Fitting BS34 carbs with a Z1000J Airbox into a Gpz1100B2

[MikeP]

Need a little help if anyone has done, or tried to do something similar. I have a Gpz1100 B2 where the injection system has been stripped and then fitted with BS34 carbs - although I'm not sure what from.

At present the carbs really don't want to work properly, coughing and spitting with very poor performance. Not sure what the main jet is (as not marked) and the needle jet is 4D31 - and unsure what that's come from, and set at notch 4. Jetting; I'm probably going to start with a Z1100R main and go from there, and set needle to notch 3. Anyone done this before?

It also has cone filters, which brings me onto installing a proper airbox. Does the Z1000J airbox fit, or possibly a Z1100R airbox, or an original B2 airbox and try to cobble together an airfilter?

Someone here must have done this before so any help gratefully received.

[Al]

Some useful info in this post Mike.
viewtopic.php?f=22&t=28714

[Al]

The 1000J airbox and Z1100R1 airbox are the same thing. Doubt that they would fit a B2 but who can say. Youd probably be better off with a B2 airbox and go from there.

From my own experience; BS 34 carbs will spit, pop and bang just perceptably when cold if set up just right or a little on the lean side. If they do it when warm then there is an issue with the pilot circuits being blocked or restricted which only ultra-sonic cleaning will resolve. If when warm; you open the throttle in a meaningful way and it bogs down or hesitates it is likely the pods are responsible. Some cheap ones can block off the air intakes for either pilot or air correction in the body mouths. If the filters are un-restrictive; opening the throttle butterflies causes the slides to hit the roof and then the springs bring them back down with a bump. All very confusing for an engine and a rider and difficult to read because it appears to have two distinct behaviours for one single action! A pic or two of the carbs in question may help to identify them. The 4D31 needle does not match with any of the listed parts for Z1000J or Z1000R or Z1100R1 and not knowing the size of the mains leaves it all to guesswork.

AL

[MikeP]

Cheers Al. Great read in that previous thread. Looks like I'll put a separate post up here if anyone has a Z1000J or Z1100R airbox.

I have a B1 too and this "B2" doesn't have any injection ports that need blanking off so it may well be a Z1000J head, or even a Z1100R head, and therefore the carbs don't sit too far back with the need for special inlet rubbers - I'm hoping, fingers crossed.

[MikeP]

The 1000J airbox and Z1100R1 airbox are the same thing. Doubt that they would fit a B2 but who can say. Youd probably be better off with a B2 airbox and go from there.

From my own experience; BS 34 carbs will spit, pop and bang just perceptably when cold if set up just right or a little on the lean side. If they do it when warm then there is an issue with the pilot circuits being blocked or restricted which only ultra-sonic cleaning will resolve. If when warm; you open the throttle in a meaningful way and it bogs down or hesitates it is likely the pods are responsible. Some cheap ones can block off the air intakes for either pilot or air correction in the body mouths. If the filters are un-restrictive; opening the throttle butterflies causes the slides to hit the roof and then the springs bring them back down with a bump. All very confusing for an engine and a rider and difficult to read because it appears to have two distinct behaviours for one single action! A pic or two of the carbs in question may help to identify them. The 4D31 needle does not match with any of the listed parts for Z1000J or Z1000R or Z1100R1 and not knowing the size of the mains leaves it all to guesswork.

AL

The pods don't look in the best of health and will be the first to be discarded, and hence my quest for a better solution. You responded before my previous reply so perhaps you're right and I'll look for a B2 airbox and cobble together a filter.

I did look in the original manual for the needles but 4D31 wasn't there so god knows what they're off. I'll try to find so markings and take a photo which might help. The mains don't look like the style on my Z1000R2, and with them not being marked I'll be starting again.

[Robw]

I have a b1 which has 34mm carbs fitted with APE cone filters, it goes extremely well and all the plugs are a good colour. You will need the LEDAR jet kit, if you use them. I tried to fit a j airborne it didn't have the clearance as the battery box is lower on the b1 and probably also the b2. Having a non injection head will help with clearance as the b1 inlets are quite long compared to j ones. All you can do is try it out.
Rob

[Mr Bump]

The B2 head doesn't have injector ports in the head, so you might have the right head.

As the man said, z1000j airbox doesn't fit as it fouls the battery box.

A gpz750 unitrack airbox fits well in a B2 with bs34's. The lid has a long funnel on it that you want to cut off to unmask the whole filter then put a new K&N in. Allows a standard motor to make plenty of power.

If the needles are unusually thick then the carbs may be off a 750 unitrack. A standard motor will run well on them with bigger mains and an airbox.

I'm just trying a new setup with Z1100A shaft carbs, dynojet kit and 4x k&n pods. It runs very clean in the workshop but I haven't ridden it on the road yet as the rest of the bike isn't ready - hopefully it won't be a world of pain setting them up. If I can't make it run right I'll refit the 750 uni airbox.

If it all works well I'll post the dynojet kit number etc on here.

Olly

[MikeP]

The B2 head doesn't have injector ports in the head, so you might have the right head.

As the man said, z1000j airbox doesn't fit as it fouls the battery box.

A gpz750 unitrack airbox fits well in a B2 with bs34's. The lid has a long funnel on it that you want to cut off to unmask the whole filter then put a new K&N in. Allows a standard motor to make plenty of power.

If the needles are unusually thick then the carbs may be off a 750 unitrack. A standard motor will run well on them with bigger mains and an airbox.

I'm just trying a new setup with Z1100A shaft carbs, dynojet kit and 4x k&n pods. It runs very clean in the workshop but I haven't ridden it on the road yet as the rest of the bike isn't ready - hopefully it won't be a world of pain setting them up. If I can't make it run right I'll refit the 750 uni airbox.

If it all works well I'll post the dynojet kit number etc on here.

Olly

Cheers Olly, you mentioned that if the needles look thick then they're off a unitrac; you may have hit the nail on the head as they did look particularly thick. I'll have a look in my files for the Gpz750 and see if the 4D31 is mentioned. It'll be good to know where I'm starting from in terms of the carbs.

Also using the associated Gpz750 airbox will help with an existing connection to the carbs. Thanks for those very useful nuggets of info

[Richard L]

Hi Mike , Also B2 owner and been exactly where you are fitting carbs. Mine has been running for 10 years now without problem but it took some time and a lot wrong turns before a good set up was found. As Mr Bump says 1000j and 1100r air boxes will not fit unless you change the frame with regards battery mountings. B2 airbox fits obviously, but the carbs are wider than the injectors so that doesn't work either. I have seen various B2 s with a unitrak750 airbox which appears to fit but doesn't have the shiny metal sidecovers so doesn't look totally original.I too went for Z1100 shaft carbs ( these do not have the "coaster valves" fitted to some 1000j BS34's)
and were easier to find than 1100r versions. Fitted is a Dynojet kit stage3 and proper K and N filters RC 0984.
My bike is purely a road bike for fun and has not been on a dyno but starts and runs fine is totally reliable and produces enough power for me . It also has the added advantage that you can remove and strip the carbs in 10 minutes and a lovely induction roar when you open the throttle!
Richard

[MikeP]

Hi Mike , Also B2 owner and been exactly where you are fitting carbs. Mine has been running for 10 years now without problem but it took some time and a lot wrong turns before a good set up was found. As Mr Bump says 1000j and 1100r air boxes will not fit unless you change the frame with regards battery mountings. B2 airbox fits obviously, but the carbs are wider than the injectors so that doesn't work either. I have seen various B2 s with a unitrak750 airbox which appears to fit but doesn't have the shiny metal sidecovers so doesn't look totally original.I too went for Z1100 shaft carbs ( these do not have the "coaster valves" fitted to some 1000j BS34's)
and were easier to find than 1100r versions. Fitted is a Dynojet kit stage3 and proper K and N filters RC 0984.
My bike is purely a road bike for fun and has not been on a dyno but starts and runs fine is totally reliable and produces enough power for me . It also has the added advantage that you can remove and strip the carbs in 10 minutes and a lovely induction roar when you open the throttle!
Richard

Thanks Richard, I knew there were others here that'd done this mod to their B2. Like yourself I'm going for a road ride able set up so I'll replicate your airbox set up as I hadn't thought about the metal side airbox covers - but now you mention it it'd look more original. Unfortunately I'm stuck with the Gpz750 unitrac BS34 carbs (limited funds so can't stretch to 1100 shaft carbs) but will look into a Dynojet kit to get it running right.
Thanks again

[MikeP]

Had a better look at the carbs today and there's a solitary marking of 180 on the main jet. The pilot is 37.5. The needles are definitely chunkier than what I've seen on other carbs so perhaps they're Gpz750 unitrac carbs. There's also a jet in the mouth but without a marking on:

Is this a unitrac carb? Trying to find a starting point.

[8 Valve Mark]

those look like z750 carbs with acj's fitted mike, (std 750 mains would be 130's, pilots #35 needle in 3rd slot ) gpz carbs are finished in black.

[MikeP]

Thanks to 8 Valve Mark, those are Z750 carbs and from threads on Facebook with Glyn Williams, it seems that the Z750 carbsit are a nightmare to get working. Thought I'd try my 1000R carbs on the 1100 B2 and hey-ho it's now running reasonably well. I say reasonably as above 4000 revs it bogs down. It still has the pods but gives me a better starting point.
Mark has also kindly offered a set of 1000J carbs, as they're similar to the 1000R ones, so has anyone jetted these to suit the 1100B2?