FJ 1200 carbs

[steptoe]

sorry guys,, have just got back home and sat down,, you fella's have been busy,,

Xtrian,, will give you a quick bell this w/end

[Christian Raith]

The Boyer makes a huge difference

[petejw1966]

i sent madbill an email a while back
and he wanted i think about 200 euros
which at the time was about $300-350 aud.

it would be interesting to see how the boyer
ignition would be, compared to the set up
your running atm pg.

[Christian Raith]

Mad Bill in Germany did the setup I have on my bike, bolts straight on after a few mods to the back plate.
Makes the bike run much smoother.
Good partnership the XJR carbs and Boyer.
Some people (purists) say that it is not standard but if Yamaha had the stuff available to standard bikes back then they would have used it.
They were built for reliability and performance and XSelled at both.

[pgnz]

Chris,  those micro digital ignitions sound like they'd be a nice upgrade,  is there much involved to fit them,  and what sort of price are we looking at?  Cheers

[Christian Raith]

Leave everything the same but put in the 137.5 main jets from your old carbs..
That is how my XJR1200 carbs are set for the XS, runs fine AND better fuel consumption, as far as the vac advance goes I've got a Boyer Bransden ignition so it is not needed.
KIT00090      SUZUKI GS550/1000

http://www.boyerbransden.com/index.html

[pgnz]

I'd say any carburation issues are in the carbs themselves,  not to do with a bikes' timing curve or vac-advance setup,  any suitable carbs in good nick are going to run fine on an XS11, no different than any other bike in that regard. (I've never run a later model 80-81 like Pete's, so don't really know anything about their ignition system)

 The earlier centrifugal timing just normal for bikes back then, the timing curves weren't all the same either,  I've got a 3H3 centrifugal unit with different sized springs than a 2H7 unit, and the mechanical vac advance really just an optional extra that most bikes didn't bother with,  it only comes into play occasionally in certain situations when there's little load on the engine, more modern stuff use an electronic TPS to do the same thing.   Vac advance isn't a power/performance thing. Gas the bike on the road and it doesn't apply.

   Actually when the vac-unit is disconnected and plugged,  you won't even notice any difference on the ride.  All you need do is feed the vac-unit a bit of manifold vacuum (stifled to keep things smooth - same as with synching with vac-gauges) and she's all good.

 I've checked mine with a timing light, the timing drags up to the 50 degree mark at hi revs/no load,  doubt that happens much on the road though,  maybe downhill or in a tailwind with feathered throttle.  Disconnect the hose and the timing immediately drops to a normal 35 or so degrees.  Mine still sits on the 'F' notch (a slight lie, as I advanced my timing a couple of degrees) and from memory that idle position doesn't change whether vac is connected or not.  As long as the carbs are all good you should be sweet,  usually you need to shag around a bit with jetting and stuff though

[Christian Raith]

Steptoe let me know when I can give you a call and I will call you back and talk you through the carbs.
As you know I have the XJR's on mine, Work well once you get them going.
Any of the newer side draft carbs will be bEtter than qur 30 year old Mikuni's but the XJR and FJ fit so that makes them the best choice.

[petejw1966]

mines a 5n5
the 81 model, and yep thats mine in the avatar. 

i was watching a video that pgnz posted on the
uk site, hes running the zrx? carbs and hes got that
running really sweet, so if you got the time to mess around
with the other carbs, might be well worth the try,
but in saying that he has the 78 model with mechanical advance
so i dont know if that would make any difference.
im sure if he reads this he'll chime in..

[steptoe]

if your's is a 5n5 81 mns it's the same as mine

if the picture in the square is your's then they're the same

[petejw1966]

i got my shaft seals from mikesxs,
i had bought some from yamaha but the outer
diameter was too small.
ive got a packet in front of me part no: 48-5021 these
definately fit, now in saying that they fit my bike the later carbs
not sure about the other models.

there is a cpl of little tricks to do when replacing the seals,
if you eventually want to change them, let me know and ill
help you thru it.

[steptoe]

am only changing cuase of the shaft seals,,

even after all these yrs of working on these bikes tearing into shaft seals is a bit daunting, plus don't want to order the  shaft seals from the other side of the world and find I ordered the wrong ones,

having played with the mixtures, may even put it off for a while now

[petejw1966]

i was messing about with suzuki carbs,
but put the stock carbs back on because
of the vac adv, personally i wouldnt
bother with different carbs unless you changed out
the ignition and get rid of the vac adv unit.

while you have your stock carbs fitted try
connecting up a cpl of vac guages to your no 2 carb nipple
and another one to the intake nipple and take the bike for a ride
youll see how different the needles  react to each other, except at cruise
where the needles  were almost equal.

[steptoe]

hadn't thought of the vac adv, yet but will certainly have to look at that ,, had what I thought was a blocked jet the other day so adjusted slide needle leaner on all 4 while in there and is running quite a lot better ,,turned out to be a dead plug, , 2700klm

thanx for the thought, will look at it

[petejw1966]

hey steptoe,
im not familiar with those particular carbs, but
id say the bottom t is for fuel and the top t is a
vent for the floatbowls which would of been attached
to the air box,
dont cap of the upper vent or youll flood the carbs.

being a vent if that t piece is a little loose i wouldnt worry
to much about it.

also if ypour putting on aftermarket carbs, the vac advance
will either have to be disconnected or attached with a restrictor
to a carb nipple.