Power Valve Reassembly & Adjustment

Homer

Homer

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Joined
Sep 10, 2006
Messages
40
Age
56
Location
Minnesota
Hi all-

I figured i'd clean the power valves on my Viper. Like a dummy, I did not pay attention to which way the valves came out. I assume the large bevel end is the bottom of the valve and the small chamfer end is the top. If someone could let me know for sure that would be great.

Second, I downloaded in the tech pages the power valve adjustement proceedure. I do not understand the gap that is talked about. Could some please explain the proceedure in detail that would be great.

Thanks in advance!
 

With the Servo at the full open position, the cable should have only about 2 - 3 mm play in it. This is measured (Yamaha method) by loosening the 2 - 4mm allen head bolts where the cable housing connects to the PV assembly and checking clearance. Be sure to double check that the servo did not turn.

That said, many peeps take the exhaust lead pipes off and check for flush with the port at the servo full open position.

There are 2 basic ways to find servo full open position.
  1. Use a wiring harness and power supply specifically designed to move the servo to full open.
  2. Drop the engine RPM's while runnning to 900 using either the starter circuit (some call it a choke) lever, or turn the idle screw. Some simply shut it off, which also is suppossed to go full open. If you use this method, you will want to do it several times to be sure that you have full open.
Whichever method you use, you can simply mark the location at the servo after taking the cover (3 screws) off.

On the Vipers there is also a cleaning cycle where the servo goes through the full range of motion at startup. I like to double check this motion while the sled gets started to ensure that it is not turning past my mark for full open.

If the servo turns farther then where it was when the vavles were adjusted, it can pull the cables through the end of the valves. You don't want this to happen as the valves are expensive.
 
Thanks fellas. She's all back together and fully adjusted & cleaned. I got a little flustered this morning at the start of this project when I found that the last guy to clean the power valves broke a ball-nosed allen off in the cap screw that holds the mag side power valve assembly. I spent a good 2 hours trying to get the screw out.
 
Hey I did that once (broke a ball-nosed allen tip off) only I removed it. Now I always remember what size the PV screws are . . . The allen wrench that is broken. I also replace the screws every so often to make removal easier.
 
I assume the large bevel end is the bottom of the valve and the small chamfer end is the top
Click to expand...

The large beveled edge goes down
Click to expand...


jsut to clarrify. seems ther are two interpretations to the :chamfered end"

the chamfer has two radii, one on each end. one radius is on a smaller surface than the other.

which radius is down, the larger , or the smaller
or in other words. is there more material on the top, or more material on the bottom.

someone show a pic please

Ramb
 
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On the same note: I'm doing the same with mine, is it necessary to replace the spring in the the unit? I have replacements, but don't know what to do with them. I hope this isn't hyjacking, I thought it was relevant to the subject.
 
Another question Rambunctious looks like he did not remove his cables and i did not remove mine either. Here's the question is it nessessary to ajust the cables if you did not take them off?
 
fyi, the pic is from someone else,

but it is easy to adjust once reassembled ( partially).
I used an 1/8" diameter drill bit. backed off teh allen bolts on the housing and adjusted the cables at the servo to the 1/8" gap by placing the drill bit bwtween the two aluminum housings.

as mentioned, mark the servo in it's open position as inevitably you will rotate it as you adjust the cables.

Ramb
 
Ahh, now I understand. when you loosen the valve houses, a gap is created, then you tighten the cables at the pv motor, and when you tighten the houses back together, because of the gap that was there while you adjusted them, that is what makes the freeplay you are supposed to have in the cables? I think I would prefer to use a 2,5 mm allen wrench between the houses, when setting the gap.
 
Since i normally have the pipes off to remove and clean the PVs i alway go the next step and pull the headers and use the "feel for flush" method. It really only takes an extra 15min to know they are adjust perfectly, but that just me i am a little picky that way..............James
 
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