Does the throttle stop have a use? And a question on the pilot screw adj thread..


8 replies to this topic
  • cjard

Posted February 17, 2012 - 12:37 PM

#1

Hi guys

I ask, because several bikes I've seen now don't have the throttle stop screw end touching anything.. If I wind it in so it is pushing on the throttle drum assembly even just the slightest amount, the idle jumps up to an idle that just... sounds too high. it seems almost impossible to get the bike to idle just above the "slow" sounding putputput that I get when the stop screw doesnt touch


When the pilot screw adjustment thread says:
"Gently turn the screw all the way in. Now back it out two turns. [color="#0f72da"][color=#0F72DA !important][font=helvetica, arial, sans-serif][size=4][color=#0F72DA !important][font=helvetica, arial, sans-serif][size=4]Start[/size][/font][/color][/size][/font][/color][/color] the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed."

I dont understand why it says to go for a ride, then set the idle high, then set it low.. What's the use of setting the idle high? To warm the engine? or is that what the ride did? If so why tell us to wind the idle up then when it's warm (it's already warm - we took it for a ride!) wind it back down

  • Stealth13

Posted February 17, 2012 - 12:54 PM

#2

What I did is ride it for a while then adjust it as low as I can with the engine still sounding good. Makes it not overheat so much. When I first turn it out I have to leave the choke open for a few minutes or it will die if I close it right away because the rpms are lower

  • cjard

Posted February 18, 2012 - 01:59 AM

#3

Having adjusted my pilot so there's no hanging idle, no popping on decel, and the bike ticks over nicely, i find it won't start cold without the hot start nob on as well as the choke (without hot start it tries, but dies after one or 2 fires) .. i take it this means it's currently too rich?

  • miweber929

Posted February 18, 2012 - 06:35 AM

#4

If you are following Williams sticky at the top it's to make sure the engine doesn't stall while adjusting. If you are not following Williams sticky, follow that proceedure.

Throttle stop screw is to stop your throttle from over-opening and possibly sticking wide freaking open.

Some people pull theirs instead of buying a YZ or modifying theirs correctly; those people are pretty dumb in my book as its a cheap price to buy it and 10 minutes to modify it. At that point you won't have to worry about a stuck throttle shooting you into a tree, car, cliff etc. or blowing your motor in a crash.

YMMV, however.

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  • MANIAC998

Posted February 18, 2012 - 07:06 AM

#5

I'm not sure, but I think you are turning the wrong screw. What William is telling you to do is to lightly turn the air/fuel mixture screw all the way in, and then back it out two turns. This is how you get the air/fuel mixture screw in the recommend setting range. This is the one in the very front of the carb that requires a screwdriver, or you purchase an extended one that sticks out of the bottom of the carb, which makes it much easier to adjust. Not the cable mounted idle adjustment knob that comes from the factory. Maniac

  • Stealth13

Posted February 18, 2012 - 05:36 PM

#6

Hey maniac maybe mine needs the air fuel screw adjusted too? All I've done is the idle speed screw

  • cjard

Posted February 22, 2012 - 01:19 AM

#7

Throttle stop screw is to stop your throttle from over-opening and possibly sticking wide freaking open.


Doh.. I've been thinking it's a screw that stops the throttle from closing fully, I.e. the idle speed screw.. This diagram:
http://slorider.com/...eihin_FCRMX.gif
Refers to 90 as the step screw, and 91 and 92 as the stop screw washer and stop screw sprint.. I thought step screw was a typo of stop screw... Pprobably the other way round (91 and 92 should be called step screw xxx)

So when I sid stop screw before, I meant the screw on the end of the bendy wire with the black knob that you turn to adjust the idle :/


Question remains though... Why does william's sticky tel us:
1) go for a 10 minute ride to warm the engine
2) screw the idle speed knob in to get 1500 - 1800 rpm
3) once warmed, slow the engine down to as low as it will go

I'm still not getting the point of part 2) in combination with part 3) - if you warmed the engine already, why would you not just skip straight to 3) ? What does using the idle speed knob to rev the engine up do that using the throttle doesnt do? Why dial an engine's sped up, and then straight away dial it back down?

Edited by cjard, February 22, 2012 - 01:20 AM.


  • miweber929

Posted February 22, 2012 - 08:35 AM

#8

Question remains though... Why does william's sticky tel us:
1) go for a 10 minute ride to warm the engine
2) screw the idle speed knob in to get 1500 - 1800 rpm
3) once warmed, slow the engine down to as low as it will go

I'm still not getting the point of part 2) in combination with part 3) - if you warmed the engine already, why would you not just skip straight to 3) ? What does using the idle speed knob to rev the engine up do that using the throttle doesnt do? Why dial an engine's sped up, and then straight away dial it back down?


Yeah, I re-read it and it's not worded 100% smoothly, but I believe what he is saying is to warm the bike up, set your idle up so that it runs smoothly around 1500-1800 RPM so that you know what it sounds like, feels like and to be sure it does in fact idle high enough to not stall the bike. Once you go farther into the instructions it sort of makes sense. The additional warming of the engine seems to be sort of a misprint as you are right, the motor should be already warm. I'd crack the throttle a few times to be sure it's "cleaned out" and settled down smoothly.

Mike

  • grayracer513

Posted February 22, 2012 - 09:12 AM

#9

These may help, the second one in particular:

http://www.thumperfa.../jetting.htm#PJ

http://www.thumperta...ad.php?t=327405




 
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