Gsxr cutting out

[carlinmidarlin]

Hi all , I bought this a couple of months ago but only been out proper today , it's a 750 j but has a 1200 bandit donkey init , when it starts up its always abit fluffy , I went out today and it's a blast until you pull up at a junction or lights then it cuts out 99% of the time , pissin me off now as when you ride it there's no flat spots or anything and pulls really good , any info please before I go stripping carbs

cheers mick

[Gixer1460]

Basic questions what are carbs from? 750 or Bindit? May be both 36mm but quite different jetting! The pipe and can will have an effect - initially i'd guess lean on decell / stopping - does it pop or bang? Does using the choke make it better or worse? Hopefully it'll have the bandit ignition and not the 750's!

[carlinmidarlin]

Looking at the bike it's all 1200 bandit stuff I'd carbs , Cdi etc , as for running its good apart from the pulling up to a stop , it's just like you have hit the kill switch but hit the starter and it starts again

[Gixer1460]

Well that's one thing off the list. If its all low end / idle range then its possible those circuits are dirty / blocked - carb strip time! What is the idle rpm set at? Does it idle ok?

[carlinmidarlin]

Yeh it idles fine mate but the Rev counter only starts at 3000 so it doesn't show much on choke

[Jaydee]

Has it got standard cams? Were the valve clearances done recently? Inlet leaks (from valves not closing fully) through timing set wrong or cam overlap causing decompression at low revs(?) Just throwing ideas out there. Very easy to overlook as we all tend to go straight at the carbs.

My blandit 12 would SOMETIMES die in a shot (like hitting kill switch) at low revs or coming to a stop, a pisser in heavy traffic. I tried 2 sets of ultrasoniced carbs and same with the coils. Same symptoms, stop dead every now and then so ruled out carbs and spark. I had a gsxr11K inlet cam in the motor that was causing a bit of cam overlap. You could feel slight blow back from the back of the airbox. Reckon the inlet needed dialing in. (just unlucky in my case with my engines unique tolerances, next guys motor might be a different story) Cheapest option (I'm skint) was to put back in the b12 cam. Done 1500 miles now. Hasn't died once. Still going to put a lumpy cam back in but optimise the timing when I can afford a dial in kit.

[colinworth79]

with anything new and unknown start with the basics. New plugs , fresh fuel , air filter, check over the wiring , check battery . I would pop the carbs off and check what jetting is in there and quick clean with carb cleaner . Then you know what your starting with. If the engine is just stalling I would try just winding up the idle a bit once I new everything else is as it should be .looks a good start to a project. I just purchased a 750 l and got some starting problems and its the vac petrol tap that's shot but going over it before I take it for blast.

[jonny1bump]

On 26/08/2016 at 10:34 PM, Jaydee said:

Has it got standard cams? Were the valve clearances done recently? Inlet leaks (from valves not closing fully) through timing set wrong or cam overlap causing decompression at low revs(?) Just throwing ideas out there. Very easy to overlook as we all tend to go straight at the carbs.

My blandit 12 would SOMETIMES die in a shot (like hitting kill switch) at low revs or coming to a stop, a pisser in heavy traffic. I tried 2 sets of ultrasoniced carbs and same with the coils. Same symptoms, stop dead every now and then so ruled out carbs and spark. I had a gsxr11K inlet cam in the motor that was causing a bit of cam overlap. You could feel slight blow back from the back of the airbox. Reckon the inlet needed dialing in. (just unlucky in my case with my engines unique tolerances, next guys motor might be a different story) Cheapest option (I'm skint) was to put back in the b12 cam. Done 1500 miles now. Hasn't died once. Still going to put a lumpy cam back in but optimise the timing when I can afford a dial in kit.

Use carbide burr and slot your original cam sprockets.

[Jaydee]

1 minute ago, jonny1bump said:

Use carbide burr and slot your original cam sprockets.

Still going to need to get the degree wheel, positive stop, dial gauge and brackets etc. I can get the wheels slotted handy enough. It's optimising them that's the problem. It was cheaper to swap cams back (at the mo) till I can get a degree kit together. 

[colinworth79]

10 hours ago, Jaydee said:

Still going to need to get the degree wheel, positive stop, dial gauge and brackets etc. I can get the wheels slotted handy enough. It's optimising them that's the problem. It was cheaper to swap cams back (at the mo) till I can get a degree kit together. 

make the bits up yourself , I printed out a degree wheel disc then stuck it to some aluminium . Positive stop tool get an old spark plug break out the ceramic and thread the middle for a bolt . Dial gauges are cheap as chips !

[busa ash]

as colinworth79 said  turn up yhe tick over , then try it could be that simple 

[banoffee]

Mine used to die at traffic lights when hot, turned out to be hairline cracking in the coils. Was a good excuse to get Dyna replacements.

[carlinmidarlin]

Right , sorry it's been a long time since I've touched this bike again , I took the bike to a mate for a mot and to see if he could sonic the carbs to clean them , but he's rung me to say the air box has a big crack half way through , so do I drop the engine and fit a newish air box or dynojet with filters , please help as the suns out now

cheers mick

[Simbec1863]

Had the same issue on my slabbie carbs had been cleaned and rebuilt but when it was hot it cut out everytime I shut the throttle coming to a stop so turned up the tickover which compensated but eventually found issues with the coils(hairline cracks) changed them for dyna ones and never had the problem since, was even able to turn down the tick over again.

Its all about working your way through and eliminating the obvious you will then eventually get it sorted although its damn frustrating when the suns out.

Good luck hope you get it sorted

[Captain Chaos]

9 hours ago, carlinmidarlin said:

so do I drop the engine and fit a newish air box

you can change the airbox with the engine in the frame. Just remove the generator and intake rubbers and oil lines, gives just enough space.

[carlinmidarlin]

Anyone else tryed this way as I'm gonna start it in 10 mins

[Simbec1863]

48 minutes ago, carlinmidarlin said:

Anyone else tryed this way as I'm gonna start it in 10 mins

Done it on a slabbie years ago worked ok used a bit of wd40 to ease the plastic and rubber parts off and out of the frame

[carlinmidarlin]

Well that weren't to bad as me airbox was split in half cheers captain for the heads up , now do I plastic weld up the airbox or use a stage 3 dynojet kit and Ryanair filters as the bike has a full micron system

[carlinmidarlin]

Sorry it's a std system with a slip on end can