LSN fuel line Pinch Test

[Steve-O2021]

Is it right that if you Pinch the fuel line and you -

 

Instantly cut out = your LSN is to Lean

 

Keep running for over 6 seconds = your too rich

 

Engine RPM starts to climb after 2 or 3 seconds and you cut out and engine dies around the 4 or 5 seconds mark = your in a good LSN spot?

 

 

[locky]

The results of the pinch test can vary so dont rely on them to tune, but your description is the common guideline. Performance and sound are the best, Try to to tune your ear for too rich and too lean. It wont significantly hurt the engine if it is too lean for a short period. Always tune when engine has reached typical operating temp.

[Steve-O2021]

On 03/05/2023 at 13:58, locky said:

The results of the pinch test can vary so dont rely on them to tune, but your description is the common guideline. Performance and sound are the best, Try to to tune your ear for too rich and too lean. It wont significantly hurt the engine if it is too lean for a short period. Always tune when engine has reached typical operating temp.

 

Thanks, is one of them temp guns with a laser ok to use, got one from Aldi years ago 👍 

 

Also do you just aim it at the glow plug for the temp rating?

 

Thanks

[locky]

The accuracy of value infra red temp guns is questionable but it will give an indication of temp range +/- say 30F. Dont tune according to a desired temp. Just use it to prevent the engine getting too hot for prolonged periods.  This is usually 300F or about 150C.  You want to see the temp decrease at idle after longish full throttle run.s. The laser is just a pointer and the sensor location maybe further away from this point. I would measure at glow plug and on side of crankcase. Check whether measuring distance and surface/material doesnt significantly alter reading.  Infra red usually give lower readings on reflective surfaces. You could try testing on a metal kettle where surface should be around 100 deg C, if your at or around sea level.  Try get to get used to feel and sound at different needle settings so that you know what too rich and too lean do. It wont  harm the engine for brief up and down runs. HSN controls majority performance after initial acceleration, LSN is the initial punch from stationary and idle rpm, idle rpm is also related to carb gap. Usually those starting to learn to tune go too lean on HSN and too rich on LSN.

[Cactus]

Pinch test? Another over thought almost useless thing which doesn't really do anything useful.

 

When you're tuning all you need to do is listen to the sound of the engine, and also how it feels, bogging (Rich) or hesitation (Lean)

 

Any messing around pinching fuel lines, taking temp readings etc are a waste of time dude.

Having said that, some people like to do things like that to make the tuning prosess seem more difficult.