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Discussion Starter #1
Hi Chaps,

I am currently in the middle of an FCR41 conversion on my 03 LC4 640SM. I have removed the standard Mikuni and placed the Keihin on the inlet port. The carb I have has the throttle cable connections on the right (rear brake side) but the Mikuni `s connection was on the left. This makes the black cover tight to the frame. Is this right? The carb came off a Honda CRF450 and I am wondering if the top end is different for that bike. Any advice would be grfeatly appreciated.

Cheers
 

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Hi Chaps,

I am currently in the middle of an FCR41 conversion on my 03 LC4 640SM. I have removed the standard Mikuni and placed the Keihin on the inlet port. The carb I have has the throttle cable connections on the right (rear brake side) but the Mikuni `s connection was on the left. This makes the black cover tight to the frame. Is this right? The carb came off a Honda CRF450 and I am wondering if the top end is different for that bike. Any advice would be grfeatly appreciated.

Cheers
thats normal, ive seen a few without the black cover on but most sit on the frame or a few mm away.
 

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Discussion Starter #3
Thanks Tats,

Do you or anyobody else know if there are any other major differences I should know about. I have read up on some of the conversion things to look out for. I think I can reroute the wiring loom that goes from the frame over the carb and alongside the airbox. It looks like I might have to get an adaptor made up for the air box to connect to the rear of the carb. I think the throttle position sensor is not used although I dont know if you can just have it not connected or whether it will need some kind of dummy connector. Again, any help would be dandy.
 

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leave the tps unpluged matey. is the rear of the carb bolt on as you could get the right size mouth? if not making a bit up is easy enough. get it on a dyno and set up nice and hey presto
 

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Discussion Starter #5
You`ve answered me next question too. I was gonna ask about jetting seeing as it came off a 450 but like you said, probably just as well getting the jetting done at same time as a dyno run. Is it better to try and get the original air box to connect to the carb or would it be better to go for a K & N. I know the mikuni connector is offset as well as a reducer but the keihin looks miles away from lining up. Could be just cause I have the airbox loose I suppose.
 

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You`ve answered me next question too. I was gonna ask about jetting seeing as it came off a 450 but like you said, probably just as well getting the jetting done at same time as a dyno run. Is it better to try and get the original air box to connect to the carb or would it be better to go for a K & N. I know the mikuni connector is offset as well as a reducer but the keihin looks miles away from lining up. Could be just cause I have the airbox loose I suppose.
a dyno and jet to suit is what you want or no point fitting a badly runnin carb you wont get the gains, i dyno a few and have had them come in running worse less bhp etc with an fcr then with corectly setup standard lol.. i would leave standard airbox on a 640 if 660 maybe id say yeah but no real gains unless you tuning a few engine mods etc.
 

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Discussion Starter #7
Right you are chap. Thanks for all the info, will get back on here in a short while no doubt!
 

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good luck lol
 

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The problem I had was the bolts on the floatbowl cover touched the exhaust.
Are you using the standard 625/660 inlet rubber (carb to engine)
 

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Discussion Starter #10
I asked Tats whether or not to use the standard airbox or bin it and fit a K & N. If no engine mods are done there isnt much gain from ditching the standard airbox. I have the rubber connector but when the Keihin is connected to the inlet port the rubber looks like its never gonna line up. I am just hoping the reason for this is the airbox is still loose from taking the Mikuni out. Did you manage to use the standard rubber?
 

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No I bought new rubbers for a 660 and the one between the engine and the carb had an offset. I also binned the airbox and fitted the K&N
 

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Discussion Starter #12
Thanks Bags. Has the 660 got an FCR as standard then? Probably would have been cheaper and easier to have bought a 660 instead but there you go, thats what you get for being a lazy fooker who wanted an electric start. Would you recommend buying the 660 rubbers, sounds like it will make the install much easier. How much more room will it give you on the throttle side. I would have thought that having an offset would have restricted the flow. Did you have any other problems?
 

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Discussion Starter #13
Forgot to ask Bags, the tail tidy on yours is the absolute business. This will be my next project after the carb is sorted. I`m in a bit of a dilemma cos mine is an 03 and has a doma pipe on the left. I have been thinking about a twin tail pipe conversion like the model after mine so I think the tail tidy will have to be done at that time. Is yours bespoke or off of a different model?
 

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Hi I am also planning on this conversion of the CRF FCR41. (£85 Good ole ebay).
Can anyone post the part numbers for the rubbers as I ordered the air box side from Jersey and it doesn't even fit the carb or air box.

SM 03 with small air box.

Thanx in advance.
 

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just to reinforce what mr tattoo said about leaving the tps unplugged, i did this on mine a while back now and it runs a little smoother and has never caused ne problems only bennefits, i know some will say it`s there for a reason but from research that reason is eu regulations on emitions etc!!! mine runs better and the fueling is fine (has bin on dyno and fueling is spot on)
 

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Discussion Starter #16
Hi Tattoo, Your name is always the one that crops up when an FCR job is mentioned so I hope you dont mind me asking you a couple of questions. As you said earlier in the thread, I have got the carb onto the standard inlet rubber although its a bit tight. What do I need cable wise. I have had both original throttle cables connected but they dont seem to move too freely - I think its probably as a result of being twisted to fit. The main problem is the choke cable, the connector on the carb is different as you know. Do I need a special cable or a standrad choke cable from a 660. Is it worth changing the two throttle cables too? Any advice would be cracking
 

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idealy you want the cables and tube to suit the carb but can be all made to work with a bit of messing about re directing them etc. have you not got a choke lever on the carb not a cable operated one/lever? maybe it has a hot start on the carb?
 

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Discussion Starter #18
I`ll check tomorrow but I`m fairly certain the choke isn`t a pull lever on the side of the carb. There was a cable fitted to the carb on the opposite side from the throttle connections. Its a black plastic elbow with a hexagon nut and thread about 10mm thta scfews into the carb. Would you normall expect to see a pull type directly on the carb?
 

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the FCR carb is standard on the 660 and there`s no cable for the choke it`s just a small black pull lever a little higher and on same side as the hot start pull lever
 

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Discussion Starter #20
Thanks Scott,
I was a bit confused cos I downloaded the 625 and 660 manuals last night and the 625 shows a pull lever but the 660 shows a cable. On the carb I have the black pull knob which sticks out further and is nearest to the inlet port. The cable was connected above the inlet port. So is the black one the hot start and I will need to bin the cable and by a choke knob for the 660 from a KTM agent.
Many thanks as always
 
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