Rough 'Bird

[Windy Miller]

Hi Guys



I have a problem on a Carb model ?Bird that is driving me mad: I bought this bike a couple of weeks ago, and was told that it has a slight ?flat spot? at about 70 mph.



The bike has done a genuine 14000 miles, and sounds absolutely perfect. Slow speed riding is no problem, but between 70 and 120, it is dreadful! It surges and pulls back so violently it feels like the engine is being turned on and off! Above 120 it pulls like a train!



Looking through the paperwork that came with the bike, I found a job sheet from a garage which has been trying to fix the problem. They had performed all the checks that I would have done, including coil check, ECM swap out, Carb swap out, separate fuel supply, blanking off air filter (??? read on ? all will be revealed!). No success though. The bike has been back to a main dealer for testing. No success though.



This weekend, I changed the plugs, and dropped in a new air filter. No success though.



The only odd thing that I found was that the guys in the garage had left one of the air box intakes partially obscured with duct tape. Ah Ha I thought! That?ll be the problem. I took it off and went out for a blat. The bike is virtually unrideable now! It?s absolutely awful! In 3rd gear you can feel a slight pulling back, and from there it gets worse and worse. Motorway speeds are impossible, and it was all I could do to limp the poor old thing home again!



I?ve got 2 Blackbirds, one leaks oil all over my boot, and the other one wont go more than 40! Good job I still got the SuperMoto to ride to work!



Any suggestions?

 

[Demonbane]

remove air filter all together and then give it a run.

i had a old New CX650 that used to hit 3rd and die, went through 3 garages with no success, spent ?350 in bills and still no fixed it.

in desperation i ripped out the very clean looking air filter and bingo, she flew !


one trip to honda and they wanted ?75 for a new filter!

went to grans and borrowed her knitting needleand popped some holes in it:-:

cured .
( also, the exhausts.. pull em off and make sure nowt blocking the gas flow out, they can look shiney but be bolloxed up on the inside )

 

[andyBeaker]

Crikey.

I always think it is all too easy to chase red herrings with this sort of problem (I have spent 4 hours trying to get a Fazer started before I checked the kill switch so I know about these things..........

)

I am not an ace mechanic, but if removing the duct tape makes it worse (or even better) this suggests that there is a problem with the fuel; air ratio rather than anything else. Have you got after market cans??

Might be worth ?30 or so to have a rolling road session?

does the bike rev properly when not in gear? If it does, then suggests it is a 'running' problem suck as electrics? Have you checked for mechanical interfence such as warped discs? Sounds stupid, but you never know!!

Remember, the answer is there and probably staring you in th face..

Keep posting, someone will have the answer.

How about fuel? How long has the fuel been in the tank for? Might have 'gone off'?

 

[Bluey]

Just thought

Carb diaphragms not sealed correctly

A leak on the Carbs mounting points

Hope you get it sorted and as it is the carb model i doubt if is an electrical fault but what do i know

 

[AlexJ]

Just my 2p worth had the same problem with mine after putting it back together and i had some plastics missing just above the rad which made the bike run like you were saying, basically the bike was getting to much air once it was over 40 mph and choking up.

Might be worth looking into but i am no bike expert...

 

[hellraiser]

I had a bandit 1200 and for know reason it started runing shit I found out a former owner had drilled a hole in the airbox and coverd it with tape .The tape had come off and thats why it started runing shit. I sealed the hole with new tape and it ran great.

 

[Windy Miller]

Thanks for all your replies Guys.

I had a play with it again last night, and put some duct tape over the air intake again - it still holds back, but at least it's rideable now!

As Andybird mentioned, it certainly seems to be summat to do with the air fuel ratio, or at least summat to do with air and fuel! AlexJ - you may have a point there - I get the other 'Bird back tonight, so I'll see if there are some extra bits of plastic needed.

Although the paperwork says that an alternative fuel supply had been rigged up, I am wondering if it's a fuel tap diaphragm thing...

Feel free to shoot me down in flames here, but how about this: the diaphragm has a small hole, but to a degree is still working (at a reduced efficiency). At town speeds enough fuel is being delivered to meet the requirements of the slow running engine, and the bike runs fine. At (legal) motorway speeds, the demand for fuel is such that the holed diaphragm cannot cope, the float bowls run dry, with the result that the misfire occurs. A downshift or two, a massive frustrated handful of throttle, and the increased vacuum in the manifold is enough to overcome the limitations of the leaky diaphragm. The fuel is once again delivered to the float bowls, which only slowly fill up due to the massive demand from the screaming engine, and gradually things get smoother as the reserve of fuel in the float bowls builds up. Eventually the fuel being delivered to the carb is more than the engine requires, and everything runs as normal again!

So! What do you think? Possible? Unlikely? Crap? :dunno: Answers on a postcard please...

 

[AlexJ]

I racked my brains and probaly drove Jaws mad trying to figure out what it was with my bike, the guy who helped me put back together even put bigger jets in it to try and stop the hesitation at speed and also taped one of the airbox holes.

All it was in the end was the bike was getting to much air, i think someone said to me it was running with to much air entering the airbox hence the hesitation, once i put the new plastics on it cured all the problems straight away as it reduced the airflow going in to the airbox.

Good luck anyway..

 

[Windy Miller]

Cheers Alex - I will check the plastic situation out and let you know the outcome

 

[Windy Miller]

RESULT!

<Phil Mitchell voice on> Sorted! </Phil Mitchel Voice off>

Alex - I owe you a pint or three Mate!

At long last I was able to get both Blackbirds in the same place at the same time, and when I compared them, sure enough there are some plastic panels missing! I am short of the vertical panels that go down from the fairing infill panels down to the radiator.

I was going to quickly swap the bits from one bike to the other, but it looked like a bit of a mission and it was getting dark, so I did a quick professional bodge.

I made up a couple of panels from some flexible plastic sheeting that I had knocking about and stuck them in with some duct tape. Bish bash bosh, job's a goodun! No more misfiring! It runs a treat now!R#?

Thanks for all your advice peeps, especially to Alex who put me on the right track. It looks as though there was just far too much ram air going on. Next rideout, the tea's on me!!

 

[gerryc]

<Phil Mitchell voice on> Sorted! </Phil Mitchel Voice off>

Alex - I owe you a pint or three Mate!

At long last I was able to get both Blackbirds in the same place at the same time, and when I compared them, sure enough there are some plastic panels missing! I am short of the vertical panels that go down from the fairing infill panels down to the radiator.

I was going to quickly swap the bits from one bike to the other, but it looked like a bit of a mission and it was getting dark, so I did a quick professional bodge.

I made up a couple of panels from some flexible plastic sheeting that I had knocking about and stuck them in with some duct tape. Bish bash bosh, job's a goodun! No more misfiring! It runs a treat now!R#?

Thanks for all your advice peeps, especially to Alex who put me on the right track. It looks as though there was just far too much ram air going on. Next rideout, the tea's on me!!

I'm getting exactly the same symtoms running lean high up throttle becomes an on off switch between 5-7k from 85-110mph, thing is when mine was new it had a 1200 engine with ram air induction, but I've had to swap back to an 1100 for now and am getting this problem, can anyone point me in the direction (photos?) of these infill panels as mine was never fitted with them.
I was getting set to pull the bike apart tomorrow to mess about with the jetting and possibly lift the needles up a notch or two but if it can be sorted this quick please let me know:dunno:

 

[Windy Miller]

GerryC

I have had a look on the parts list, but it's not very clear which bit's which. As a temporary measure, just rig up summat that will stop the air blasting right into the air intakes on the air box. Try it and see if it works before you go buying bits that might not work!

The bit that is missing on mine is the panel that fits vertically down the inner edges of the infill panels that go from the sides of the tank up towards the clocks. you should find that there is a gaping hole there that you can see (feel?) the air intakes through. Just get a bit of rubber matting from the footwell of your car and cut it roughly to shape. Stick it in with gaffa tape and off you go. Be careful not to obscure the radiator though!

I'll be at the Bike Pavillion in Letchworth tomorrow if you are close by - you can have a look at my bodge if you like...

 

[AlexJ]

No worries dude glad its sorted, Jaws helped me get my head around what alot of the issues were, so a big thanks to him as well...

I have the receipt for the panels i will get the part numbers for you over the weekend and post them on here, i originally tried David Silver but they couldn't figure out what part i meant, i ended up going to a main stealers and the parts only came to about ?30.

The only issue was when the guy fitted for me he had to drop the forks out to put it in properly.

 

[gerryc]

cheers for the reply, I'm going to try changing the coils for the spare set I've got cause it only seems to be really bad after thrashing the sh1t out of it so possibly to do with heat,

there is an intake collector under the head light on mine and hoses direct to the air box.
having had it on the dyno I know its running lean high up so was also thinking of lifting the needles a notch

 

[TANK0700]

any good to you

 

[Leftlaner]

For what it's worth, I haven't connected the air intakes on the airbox to anything. With a BMC air filter, "Fuel" slip-ons with baffles removed and 4x148 jets from FactoryPro, it runs like a dream! Combined with 6 degrees extra advanced ignition timing, there's no more flat spots in the 4000-7000rpm area, and no hesitation whatsoever. Pulls like a train from 3000 and all the way up to 10.000 :-0)


This is on a 1997 (carb) bike.

 

[gerryc]

For what it's worth, I haven't connected the air intakes on the airbox to anything. With a BMC air filter, "Fuel" slip-ons with baffles removed and 4x148 jets from FactoryPro, it runs like a dream! Combined with 6 degrees extra advanced ignition timing, there's no more flat spots in the 4000-7000rpm area, and no hesitation whatsoever. Pulls like a train from 3000 and all the way up to 10.000 :-0)


This is on a 1997 (carb) bike.

Good point that.
My original engine had an ignition advancer and I haven't put it on this one, I'll give it a try an see if it works.
The bloody bike was doing my head in the other day trying to cruise up the dualer it was either on or off so had no option but to just hold it open.

At least it meant a quick journey from Glasgow to Aberdeen:-0)
but with petrol at ?1.25.9 / litre it was also bloody expensive 17 litres gone in under 90 miles

 

[gerryc]

AlexJ and Windy top shout fellas:bow:


Finally got my mates bird round and we used his panels as a template to make me some from the lid of a B&Q emulsion tub, made for the job it is, the same thickness and flexibility as the originals and easy to cut to shape with a stanley knife on a piece of MDF.

RESULT the bike now has Turbine smoothness to go with the grunt.

If you lads are up next year for the Scottish bash next year make yourselves known I owe you a couple of beers:beer:

Oh Aye and Tank cheers for the schematic but that shows the Injected bird with the RAM Air

 

[z900guy]

Guys
Help!
Reading this thread with great interest.
Ive got exactly these symptoms between 5 and 7k.
My Bird is a 1200 with ram air though, so Im unsure whether you can advise.
I notice that one of you has a similar setup ie ramair. Please can ou describe where exactly these panels are, or send me a pic to pabxxv@aol.com?

I'd be really grateful, its sending me bloody mad.
Bike's had a compression check (195-205psi all accross)
New Reg rec and battery owing to overcharging
Ive tried cdi swap
Swapped coils
Its been on teh dyno and they are struggling with it big time

Please help if possible

Thanks

 

[gerryc]

Guys
Help!
Reading this thread with great interest.
Ive got exactly these symptoms between 5 and 7k.
My Bird is a 1200 with ram air though, so Im unsure whether you can advise.
I notice that one of you has a similar setup ie ramair. Please can ou describe where exactly these panels are, or send me a pic to pabxxv@aol.com?

I'd be really grateful, its sending me bloody mad.
Bike's had a compression check (195-205psi all accross)
New Reg rec and battery owing to overcharging
Ive tried cdi swap
Swapped coils
Its been on teh dyno and they are struggling with it big time

Please help if possible

Thanks

If your ram air is still connected these panels will not be fitted.

when I still had the 1200 engine in I was getting the same symptoms and I traced it a pressure equalising hose about a 1/4" ID hose that goes from the air collector under the headlight to a filter box under the carbs about 4"x 3" this in turn has a hose that splits in two and goes into the tops of the diaphragms on the carbs and another smaller hose to the tank breather.

without the pressure from the collector box (under the headlight) your carb sliders will be overcome by the pressure in the air box causing it to run lean. also check that the collector is well sealed to the nose cone fairing. good luck let us know how you get on

I've tried to attach pics but if it doesn't show on here properly I've sent you an email with pics and my number on it give us a shout if you get stuck