hope one on you can help. I have done the obvious, all the way up to disassembling the carb and cleaning both jets. The bike will idle only with the choke either on, or barely cracked from the full off position. It really seems like the pilot/idle circuit is clogged.

There are two adjustments on the carb, one is the idle adjust screw and the other (which is on the same side to the lower left) is a blunt nosed needle. Does anyone know what this needle is (fuel or air) and what its stock setting should be? I am trying to take care of this problem this morning so I can take my daughter out riding today.



  • Kev_XR

Posted May 27, 2002 - 08:32 AM


The second screw is the fuel screw. (If is on the engine side of the carb.) It adjusts the pilot jet.

It sounds like the bike is lean in the pilot if can only run with the choke on. Turn the pilot screw open 1/2 to 1 turns.

Once you get the bike to run and idle, slowly turn the fuel screw in and out until the engine idles the fasters. Then turn it out 1/8 turn.

Most bikes need 1 to 2-1/2 turns out from fully seated.

On my Keihin carb, I can get to the pilot jet by removing the float bowl, though on an XR70, it may be a bit different.

If the bike hasn't been run for a long time, drain the carb float bowl and look for varnish. Run some carb cleaner additive in the gas.

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  • ossagp1

Posted May 28, 2002 - 09:46 PM


The little ones seem to get lots of sitting time and plug the passages. If your low speed passage is plugged from sitting too long you may not get anything out of fuel additive carb cleaners as they generally are not strong enough to each through a total clog.

If that is the case you will need either a regular submersion type carb cleaner and quiet a few hours or to clean the passage manually with a fine wire. I use welding tip cleaners. You can actually damage the passage though so go easy. Wire from a wire brush can work too.

While you have the float bowl off, set the floats as well.

good luck and I hope she appreciates you!!

  • Flynall

Posted May 28, 2002 - 05:18 PM


I disassemble the carb and fine wired the low speed jet and pulled the plug and clean and re-gapped it. It appears that it was a compbination of a mildly carbon fouled plug and the clooged jet.

Thanks for you advice,


BTW, she is 10 now. I expect that by the time she is twenty-something that she will really start to appreciate me.

  • ossagp1

Posted May 29, 2002 - 09:25 PM


At ten they are just beginning to realize that anything she thought was a miracle from you before was an accident. I just got the greatest birthday card from my 21 year old son, so you may be right on the 20 years thing for her.

Glad the bike is working. If the plug was dark, that is from having to run the choke so long. With the passage cleared out you should not have to do that and your plug will last until she is 20.(its been done, honest)

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