XR70 stalling problem - need help

[kx100pro]

My brother has a 2000 XR70. We have owned it since new, and it has a lot of miles on it. My brother complained of a stalling probelm. I have tested it and the problem is this.

When the engine is at idle speed or low rpm and you grab a handful of throttle it will hesitate and stall. The bike does rev if you bring up the rpm a little more gradually.

I took apart the carb and cleaned it out and I leaned out the needle by 2 notches. I also installed a new filter. This seemed to help a little, but the problem still persists.

What can I do to fix this problem?

[QuantumDuck]

Does it have a manual choke on it?...If it does, pull the choke out and see if it still stalls or it runs at all...using the choke this way will help you figure out if it is stalling because of too much gas or not enough...

[alan]

I am not sure and this is a stab in the dark, but I heard one the other day which could be a problem. It was the same symptoms, a lot of guys remove the tank vent tube and replace it with one of those little one way valves. The problem is that every once and a while they get clogged up. The bike starts great but when you give it gas it starves for gas and it is hard to tell if it is starving or flooding out.Quick check remove the valve, check the bike with it off and then clean it and re install.

Alan

[ShanMan]

This is a common problem for the little XR's (both the 50 and the 70), especially if they are stock. The best way to not only fix the hesitation but also improve the high revving performance is to swap out the stock CDI box with a good aftermarket unit like Takagawa. The unit not only fixes the flat spot you describe, but also removes the rev limiter, which is set at about 9800 despite the motor making power all the way to 12,500. The cost is about $60 but makes a big difference! Hope this helps.

[John]

A stupid question - I guess you did a proper cleaning of the carburetor? What you should use is carburetor cleaning solvent or some other strong (environmentaly friendly  ) stuff and blow all channels and jets clean with high pressure air.

/John

[kx100pro]

Quantum: the bike does not run at all with the choke out. It starts up and runs without any need for the choke. If the choke is out, it will not start or run.

Shanman: We also have an XR50. It has much less use and wear than the 70. However, this bike since day one seemed to have more power than the 70. The throttle on the 50 is crisp and you can go from idle to WOT without any hesitation.

John: Yes, I did a thorough cleaning with carb cleaner and used the compressor to blow out the channels/jets.

Thanks for all the replies. I think the problem is too much fuel because of the choke. I already leaned out the needle as much as I can (clip in top groove) so I am going to try a leaner jet. I am getting an aftermarket CDI to help out the 70 with some power.

[QuantumDuck]

My next suggestion...Go with what Shanman said