Engine troubleshooting, won’t run

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Ollie

Ollie

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On a Farm in the south west of the UK
Recently bought a 30dnt truck and I’ve been having troubles with it running since I’ve got it, it just seems to idle inconsistently. I’ll get it started play with the low needle a little until it idles nice, run it for a while then bring it back to me and it will either die straight away or go to a really high idle then when I try to start it it’s just dead as anything even though I haven’t changed any settings.

Any help appreciated, many thanks Ollie

Edit: Got it sorted now, just had to play with the low needle and the idle screw, they were a long way off but got it running now
 
Last edited:
A suggestion followed by some observations of issues that were similar to yours but different vehicle.

What engine and what carb? Look up the recommended needle settings for the engine size and carb used for low and high and start there.
You may need to adjust the idle stop screw if needed.

Seems that you are leaning out once the engine warms up. It could be related to a gasket seal leak or lack of insulator if using an aluminum intake manifold. Had similar issue with a Talyor 35cc engine, had the proper insulator but found one of the gaskets had slipped out of position during assembly, it was leaning out and running erratically after it warmed up. Easy fix. Also change to a performance exhaust and high flow intake, that required a richer than recommended setting on the low and high needles.

Is the fuel tank pressurizing? If so, that can cause issues too since the carb will not pull fuel out of the tank if it pressurizes. Once that happens it will be difficult to restart unless you loosen up the fuel cap. Foamy fuel return line would be a good indicator of this. Especially when priming the bulb, it will retain air in the line. Another issue I had to tackle with a Vekta KV5TT. Tank was not venting.

Then again, it could be something else.
 
Bandit2013 said:
A suggestion followed by some observations of issues that were similar to yours but different vehicle.

What engine and what carb? Look up the recommended needle settings for the engine size and carb used for low and high and start there.
You may need to adjust the idle stop screw if needed.

Seems that you are leaning out once the engine warms up. It could be related to a gasket seal leak or lack of insulator if using an aluminum intake manifold. Had similar issue with a Talyor 35cc engine, had the proper insulator but found one of the gaskets had slipped out of position during assembly, it was leaning out and running erratically after it warmed up. Easy fix. Also change to a performance exhaust and high flow intake, that required a richer than recommended setting on the low and high needles.

Is the fuel tank pressurizing? If so, that can cause issues too since the carb will not pull fuel out of the tank if it pressurizes. Once that happens it will be difficult to restart unless you loosen up the fuel cap. Foamy fuel return line would be a good indicator of this. Especially when priming the bulb, it will retain air in the line. Another issue I had to tackle with a Vekta KV5TT. Tank was not venting.

Then again, it could be something else.
Click to expand...
It’s a 30dnt 29cc with a walbro 997 but Got it all sorted now, it may well have been the fuel tank pressurising but not sure, fuel return line broke off at some point whilst I was messing meaning there’s a hole in the grommet. got it running nicely now after much adjustment. With L needle just under 1 and 1/4. Thanks for the suggestions anyway
 
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