Suzuki GSX 750 ES running problem

[mightysaints]

Hi all

Need help. I have resurrected an old gsx 750 es 1984 model. I have replaced the cdi,coils,leads and plugs, changed the oil and air filter(stock item). She starts 1st time with a little bit of choke and runs fine through the gears. Red lines all the way but if I cane her for more than a few miles she starts to miss and just stops. I have to wait a few mins, she starts but on 2 cylinders and then starts to go ok after a few miles. Had a run out tonight and scratching around was ok but it happened again. On the motorway was running fine but the just conked out. Had to wait 10 mins and then it fired up on 2 cylinders, couple miles later was running fine. Seems strange that normal running and trip out to loonmies cafe she goes well but anything over the limit for just a short time and she lets me down.

[Tango]

Tank breather?.......could you be getting a vacuum forming in the tank when you cane it a bit.....either that or a dodgy fuel filter with restricted flow......

[mightysaints]

Forgot to say I changed the in line fuel filter as well. Please excuse my ignorance as I am not that mechanically minded, sometimes the bike runs well and then takes off like mad under hard exceleration bit like a powerband. I can only find 2 pipes from the tank. 1 is for fuel and the other comes from round the back of the fuel tap and goes into the carbs, is this something to do with vacuume and if it has a kink in it will this cause the proplem as it looks like it does. Might have to replace the pipe as it looks a bit short

[Tango]

Forgot to say I changed the in line fuel filter as well. Please excuse my ignorance as I am not that mechanically minded, sometimes the bike runs well and then takes off like mad under hard exceleration bit like a powerband. I can only find 2 pipes from the tank. 1 is for fuel and the other comes from round the back of the fuel tap and goes into the carbs, is this something to do with vacuume and if it has a kink in it will this cause the proplem as it looks like it does. Might have to replace the pipe as it looks a bit short

The pipe you are talking about is the vacuum pipe for the fuel tap.....ift that pipe is kinked it'll shut the fuel off......

[mightysaints]

I will get another piece of pipe and re route it. Hopefully this is the cure

[mightysaints]

Well I changed the breather pipe for something stronger and re routed it and changed the fuel pipe and re routed that as well. The fuel piick up point was a pig to fit as suzuki has placed it in the 1 place you can't get to without swearing. Took her for a blast down the motorway and had no cutout problems so hopefully cured. Dam rocker cover is leaking now, I spent hrs polishing it up and had a very small weep from 1 cam end but now its letting go badly so that's anther job for sat morning. Hopefully a bit of gasket sealer will do the job but hey doing up old bikes is never easy.

[mealexme]

Tank breather?.......could you be getting a vacuum forming in the tank when you cane it a bit

I know you said you have sorted it, but to me, what tango said sounds more like the cause. That, plus as soon as people say its fixed, the problem usually comes straight back.

If you have the same issue again, try opening the fuel cap and starting it again straight away. If it starts fine, then its time to check the tank breather hole

[Tango]

Hopefully that vacuum pipe has sorted the cutting out problem.......good luck with the oil leak......

[megawatt]

What Bob, Tango , said. It is not a breather pipe, it is a vacuum pipe, connected to the low pressure side of the carbs or cylinder head inlet stub. . A breather pipe is a connection to atmosphere, usually open ended. Check any breather pipes between engine and atmosphere or engine and airbox. If they are blocked, it could cause your engine to pressurise and cam seals to leak worse. Also check, AS said that tank breather is working or not blocked/pinched.

[mightysaints]

Stupid question but were do I find the tank breather hole. Just had a thought, I covered the fuel cap in a fake carbon fibre stick on cover as it was looking poor. Have i caused the trouble. Also just realised I left the breather hose disconnected to the air box, will lift tank off again and re connect. The only hose points I can find on the tank are the fuel, the one behind it that conducts to the carbs and another on the other side that is connected to the fuel level unit. There is no pipe connected to this section

[eastanglianbiker]

yes lots of tanks breathe through hole in fuel cap so covering it with carbon might of caused the problem as some have pin hole others use the key lock as part of it

[megawatt]

Most tanks breath through the filler cap, but some have a tube from the filler cap area that exits at the rear underside of the tank, near the carbs. There is often an overflow drain pipe here that drains the area under the filler cap when you overfill. When I remove the Fireblade tank I have to remove 4 tubes, fuel, vacuum, breather and drain!!!!

[mightysaints]

Oil leaks sorted (hopefully) topped up oil and going for a spin to see if all my work is ok. Going to replace the plastic screen over the clocks this weekend, got a piece of Perspex to cut and fit. Beats paying £50 for a new one. Just got to find the jig saw in the shed and fit a new headlight bulb

[mightysaints]

Had a good run out and all seems well. That's it now for doing her up over summer. Going to lay the bike up over winter and get it re spayed, sort out the fork seals and get braided brake hoses and change the exhaust. Got a Harris pipe to fit but will need to chop the down pipes and get some adapters, going to leave this till winter as well now so I can take my time