ZX9R Carb Dilemma - Megajolt (TPS vs MAP)
 

Evening all,

I have run into a dilemma with bike carbs for my 1.8l silvertop zetec engine. I originally bought a set of ZX9R carbs off of ebay which came with a fuel pump + rubbers etc for a decent price, however I didn't realise at the time that I required either a MAP sensor or TPS for megajolt to work (they are an older type without the TPS), it was only after have made the aluminium backing plate up to suit these carbs with my sausage filter that I realised.

So I decided in my infinite wisdom to buy a set of ZX9R type E carbs so that it would be an easy swap allowing me to have a TPS and solve all of my problems. Well they arrived today and wouldn't you know, Kawasaki have completely changed the airfilter side of the carbs meaning that my inlet rubbers + backing plate no longer fits.

So here comes the questions, I so far have the following options:

1) Keep my existing carbs without the TPS and fit a MAP sensor, but the question lies in how to get the vacuum tubes to connect to the inlet system as my manifold does not have them on and I do not have the capabilities to weld Ali and they are round tubes so therefore I can get a good seal to my knowledge by drilling a hole and bolting some adapters on. I think it may be possible to buy some new silicone hose with take-offs.

2) I have a mondeo TPS which I was originally planning on using to convert my carbs to use a TPS, however I've learned that its pretty much impossible to mount it onto my peddle and if it is cable mounted it is very inaccurate

3) Buy a new backing plate + inlet rubbers and use the new carbs - I really want to avoid doing this as it will cost money and require a lot more effort to make get a new backing plate to be correct to the new carbs.

If anyone has any other ideas please let me know.

take some pics of the carbs and I will compare with mine. may be able to swap them over if mine will fit your install.

TT

Well it turns out the carbs I originally bought and got my custom ali manifold made for are NOT ZX9R carbs but are in fact ZX6R carbs, I remembered that I went for ZX6R carbs as they could be had for a lot less money but will still give the same performance.

I also got a few replies on Locost, with one suggesting to use welding tips drilled out to 4mm as they are an M6 thread and are available very cheaply, so this is what I'm going to do, I think I have a few of these in the garage so I will try and do this tomorrow and will post my results.

This does mean though that I have a set of ZX9R E carbs with the built in TPS that would be perfect for someone if they would like them for £90 + postage.

I've now implemented the new welding tip vacuum take offs and drilled out the welding tips to 2.5mm, I will see how this goes as it may turn out that they need to be slightly bigger, but the restriction should hopefully act as a damper.

Are there not vaccum connectors on the top of the carbs just in front of the butterfly valve?

This is what I used when I put bike carbs on my Jester back in '98. They are usually used to connect carb balancers to.

My biggest problem was that if you connect them all together you dont get a constant vacuum down the pipe as they would suck from each other. I had to make up check valves for each line so they would only suck from atmosphere rather than the other manifold branches, that was for a servo mind you not a MAP sensor.

Cheers
Stot

Stot, my ZX6R carbs unfortunately don't have vacuum connections, I know that more modern carbs did, some even had vacuum connections with TPS sensors.

It might pay you to use a vac resovoir to stop pulses from each cylinder giving you false feedback,TDI vw have them,black plastic ball in front of the block.

you may find that you quickly lose all vac above 10% throttle and a using tps based system will be best

I'm curious, why would you loose vac signal at 10%?
I've not seen that on my setup using Megajolt log data.
I'm concerned this thread is becoming one based on supposition and not fact
Both systems have been proved to work if well setup
The vac problem has not been reported on other sites save the inclusion of a box or manifold to suppres pulsing.
TPS needs mapping as its a calculation based on revs and throttle opening not a measurement as MAP is
Lets talk more about what we have found and not we think we may find

it is because you have more air gap quicker to allow air flow with 4x throttle butterfly's and very low restriction.

you will quickly get to 90kpa at about 7-10% throttle angle where as you would have more resolution with a tps based setup that is why its a better option

vac for single throttle, tps for 1 per cyl. both would work vise versa but not as well

look at a motorcycle and it will use tps and a car and it will be vac to calc load for spark advance