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Carb conundrum (help please)


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I wish I could provide you with some answers @icpreybut I feel like I’m in out of my depth on this one. 
I borrowed a set of carbs from a friend a while back setup standard spec (112.5 mains) and they didn’t have a flat spot. Now I’ve finally got back to standard spec the flat spot is still there and dies at 1/4 throttle and yet I’ve used these carbs in the 7/12 (changing only the needle, emulsion tubes, mains) and it ran fine so it’s not the slides or the floats. I’m just at a loss

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While you know I've been battling the carb demons myself, and freaked when the same cylinder went again and flooded after double checking everything and add a loose clutch starter bolt reeking havoc, pulling the plug to clear the cylinder shows I've gone and lost spark again on Cyl 1 and maybe more, time I get to checking it.

If you think about the way you express your results now, it works on one bike but not on this one, well maybe take the carbs out of the equation.  Look elsewhere.  But I feel for you, it's your call.  I've been there before and walked away dejected.

I also met the new owner some time later who chuckled as he told me it was a ground to the firewall I had missed (car) and a 5 cent connector fixed it!

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@icpreyman I’ve chased everything! I’ve swapped CDI, coils, leads etc to prove it wasn’t electrical. I’ve cleaned, rust prepped and sealed the tank, bought a new fuel tap, new fuel lines, put fuel filters in to prove it wasn’t fuel. I even swapped the whole motor as a mechanic once said a valve might be sticking or some shit. I’ve replace everything but the *ucking frame and body work!!

anyways. I put the 1100 DJ kit back in those carbs and the flat spot has gone from 4-5k so I’ll put the tank back on and give it a test run later.

 

i did think I may have found the problem as I was putting the super long bandit 12 carb vent tubes on as I think this bike had none when I got it. I saw in the manual that this tubes are normally only about 5cm long and the bandit ones are about 40cm long! 
I forgot to test the theory before pulling them out last night. I put the 1100 DJ kit in the carbs and ran it withOut them and then put them back on but it didn’t make a difference 

got me absolutely buggered why the OEM needle/mainjet doesn’t work

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Ok so I finally got to take the bike for a spin. Last time I had the Dynojet 1100 kit in there I had 124 (dynojet) mains and the high flow airbox filter so I set it up the same. 
being that I made my own air filter restrictor to go in the existing one I thought I’d take them with me and try all three stages as they’re kinda easy to swap on the go so started with no restrictors and it’s bloody well perfect!! No flat spot like last time. Pulls really well all through the rev range! I’m actually surprised how well it does go for a 750 and the amount of bottom end torque it has! 
 

anyway.....that’s that I’m not touching the bastard again. Still can’t for the life of me understand why the OEM needles, needle jets and mains wouldn’t work. Time to bolt it all together and got on with the other bike (y)

Edited by Otatts
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