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  #1  
Old 21-02-2006, 12:14 PM
2rabbits 2rabbits is offline
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Default GS750 carb tuning

Does anyone know of someone who knows the GS range well and how to tune/modify them? (preferably SouthEast but prepared to put it in back of van and travel!).
My '79 GS750 chop came to me with unidentifiable conical gauze filters and I just cant get me head round tuning the carbs up - all the messing with jets and the stuff about E-clips is just too much for me (must be getting too old or too impatient)! I just wanna pay someone to do it now! There must be someone out there who just knows the engine well and will know an instant filter+jet set-up that works and who understands all the stuff that baffles me!
If anyone knows a good GS tuning guy....??
Thanks alot,
Cheers,
2R.
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  #2  
Old 21-02-2006, 01:02 PM
Blackjack Blackjack is offline
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If Bristol isn't to far, try Tim Blakemore Racing, Kingswood, Bristol.

He's sorted out a few things for us and I've always been very happy with it. Getting it done on a Dyno has some major advantages, you can actually tell whats causing the problem instead of taking wild stabs in the dark for a start!

http://www.timblakemoreracing.co.uk/
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Old 21-02-2006, 01:12 PM
minxy minxy is offline
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Why do you want to tune the carbs? Is it to compensate for the aftermarket filters? Is the old gal not running right?

Sometimes the best thing to do is get it on a dyno. They can adjust the floats / needles and jets if need be all in one shot and you'll get a dyno sheet to prove the old gal has lovely curves
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Old 21-02-2006, 03:07 PM
devon-tony devon-tony is offline
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thanks for the info blackjack, might not be of use to him but is to me, been looking for a decent RR tuner for a while, My Zephyrs gonna need paul daniels to get it right, wierd exhaust not quite the right length, and free flowing filter
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Old 21-02-2006, 04:14 PM
2rabbits 2rabbits is offline
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Thanks for the info so far. In reply to Minxy's question -- the unidentified conical filters on the carbs are letting in far too much air so the bike wont run. I need to put jets in that are several sizes bigger to increase the fuel flow and get the mixture right. But I've been on the GSResources forum where there's some experts and it seems that if you want it running right its not just the main jets you need to change, theres also the pilot jets and something called the the E-clip which needs to be right. I either need to mod the carbs to match the filters or ditch the filters for a known filter/jetting that we know works well. I just need someone who knows exactly what they're doing!
Thanks, Blackjack,too. Bristol's OK, I might try Tim - but any more recommendations are very welcome!! Thanks, guys.
2R
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Old 21-02-2006, 04:26 PM
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chazz chazz is offline
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i got a complete carb kit from nrp carbs in manchester,resonable price aswell,
www.nrp-carbs.co.uk
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Old 21-02-2006, 04:36 PM
minxy minxy is offline
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Usually, rough rule of thumb is 10% increase in the main jet size to accomodate for aftermarket filters / exhaust.

You say south east - StraightLine Racing are good with Suzukis and have a dyno in your area. Bear in mind though that if your exhaust system really is 'odd' then it may never 100% run properly. Mate of mine was building a fighter for a customer who insisted on having an exhaust as he designed but it was just never going to run right.

Post a pic of the bike up so we can see! I've got to see these exhausts now

For a short fix and just for your own curiosity, try taping up the filters to reduce airflow and see what happens.
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Old 21-02-2006, 04:58 PM
devon-tony devon-tony is offline
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think the one with the odd exhaust is me :P

LOL

tim is cool, spoken to him, 220 dynojet kit fitted etc, ride in ride out, or for me trailer in trailer out LOL

booking it in with him as soon as I know its going back together ok
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Old 21-02-2006, 05:22 PM
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Quote:
Originally Posted by 2rabbits
Thanks for the info so far. In reply to Minxy's question -- the unidentified conical filters on the carbs are letting in far too much air so the bike wont run. I need to put jets in that are several sizes bigger to increase the fuel flow and get the mixture right. But I've been on the GSResources forum where there's some experts and it seems that if you want it running right its not just the main jets you need to change, theres also the pilot jets and something called the the E-clip which needs to be right. I either need to mod the carbs to match the filters or ditch the filters for a known filter/jetting that we know works well. I just need someone who knows exactly what they're doing!
Thanks, Blackjack,too. Bristol's OK, I might try Tim - but any more recommendations are very welcome!! Thanks, guys.
2R
I had some grief with my GS550,Earl on the GSResources was very helpful.The E-clip they're talking about is on the needles in the slides in the carb,you use it to raise or lower the needle,raise for rich,lower for lean.It's just a wee circlip that looks like an E.I'm running pod filters,can't remember the main jet size,different carbs anyway,but as I remember you raise the needles one notch,remove the breather pipes between carbs 1 & 2 and 3 & 4 (helps cut down turbulence in the float bowls apparently),and make sure your float levels are correct and identical.If you PM Earl (Earlfor) or Keith Krausethey'll be able to give you proper settings ar at least a baseline to start from.Also they'll give you settings for themetering screws at the front of the float bowls (the ones that the Haynes book of lies tells you never to touch!).With their help anda bit time and patience I've got my 550 running better than she has in years.Hope this helps and good luck.
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Old 22-02-2006, 10:54 PM
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Just an aside really, way back when I had a GS850 GN (slide carbs) had a hell of time setting them up...turned out the o-rings under the inlet rubbers were hard and leaking. Replaced them and they tuned up lovely and balanced easy. Then worked on my brothers GS750 (with GS thou top end) and it had the same problem.

I'd check that they are all sound on your GS (or just replace them to be on the safe side), or you may have more trouble than you need. Good luck.
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