I ran into an issue the other day with my X30 - Under load it has started cutting out at full throttle. So I’ll accelerate and it’ll hit 7-8k revs and cut out (the engine doesn’t turn off completely). Then I’ll get it back on the stand and it will rev as normal, as though there’s no issue whatsoever.
I’ve had the engine since new and now has 32 hours on the bottom end without a rebuild. I get the top end done every 8 or so hours.
Anyone else ran into this problem?
I would guess either fuel or electrical…
Just some ideas to try…
New plug?
When was the last time the carb was completely disassembled, cleaned and rebuild kit done?
Is there a significant amount of air in your fuel line?
Check to verify the needle settings, especially the high.
Did you run it in the rain previous to this happening?
More questions than answers but some things to look into.
Prior to this happening the engine suddenly stopped starting on the stand (after working normally earlier in the day), and I put a brand new plug in, and it started first go, revving normally on stand. Thinking the problem was fixed. Only when I went on the track did it then start cutting out under load (but continued to work normally on stand).
Carby is regularly disassembled and cleaned with fresh kits. Can’t confirm whether there is air in the fuel line, will have to check later. If there was, what would cause this?
I tripled checked needle settings, all good there.
Yes, I had 2 sessions in the wet a week prior. Pulled the kart down after and cleaned everything best I could. Did a 3 session practise day the following week where all was good, then the following day (race day) is when the problems came about.
If it feels more air/fuely than sparky, have you checked the reeds Matt?
While not related to the immediate issue, I’d strongly advocate for a bottom end build next time before it turns substantially more expensive - That’s a lot of life on the crank pin.
Yeah mate, checked the reeds, they’re all good.
My engine builder says even 40 hours is acceptable on a bottom end. I’d be fine getting it done but he has told me a few times now that it’s not necessary at this stage. I’m a bit sceptical only because I read and hear everywhere else 25-30 max. Even if only for my own peace of mind.
If it’s dying under load but revs clean on the stand it might be electrical. Could be the stator.
Stators do seem to fail inconsistently. ie. Will run on stand, but not on track, or still produce a spark if you take the plug out, but won’t actually run.
If you’re doing top ends every 8hrs then your engine builder has a pretty regualr opportunity to check any clearences developing, so 40hrs is proabbly happy days.
I checked the ohm readings of the stator and got around 186 on all 3. Last time I checked 8 months ago they were around 198. Can the stator still be faulty/failing with normal ohm readings?
Another thought… Do you run an inline filter? I have had those crack open just enough to allow air in when running.
Based on what you said the rain would be my concern. Any chance of swapping out the ignition components with another racer?
or is it possible water got into your fuel?
What is the color of the spark plug?
When the bottom part has been used for the hours it has, there may have been a leak in the crank seals, which causes the engine to take in more air/less fuel.
Looks like this might be the issue. I’ve swapped out everything electrical and the problem persists - Struggles to start. Once it goes it revs out fine on stand. Get onto the track and it cuts out at full throttle when trying to surpass 11k revs.