Acceleration flat spot - GSX750

[Rhubarb]

My 1986 GSX750ES has developed a flat spot when accelerating out of corners.

It only does it when the engine is hot. As I reach the apex of the corner I apply throttle to accelerate out of the corner but for a split second nothing happens. Then the throttle kicks in and away I accelerate.

The moment of zero acceleration is very un-nerving and with the strong winds on the way back from the Burt Munro Rally it got quite dangerous. (I went to accelerate out of a corner and nothing happened, a gust of wind stood me bolt upright. Then the acceleration kicked in and sent me into the gravel edge and towards a ditch)

The accelerating flat spot seems to only happen when I go from no throttle to throttle. It doesn't matter if I am going from zero throttle to 25%, 50% or 100% throttle.

Does anyone have any ideas? I look forward to your input.

[hayd3n]

bumping for ya

[Rhubarb]

bumping for ya

I'm sorry I don't understand your post.

[gammaguy]

its an old bike,could be anything.check for water in the fuel might be a good start.

[Rhubarb]

its an old bike,could be anything.check for water in the fuel might be a good start.

Excellent idea and a relatively easy fix if thats the problem. It's a good place to start.
I'll flush the system this weekend. Thanks

[hayd3n]

I'm sorry I don't understand your post.

i used the term bump to bump your thread as it will keep in the top posts

i couldn't answer your question but tried to help by keeping posts current

[FruitLooPs]

Mikuni BST series carbs yeah, probably BST33's or similar?

clean them out thoroughly, check nothings blocked following this guide:
http://www.gixxer.com/forums/showthread.php?t=159718

And check your emulsion tubes which might be ovaled out by now causing excessive richness down low.

[F5 Dave]

Good call. Suzis of that era have bad tank silting problems. Open the carbs & if they have rust silt in them then they will need all the jets taken out & blown through & inspect. My old GSX SZ (kat) for example had 1cm of crap in the bottom of carbs.

Then tank will need a sealer applied or it will happen again, do a search, filter won't really help & causes other issues. Do a search if want to learn about sealers.

[Rhubarb]

Mikuni BST series carbs yeah, probably BST33's or similar?

clean them out thoroughly, check nothings blocked following this guide:
http://www.gixxer.com/forums/showthread.php?t=159718

And check your emulsion tubes which might be ovaled out by now causing excessive richness down low.

Thank you all so much for the great idea's.

My weekend is now sorted - garage bound on the GSX.

[Rhubarb]

i used the term bump to bump your thread as it will keep in the top posts

i couldn't answer your question but tried to help by keeping posts current

Ahhh .... I see. (I'm still new at this)

Thank you for your help.

[The Pastor]

could also be worn jets & needles

[Rhubarb]

Good call. Suzis of that era have bad tank silting problems. Open the carbs & if they have rust silt in them then they will need all the jets taken out & blown through & inspect. My old GSX SZ (kat) for example had 1cm of crap in the bottom of carbs.

Then tank will need a sealer applied or it will happen again, do a search, filter won't really help & causes other issues. Do a search if want to learn about sealers.

Carbs had a bit of silt in the bottom. The tank on the other hand had alot of silt / rust especially around the filter and tap.

I've replaced the air cleaner as well. It wasn't too bad but good fuel flow also needs good air flow.

I just need to search for a sealer for the inside of the tank - any idea's?

Thanks for everyones help.

[Max Preload]

Carbs had a bit of silt in the bottom. The tank on the other hand had alot of silt / rust especially around the filter and tap.

Given the bowls had crap in them I hope you also pulled the floats off and cleaned the float valve seats, needles and strainers. Not to mention the rest of the jets, needles, mixture screws & emulsion tubes.

I just need to search for a sealer for the inside of the tank - any idea's?

POR-15.

[F5 Dave]

+1 on both those comments from Max (erm +2?)

do a search on sealing tanks, has been discussed before.