Adjusting the power valves

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rx1jim

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OK, I know this topic has been beaten to death but I wanted to add my two cents on the power valve adjustment process. I tried adjusting the valves by running the engine below 900 rpm first to get the servo to open them and also by attaching a battery to the test plug. I found the use of the battery to be faster and more reproducible. I built a harness with a momentary switch so that as I adjusted the valves, if the servo moved due to the adjustment process, I could hit the switch to reset the servo to the proper position. This was a lot faster and more accurate than setting the servo once and making alignment marks with a pen.
 
SickRic, I will post the info. early next week. I am packing up for my last sledding trip for the season. Very easy to make and use.
 
rx1jim said:
OK, I know this topic has been beaten to death but I wanted to add my two cents on the power valve adjustment process. I tried adjusting the valves by running the engine below 900 rpm first to get the servo to open them and also by attaching a battery to the test plug. I found the use of the battery to be faster and more reproducible. I built a harness with a momentary switch so that as I adjusted the valves, if the servo moved due to the adjustment process, I could hit the switch to reset the servo to the proper position. This was a lot faster and more accurate than setting the servo once and making alignment marks with a pen.
Click to expand...
If servo is moving your applying too much force on the cable via the adjuster,once one gets the hang of this you should be able to do all 3 with out the servo moving at all one bit.

IMO a harness is more work,you need to get a battery out, get the harness out,unplug the protective cap plug harness in and energize vs idle down, mark servo done.

i have the actual factory PV harness tester but hardly use it,but i hear you what ever is easier for you! :)
 
rx1jim said:
OK, I know this topic has been beaten to death but I wanted to add my two cents on the power valve adjustment process. I tried adjusting the valves by running the engine below 900 rpm first to get the servo to open them and also by attaching a battery to the test plug. I found the use of the battery to be faster and more reproducible. I built a harness with a momentary switch so that as I adjusted the valves, if the servo moved due to the adjustment process, I could hit the switch to reset the servo to the proper position. This was a lot faster and more accurate than setting the servo once and making alignment marks with a pen.
Click to expand...

yes sir. setting the valves by feel, so that they are flush to the roof of exhaust port, when the servo motor is in the full open position, is most accurate.
 
mopar1rules said:
yes sir. setting the valves by feel, so that they are flush to the roof of exhaust port, when the servo motor is in the full open position, is most accurate.
Click to expand...
I would highly disagree, but not going into a dispute over it.
 
daman said:
I would highly disagree, but not going into a dispute over it.
Click to expand...

you must not fully understand what i'm talking about, or else i think you would agree w/me, but it doesn't matter. everyone will do it their way which they see best/fit.
 
daman said:
it could be, explain???
Click to expand...


On the surface, I'd agree with Mopar but also think the published procedure get's you roughly the same results. I don't think there is much of a difference if the valve ends up slightly beyond flush (unless there is tension on the cable when fully opened). But if it isn't flush the other way (protruding into the flow) then I think flow might suffer. Enough to make a difference? Don't know.

I think there is as much fudge factor when blindly feeling if they're flush with a finger as there is in the written procedure. If you had a template that matched the contour of the port and could adjust to it, perhaps it would be more accurate, but with my fat fingers I don't think there is much of a difference.

I think the critical part is that the valve still has a bit more travel when fully opened to keep excessive tension off the cable to avoid pull throughs.

I made a harness for the servo because I wanted to adjust the valves during my annual pipe removal (flush method) so starting and idling below 900 isn't an option with the pipes off. I adjusted them flush and checked them with an allen wrench and didn't find much of a difference. The written procedure ensures you have slack in the cable when they're full opened.

BTW - mine were way off right out of the box. Well, actually after the first season. Not sure if it was on the dealer prep list, but if not it should have been.
 
snomofo said:
On the surface, I'd agree with Mopar but also think the published procedure get's you roughly the same results.
Click to expand...
Roughly is right,

Yamaha's way allows for a more "even" cable free play throughout out the three because your actually measuring the distance free play vs just crank em till flush then move on,this has been posted many times over the years a search would revile this.

i adjust them the way Yamaha the designer of this system wants it to be done, not my way.
 
daman said:
Roughly is right,

Yamaha's way allows for a more "even" cable free play throughout out the three because your actually measuring the distance free play vs just crank em till flush then move on,this has been posted many times over the years a search would revile this.

i adjust them the way Yamaha the designer of this system wants it to be done, not my way.
Click to expand...


When I say roughly, my point is that IMO the published procedure's primary goal is to avoid pull throughs, with optimal valve opening being secondary. Agreed that the published procedure is usually the best, unless the goal of the procedure is to keep costs down. Is it to obtain optimal valve opening, or is it to avoid the costs associated with in-warranty pull throughs?

The published procedure doesn't require removing the pipes or outlet tubes so the labor allowance and parts list to perform the repair under warranty is less. This cost save is weighted against optimal valve opening and a decision is made. Again IMO, the published procedure is a compromise with a default of less costly valve warranty.

IMO, even free play amoungst the three cables isn't as important as ensuring the exsistance of free play. In other words, adjusting the valve to achieve optimal opening would be the goal as long as each cable has some free play.

I found that if you adjust the valve so that it is flush, there is still a small amount of valve travel left which allows for slack in the cable thus avoiding a pull through.

I think you'd be surprised what the goals are in writing a repair procedure. Cost usually overrides all others.
 
snomofo said:
When I say roughly, my point is that IMO the published procedure's primary goal is to avoid pull throughs, with optimal valve opening being secondary. Agreed that the published procedure is usually the best, unless the goal of the procedure is to keep costs down. Is it to obtain optimal valve opening, or is it to avoid the costs associated with in-warranty pull throughs?

The published procedure doesn't require removing the pipes or outlet tubes so the labor allowance and parts list to perform the repair under warranty is less. This cost save is weighted against optimal valve opening and a decision is made. Again IMO, the published procedure is a compromise with a default of less costly valve warranty.

IMO, even free play amoungst the three cables isn't as important as ensuring the exsistance of free play. In other words, adjusting the valve to achieve optimal opening would be the goal as long as each cable has some free play.

I found that if you adjust the valve so that it is flush, there is still a small amount of valve travel left which allows for slack in the cable thus avoiding a pull through.

I think you'd be surprised what the goals are in writing a repair procedure. Cost usually overrides all others.
Click to expand...

yeppers!!
 
I adjust my valves using the Yamaha procedure and two pieces of drill rod which are 0.100" dia (approx. 2.5 mm). From what I have read on this post, adjusting them using a smaller dia. gauge would gain more performance BUT would that performance noticeable to the rider?? I am going to stay with the 0.100 spec. since I don't use all the power the engine has anyway. I'll be able to make some measurements on the position ofthe valve in the exhaust port versus clearance when I rebuild the engine in about a month. Keep the great info. flowing, good discussion.
 
rx1jim said:
I adjust my valves using the Yamaha procedure and two pieces of drill rod which are 0.100" dia (approx. 2.5 mm). From what I have read on this post, adjusting them using a smaller dia. gauge would gain more performance BUT would that performance noticeable to the rider?? I am going to stay with the 0.100 spec. since I don't use all the power the engine has anyway. I'll be able to make some measurements on the position ofthe valve in the exhaust port versus clearance when I rebuild the engine in about a month. Keep the great info. flowing, good discussion.
Click to expand...


One question that comes to mind is how the adjustment affects (if at all) the forming of deposits. If the valve sits lower in the port at WOT than if it were flush, does that add to the formation of deposits? Does that direct more exhaust pressure (highest pressure at WOT) towards the valve and thus at the seal and cause it to leak sooner?
 
daman said:
If servo is moving your applying too much force on the cable via the adjuster,once one gets the hang of this you should be able to do all 3 with out the servo moving at all one bit.

IMO a harness is more work,you need to get a battery out, get the harness out,unplug the protective cap plug harness in and energize vs idle down, mark servo done.

i have the actual factory PV harness tester but hardly use it,but i hear you what ever is easier for you! :)
Click to expand...
daman said:
If servo is moving your applying too much force on the cable via the adjuster,once one gets the hang of this you should be able to do all 3 with out the servo moving at all one bit.

IMO a harness is more work,you need to get a battery out, get the harness out,unplug the protective cap plug harness in and energize vs idle down, mark servo done.

i have the actual factory PV harness tester but hardly use it,but i hear you what ever is easier for you! :)
Click to expand...
I can’t get my sled to idle under 1000 rpm. Carbs are clean, no air leaks. Has anyone experienced this?
 
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