F@#*ing bike

[Lou Girardin]

My RF's driving me nuts. It's started to miss at idle and pop and sputter on overun, it runs fine elsewhere. I've put in new plugs, cleaned the carbs, checked for air leaks. But it's still the same. It was OK for a while, straight after I cleaned the carbs out, but started playing up after 80 km's or so. I'm starting to think plug leads or coil pack breaking down when they get hot. But that doesn't really make sense.
Anyone had a similar prob?
Lou

[Drunken Monkey]

Yep - Myself and others have had pretty much the same problem on our old GSX-R's...Every time it was the coils. Checking for spark doesn't work either, as a weak coil can still give a visible spark, without getting to the required voltage to produce clean combustion. I would put $$$ on your problem being the coils.

[Posh Tourer :P]

As would I.....I had that type of problem on the MZ. Coils were at fault. Another thing to check maybe is the output voltage of the battery.

Also, when you clean up the plugs it takes a while for them to foul up again. Another issue I had was that it was intermittent, as the coil was slightly cracked, with a very small amount of water in it, that shorted it at random times after a while of vibration and capillary action or something. After sitting round I guess the water flowed to somewhere not harmful, so it was ok when i first took off... At one stage, it was so bad, it would only do 6miles before the plug needed changing, or 12miles if I didnt ride with the light on

[Eddieb]

I'd go for coils as well, had the same problem with my old GSXR250RR, Suzuki coils don't seem to age well and don't like getting hot.

[Big Dog]

I hate to be the only voice of dissention, but I know nothing about coils and a bit about fuel. Sounds like the problem I had with my old bike after many dollars spent replacing bits, that I didn't know what they did but the bike shop said it was the highest probability, it turned out to be a cracked fuel filter. Allowing pockets of moisture to suck through under pressure causing uneven firing and sometimes backfiring whenever I buttoned off. Because it was only on the down spin the plugs etc were always clean.

Check your coils as that seems to be the consensus and it won't hurt, but if not check your fuel lines and even the gasket to your fuel cap/tank/tap/carb etc.

[Jackrat]

Big dog may have something there.If as you say it ran ok for a while after cleaning the carbs it may be something geting dragged though from the tank.
My own model of bike is pretty well known for this.
Mind you Iv'e also had the coil thing as well,but that has always come on when the bike was hot and wasn't intermitent.
Good luck with it what ever it is.

[Posh Tourer :P]

Always check the cheapest, easiest things first..... Good post BigDog, I certainly hadnt heard of that issue before.....Worth having a look...

[Lou Girardin]

The fuel system is clean now, next step - coils. Bugger$

[Big Dog]

The fuel system is clean now, next step - coils. Bugger$

Ya, but fuel filter new lines and a swill out of the tank should cost less than $30 and will at the very least increase the availible flow rate (most japanese market fuel filters are more restrictive than NZ manufactured ones). In the Trader I remember reading in their spanner section that this alone can yeild power gains of around 1-2percent, but can require remapping in early fuel injection. Coils can cost upwards of $200 depending on the model. Which is why I said fuel first.

If you are competent with carbs try pulling out the diaphram and checking it for cracks (these can screw up your mix on the down spin, also according to the trader).

If you dont have a diaphram check your jet returns ( I think thats what they are called anyway spring returns that govern the flow rate in non diaphram carbs) as these sometimes stretch when you open up a lot meaning ( ) one jet is not returning fully meaning you end up with a really rich mix on the down spin. These were the offenders on a mates suzuki 150 many years ago. after many $ spent trying to resolve the backfire on the down spin problem it turned out to be a $1 part + fitting.

Basically it sounds rich on the down spin to me.

As you feel it is more of an issue after reaching operating temp have your earth ohms checked at temp compared to cold, in theory there should be less resistance but if your lead is deteriorated there will be more. After $800 (trade price parts) spent on replacing every single other part of my ignition on my falcon it turned out the heat sink was coming from a deteriated engine earth. $9 for the genuine bosch part.

IMHO check every thing that is free or cheap before you spend the big kahuna on something you are not certain about (unless dioagnosed by a pro who will stand behind the work.)

[F5 Dave]

Yeah I’m doing some sorting out on my RF’s carbs at present though I don’t have those symptoms. (The coil idea is interesting though). Seems a common problem with the carbs is the needle jets wear oval, if you do take the diaphragms out have a look at the needle jets for slight ovality. Another thing is apparently the thermostat is very cold at 76.5 deg, most bikes are 82 ish or higher. I am experimenting with trying a 91 deg one soon. Check out the Factory website, they have a bit of interesting info there.

PS: don’t know the float height do you? Mine was at about 20mm & it didn’t like running uphill. I raised the level a bit & it got better but still a bit dodgy sometimes.

[Big Dog]

PS: don’t know the float height do you? Mine was at about 20mm & it didn’t like running uphill. I raised the level a bit & it got better but still a bit dodgy sometimes.

Nope. Not a mechanic, just can't afford one.

If you still have your manual it may be in there on the servicing page along with gaps etc.

If not try and find out from other owners of your model I found out all sorts of $H!% by doing a MSN / google on my specific model (just used the gsx1100f and hit search). It came up with 11000 matches, mostly websites or pages created by enthusiasts, often pages and pages of the most unlikely details.

[Lou Girardin]

PS: don’t know the float height do you? Mine was at about 20mm & it didn’t like running uphill. I raised the level a bit & it got better but still a bit dodgy sometimes.

Float height is 6.9mm +/- 1mm. Measured with the carbs inverted, from the top of the float to a line level with the main jet. Hope that's clear.
What's the factory site address?
Lou

[F5 Dave]

Cheers, was of course measuring from gskt face to get that measurment but will look at Mainjet mark.

http://www.factorypro.com/

Have to look around a bit to find all the info there.

Still have the manual?!? How many 2nd hand bikes have you bought that you got the manual? Or the toolkit for that matter. Besides the ones you get from new just tell you to : ‘See your authorised Dealer’ if you want to fill the petrol tank up.

[speedpro]

Cheers, was of course measuring from gskt face to get that measurment but will look at Mainjet mark.

http://www.factorypro.com/

Have to look around a bit to find all the info there.

Still have the manual?!? How many 2nd hand bikes have you bought that you got the manual? Or the toolkit for that matter. Besides the ones you get from new just tell you to : ‘See your authorised Dealer’ if you want to fill the petrol tank up.

Last year I bought a MB100 with the original toolkit still in it's plastic tube. No signs of use. Probably because you needed a screwdriver to get the sidepanel off to get the tools

[F5 Dave]

I think the key is supposed to work

Yeah MY YZF needed a substantial screwdriver to access the toolkit

PS email me your postal address.