.... Mikuni Flatslides - Wrist Twisters
 
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post #1 of 13 Old 09-29-2011, 06:11 PM Thread Starter
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.... Mikuni Flatslides

...... Is there anyone in the group, that has a set of Mikuni F/S's on their bike??
If so, do you have an issue, with the RPM's not dropping, with the return of the throttle??.... and yes, I do have the push-pull system.

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post #2 of 13 Old 09-29-2011, 06:34 PM
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sounds like a clogged slow jet circuit paired with to high of an idle set.

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post #3 of 13 Old 09-30-2011, 11:55 AM
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Quote:
Originally Posted by nd4spdbh View Post
sounds like a clogged slow jet circuit paired with to high of an idle set.
sounds right, or a sticky choke due to clogged slow jet circuit. either way, clean out the carbs for sure.

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post #4 of 13 Old 09-30-2011, 10:36 PM Thread Starter
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..... Thanks for the help......I will clean again!!

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post #5 of 13 Old 09-30-2011, 11:58 PM
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Quote:
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..... Thanks for the help......I will clean again!!
those lil slow jets and slow circuit's clog really easily... make sure u get the bowls REALLY clean as well as the slow jets etc.

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post #6 of 13 Old 10-02-2011, 12:03 PM
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again i agree with nd4spdbh, more so on those specific carbs! if you're struggling to get em cleaned well, strip everything off of the carbs until all you have are the carb bodies themselves, and put them into a pot of boiling water for 10 minutes or so. when you take them out, let them cool back down on its own. before you reassemble, blow air through every passageway you have to clear out any sitting water and you'll be set to go.

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post #7 of 13 Old 10-02-2011, 07:23 PM Thread Starter
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...... Thanks guys,.. the carbs. are fairly new. and I have had them apart many times, changing main jets, pilot jets, and the height of the needle jets and float levels.
I do use compress air with wd40 to clean, every time. ..... one thing about the Mikuni 38mm F/S's,... they have very few parts.

I do believe, that some of the problem with the throttle sticking wide-open is, high vacuum pressure. even with the push-pull system..... the new motor, creates a tremendous amount of vacuum.
so, I am not sure, if this can be fixed. I heard some where, that Mikuni stop building flatslides, for the street..... just for that reason.

Keihin F/s's, have ball bearing on thier slides. but, they cost, almost twice as much as the Mikuni's. and, I also heard, that they are a bear to keep tuned.
what to do ??

thanks

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post #8 of 13 Old 10-02-2011, 07:27 PM
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Quote:
Originally Posted by brook View Post
...... Thanks guys,.. the carbs. are fairly new. and I have had them apart many times, changing main jets, pilot jets, and the height of the needle jets and float levels.
I do use compress air with wd40 to clean, every time. ..... one thing about the Mikuni 38mm F/S's,... they have very few parts.

I do believe, that some of the problem with the throttle sticking wide-open is, high vacuum pressure. even with the push-pull system..... the new motor, creates a tremendous amount of vacuum.
so, I am not sure, if this can be fixed. I heard some where, that Mikuni stop building flatslides, for the street..... just for that reason.

Keihin F/s's, have ball bearing on thier slides. but, they cost, almost twice as much as the Mikuni's. and, I also heard, that they are a bear to keep tuned.
what to do ??

thanks
intresting. what are the fuel screws set at. sounds like you have a modified motor... have you gone up in the slow jet sizes? i know on my crf250x its stock 40 size pilot was alright ... open up the airbox and it just wasnt enough, it would idle but you had weird idle drop issues like your describing... simply bumping just a lil to a 42 solved all problems.

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post #9 of 13 Old 10-06-2011, 02:14 PM Thread Starter
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..... sorry for the delay, by the owners manual, the fuel screw is set at a 1/2 turn out.

about the motor, the FJ1200 starts out at 1188cc's, it is now 1349 with some extra goodies.
..... nd4spdbh, I think I found the problem. I went for a ride last night. and it was bad..... to the point where I had to speed shift to keep the r's down.
..what I think it may be is, [along with the vacuum], the throttle springs, I changed the stock springs, because they were to hard on the wrist [to stiff]. so, I went to a softer spring. need to find a in between.

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post #10 of 13 Old 10-06-2011, 06:08 PM
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Quote:
Originally Posted by brook View Post
..... sorry for the delay, by the owners manual, the fuel screw is set at a 1/2 turn out.

about the motor, the FJ1200 starts out at 1188cc's, it is now 1349 with some extra goodies.
..... nd4spdbh, I think I found the problem. I went for a ride last night. and it was bad..... to the point where I had to speed shift to keep the r's down.
..what I think it may be is, [along with the vacuum], the throttle springs, I changed the stock springs, because they were to hard on the wrist [to stiff]. so, I went to a softer spring. need to find a in between.
ah ya, if the slides cant move back down then theres your problem.... you might consider taking the slides out n making sure there are no burrs or anything, then maybe spraying with a teflon lube or something.

that never any fun having a runaway bike of sorts.

You can also go back to the harder springs, but run a smaller tube so you get an overall softer feel at the throttle, but still same original stiffness in the carbs.

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post #11 of 13 Old 10-07-2011, 06:10 PM Thread Starter
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......yes, I did check for burrs,.... did not use telflon lube, good idea.[will next time]
did change the spring, [last night] it's not to stiff and has a good spring-back.
going out tonight.

thanks

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post #12 of 13 Old 10-13-2011, 05:29 AM
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Some flat slides have been known to stick, engine vacuum sucks them to the side of the carb, springs may be the fix.

I'm also riding a FJ1200, great machines!

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post #13 of 13 Old 10-15-2011, 11:33 PM Thread Starter
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......I think I have the carb. problem fix......[ right now, I am working on the wiring harness]

that's great to hear, not many FJ's in my area!!
Can you tell me a little about it?? what year? is it stock? how does it run?

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