Exhaust Leak & Flat Mid Range

[Inazuma750]

Just bought this bike, it's a 2000 GSX750 and it's flat as a fart at anything above 1/4 throttle. If you go full throttle it try's to accelerate but struggles, then when you back off it picks up.

The carbs are what I believe to be standard Keihin CVK type. And the exhaust is standard.

It also has a leak at the link pipe to header pipe joint. I believe this is a fairly common thing and that the exhaust system is very similar to a bandit. 

1. Is it possible that the 2 problems are linked? i.e. exhaust leak is causing the lack of mid range?

2. If not the above what is a likely cause? Symptoms to me suggest a lack of fuel. I am planning on whipping the carbs off to give them a good clean in the hope this will sort it out.

2a. Anything I should be aware of with these carbs and pay particular attention to?

3. Is it the link pipe or the headers that rot away? I haven't taken it apart yet to find out. Any common fixes? 

Thanks in advance,

Jim

[Askamaskinservice]

Do you have the original airbox still on your motorcycle?

[Inazuma750]

Yeah the airbox is standard. I've ordered a new air filter for it, should arrive tomorrow.

[Shill]

It's specifically the collector box that rusts away, where the link pipe connects. That whole collar underneath can be taken off a new bit welded on - the actual downpipes and link pipe are fairly robust in my experience. Sounds like you're on the right track with carbs / fuelling, I don't have too much experience here I'm afraid! No  inline filter  or other restrictions in the fuel line?

[Inazuma750]

9 minutes ago, Shill said:

It's specifically the collector box that rusts away, where the link pipe connects. That whole collar underneath can be taken off a new bit welded on - the actual downpipes and link pipe are fairly robust in my experience. Sounds like you're on the right track with carbs / fuelling, I don't have too much experience here I'm afraid! No  inline filter  or other restrictions in the fuel line?

Thanks Shill, that makes sense, I'll get it stripped down and some tube ordered to fix the headers.

I can't see an in-line filter but till I get the tank off I don't know but thanks for the heads up.

[Gixer1460]

I'd be looking at slide diaphragms and springs, maybe needles/emulsion tubes in the carbs but after checking all the std. service items - plugs, leads, coils, valve clearances and air filter. An exhaust leak is unlikely to hurt power significantly - if it sounds like a tractor then maybe!

[Inazuma750]

1 hour ago, Gixer1460 said:

I'd be looking at slide diaphragms and springs, maybe needles/emulsion tubes in the carbs but after checking all the std. service items - plugs, leads, coils, valve clearances and air filter. An exhaust leak is unlikely to hurt power significantly - if it sounds like a tractor then maybe!

Thanks for this, I'll check these things too. Gut feeling says it's fueling, bike has only done 13k miles so my guess is there is some old gummy fuel in the jets, but I will give it a thorough service too.

[Askamaskinservice]

You have a filter screen in the fueltap that could be blocked or kinked fuelhoses is another option.

Somebody lifted the tank and didn't look how fuellines are supposed to run, when reassembly.