WM-388 Series Air Throttle Cylinder

opus · May 23, 2011, 04:22:16 PM

Well, at least thats what mine looks like. The issue I am having is that there is no "feathering". It is very sensitive and jerky. Here is a pic, maybe something isnt in the right hole?

luvrbus · May 23, 2011, 05:18:40 PM

The vents are plugged on the pedal up front or you have a o-ring bad on the pedal allowing the air to bypass

good luck

opus · May 23, 2011, 05:22:12 PM

Should I be hearing air from the pedal, seeing you say there are vents? I dont, at this time.

luvrbus · May 23, 2011, 05:53:22 PM

Clean the breather on the treadle get your mode numberl and check the pressure setting and match the pressure to the model number lots of different treadles and air pressure setting for the Williams you probably have a 453 B or C on a BB

www.tectran.com I think that is right

good luck

opus · May 23, 2011, 06:53:38 PM

Was just out fiddling with it. The vents are not blocked, there is air releasing from the vents. Looking at the linkage arm on the fuel pump in the picture, I see it must have before been at the top of that arm. I am wondering if we're not talking about a leverage angle here. I would think if it was at the top, it would be smoother than where it is.

Cary and Don · May 23, 2011, 07:37:30 PM

Has it always been like that? The Eagle we just bought had full throttle or none at all. Couldn't feather it. The owner swore it was right and had always been like that. We new it was wrong, our other bus didn't have this problem. Williams told us we had a 65lb throttle peddle and a 35lb rear valve. A new spring for the rear valve and ten minutes and it was fixed. We can't imagine driving it for years like that.

Don and Cary
1973 Eagle 05
GMC 4107
Neoplan AN340

opus · May 23, 2011, 07:54:34 PM

I have only had it going on a year, and yes its always been like that. When I got it, the high idle switch would shoot it up to full throttle. I fiddled with a nut on the unit and brought it down to 1100 rpm for high throttle. That is all that I have done to it.

The biggest problem is taking off from a dead stop. You touch the throttle and it shoots up about 500-600 rpm it seems. I should have noticed it today but didnt think of it. Then when you let off, there is no easy let off. Accel/decel should be one even flow from start to finish. With this is seems more like an EKG chart.

TomC · May 24, 2011, 07:21:02 AM

Two things-maybe try to move the linkage up close to the hinge of the air cylinder at the engine. Or try putting a spring on the engine side for more resistance. I have an air throttle and except for a slight delay, you can't tell the difference. My King cruise control works off the gas pedal and works perfectly. Air throttles can and do work like a regular mechanical throttle if adjusted properly. Good Luck, TomC

luvrbus · May 24, 2011, 07:40:11 AM

Those units with the fast idle are a PITA to adjust you get the fast idle right then the response is off

good luck

opus · May 24, 2011, 07:42:48 AM

Ok, I believe you. Is there a proper way to set this thing up...ignoring the fast idle? As it sits now, idle is 900 and fast idle is 1100.

luvrbus · May 24, 2011, 08:04:58 AM

Start with the idle setting 900 rpm seems high to me what engine do have that is in the fast idle range for most engines

good luck

opus · May 24, 2011, 08:24:49 AM

8.3 Cummins with a MTB643.