Hi everyone,

I have a CF500a from 2012. It has about 8000km on it and mostly runs fine. There's been a serious issue bugging me which has prevented me from going on longer trips.

After some time of intense riding +40-65km in 2ish hours, usually mostly off road at high intensity (constantly pushing it), I notice some loss of power. I would start driving slower and easing up on the throttle however the engine will eventually completely die on me, no matter how slow I drive. Once it dies, if I take a 5min break and go again, I'm good for a few minutes (with significantly reduced power) before it will die on me again. Sometimes it won't start at all after it starts.

The time between the loss of power and completely dying on me, is very minimal, perhaps a minute?

Eventually, after a few tries and longer breaks, the engine will behave normal again for some time. If I push it again, the issue will happen again.

I've checked the air and fuel filter and can't notice anything unusual. I'm going out for a longer trip in a few hours and was looking to get some feedback as to what to look for and what to try.

Possible issues i keep in mind:
- lack of fuel for some reason. I read that there were some cfmoto's where fuel lines would be too close to the engine and flat out boil? I will check this tomorrow.
- lack of air somehow. This is highly unlikely though since the engine doesn't recover immediately after taking a break...
- another issue with the carb? Not sure what it could be.

I bought the cfmoto 2 years ago and always had this issue from what I could remember. I sometimes let my family use it but they obviously don't push it as hard as I do so they don't run into the issue as often.

I would really appreciate any feedback or help as I'm not experienced with this stuff

Thanks!

[2015 Z Force 800 53/Trail EPS]

Sounds like the tank check valve is stuck shut. Next time it does this loosen the gas cap enough to relieve any vacuum it might have and re-tighten. If the problem goes away for a bit...you have your answer. Otherwise...a 2012 500 with 8000km on it...she's probably getting pretty tired...may be time for a rebuild.

Sounds like the tank check valve is stuck shut. Next time it does this loosen the gas cap enough to relieve any vacuum it might have and re-tighten. If the problem goes away for a bit...you have your answer. Otherwise...a 2012 500 with 8000km on it...she's probably getting pretty tired...may be time for a rebuild.

Thanks. I'll see if it's this.

Since it's a 500cc, how unhealthy is it to push this thing to 60-70km/h frequently and could that be the cause?

[2015 Z Force 800 53/Trail EPS]

Sounds like the tank check valve is stuck shut. Next time it does this loosen the gas cap enough to relieve any vacuum it might have and re-tighten. If the problem goes away for a bit...you have your answer. Otherwise...a 2012 500 with 8000km on it...she's probably getting pretty tired...may be time for a rebuild.

Thanks. I'll see if it's this.

Since it's a 500cc, how unhealthy is it to push this thing to 60-70km/h frequently and could that be the cause?

With that many miles/KMs on it many things are getting very warn..especially valve train parts like the chains and guides. You need to assess where it is in it's life and adjust accordingly or..plan on a rebuild if tests warrant it.

If it can run hard for 2 hours, my guess is the engine is in fine shape.

Vapor lock (boil/bubbles) and tank vacuum are two good guesses given the symptoms. Vapor lock may be harder to diagnose.

Something else to consider is potential for rubber components to soften up with heat making them more prone to collapsing. I've seen this happen on an intake plenum on a 2020 Z8 trail (CFmoto has a replacement bit for this issue).  If a plenum or vacuum line collapses then attached components don't function correctly.

Replace the spark plug if it is old and check that the plug wire is in good nick.

I have had this problem with my 2013 model. The fuel hose runs too close to the exhaust and I cured it by buying longer quality auto fuel hose and putting it inside a heatshield sleeve from a stationary engine (cannot remember what make) and ran it around the left side and under the carb to the fuel inlet. Also used a wix brand filter from a car to give extra fuel capacity.