Tys

Yet another FCR Install Question

14 posts in this topic

I bought the thumpertalk fcr39 kit and am having someone else install it. I have read different posts about o-ring mods, removing pilot air jets,not removing pilot air jets, wire mods ect ect and looking at the directions included with the carb it says nothing about these other than the kit coming with an "adapter" o-ring. Am i overthinking all of this or are there other things that will need done than on included instructions?

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My understanding is leave PAJ alone on current TT fcr39 kit and the AP o ring mod is something you will want to do. Some people just use safety wire instead of the O ring as it doesn't wear out and less inclined to fail overtime.

I just installed mine a few weeks ago and strongly recommend you consider doing the work yourself. It's not very difficult, just take your time and read over the FAQ/tutorial here on TT.

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Tys , there are two different types of FCR , the slant body and the MX . The older slant body is the one that needs the o-ring mod and coast enrichener delete . The newer FCR/MX has changed from when it was first available . We used to have to remove the pilot air jet as it was probably sourced from a different application ( bike ) . But now , if you buy a new FCR/MX from the TT store , it will bolt straight on . The only thing you will need to do is check all of the jets and needles and make sure it is suitable for what you have , greg

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2 hours ago, hinksy said:

 The newer FCR/MX has changed from when it was first available . We used to have to remove the pilot air jet as it was probably sourced from a different application ( bike )

Not true; Neither Sudco nor Keihin designates a difference in any of the FCR's for that time period. It is a myth started by a guy who bilked a lot of people out of parts and money. :(

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If I take out my air jet it wont run very well , If i dont leave it in , on a newer one  , it wont run very well . It may still be an FCR/MX , it may still have the same part number , but they are different

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I have the same kit that I bought last fall.

Leave the pilot air jet in.

Take the time to measure the float level as it could get messed up during shipping.

You do need the o-ring mod or it will bog. Another option is the Merge Racing spring. It's a stiffer replacement for the spring on the arm.

I suggest removing the airboot and fitting it on the carburetor off the bike to stretch it prior to installation. Otherwise, you will play hell trying to get it on.

The easiest way I've found to install on the bike is to remove the tail pipe, rear master cylinder guard, the bolt from the coolant recovery tank, lower subframe bolts and swing the subframe up to the handlebars.

Fit the carb into the intake.

Fit the airboot onto the rear of the carb.

Drop the subframe back down.(pay attention to the coolant tank)

Loosen carb from intake and fit airboot back onto the airbox.

Use a big screw driver or pry bar to stretch the boot(pulling the carburator forward) and put the carburetor back in the intake boot.

It sounds like a lot but it's not. It's much better than having an unseated carb leaking air and causing jetting issues for us to guess over.

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20 hours ago, hinksy said:

If I take out my air jet it wont run very well , If i dont leave it in , on a newer one  , it wont run very well . It may still be an FCR/MX , it may still have the same part number , but they are different

What size idle jet are you running? I went  from no air jet and a 42 idle fuel, to a 100PAJ and a 40 idle fuel, just like the JD kit recommended and my bike idles much more consistently now.

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I would love to install myself but here lately i just dont have the time, thanks for the replies everyone.

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I installed my new FCR last weekend and took about an hour, but I had the stock carb out.  The spring, purchased from PROCYCLE , was the biggest PITA to install and very time consuming. 

Tys, it is quicker to install than you think.

Edited by RAE129

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31 minutes ago, RAE129 said:

The spring, purchased from PROCYCLE , was the biggest PITA to install and very time consuming.

You may want to keep an eye on that spring. I messed with it for a couple hours a few days ago and ended up going back to the stock spring.

Once I got the spring installed, I found that it was binding on the post and that wouldn't return the pump lever to idle. In all honesty, after messing with it I've concluded that I must be missing something as a rationale for this mod. Sure it hits the pump lever harder, which I guess produces a stronger squirt, but why does it run for 3+ seconds after the throttle is opened?

Seems to me most guys are trying to minimize the duration of the squirt?

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On 3/20/2017 at 6:26 PM, hinksy said:

The older slant body is the one that needs the o-ring mod and coast enrichener delete .

I thought that was only for FCR39MX, no?

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41 minutes ago, thnksno said:

You may want to keep an eye on that spring. I messed with it for a couple hours a few days ago and ended up going back to the stock spring.

Once I got the spring installed, I found that it was binding on the post and that wouldn't return the pump lever to idle. In all honesty, after messing with it I've concluded that I must be missing something as a rationale for this mod. Sure it hits the pump lever harder, which I guess produces a stronger squirt, but why does it run for 3+ seconds after the throttle is opened?

Seems to me most guys are trying to minimize the duration of the squirt?

I had that issue prior to installing the E-clip.  Once the E-clip was installed, all worked well. 

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30 minutes ago, RAE129 said:

I had that issue prior to installing the E-clip.  Once the E-clip was installed, all worked well. 

For me it worked fine before the e-clip. What was happening is the spring binds on the brass shoulder or the brass post, then it forces the black plastic pump lever up into the washer and e-clip causing it to bind. I tried opening the spring up to allow clearance for the brass shoulder and it lessened the binding somewhat, but it eventually bound up again. So, I widened it some more and it would still bind. Then I threw it in the scrap metals bin.

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1 minute ago, thnksno said:

For me it worked fine before the e-clip. What was happening is the spring binds on the brass shoulder or the brass post, then it forces the black plastic pump lever up into the washer and e-clip causing it to bind. I tried opening the spring up to allow clearance for the brass shoulder and it lessened the binding somewhat, but it eventually bound up again. So, I widened it some more and it would still bind. Then I threw it in the scrap metals bin.

I posted some pics of my install in your thread about the spring.  I have my FCR on the bike now and the throttle opens and closes perfectly with no snagging.  I wonder if the spring I received is different from yours.  Take a look at the pics on your thread and let me know.

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