2018 YZ65 Jetting Issue?

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1/8/2019 5:21 AM

Bike runs great on the track but we are having issues with taking off at lower RPM's. If you launch the bike hard it will take off hard. If my son just tries a nice smooth lower RPM takeoff the bike will start to go then immediately bog 5-6 times and stall.

Bikes still brand new maybe 2 hours but I think there is definitely a issue there.

Thanks for help

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1/8/2019 11:35 AM

I ran my daughters yz65 in 2 weeks ago. Still had the same fuel in it that the dealer put in back in October when i bought it. Bike ran perfectly. Has your son ridden a 65 before? Maybe he just needs to get used to the clutch.

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1/8/2019 12:01 PM

chump6784 wrote:

I ran my daughters yz65 in 2 weeks ago. Still had the same fuel in it that the dealer put in back in October when i bought it. Bike ran perfectly. Has your son ridden a 65 before? Maybe he just needs to get used to the clutch.

He's only rode it once but he's a fast 50 kid. It could be he's just dumping the clutch to fast and not enough throttle. It's weird because there bike will take off briefly then start bogging and stall in about 5-10'. Once he's going and on the track no issues at all.

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1/8/2019 4:33 PM
Edited Date/Time: 1/8/2019 4:35 PM

1) Bad gas
2) Clogged pilot (check to see if the bike will rev on the stand. #1 and #2 go together all the time.)
3) Kid still learning the clutch. My 13 year old took about 5 to 10 ride days and maybe 10 hours before she got it.
4) Fouled plug

Pull the spark plug and see what it reads. Odds are good it's oil fouled. OEMs like to jet bikes pretty rich from the factory to make them last longer.

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Braaapin' aint easy.

1/8/2019 5:02 PM

Definitely not bad gas bike runs awesome on the track. Pilot could be plugged bought the bike and it sat for a month. Bike idles and revs clean on the stand. Is it possible for a plug to be fouled and still run good on the track?

Could be the way he is launching the bike. If it's there pilot how do I tell if it's a rich or lean bog?

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1/8/2019 6:04 PM

Hey Joe.
Im familiar with your issues. Ive experienced the bogging when my son first began riding the 65, as if the bike is still cold or "loaded up" but have obviously warmed up the bike and like you said revs fine on the stand. I feel like I could hop on the bike and take off just fine as an experienced rider knowing when to throttle up and maybe work it through the "bog" if you know what I mean. I will agree that it may be a learning curve with the transition to clutch life..
Here's what I've come up with. If your plug fouls the bike will not run. Or will sound very unhealthy when revving if it is running, but will eventually die. I've got an '18 yz65 for my son and have had a plug foul. What fuel ratio are you running,and what jet set up? I've had a good relationship with Pax Racing throughout our 50cc career lol and talked to them about jetting and fuel ratio. 135/50 and 40:1 is their advice. I know this has helped us out, and the bike is ripping great and no more problems

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1/8/2019 6:23 PM
Edited Date/Time: 1/8/2019 7:57 PM

metzger719 wrote:

Hey Joe.
Im familiar with your issues. Ive experienced the bogging when my son first began riding the 65, as if the bike is still cold or "loaded up" but have obviously warmed up the bike and like you said revs fine on the stand. I feel like I could hop on the bike and take off just fine as an experienced rider knowing when to throttle up and maybe work it through the "bog" if you know what I mean. I will agree that it may be a learning curve with the transition to clutch life..
Here's what I've come up with. If your plug fouls the bike will not run. Or will sound very unhealthy when revving if it is running, but will eventually die. I've got an '18 yz65 for my son and have had a plug foul. What fuel ratio are you running,and what jet set up? I've had a good relationship with Pax Racing throughout our 50cc career lol and talked to them about jetting and fuel ratio. 135/50 and 40:1 is their advice. I know this has helped us out, and the bike is ripping great and no more problems

I spoke to Johner yesterday about it and he is sending me a 135. Do you happen to know what pilot is in there I haven't got into the carb yet?

We are running Maxima K2 at 40:1

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1/9/2019 3:03 AM

JoePit wrote:

I spoke to Johner yesterday about it and he is sending me a 135. Do you happen to know what pilot is in there I haven't got into the carb yet?

We are running Maxima K2 at 40:1

I'm pretty sure it was a 145 or 148 that was in the bike stock when I switched to the 135. Its has made a difference for us. ✊✊

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