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Betty has a fever :( -spluttering/backfiring


mealexme
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Yes, I named my bike Betty haha.

The beginning of this post is just an intro, the problem is highlighted in red


Anyway, I spent all that time making sure I had booked time off work for the France trip. Then that got cancelled, so I scaled down my plans to go on a trip round England for a week with Jam, but that got cancelled too, so then I plan to do a trip round cornwall for a day with a group, then the bike almost dies :( Such a waist of holiday... Nevermind, its not even that warm today. I will have to just get her sorted and be a loner on my holiday.


Anyway, so the problem started about a week ago when for the first time ever, she wouldnt start just on the button (with choke) but had to be coaxed into life with a bit of throttle, else she would stall. I thought nothing of it as she was running fine when started. No bug deal


Then for the first time ever, a few days ago she popped (backfired, but not very loud) on first start.


Yesterday I gave her a wash and she started to idle really roughly. I put that down to water getting into somewhere it shouldn't, thinking it would evaporate overnight/once the bike warms up


Then today it starts backfiring whilst im riding. It also sounds like crap under about 3.5k. It feels fine above about 2.5k, but anything under that it will judder (ie coming up to lights, pulling away at junctions etc. I stopped and thought I smelt petrol. I got off, shut it down and had a look around. Couldn't smell it any more. Running the engine whilst stopped did not show up any leaks. No petrol on the floor, no smell of petrol any more either. Also no air leeks as far as I can feel (shoving my hands in random spaces, and there is no breeze).

At the moment I am thinking the smell of petrol is from backfiring, and its backfiring from a spark plug on its way out, not burning the fuel properly?

But then, if that were the problem, surely it would still run like crap all the way through the rev range would it not?


Advice welcome! Also I don't want to start messing with it/taking it apart before I know what I should be looking for lol


Thankies

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check the air filter and make sure the filter is not blocked and that the intake into the airbox hasnt got a leaf or mouse nest in it,if you havent changed the plugs for a long time then it might be worth changing them to see if that improves it,have you filled up at a different garage to normall?

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Check the exhaust for leaks too Alex.......air getting in around the headers can cause backfiring..... :wink:

Another thing also is coils......if a coil is starting to break down you'll get rough running at lower revs...... :wink:

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First thing first I would say, Has it been standing for any time as the fuel may have gone sticky. It sounds like the pilot jets are a bit gummed up so it's either remove clean and replace or my call would be to throw a load of Redex down it, I know a lot of people don't rate it but I normally put a bit in if I'm going to leave it standing for any more than a couple of weeks. After that then you can start pulling it to bit's and move on to more complicated thing's.

ATB

John

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failing that ..................buy a honda :mrgreen:

All in good time my friend, all in good time... (October is a good time :D )



I ran the bike yesterday without backfiring/stalling on idle. All I did was run some carb cleaner through it and adjust the idle speed. I am hoping some crap got into the air filter (I did give it a good wash with the hose round that part, so it may have launched some dirt in there) and I possibly turned the idle knob when washing it (although it is hard to do by accident). I shall go for a ride later and see if its magically fixed it. If not I shall be trying ALL your ideas! Even the "buy a honda" one haha


Thanks guys


PS its been ridden almost every day, so not been sat

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check the carb manifold. splits in the rubber manifold will allow air into the engine after the carb has very carefully atomised and mixed the air/fuel. this will cause all sorts of rough running and spluttering.

 

Check the exhaust for leaks too Alex.......air getting in around the headers can cause backfiring.....

really? I might be wrong but i just cant see how the exhaust could act like an inlet and still have a functioning engine. surely the only way air could get sucked into the exhaust side of the engine was if the valves were not opening and closing at the right time.


true, leaking headers can cause backfires in the airbox but i was under the impression that this was down to the unstable back pressures.

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check the carb manifold. splits in the rubber manifold will allow air into the engine after the carb has very carefully atomised and mixed the air/fuel. this will cause all sorts of rough running and spluttering.

 

Check the exhaust for leaks too Alex.......air getting in around the headers can cause backfiring.....

really? I might be wrong but i just cant see how the exhaust could act like an inlet and still have a functioning engine. surely the only way air could get sucked into the exhaust side of the engine was if the valves were not opening and closing at the right time.


true, leaking headers can cause backfires in the airbox but i was under the impression that this was down to the unstable back pressures.

The old Bonneville I had years back had the headers just pushed into the head.......there was no way to clamp them.......and on the overrun it used pop and bang quite nicely.......a similar effect can be achieved on modern bikes with some aftermarket exhausts if the Seconday Air Injection isn't disabled or blanked off....... :wink:

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Its been such nice weather that its been depressing seeing it parked up, so its been locked in the garage, out of site. I did get started on it though, had the petrol tank off... Annoyingly its a full petrol tank, so heavier than it could have been.


So far I am working my way from the back to the front but started with the air filter box, its a bit crappy in there to be honest, a lot of dirt for a filter thats under a year old.


Anyway, my only concern so far is that there is petrol in the air filter box. I think the set up of the bandit differs from others. I think its an overflow system for something, but I'm not sure what overflows into it. The fuel has been drained via the drain pipe into a small jar, which I then kicked over, so there goes my environmental awareness...


anywhos. Anyone know what its for?


I've only been in two of the carbs, but they look nice and clean so nothing is blocking them. I will be looking into the other carbs tomorrow. If I can't work it out then its booked into the garage on thus because I wanna get out on it!


I may get them to do my valve clearances as it may be making things worse, and even if it isnt it needs doing and I really cannot be bothered to buy all the tools I need lol


I'll check plugs etc etc tomorrow :)

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Mate try draining the float bowls,on my fazer I changed plugs coils plug caps then someone suggested draining the float bowls and guess what it only effing cleared it !!!

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Well, I took the plugs out and checked them. The left one was wet with fuel even though I hadn't run it for 24 hours. I also found a load of petrol in the air box, so I think what was happening was whilst the bike was on its side stand, it was sucking through excess fuel from the air box and not igniting. Anyway, air box drained, carbs checked over by the garage (who didnt find anything untoward) and it runs smooth again... Well as smooth as a bandit can.


The only worry is, I dont know why I keep flooding it. I emptied it this time last year too... Should it really be filling once a year?

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in the bottom of the air box there is a drain hose that goes down the back of the engine and can drip out onto the road it has like a one way valve in it normally and sometimes they block up might be worth tracing it down and checking end of the pipe is clear failing that turn your fuel tap to the off position when bike not in use unless its a vacuum tap in which case there isnt an off position

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