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Discussion Starter · #1 ·
Hello everyone :wave:

I have a 2004 f650gs twinspark. It's my first proper bike as I my bike license is only couple months old :) Love it. So far: changed spark plugs, oil and air filters, new chain, front sprockets seals, oil, front tyre and rear break disk pads..hmm that's it.

However, we bought another one a 2002 single spark for my colleague and it's just so much faster, unbelievable. It just flies in comparison to mine. His bike done 17k miles (speedo might be changed) and mine did 38k.

The issue I have it does not rev to more than 6k - 6.5k rpm on the 4th and 5th gears. I thought it might be because of the exhaust, as the gas flows only through the right one, but last night I removed the exhaust pipe completely and had a quick ride around the area (neighbours were not happy) and it rides a little bit better, but just a little bit.. not even close to my colleagues. Mine does not accelerate more than 75-80mph while I did 90mph on my colleagues easily.

Thought might be an issue with an air flow sensor that screws in to the air box, but tried disconnecting it (unplug) and the bike felt even worse...

Any ideas? Fuel filter, air flow sensor? Valve adjustment? HELP :)

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Sounds like it could be restricted. Depending on the age of the bike, it would either be a plate on the throttle body which restricts the full pull of the cable or a second position on the cam for the cable which does the same thing.
 

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May well be 33hp limited, you'll see the throttle cable at the bottom end can be put on either of two pulleys, it'll be clear when you get there which one opens the throttle fully and which doesn't.
 

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Some bikes are sensitive to fuel pressure too - either the filter being clogged or the regulator being at the bottom end of the allowed tolerance. Replacing the filter/ regulator doesn't always help as much as it should as it appears that the factory is aware of the problem and checks the pressure regulators, fitting the better ones to the new bikes and selling the dud ones as spare parts. Most new Auto manufacturers recommend that you run a dose of fuel system and injection cleaner through the system regularly, every three months or so, so that may be an easy starting point too.
 

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Discussion Starter · #8 · (Edited)
Hi Guys, thank you for all of your replies. Today I swapped the position of the cable to the other position (check the image attached to this post). I can feel it revs a bit better (higher revs) but still the bike does not perform as great as it should.

Can somebody confirm that this is correct? http://marks-adventure.smugmug.com/photos/125186477-M.jpg

If that's correct so my next step is to use some fuel system cleaner and maybe replacing a filter. Any recommendations?

By the way, I should mention that the throttle rotation angle has decreased by at least 30% :)

Any thoughts?
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Discussion Starter · #10 ·
Just before I read this I actually found a problem myself! :) It was that bloody bracket that I need to order now :) Have a look at the video and THANK YOU ALL FOR THE SUPPORT! This is a great community and if you guys plan to do a road trip (Southampton or 30 miles range) please PM me :)

https://www.youtube.com/watch?v=q3cXml8pj2o

:bowdown::bowdown::bowdown::bowdown::bowdown::bowdown:
 

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I'd also bet that bracket is stopping it open as far as it should, it hits the stop just as the cable slips. Get that bracket and you should be fine :)
 

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I agree - my bike came like that - restricted bracket but cable on the full power cam. It was worse than restricted as the cable jams.

You'll need to order the unrestricted bracket (about £6). You'll also need a security torx key to get the bracket off. I got a set from Halfords for about £10.

It'll transform your bike.
 

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When you are unscrewing the bracket be careful to support the throttle valve body, as it is only supported by the rubber inlet manifold which is bonded to the metal fixing plate at the cylinder head, and if you are crack handed enough it is possible to pull the rubber away from the plate - DAHIK.
 

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Discussion Starter · #18 ·
Hahaha, finally, got part and replaced it today. Yes, the bike is absolutely lovely. Did not expect it has so much Juice in it :) Done 100mph but it became a bit wobbly, so I thought it's not worth going faster. Anyway, thank you for all the support, I would not sort this out without your help. Appreciated. :bowdown:
 
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