Choke revs engine really high. Normal?


10 replies to this topic
  • RMK800

Posted April 12, 2013 - 04:34 AM

#1

Just purchased a 2007 WR450, I can't never leave the choke on full when initially starting it revs Really high, is that normal? Anything out of tune with the carb? I have to hold choke between 1/2 and 3/4 until it can warm to idle.

  • Krannie McKranface

Posted April 13, 2013 - 09:37 AM

#2

Not normal.
Properly adjust your fuel screw.

What state of tune is your carb in?

Edited by Krannie, April 13, 2013 - 09:38 AM.


  • RMK800

Posted April 13, 2013 - 10:12 AM

#3

When I bought the bike it wouldn't start had set for a while. I took the carb out and ther was green varnish on all the jets. I soaked as much of the carb with see foam and cleaned with carb cleaner and air. I have not unscrewed the choke. Took the bike to my hometown and rode it pretty hard. It ran good, the fuel screw was difficult to get at so it wasn't starting the best.

I have since put in a merge brass fuel screw and dropped the leak jet to 40 based on the FAQ. The bike rips through 1-3rd gear but seems to have lag on 4th and 5th. 1 thru 3rd are more important but considering going to a 50 from the stock 60.

I guess I should pull the choke, maybe there is varnish in there?

  • RMK800

Posted April 13, 2013 - 10:23 AM

#4

With the new fuel screw I believe I have it adjusted. I have it at 2 1/4. Right now it's 50 degrees and the 45 pilot is popping on decel. I don't ride much at this temp and this should go away when it get warmer. I'm hesitant to change pilot until it warms up. I know I'm on the verge of one with this tempature and my fuel screw out 2 1/4.

My main is 162 considering 160 when it gets warmer. Plus seems a tad on rich side. I think it's a stock needle, there are no other clip positions. Is that stock?

Im at 3800 and ride to 9000ft.

The bike has the pipe snorkel, grey, sky blue disconnected and air box mod. Still has AIS connected.

  • Krannie McKranface

Posted April 13, 2013 - 10:32 AM

#5

Popping is from the AIS.
Your choke and hotstart will be corroded inside....
Replace the nut on top of hot start too, as they crack and leak air.

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  • RMK800

Posted April 13, 2013 - 11:36 AM

#6

Ok I'll do that with the hot start nut, pain to hookup. I'll look at the choke.

This is a side question. Done a lot of reading on jetting,o-ring mod etc.

When I first ride I notice slight hesitation so I went with the 40 leak and now 1st thru 3rd seem on but the other gears lag some.

William mentioned a smaller leak # for trail and larger for wide open.

I haven't done the oring mod, My question is, should I go back to to stock 60 leak and do the oring mod? Or change my leak to like a 50, something in between?

Would you do the oring mod no
Matter what?



  • Krannie McKranface

Posted April 13, 2013 - 01:45 PM

#7

The oring mod affects throttle opening issues, and has nothing to do with rpm or gear or speed.

The leak jet is a bypass jet that fills up the apump system. It affects apump squirt duration, only.
It is not a 'jet' persay, as it is static, and even works if the motor is not running.
Changing it will do nothing to how the bike runs, just throttle response, which will be vastly improved.

The merge racing apump linkage spring is a much better choice over the oring.

  • RMK800

Posted April 13, 2013 - 02:07 PM

#8

Thanks for that info. So when William1 talks about a lower leak jet for woods and slower riding and higher for faster. What is he saying there? Because what he is saying seems to effect lower slower gears vs higher and faster gears or maybe it has to do with throttle position. I really don't know, just trying to understand his comments in the o-ring forum with the leak jet.

  • Krannie McKranface

Posted April 13, 2013 - 03:08 PM

#9

He is defining the apump tuning for squirt duration, by changing the leak jet.
Small, smooth, on-off throttle openings are common for woods riding, so a more 'detailed' throttle response can be had with a larger leak jet.
Harder, quicker, longer on-off throttle openings are common for off-road and MX, so a smaller leak jet (more fuel, longer squirt) is desired, with a small tradeoff in the partial, quicker opening riding.

In my opinion, un-plugging the TPS, adding the merge racing apump linkage spring, and adding an R&D powerbowl II makes the motor feel pretty close to FI quality.

  • RMK800

Posted April 13, 2013 - 07:04 PM

#10

Ok, that explains thing. Thank you. I'm going to do the spring.

If you use the Merge spring do you have to mess with the AP adjustment? I looked at their install guide and this part is what worries me, on their doc they say the spray should just miss the slide. Thats straight forward even though i haven't seen that yet....Then they say if the slide moves a "few millimeters" then it's late and you have to adjust. I mean a few millimeters is not much. Maybe I'm over analyzing but this part isn't straight forward. Can I just take the approach and adjust for barely missing the slide I'm not sure about the late part.



  • Krannie McKranface

Posted April 13, 2013 - 07:28 PM

#11

Ok, that explains thing. Thank you. I'm going to do the spring.

If you use the Merge spring do you have to mess with the AP adjustment? I looked at their install guide and this part is what worries me, on their doc they say the spray should just miss the slide. Thats straight forward even though i haven't seen that yet....Then they say if the slide moves a "few millimeters" then it's late and you have to adjust. I mean a few millimeters is not much. Maybe I'm over analyzing but this part isn't straight forward. Can I just take the approach and adjust for barely missing the slide I'm not sure about the late part.


You are not over analyzing just not understanding it's purpose.....to fill the intake with a squirt of fresh un-vaporized fuel into the intake, immediately after the throttle slide lifts, and in direct proportion the the amount of lift and speed of lift.

So, if you adjust the squirt to hit the slide, and then keep adjusting the delay until it stops hitting the slide, no matter how you turn the throttle.....you are done.

It's best done with a flashlight, a well ventilated garage, a chair, and a friend to turn the linkage screw adjuster.

It takes about 5 minutes to adjust....plus the 20 min to get the subframe lifted up....

If the squirt is too short (does not fire all the way into the intake port), your leak jet is too big, or, your diaphragm is the wrong kind (long rivet).

If the duration of the squirt is too short (should be 1 full second) its usually the fault of the stock linkage spring not keeping up with the throttle linkage. Hense the upgrade.

Edited by Krannie, April 13, 2013 - 07:31 PM.





 
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