AP Mod - I think I just Wasted my time!


26 replies to this topic
  • twenty34

Posted January 05, 2007 - 07:17 PM

#1

Folks, following the AP Mod instructions per REDBEARDS .PDF from the Honda forum, I just ripped my bike apart only to discover that I have NO gap on my linkage when holding the throttle wide open. The mechanism follows through as if it has a wire holding it together already (which of course it does not). This said, it appears there's nothing I need to do, correct?

Is the assumption when performing this mod that all YZ/CR's have this inherent gap? My bike doesn't have ANY gap at any throttle position.

So glad I just removed the entire rear end of my bike and shock for nothing.

  • Baron Von Beard

Posted January 05, 2007 - 09:26 PM

#2

You are missing the point. The lever will follow through but if you wick the throttle from closed to WOT quickly, you will see the black lever lag behind. This causes an excessively long AP squirt that creates bogs and lousy response. If you wire both levers together the AP squirts instantly, quickly and for only as long as the throttle is moving. Checking for a gap is only to make sure that the diaphragm rivet isn't bottoming which could cause binding in the throttle when wired.

Do this...
1. Turn the AP timing screw counter-clockwise until it just start to come out the other side of the tab. This will make the AP squirt happen as early as possible.

2.Next wire the metal tab with the screw to the black plastic link lever so they move as one.

3.If you want to fine tune, go with a 70-80 sized leak jet and call it fast! Just be careful not to over tighten the safety wire. If you get overzealous you could break the link lever.

  • aford541

Posted January 06, 2007 - 01:24 AM

#3

wiring the ap has been the killer mod for me since 03.

  • krony506

Posted January 06, 2007 - 05:12 AM

#4

Can this be done on a 07 YZ450F?

  • Ga426owner

Posted January 06, 2007 - 08:24 AM

#5

Folks, following the AP Mod instructions per REDBEARDS .PDF from the Honda forum, I just ripped my bike apart only to discover that I have NO gap on my linkage when holding the throttle wide open. The mechanism follows through as if it has a wire holding it together already (which of course it does not). This said, it appears there's nothing I need to do, correct?

Is the assumption when performing this mod that all YZ/CR's have this inherent gap? My bike doesn't have ANY gap at any throttle position.

So glad I just removed the entire rear end of my bike and shock for nothing.


Go ahead and wire per the instructions....since it is off...I know it was fun taking the carb off as mine is out of my bike right now...for this and other mods. Leave the shock off as it will be much easier to install the carb when finished. Also this is a great time to flush out the carb, check the diaphram condition, etc........you may as well get the most out of removing it... :lol:

  • tammie

Posted January 06, 2007 - 09:41 AM

#6

can someone send me a pic of this im not exactly sure........I just put on the boyeensed quickshot AP cover.......i see the black lever and screw your talking about but is there any pics ?

  • twenty34

Posted January 06, 2007 - 10:02 AM

#7

Well, Thank you for taking time to write back, however, wicking the throttle still does not create ANY lag of the lever or ANY gap whatsoever. I flicked the throttle about as fast as I can and it just follows as if it's connected invisisibly. I'd hate to wire it up if there's no existing gap? I tried everything and there's no gap wide-open, closed, quick throttle close to WOT, etc.

Not sure I'm convinced this mod is for every bike.

You are missing the point. The lever will follow through but if you wick the throttle from closed to WOT quickly, you will see the black lever lag behind. This causes an excessively long AP squirt that creates bogs and lousy response. If you wire both levers together the AP squirts instantly, quickly and for only as long as the throttle is moving. Checking for a gap is only to make sure that the diaphragm rivet isn't bottoming which could cause binding in the throttle when wired.

Do this...
1. Turn the AP timing screw counter-clockwise until it just start to come out the other side of the tab. This will make the AP squirt happen as early as possible.

2.Next wire the metal tab with the screw to the black plastic link lever so they move as one.

3.If you want to fine tune, go with a 70-80 sized leak jet and call it fast! Just be careful not to over tighten the safety wire. If you get overzealous you could break the link lever.



  • twenty34

Posted January 06, 2007 - 03:56 PM

#8

Do this...
1. Turn the AP timing screw counter-clockwise until it just start to come out the other side of the tab. This will make the AP squirt happen as early as possible.

2.Next wire the metal tab with the screw to the black plastic link lever so they move as one.

3.If you want to fine tune, go with a 70-80 sized leak jet and call it fast! Just be careful not to over tighten the safety wire. If you get overzealous you could break the link lever.


Ok, since I had the bike apart I did take your advice and turned the screw CCW until it was almost out. After doing this, you can then see the gap that is created, but only after you back out the screw. I then used a small Zip-Ty to hold the screw and level together. This actually worked better than I thought it would. It holds very well, but for redundancy, I also used some thin wire. Seems to hold pretty tight either way.

I put it all back together and the bike started right away. I took it for a short spin and it seems to be working fine. Too soon to really tell how much impact this is having, but it did seem pretty responsive to throttle control. I'll see at the track how noticeable the difference appears. I also put in a larger leak jet (55 stock to a 65). It certainly isn't worse that's for sure so hopefully it feels more responsivess at the track. I'm sure it will based on ride reports here.

I guess the only confusion was that there's no GAP to see until you reverse the screw that connects to the black arm. Only then will you see the gap as reported. Pretty simple and fun job once you take off the subframe (with air filter), shock and side panels. It's really the only good way to work on your carb, IMO.

:lol:

  • twenty34

Posted January 06, 2007 - 03:58 PM

#9

Check the thread in the CRF forum. It's at the top and you can view a PDF. You can't miss it. Has all the images and instructions in tact.

  • Baron Von Beard

Posted January 07, 2007 - 11:10 AM

#10

Be careful with the gap and wiring things together. At WOT it will pull and bend the black link lever if you don't get rid of the gap by shortening the AP diaphragm rivet.

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  • twenty34

Posted January 07, 2007 - 11:48 AM

#11

if you don't get rid of the gap by shortening the AP diaphragm rivet.


On the YZ's you don't have to change the AP Diaphram. This seems to be the case on CRF's however.

  • Baron Von Beard

Posted January 07, 2007 - 01:10 PM

#12

Didn't you say that there was a gap between the lever and screw after the screw was turned out? This would necessitate shortening the diaphragm rivet.

  • twenty34

Posted January 07, 2007 - 03:08 PM

#13

Didn't you say that there was a gap between the lever and screw after the screw was turned out? This would necessitate shortening the diaphragm rivet.


Yes, this is true. I didn't think this was required on the YZ? Also, the bike seems to be working fine. Should I anticipate problems moving forward if I do not shorten the diaphram?

Was I the only person on this forum that experienced this or did othesr have to also shorten or replace their diaphram on their YZ? Again, I thought this issue was focued on the CRF's, not the YZ's. :lol: :confused: :confused:

  • Baron Von Beard

Posted January 07, 2007 - 03:40 PM

#14

Any gap indicates that the rivet is bottoming and keeping the link lever from following the timing tab through the stroke. Wiring the levers without shortening the rivet will cause the timing tab to pull the link lever to close the gap at WOT and can...
(A) cause the throttle to bind
(:lol: Keep the throttle from opening fully
© Break the link lever and/or bend the timing tab.

You can just turn the screw in to close the gap at WOT before wiring but this will delay the AP squirt.

  • DaveJ

Posted January 07, 2007 - 08:42 PM

#15

Ok, since I had the bike apart I did take your advice and turned the screw CCW until it was almost out. After doing this, you can then see the gap that is created, but only after you back out the screw. I then used a small Zip-Ty to hold the screw and level together. This actually worked better than I thought it would. It holds very well, but for redundancy, I also used some thin wire. Seems to hold pretty tight either way.

I put it all back together and the bike started right away. I took it for a short spin and it seems to be working fine. Too soon to really tell how much impact this is having, but it did seem pretty responsive to throttle control. I'll see at the track how noticeable the difference appears. I also put in a larger leak jet (55 stock to a 65). It certainly isn't worse that's for sure so hopefully it feels more responsivess at the track. I'm sure it will based on ride reports here.

I guess the only confusion was that there's no GAP to see until you reverse the screw that connects to the black arm. Only then will you see the gap as reported. Pretty simple and fun job once you take off the subframe (with air filter), shock and side panels. It's really the only good way to work on your carb, IMO.

:lol:



A few things.

First, if you don't have any fuel in the AP chamber you won't see the delay.

Secondly, you can create too much a gap on this carb since it seems to pull the follower away from the cam, causing a delay when you twist the throttle.

Look for this and it will make total sense. My earlier FCRs didn't do this. Just make sure that the pump begins to work as soon as the slide lifts.

Lastly, understand that there are some conditions when you may want a prolonged AP spray, or some at least something that is not as fast or connected as the wire or zip tie approach. Consider using o-rings of different sizes as to create the proper delay in accordance with how long the revs take to climb.

Oh..one more thing. There is a Yamaha technical bulletin that has been posted that shows all the Yamaha part numbers to all the various diaphragm pin lengths that are available. It also has some additional tips and reasons for bogging. An excellent reference to have on hand.

  • twenty34

Posted January 07, 2007 - 09:19 PM

#16

There is a Yamaha technical bulletin that has been posted that shows all the Yamaha part numbers to all the various diaphragm pin lengths that are available. It also has some additional tips and reasons for bogging. An excellent reference to have on hand.


Thanks...Do you have a link to this technical bulletin? I'd like to read it.

:lol:

  • DaveJ

Posted January 07, 2007 - 10:15 PM

#17

Thanks...Do you have a link to this technical bulletin? I'd like to read it.

:lol:


There is a TT member that deserves credit for this but I can't remember who it was/is. In either case, he has served us well. :confused:


http://m.bobbitt.hom...fm/tech/ap1.jpg
http://m.bobbitt.hom...fm/tech/ap2.jpg
http://m.bobbitt.hom...fm/tech/ap3.jpg

  • Ga426owner

Posted January 08, 2007 - 08:06 AM

#18

here are the part numbers for the 3 different length diaphrams
5JG149401700 - stock 7.0mm
5JG149401600 - 6.00mm
5JG149401800 -8.0mm

  • Goosedog

Posted January 08, 2007 - 09:41 AM

#19

Any gap indicates that the rivet is bottoming and keeping the link lever from following the timing tab through the stroke. Wiring the levers without shortening the rivet will cause the timing tab to pull the link lever to close the gap at WOT and can...
(A) cause the throttle to bind
(:lol: Keep the throttle from opening fully
© Break the link lever and/or bend the timing tab.

You can just turn the screw in to close the gap at WOT before wiring but this will delay the AP squirt.


I just installed a JD jet kit in my '02 426 and put the smaller o-ring (it comes with) on the link lever/timing tab without doing any adjustment to the screw position or the diaphram rivet. The instructions didn't say any thing about this, should I go back in...the bike seems to run OK?

  • Baron Von Beard

Posted January 08, 2007 - 10:38 AM

#20

I like the AP squirt to start as early as possible to avoid a hesitation so I recommend setting the timing if you want the most out of it. If you are fine with it and have no issues, then run it as-is.





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