Air pre cleaner

[Vulgunx]

If i take the air pre cleaner off (MUSHROOM) off when running it on full revs will it damage the engine?
since i went to chipping steam fair the other day for the weekend and on the tractor runs i had grey fergies over taking me and couldent keep up with them? so on the way back home i was experimenting and took my mushroom off and the speed difference is huge i was only getting 15 before and im getting 22-23

[Brian Cox]

oh no! not grey fergies

[Bensdexta]

Check out the vanes on the mushroom. Maybe they are not open enough? Is it a repro mushroom?

[Brian]

Have you ordered your new engine yet? If you are getting 22 mph you are way over-reving her.

Your maximum revs should be 2000 -2200 rpm and top speed at these speeds is around 17 mph.

[marcusgs]

Hi,

I am only getting 1800rpm on my standard dexta. I know that the air filter is clear, because I took it completely to bits and washed it all out, including the gauze.

The mushroom is a reproduction one, where should I look first please?

Thanks,

[Bensdexta]

The mushroom is a reproduction one, where should I look first please?

Have a look at the vanes underneath the mushroom. If they are too closed up your engine won't get enough air.

If you bend them open a bit, as Brian says, be sure not to overspeed your engine!

[wfillingham]

assuming this is a 1961 Dexta with the vacuum operated governer then make sure that everything is adjusted correctly,.... ie that when the throttle is fully open that the butterfly in the manifold is actualyl fully open....

as mentioned above, when the vacuum governer is operating correctly, you should be seeing max 2200rpm....

similarly, to prove that the governer is operating correctly if you went along the road at 2200rpm.. then go up a hill.... it should hold those revs...... the only thing that i can suggest with yours is that either this butterfly in the manifold is not adjusted correctly, or that the diaphragm in teh back of the pump has a hole in it....

also, most importantly, check the metal gauze breather for this in the pump....otherwise the diapraghm will be attempting to suck against a vacuum rather than actual atmosperic pressure.... hence causing it to not move correctly.

I would check all these bits first before trying to change anything to non standard....

Though... if its not vacuum operated and in fact is a super Dexta with mechanical governer then that will need taking to bits and rebuilding...... as the weights would be not moving correctly.

Also, you may be getting fuel starvation?

when my lift pump failed it still ran, but would be slow to pickup revs, as the injection pump was having to suck fuel in effect from a gravity feed.. rather than being pumped in with the lift pump....

I since replaced with a new lift pump, and new filter housing and filter.... and its been happy since then...