Bike stutters at full throttle

[ChewyZA]

Hi all,

I am new here and its been my dream to own a 400cc grey bike so I bought one today! I bought a Suzuki Gk76 ok so I am expecting some problems to be worked out but this issue has got me clueless. The bike starts up immediately when pressing the starter, when I get on the road and I give it some gas she goes but when I begin to open the throttle by lets say more than 40% its like its bogging and struggles to gain revs and the bike would sound like cutting off revs at so 8000 - 12000rpms. If you slowly give it gas and let the revs build up it will go up to 13000rpms but try to open full throttle from low revs and it start bogging again between 8000 -12000 revs. If I hold in the clutch will riding and give it full throttle the revs jump to so 10000rpms and immediately the rev needle will sit at 6000rpms will I am still giving throttle. Any ideas?

[Variablevalves suck]

Hi, does it need choke to start?
Have a look if its smoking when you give it throttle, sounds like it might be rich.

[ChewyZA]

Thanks for the reply, I will try checking the choke and see for exhaust smoke as I get home and see what happens, also I noticed the fuel tap was on reserve don't know if this has something to with it but I will switch it to primary and hope it works

[ChewyZA]

So I got home and tried starting the bike, it wouldn't start. I noticed one of my carbs were leaking petrol and it gets worse as I open throttle, I did manage to get her started by pushing starting it and it idles fine just that petrol keeps leaking. Before I bought the bike I was aware that it was standing for 6 months. So this may sound stupit but the mechanic cleaned the carbs by soaking it in petrol for a whole day (his the mechanic so who am I to question his methods I just wanted to hear the bike running). Image of the leak below, if I am sitting on the bike its the carb on the far right thats leaking the rest appear fine. What should I do?

https://drive.google.com/file/d/0B152-u ... sp=sharing

[Variablevalves suck]

You most likely got a sticking float so will need to check that carb out.

[ChewyZA]

Found a video on Youtube video on how to take off the carbs, thank you Glimmer!
So I took off the carburetor and gave it a good clean, I found the one carburetor that was leaking petrol from the vent below that the slow jet was missing a rubber and another one of the carbs had badly damaged rubber on the slow jet. I managed to get this rubber and it fits nicely. The floats were all different height levels, the float in the carb that was leaking petrol had the lowest height and from each carb next to it the float height increased till the last carb. So I adjusted the float of all the carbs to match the height of the carb with the most raised float, was this the right thing to do? I put everything back together and tried to start the bike, no joy. I was told my issue is the carbs arent supplying the petrol because I just cleaned it and it will be dry and that I had to spray petrol through the through the 4 holes that lead to the carb from the Air filters box and she started! Does everyone have to do this when the start the bike after cleaning the carbs?

[mcglynn]

Should just have to move the tap to the 'prime' position mate. This is used to fill the carbs then the tap can be moved back to the on position

[james724clapp]

There is also a known issue with o rings used in these carbs, search for "the great GSXR400 carburettor saga" loads of good info, my save you a whole world of pain.

[mcglynn]

I replaced the orings in mine recently and had to squirt a bit of petrol into the airbox to get it going.