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SB6R, question
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lorenzo



Joined: 20 Aug 2018
Posts: 35

PostPosted: Mon Aug 20, 2018 11:23 am    Post subject: SB6R, question Reply with quote

guys good morning to everybody.
my name is lorenzo, writing from Italy.
sorry for my bad english..i'm italian, driving on the ...wrong side!!

anyway i have three motorbike BMW K 1200GT, RGV 250 gamma, and....bimota SB6R.

the bike is old 1998, but only 1493 km are on the cockpit !

now in general motorbike is ok the only problem is the following:
- i clean all bike, changed oil, oil filter....and air filter
- i bought a new filter apparently a good one, double side (one is with big structure and the second is much more fine)
- and now i'll explain you the problem.

installing the new filter the engine is not rising well, at 3000 rpm i'll get an huge hole ...
but if i'm putting a small piece of cotton (tshirt) on the foam's filter the engine is perfect.
it is clear that probably the filter is to much ...open !!
my question is ...the engine is really so sensible at air filter ?

i can change the filter ...but before to do that i would like to get your comments.

thank you to welcome me in this forum !!!


th
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Mon Aug 20, 2018 12:20 pm    Post subject: SB6R Reply with quote

Lorenzo welcome.

First thing, is the new foam filter oiled? If it is dry, it may be flowing too much air.

However, more likely is that the bike is not getting enough fuel, rather than too much air. The most likely cause of this is the fuel pump in the air box, if it has not been removed by a previous owner. If it is still there, you should remove it, as the bike works perfectly well on gravity.

With so few kilometers, the bike has clearly stood for long periods of time - this could have resulted in dirty carburettors. If it has had ethanol blend petrol in, this could have resulted in degradation of the lining of the fuel tank, which will have resulted in a grey paste blocking some of the jettings downstream of the throttle butterfly.

I would start with removing the fuel pump and then take the carbs off for a look/clean.

Good luck & let us know how you get on.
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Mon Aug 20, 2018 12:24 pm    Post subject: SB6R Reply with quote

Sorry, should have said that the fuel pump is usually guilty of providing too much fuel rather than too little, but if it has stopped working altogether (works off engine vacuum) it will be impeding flow of fuel.
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lorenzo



Joined: 20 Aug 2018
Posts: 35

PostPosted: Mon Aug 20, 2018 1:32 pm    Post subject: Reply with quote

hi Johnny !!!

wow interesting proposal

concerning the carburettors...when i bought the bike there was red gasoline in side (lucky me) and the carburettors were clean
in any case i took out them and cleaned it very well looking at all specifications reported in the maintenance manual.

i'll follow your recommendation taking out the vacuum pump.

btw the filter was oiled before installation

i'll keep you posted
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lorenzo



Joined: 20 Aug 2018
Posts: 35

PostPosted: Mon Aug 20, 2018 1:54 pm    Post subject: Reply with quote

ciao again

in case i need to clean again carburettors ...which is the best solvent to do the job ?

or only mechanical cleaning ?

th
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Mon Aug 20, 2018 2:35 pm    Post subject: SB6R Reply with quote

You can buy contact cleaner, but really the answer is to have them ultrasonically cleaned. However, if the bike has a good steady idle, they probably don't need cleaning, as the idle jet is the smallest and if that isn't blocked, the rest are probably ok.
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SuziEngine2



Joined: 24 Jul 2018
Posts: 15

PostPosted: Mon Aug 20, 2018 4:07 pm    Post subject: Re: SB6R Reply with quote

Jonny B Bad wrote:
You can buy contact cleaner, but really the answer is to have them ultrasonically cleaned. However, if the bike has a good steady idle, they probably don't need cleaning, as the idle jet is the smallest and if that isn't blocked, the rest are probably ok.

When I had to get my carbs cleaned it would idle fine but respond to throttle very badly between idle and 6000 rpm. Twisting the throttle killed the engine when still cold, warm it would cough and splutter all the way up to 6000rpm and then go like a rocket.

I keep reading about that vacuum powered pump. The one on my SB6R is electric. It runs for a second or so when the ignition is switched on and I assume it is running when/after the engine is started. AFAIK the electric pump is standard factory. Maybe the vacuum one is SB6?

The fuel cock is vacuum driven, but that's a different component.

Unfortunately, the workshop manual shows both the pump and the cock (Fig. 01-9), but does not discuss the pump anywhere. It discusses the fuel cock briefly and then switches to the carburettors.
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Mon Aug 20, 2018 4:58 pm    Post subject: SB6R Reply with quote

I've seen quite a few 6Rs and they all started life with a vacuum pump and an electric fuel cock. I guess some 6R owners will have replaced the original iffy vacuum pump with an electric one.
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Jonny B Bad



Joined: 05 Dec 2009
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PostPosted: Mon Aug 20, 2018 4:58 pm    Post subject: SB6R Reply with quote

I've seen quite a few 6Rs and they all started life with a vacuum pump and an electric fuel cock. I guess some 6R owners will have replaced the original iffy vacuum pump with an electric one.
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Mon Aug 20, 2018 5:10 pm    Post subject: Reply with quote

SB6 never had a fuel pump (vacuum or electric) from factory. Only the 6R had a pump
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Evilchicken0



Joined: 12 May 2010
Posts: 2996
Location: London

PostPosted: Mon Aug 20, 2018 5:15 pm    Post subject: Re: SB6R Reply with quote

SuziEngine2 wrote:

When I had to get my carbs cleaned it would idle fine but respond to throttle very badly between idle and 6000 rpm. Twisting the throttle killed the engine when still cold, warm it would cough and splutter all the way up to 6000rpm and then go like a rocket.

I keep reading about that vacuum powered pump. The one on my SB6R is electric. It runs for a second or so when the ignition is switched on and I assume it is running when/after the engine is started. AFAIK the electric pump is standard factory. Maybe the vacuum one is SB6?

The fuel cock is vacuum driven, but that's a different component.

Unfortunately, the workshop manual shows both the pump and the cock (Fig. 01-9), but does not discuss the pump anywhere. It discusses the fuel cock briefly and then switches to the carburettors.


Up to 6k revs would suggest the idle jets.
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Evilchicken0



Joined: 12 May 2010
Posts: 2996
Location: London

PostPosted: Mon Aug 20, 2018 5:17 pm    Post subject: Re: SB6R, question Reply with quote

lorenzo wrote:
guys good morning to everybody.
my name is lorenzo, writing from Italy.
sorry for my bad english..i'm italian, driving on the ...wrong side!!

anyway i have three motorbike BMW K 1200GT, RGV 250 gamma, and....bimota SB6R.

the bike is old 1998, but only 1493 km are on the cockpit !

now in general motorbike is ok the only problem is the following:
- i clean all bike, changed oil, oil filter....and air filter
- i bought a new filter apparently a good one, double side (one is with big structure and the second is much more fine)
- and now i'll explain you the problem.

installing the new filter the engine is not rising well, at 3000 rpm i'll get an huge hole ...
but if i'm putting a small piece of cotton (tshirt) on the foam's filter the engine is perfect.
it is clear that probably the filter is to much ...open !!
my question is ...the engine is really so sensible at air filter ?

i can change the filter ...but before to do that i would like to get your comments.

thank you to welcome me in this forum !!!
th


This is a flat filter that has been adapted to fit the standard airbox ? It sounds like you need to have the bike set up - take it to a Dyno Tune
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lorenzo



Joined: 20 Aug 2018
Posts: 35

PostPosted: Mon Aug 20, 2018 7:04 pm    Post subject: Reply with quote

thank you guys

appreciated all comments

i have SB6R, but tomorrow i'll try to taking out the pump and go with gravity

i'll let you know !!!

th
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lorenzo



Joined: 20 Aug 2018
Posts: 35

PostPosted: Tue Aug 21, 2018 2:58 pm    Post subject: Reply with quote

guys quick update.
this morning i removed vacuum pump and ok, a little bit of work to be done but ok.

concerning my problem...no differences.

i remove the portion of textile in the filter and again same trouble around 4000 rpm.
later on i try to move the position of the setger in the needle (position 3 or 1 or 2) but every time same huge flession around 4000/5000 rpm like the engine is without gasoline !!

now i back again at original position (3) and there is a small hole around 4500 rpm but not bad.

maybe this winter i'll try to clean deeply the carburetors

th
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Evilchicken0



Joined: 12 May 2010
Posts: 2996
Location: London

PostPosted: Tue Aug 21, 2018 10:16 pm    Post subject: Reply with quote

Take it to a dyno and it tuned
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