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Discussion Starter · #1 ·
what is the part number or wahat is the return spring off of that replace the one on fcr 39mm carbs to make the thumb throttle easyer I ask the guy at the local cycle shop and he sead he didnt know
 

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I got mine from Terry Gesick. You can also unwind part of the spring that is on it IIRC. Willykiller was talking about this at one time but I have never done it to mine personally.
 

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Call Terry that is were I got mine from.
 

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Discussion Starter · #4 ·
im runing 175 jets on my 720 it seams like its loading up but if i give it 3/4 throttle it runs fine I had a set of 162 I put in thay were to small but it still had the same sound as 175s what uther adjustment can I do I think the 175s are the right size
 

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Have you done done WOT runs and pulled your plug or "plug chops"? If 175 sounds like its "loading up" but 162 is too small then you need to look at your plugs. What are the symptoms of "loading up" that you are experiencing? Power loss after long full throttle runs?
 

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Discussion Starter · #6 ·
If I try to give it like 1/4 throttle and run it around the yard in 1st or 2nd it runs roughkind of poping but if I hit the throttle it picks up and runs good its the puting around that it dont want to do and if I give her hell and go through the gears and win im ready to stop and idle it wants to die I have the idle turned up as far as it can go ill cheack the plug tonight thanks for all the help im tired of dealing with the shops around hear ya pay them and it still dont run right I built this one frome the frame up
 

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Discussion Starter · #8 ·
the plug was black with a lil carbin build up
butt i was starting it and leting it idle a fue times after I got all the parts on I needed to start the motor
 

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If I try to give it like 1/4 throttle and run it around the yard in 1st or 2nd it runs roughkind of poping but if I hit the throttle it picks up and runs good its the puting around that it dont want to do and if I give her hell and go through the gears and win im ready to stop and idle it wants to die I have the idle turned up as far as it can go ill cheack the plug tonight thanks for all the help im tired of dealing with the shops around hear ya pay them and it still dont run right I built this one frome the frame up
If it runs fine at full throttle then you need to get your main dialed in first. Get some new plugs and do plug chops. If your needle/pilots aren't right then it will give you a false reading (for your main) if you putt too much.

Main - WOT through all gears (preferably on slight uphill and hold in 5th for a little bit), pull clutch and shut off. The main jet will affect the base of the porcelain and you will likely have to cut the threads off to see it.

After the main, adjust your needle close. The pilot/screws can be adjusted to get a good idle and transition into the higher RPM range. If its loading up from "putting" then likely your needle/pilot need some tweaking.

You want to start from the top down with the jetting but obviously you need to double check the main again when its all said and done.
 

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Discussion Starter · #10 ·
I talk to the guy that clean up my fcr's and rebuilt them he sead he set the needle is set in the middle im gona try to drop it a clip I just go in from the top of the carbs to get to it ? Iv never workt on carbs before
 

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Yes. You should be able to pull the tank of and access the needles/slides from the top. You will need some good allen wrenches.
 

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Discussion Starter · #12 ·
took the tank off and seen what I think is a vac line I didnt hook up its at the top back side of the carbs above the air box tubes in the middle if it is the one that goes to the air box do I need to hook it up im runing a aluminum air box with a k&n no lid ?and I let the bike run till it got good and wormed up with the 162 jets and it runs chopy like the 175s did same spots on the throttle about 1/4 throttle
 

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what about that line I was talking about ? Im tryn to get it ready to go to the local track sunday if I can
Its a vent line put a one foot hose on it...............let it hang down but secure it.........
 

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Discussion Starter · #17 ·
do I move the clip on the needle one clip or two at a time ? I called sandtracks he sead move it two clips to do any good I downloaded a fcr tuning manual and it sead to move it one clip at a time
 

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It depends on how much change you want to see at once. Moving the needle one position at a time gives you finer tuning... moving two will affect the change more.
 

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Depending on your portwork. If both the left and right intakes have been matched pretty close in the head then yes. If the left intake mainly feeds the left valve and the runner to the middle valve hasn't been increased then the left/right carbs will have different jetting/needle possitions.

Both of my carbs are jetted identical because my portwork is identical for the left/right intakes.
 
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