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Collection, Preservation and Display of Old Lawn Mowers

Villiers carb tapper needle adjustment

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Morning 

ive searched for the correct setting of the tapper needle in the main jet centre piece on a Villiers carb fitted to a MK25. It looks very similar to an S19, see picks below. It ticks over nicely but it won't go to full speed. I'm about to dismantle again to check for blocking but want to make sure the needle is set correctly. 

Forums

wristpin Tue, 27/04/2021

Warm it up, then move it and listen! Full speed is more likely to be affected by the Governor setting . At its current full speed , push  the Governor arm to increase it, if then it runs out of puff, richen it a bit and see whether it makes a difference.

Worth investing in a tachometer so that you know what rpm it’s actually doing . The. Highest power rating shown in the Mk25 manual is at 2500rpm which will sound quite slow compared with some  current engines.

mikehpw1 Tue, 27/04/2021

Hi Wristpin

thanks again, you've confused me with someone who's on you wave length :-) I take it you mean move the needle but I can't without stripping it down, moving it by throttle lever doesn't increase rpm. I'll fiddle with the governor arm. By the way can you reco a taco for small engines?

Regards

mike

 

 

wristpin Wed, 28/04/2021

Tachometers. The most useful one for a mower man is an Impulse one; just point it at the spark plug lead and it turns the impulses into a digital numeric display and is just  a bit bigger than a credit card . I have a Stihl branded one but similar ones appear under different brand names.  Another , sometimes sold as the Tiny Tach is a bit more chunky and, I believe requires a pick up wire wound around the plug lead.

If I understand your set up correctly you have a throttle slide with a needle controlled by cable from the throttle lever and an additional manifold mounted throttle butterfly controlled by the engine’s internal and external governor linkage. With the handle bar control at full speed , check the top no load engine rpm. If it’s at 2500 the engine is at it’s rated speed to produce 3 HP which is probably right for your machine. At 2000rpm it will be producing around 2.5HP. 

The first thing to do is to ascertain the current top no load speed with your current set up.