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jets needles and more hassle

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curryhead
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Joined: 19 Jun 2002
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PostPosted: 10:39 - 19 Aug 2002    Post subject: jets needles and more hassle Reply with quote

if i wanted to put a sports exhause with the down pipes and end can on a two squeak err say a dt 125r for instance would i have to rejet the carb even though the manufacturers have said that i wont need to. but you usually do dont you and you need a rolling road to set it up properly. am i right?
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Joe Camel
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Joined: 19 Jul 2002
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PostPosted: 15:35 - 19 Aug 2002    Post subject: Reply with quote

Rejetting is not ALWAYS needed, see how it runs first...

for example, if it runs OK high up the revs but crap low down, then you need to add more fuel in the midrange, try dropping the needle one notch at a time and see if it improves. Conversely, if it is OK low down but runs out of puff high up the rev range, lift the needle ONE NOTCH AT A TIME. this can make a massive difference.
If you do put a bigger main jet in beware of overfueling, this will give you lots of "bogging down" as you open the throttle.
Also with a bigger jet there will be less vacumn to lift fuel. slow throttle response is often a symptom of this, try the pipe, with a good filter, ie K&N or powerflo, befroe messing with carb.
This will end in tears without the proper test equipment,

good luck.
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Hunter
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PostPosted: 17:25 - 19 Aug 2002    Post subject: Reply with quote

You maybe able to get away with messing about float levels and needles in the carb. A plug chop should tell you what exactly is going on inside the engine when you put a new pipe on.
Cool
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 22:49 - 19 Aug 2002    Post subject: Reply with quote

zx7ruk wrote:

for example, if it runs OK high up the revs but crap low down, then you need to add more fuel in the midrange, try dropping the needle one notch at a time and see if it improves. Conversely, if it is OK low down but runs out of puff high up the rev range, lift the needle ONE NOTCH AT A TIME. this can make a massive difference.


Err, wrong way round. You drop the needle to lean the mixture and raise it to richen the mixture

Most road bikes are jetted fairly rich for safety. You will probably get away without rejetting but if you are unlucky or the pipe is substantially different then it will cost you a piston!

All the best

Keith
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Ropehead
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Joined: 02 May 2002
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PostPosted: 23:31 - 19 Aug 2002    Post subject: Reply with quote

the Dt and TZR hav a 170 Main jet , when i put a race exhaust i ended up tacking it up to a 180 to get it right, so not a HUGE diffrence.

Just have a play about and do some PLUG CHOPS
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curryhead
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PostPosted: 07:51 - 20 Aug 2002    Post subject: Reply with quote

plug chops? en anglais s.v.p.
but could you ride it around without causing any dammage to it with the smaller jet instead of putting on a 180
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Ropehead
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PostPosted: 12:42 - 20 Aug 2002    Post subject: Reply with quote

PLUG CHOPP>
drive along keeping the engine at about 8,000 then press the KILL swich pull the cluch in and roll to a stop, remove the plug and check to see what its like,,, it should be coffee brown ,,, lighter. to hot needs bigger jet... oily brown needs smaller jet..

EASY Wink
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curryhead
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PostPosted: 15:21 - 20 Aug 2002    Post subject: Reply with quote

doesnt matter now any way as ive just bought my mates mini for a hundred quid. il just have to wait untill the ti rod comes out before i can ride another bike so see y'all in 5 years at bh
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