Fuel Problems

Viewing 13 posts - 1 through 13 (of 13 total)
  • Author
  • #5724

    I have a Z750 CSR.
    The bike would run for about a mile then cut out when I had the tap turned to ON. When the tap is turned to Prime It seems to run ok.
    I have changed the diaphragm in the pet tap (The old one was Knackered)but no luck. Still the same. Is it ok to run the bike on prime? Any Ideas would be a great help
    An other question. I have seen an exhaust system on the internet made by MAC .Has anyone used these and are they any good. Also do you have to pay import duty as it’s from the USA.
    Cheers Lee.


    Hi Leema
    Firstly the fuel. Turning the fuel tap to PRIME just bypasses the diaphragm of the tap. This is operated by 2 pipes that come from the carbs (1 from each carb at the top) that go into a TEE piece that in turn connects to the fuel tap. This is the smaller of the 2 pipes on the tap. When the engine is running the carbs create a suction on these pipes which causes the diaphragm to open and let fuel through to the carbs. As the bike runs fine on prime then this implies your issue is NOT internal to the carbs. My guess is now you have change the diaphragm that there is an issue with the vacuum pipes just described.

    It is safe to run on prime but I would strongly advise turning the petrol tap to on every time you turn the engine off to prevent flooding and fuel loss.

    With regards to the MAC exhaust system I also have experience. They are built for the USA market which generally has much more bike friendly weather. My experience was bad. I first got black downpipes which were rusting in less than 2 weeks. Secondly within a month the baffle plate had torn out and I had to get it welded in.

    I had several issues of damaged systems being sent to (3 in all) They got my address wrong so delivery took far longer than it should as the exhaust was sent to Uzbekistan instead of England and then when finally on its way it spent a couple of nights in Paris.

    Yes you will have to pay import duties which in my case were about £40.

    My advice would be to stay well clear. The best aftermarket system like original is the BSM system from Holland but these are quite hard to come by.


    Thanks KK

    Looking at the fuel/air pipes on the bike and they seem to be wrong. I think someone has by-passed the diaphragm system. There seems to be a Tee piece missing. Fuel Pipe goes directly to carbs. Didn’t have this problem on my old B1.

    Thanks for the advice on the exhaust. I will keep looking.

    Still looking for a set of clocks bracket + wiring. Are they generic or what other clocks would fit. Do you know the ratios if I bought some custom clocks.

    The bike has been butchered a bit in the past but I love that engine. Was it you who bought the CSR on ebay?

    Going to Kempton Jumble this Sat in Search of a few bits.

    Ride Safe



    The fuel tap on the B is gravity fed. Are you saying there are no vac pipes from the top of the carbs?

    There are clocks about for the CSR but you are looking abroad. New ones go around £65 each plus postage etc. Second hand ones are a guess. The ones I have are tatty but depending on your skills can be refurbished.

    There are/were 2 CSR’s on ebay and a CSR engine badly advertised as a B engine but no I didn’t get any.

    Good luck at Kempton on Saturday.


    Hi Guys

    Just a quick update.
    I have sorted out my fuel Problems. The previous owner had by-passed the vacuum so all I needed was a T piece and a bit of tube. Runs fine now. Cheap £3 fix.
    Managed to find a set of clocks at the Kempton jumble including bracket and idiot lights for £8 in good condition. The speedo is correct for the model but the red line on the rev counter is too high for the twin but what a bargain.
    Would love to come down to the ace in april on the bike but have just stripped the bike down. Frame off to be powder coated soon. Maybe come down on the Honda if they let me in. Are you taking your CSR K.K ? Would be good to see it.
    I have seen some cast wheels on ebay off a 1980 Ltd. Single disc and drum. Would they fit straight on the CSR also where can I get some standard piston rings? Have tried all the places I know.

    Hope to see you at the ace.



    Hi Leema

    I am glad the advice on the vac tap proved good and it was a cheap fix for you.

    What is the red line set at on the rev counter?

    Standard piston rings on EBAY

    Ace café Kawasaki Day on a Honda??? 😆 I don’t know anything about that

    Speed up with your rebuild you’ve nearly 4 months man!!!


    Hi Lee,

    I expect that you have found the instruments of a Z-Four (Z650?)
    Red line is about 8.500 rpm or so then.

    Should show the rpms correctly.
    Just bear in mind the red line with our Twins is at approx 7.500 rpm.

    Just place an additional sticker to the tachometer to point out where the red line really is 😉

    Good luck !
    Cheers, Michael


    Thanks Michael I think you are correct about the red line. I would never rev the twin that much.

    Thanks for the tip on the rings K.K
    I guess they are the same for all models.

    I know the winter nights up norf are longer but darn sarf I make it less than 3 months to Kwak day.

    The problem I have is that the original wheels are a bit kwakered.
    Rusty and rear rim has a dent. That’s why I was asking adout the 80 LTD wheels .(Cheaper option for the moment) until I can get them re-built.

    Hope you make it up from the floor from laughing.

    What tyres do you prefer for the CSR?


    I may be able to help with wheels.

    I had mine respoked with stainless spokes using original rims and getting the centres bead blasted. I can’t remember the final cost as I had other things done too but seem to recall about £80 each wheel in the end.

    Before that I did a refurb on my wheels which went quite well. I painted the spokes and nuts with silver hamerite and a brush. It looks quite amazing even close up. I painted the hubs also with hamerite

    The rims I tidied by rubbing wet tin foil other the pit marks. WOW what a difference that makes.

    I think I might have spare CSR (Chrome Spoke Rims) wheels if your interested. They will need to be tidied but at least the rims are not dented.

    For tyres it’s BT45,s everytime.

    I did spot my mathematical error and got side tracked then forgot to modify the post. Ah well . . .


    Hi KK,

    as we are talking about the CSR twin model I wonder if it was an accident or your intention to use that same abbreviation CSR for Chrome Spoke Rims ?

    Cheers, Michael


    Hi Michael.

    It was intentional. That is what I believe it stands for and certainly makes sense with our twins. I was told this some years ago by someone in a Kawasaki shop


    Hi KK

    Not heard the one about the Foil before. I will give it a try. Is Tesco foil ok 🙂
    That sounds cheap for a respoke.
    The chrome is good on the front rim but its the spokes that have surface rust on them. I might try some rub n buff on them. Heard that this is great stuff.

    I am interested in the rear wheel though.
    What’s the chrome like? How much do you want for it? Any chance of a photo.
    The CSR is a great looking bike but it’s a shame it didn’t come with ali rims.


    If the foil doesn’t work out get an old toothbrush and a tub of Eucyrymol from Poundland. Every bit as good as Autosol and much better smelling!

Viewing 13 posts - 1 through 13 (of 13 total)
  • You must be logged in to reply to this topic.

Share this