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bike carbs questions

Posted: Fri Jun 06, 2008 7:56 pm
by Hardcore
hi there. im really wanting to put bike carbs on my polo 1.4 6n 8v. iv oticed there for sale all over clubpolo forums for lyk £70. i just wonderd if anyone could give me advice on which ones to buy, and what else do i need exactly to fit them. can someone please give me a list of materials that i would need to buy to do the job properly and how hard is it? cans someone give me a rough idea on how much BHP i would be gaining and what cars i would be able to keep up with for an exampe.also can someone explain exactly what they do lmao. iv just herd abotu them on here and thought. hmm ill look into that :)

-thanks poeple!

Posted: Fri Jun 06, 2008 8:49 pm
by polo-sib
Wikipedia is your friend.

http://en.wikipedia.org/wiki/Carburetor
and
http://www.bikerenews.com/Stories_Archi ... etors.html

I don't know much on the topic of carbs, but what you will be looking at is creating a new inlet manifolds (expensive to get custom made unless your making yourself) to let the carbs sit on. Secondly you will have to tune each carb for idle speed and fuel mixture via the needles/valves so the mixture is not to rich or lean as well as fitting it with the CO2 emission standards, to do this you will need a gas analyzer to hit things spot on and maybe some rolling roads while tuning (a guess).

I imagine the sizes of the throttles would have to be taken into consideration as well as what engines they where initially designed for so that they run closer in ratio with your current engine size that you are converting.

I'd also imagine every carb (depending on the carb(s) aswell, such as single, twin carbs etc) has a butterfly valve on each body which means you will have several links possible, not sure if you would have to link all multiple links to the pedal box or maybe there is a simple solution such as multiple links could be pulled by one link., maybe custom linkages.. who knows, but I'm sure someone can shine some more light.

More Useful links:
http://z3.invisionfree.com/Mk1_Polo_Clu ... owtopic=25
http://z3.invisionfree.com/Mk1_Polo_Clu ... wtopic=130
http://z3.invisionfree.com/Mk1_Polo_Clu ... wtopic=102
and
http://www.clubpolo.co.uk/forum/lofiver ... 06864.html
(I know its in regards to older cars but same principle)

Posted: Sat Jun 07, 2008 5:22 pm
by LeMeph
spot on sib. Only thing i can say is i dont think its quite that expensive to get a manifold made up. It all depends on how you want to do it. What im told is you can get an 8v manifold of a mk2 scirroco or golf, cut off everything to leave you with the base plate and enough tube sticking up to attach some samco hoseand well... you can guess the rest ay!

Posted: Tue Jun 10, 2008 5:21 pm
by Hardcore
ah i see. sounds a little bit complicated then to tune the carbs. dunt matter anyway i got a mechanic for said he cna do it all if i buy the parts. what exactly would i need?

Posted: Tue Jun 10, 2008 7:38 pm
by polo-sib
Hardcore wrote:ah i see. sounds a little bit complicated then to tune the carbs. dunt matter anyway i got a mechanic for said he cna do it all if i buy the parts. what exactly would i need?
Part needed are more or less dependable on the carbs being used. Easiest way as LeMeph said was use a a set of 4 carbs from an older car, this way only one linkage would be used and you could just duct it on with a few pipes (no need for manifolds).

But if you go for bike carbs like twin carbs you will need two, then you will have to make there linkages work together and possibly a custom manifold made to sit them on.

Its really dependable on how much money you really want to spend, the basic options easy and cheap. Whilst using multiple bike carbs is more expensive as more works involved but would look individual

Posted: Wed Jun 11, 2008 3:55 pm
by Hardcore
oh i see. andd. is there a lot of an a power increse? and what are the chances of it cvausing damage to the enginee. money isnt really the first thing on my mind :) im willing to spend a bit lol.

but then. if i spend the money on this, with a GT camshaft. would it not be cheaper to just buy a 16v? would a 16v still be faster?

Posted: Wed Jun 11, 2008 4:56 pm
by polo-sib
Engine will take it, as it's not like your trying to wayyyyyyyyy over power it with things it cannot handle to the extremes. Power increase you should be able to get around 100bhp if not more if all is tuned well putting you in the same league as a 16v (thats a guess on the output, so don't count on it as I could be wrong), but I'd imagine you would be able to push it more and more if you used parts of the 1.6 block. As the 1.4 and 1.6 had very similar inside, just eveything on the 1.6 was bigger.

So I'd uprate the 1.4 with the 1.6 main block and heads block and whack a GT cam which would put you on around 75bhp with injectors, then you can push it further with carbs etc. This will basically make your engine almost like a 1.6 and I've heard people tuning 1.6's to 150Bhp with a hell lot of work.

All depends what your after, you can uprate the 1.4 8v with what I sugested or switch to a 16v, but that would require alot of wire looms etc to change to 16v.

Its all down to you whether you want something generally faster, then get a faster car, but if your after pure uniqueness then go for it!

Posted: Wed Jun 11, 2008 8:36 pm
by LeMeph
PostPosted: Tue Jun 10, 2008 6:38 pm Post subject:
Hardcore wrote:
ah i see. sounds a little bit complicated then to tune the carbs. dunt matter anyway i got a mechanic for said he cna do it all if i buy the parts. what exactly would i need?


Part needed are more or less dependable on the carbs being used. Easiest way as LeMeph said was use a a set of 4 carbs from an older car, this way only one linkage would be used and you could just duct it on with a few pipes (no need for manifolds).

But if you go for bike carbs like twin carbs you will need two, then you will have to make there linkages work together and possibly a custom manifold made to sit them on.

Its really dependable on how much money you really want to spend, the basic options easy and cheap. Whilst using multiple bike carbs is more expensive as more works involved but would look individual
did i say that? Or did you guess wrong? loool.Dont know what you mean by using a set of 4 carbs from an older car?

Though you have given me an interesting idea just now off using twin (and get this...) standard carbs!!!! lol. Itcould work and i guess it wouldnt work too shabby if you got it set up right enough!

Anyway what i was trying to say in reference to the old carburettors of the 1980's is that the cast iron/steel manifolds of those engines share the same fitment as the AE series engines off the 90's. So the easiest way to make a manifold to fit your engine would be to cut down an 8 v manifold off the older sciroco or golf then attach silicone hosing at a rigth angle to the motorbike carburettor's.

Hope that clears up everything i was trying to say!

Posted: Wed Jun 11, 2008 8:52 pm
by polo-sib
I think loads of small bike carbs look better than just one carb, so I assumed you was going for that look as it would be like sex!

Posted: Thu Jun 12, 2008 7:45 pm
by LeMeph
oh yeh no doubts about that. sounds fooking sexy aswell!

Posted: Thu Jun 12, 2008 7:47 pm
by polo-sib
Haha I think I want a carb conversion now!

Posted: Sat Jun 14, 2008 12:09 pm
by LeMeph
you should :)