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Discussion Starter #1 (Edited)
Hi guys. Im new to the site so go easy on me. Im not a mechanical mastermind so be nice :)

I have just bought a 520 exc 2001 to go over to the Isle of Man on for road use, but im having problems. Theres a list so be prepared. So its a 520 exc, been sitting for 5 years according to the seller.

1. The main issue I have is the bike runs on choke, idles low. But pops and bangs if i rev and let off the throttle when the choke is off and it cuts out if i dont rev it.
Ive heard there 2 chokes, one with a nipple on the end, and one with out. I think mine is 'with' because when i push the choke it i see a little thin bar block a hole on the carb (the carbs off the bike and i took the 'Flat CR' marked top off)

2. Ive looked in the repair manual and the carb specs mention a restricted version 12.5kw with a different jet needle. How do i know if mines the restricted one? does the slide door open less?

3. All the pictures on google suggest the fcr mx 39 has a hot restart knob. Mine only has a choke, no red knob. Has someone installed a standard fcr 37 or 39?
*Edit; I think some MX carbs have the hot re-start, and some dont. Fleabay number example; 270913786310 !Confused!

4. Is it worth getting new jets just to be safe? If so can you recommend jetting for road use, and where to buy from. I need fastish delivery and money is an issue at the min.

A thank you in advance, all help will be appreciated.
 

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been sitting for 5 years according to the seller.

well that is the main problem. you need to take the carb off and clean out every jet and airway using a high pressure airline, carb cleaning sprays. i also use the nossle cleaning tool from a oxy act set to make sure the jets are clean.
REMOVE all jets and emultion tube to clean. don't give them a quick spray and come back on and say its 'been cleaned'. the old petrol in the carb will have gummed up all the small holes and airways.
 

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Discussion Starter #3
Thanks for the reply John. The carb is still off, so that will be my next job.
Would it be worth soaking the jets in carb cleaner over night and then doing the steps you suggested aswell just to make sure?

With the emusion tubes. Are they deep in the centre of the carb, or easy to get to. Ive had a search through the repair manual and on google + images.

Ive printed of the repair manual, and planning on taking the carb apart, step by step this evening hopefully.

Thanks for the reply
 

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the emulsion tube is below the main jet in the centre of the carb. the jet screws into it. use a 7mm (? or 8) spanner to undo it. clean out all the side holes if they are gummed up. also there is a smaller jet that has tiny holes that need cleaning out. take out the mixute screw too and blast it all clean. should run ok after that.
 

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Following advice from KevInYorks (the guy is a genius)

OBEMN needle with clip at 3, 160 main, fuel screw 1.75 out

I did this to my 520 and it made Starting a lot better and it is smoother throughout now.
 

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Discussion Starter #6
Thanks guys.

John, I will give that a go soonish. A mate has a compressor, so I will con him into letting me use it.

Chris, Any idea where you can get the parts... cheapish. With the needle clip, is that 3rd from top? or bottom?

Thanks again!
 

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3rd from top.

Allens Performance for jets.... its worth fitting new ones regardless.

It it was restricted (which it wont be) there would be a big plastic cover over the air filter, a pepperpot in the end of the exhaust and a throttle stop screwed in to replace the needle allen screw.
 

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Discussion Starter #8
I want to get new jets, but money is very very tight at the minute after buying the bike. Should be using the compressor on them tonight. I will get some photos up of progress at some point.

I checked the markings on the needle, and they matched the non-restricted specs in the repair manual. And it hasnt got anything youve listed!

There was loads of dust and dry dirt under the diaphragm, and some of the same stuff elsewhere. I would imagine after using the carb cleaner there would be an improvement, but im sticking to John's advice in using an air compressor :)
 

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the new jetting / needles you've been advised to buy do make a difference. made my 450 hit very hard out of turns. not very expensive either. less then a tenner as far as i can remember.

ref the compressed air. i fix a flexible plastic hose to the air gun and press this against all the openings and blast it through. hold up the jets and tubes etc to the light as you can often see if its blocked a bit.
 

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When you take the fuel screw out the bottom of the carb there should be a spring, washer and O ring in that order. Get them out before you start with the airline cos you will never find them when they fly across the garage!
 

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Discussion Starter #11
@John, Im gonna give Allens Performance a call in a sec, to see if he has a OBEMN needle. Already ordered a 160 jet and a '22. GASKET WASHER THROTTLE VALVE' <<< ref from speedaway.co.uk because it changed shape under the carb cleaner.
*Edit; just got off the phone, they said they only do the OCEMN needle, which the brass equivalent. as the OB is aluminium.

@Kev, I got the long mixture screw out with the spring, but had no luck with the o-ring. It does suggest using a compressor to get the spring and o-ring out in the manual. I might do it in a bucket or small space, so if it does fly out, it wont go far. *fingers crossed*
 

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Discussion Starter #13
I just paid £10.32 for the needle include VAT and postage. Shame I didnt get the Jet from their to, as I paid £6-7 from Speedaway.
 

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Discussion Starter #15
I just read over your first post, about the fuel screw, o-ring washer and spring.
When i took out the mixture/fuel screw (same thing?). I remember there being the long screw, the spring and the oring is stick in the bottom. But a washer? Im sure I didnt see a washer
 

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Buy a spare clip for the needle cos they can sometimes go under cover on the bench or make a desperate attempt to escape... just as you were confident you had the little bugger under control ;)
 
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