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FCR39 conversion- airboot too short?!

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Hey fellas,

I've hit a problem when trying to install my FCR39. After a lot of swearing, I finally got the carb out and got it installed. It lines up perfectly, but I noticed that the airboot is too short to make a seal with the intake of the FCR. 

The FCR39 is from an mx shop, as I live in Europe and the TT kit would end up costing a TON of money when taxes are paid. It doesn't have a removeable adapter, like the TT one does.

So, what can I do? I was thinking about getting an airboot from the E model, as it has the same carburator(?), and I'm guessing it's longer.

Also thought about getting some radiator hosing to make up for the gap, so it'd fit inside the airboot, but that isn't exactly a great fix.

Any help will be greatly appreciated guys!

 

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I think you need an fcr mx carb with removable intake. Also you will want to connect the rear intake connection to the carb first and then pull the carb towards the motor connection boot.

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You will need to get your thinking cap on if you've bought the carb with the non removeable intake

Easier to sell it and get the proper one imo

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I'd love to get the proper one, but it'll be ridiculously expensive, as I live in Europe. You can add about 30% of the price to the price on Thumpertalk, and that's not including shipping. I bought this for 400 dollars, used and completely overhauled by an mx mechanic. I got a jet kit, upgraded AP spring and an extended fuel screw also.

I managed to sorta fix it, I took some heavy duty radiator hosing which fits quite tightly over the airboot and is snug on the carburetor. Just need to clamp it down now.

It's running quite well- has a 160 main jet, 48 air jet, EMN needle 3th position. Still playing with the mixture screw, it's about 2 turns out now, but I'm not quite sure how to dial it in.

Setup is FCR39, K&N filter, 3x3, ABP header, Leovince LX3 muffler.

 

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don't worry , a workshop with a lathe can make an aluminium pipe having proper length and diameter. they remove the small step from the carb side and slide the new thin aluminium adapter. one end goes against the carb , the other to the boot. do not make it too long or carb will be difficult to fit

Edited by 30x26
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That's what I'm doing , a little adaptor pipe. Probably will have it so the id slipped over both ends with an o-ring on the inside for sealing , just need to make a way to clamp the carb .

Edited by jjktmrider
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yes, i  did one.  mine was for a removeable intake. for a fixed intake it's the same,  pipe will go against the carb instead of against the fixing screws.

being careful  not to dirty the air jets   it's also possible to seal the adaper from the inside.

Edited by 30x26

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I actually have a lathe myself. Good idea. 

The hose seems to work though. Can't ride it before tomorrow, as it's night here.

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I went the same route.  

I needed to make an adapter ring from the carb to the airboot.

It was just a simple aluminum tube.

You will need to file the little lip off the carb.

I stuck it on the carb with Silicone RTV.

Like other have said, you will need to change all the jets and needles.

Nothing too crazy, just go to any half decent dealership or order the jets online.

A RD racing flexjet makes tuning the mixture screw simple.

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I got it working with the hose, but I might do the same as you, Stuwy. 

I went for a ride today, bike runs well but I noticed a whine whenever I twisted the throttle over a certain amount. Any ideas?

EDIT: Will be removing the PAIR soon. I could imagine it causing the whine I was hearing. 

Edited by v0nsild

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By the way, do you think it's possible to drill the hole in the FCR39 to accept push/pull throttle configuration? I liked the feel of the throttle more with it.

 

I noticed there's what appears to be a "hole" for the push cable, but it isn't drilled all the way through.

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By the way, do you think it's possible to drill the hole in the FCR39 to accept push/pull throttle configuration? I liked the feel of the throttle more with it.

 

I noticed there's what appears to be a "hole" for the push cable, but it isn't drilled all the way through.

 

VOnsild , they come in many different configurations for many different applications , so if you have the blank parts and the two cable wheel on your carb , all you have to do is machine and tap it to take the cable .

 

I got it working with the hose, but I might do the same as you, Stuwy. 

I went for a ride today, bike runs well but I noticed a whine whenever I twisted the throttle over a certain amount. Any ideas?

EDIT: Will be removing the PAIR soon. I could imagine it causing the whine I was hearing. 

 

The whine you are hearing is the throttle plate vibrating , it sits loose on the slide and makes a whining /turbo sort of noise under hard acceleration . It isnt the pair valve making that noise and yes get rid of it as it is usless junk used to fool a gas anyliser , greg

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Oh, right. I just thought it was weird, lol. Sounded like a turbo and was only audible at around 4200 rpm. Thought it had something to do with the pair sucking air from the vacuum hose. Anyhoo, I'm almost done making a pair blanking plate, and will manufacture the adapter for the FCR so I can get my bike up and running.

Thanks for the answers everyone!  :thumbsup:

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Hmm. I think I'm going with the pipe solution.

Just not sure how to remove the ridge / step. Either file it by hand, or mount it in my lathe.

File is safest, but the lathe is going to be more accurate, with the risk of the carb launching through my workshop.

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File.

It's aluminum. 

It would take you longer to center it on the chuck in the lathe.

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I ended up using a dremel to sand the collar, and finishing it with a file. Finished the adapter, which just needs a thin layer of liquid gasket and then seal with the carb.

 

Thanks for the answers everyone!

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Looks good.

Your adapter might be a bit longer (just eyeballing it). Looks like you might have measured from the carb to the boot with the subframe disconnected (top bolt removed).

A quick test fit will help ya figure that one out before you silicone the adapter on.

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It IS actually too long. I'd rather remove some material than make a new. Going to remove 10mm from it today, which should make it a perfect fit. Might be hard to get it in there though.

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Perfect fit. Like literally perfect. It can't be rocked when you wedge it in place. Sealed it up and it runs just sweet now.

Only need to jet it now.

Currently at 160 main, 48 pilot which I'll back down to a 45, and an EMN needle 3rd clip.

Setup is 3*3, KN, stock cylinder and gasket afaik, 41mm header similar to the E I think, and an LX3 muffler with no baffle.

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