Hello Folk, ALthough I'm waiting for a Haynes manual to arrive, I'm not sure what it will tell me about carbs, and so, whilst I clean up the carbs and tank, I would appreciate your help in identifying my carb, and a statement as to what standard jets etc were on a 600 SS running Mikuni 38 MM carbs, flat throttle valve (registered1997 apparently). See photo attached of throttle valve. I believe it is the TM series of carbs, possibly known as BDST38. I haven't seen any ID markings on the carb, although I've stripped them down. These are the dimensions and markings I've identified only carbs: =============== Bore: 38mm Spigot Mount: 47mm needle jet 611 ☐ Y6 jet R☐70 (correction = pilot Jet) jet 148 (correction = main jet) jet needle - no marking Probably not standard, I'm thinking. It has a K&N air filter and a cutaway air filter box. Thanks, John
Hi, Im going by memory here I dont have carbs in front of me. The carbs should be the same as the 750 and 900, however I think the needle is different on the larger capacities. Someone with a bit more knowledge about the wizardry of carbs will be along to say for sure... Ian
Immediate thought, you have a Dynojet kit fitted.....Needle no marking is normal for that. Any standard jet will have a little square logo by the number, as will any part like the needle. However those jet sizes seem to be all over the place for either OEM or Dynojet; unless you have got your jet descriptions muddled up......A 148 would be / should be a Main Jet and that would also mean a Dynojet one.
Thanks Arquebus, You're right, being unfamiliar with the carb and only a poor diagram, I see that had the jets mixed up; here's the corrected version of marks I can see, my carbs =============== needle jet 611 ☐ Y6 pilot jet R☐ 70 main jet 148 jet needle - no marking The needle has been set to the 4th out of 6th ring from top of needle. So, the main jet a 148, without any square logo - appears to be non-standard/dynojet. The needle jet and pilot jet have the square logo, and appear to be 'standard'.
Post a picture of the needle and the spring; or compare with the one below....... Subject to the needle and spring macthing the Dynojet ones in the pic, I would say that you have a correct Stage 2 Dynojet set-up (in the correct OEM carbs). Note.....When you strip them for cleaning; if you have known the bike to have been running alright, take my advice.........don't attempt to alter the float / fuel heights (and don't muddle up which carb they belong to). Also be very careful when removing the pilot screws......It's easy for them to break the slot or the float bowl recess; because they have seized........ It is important to note how many 'turns out' each pilot screw is from 'fully in'. Be careful when screwing them in.....don't force them when you feel them 'stop'. When you have got the screws out, note that there should be a spring, washer and a very small O ring....sometimes the washer and o ring stick in the hole and the washer looks like the carb body, so you can't see the O ring. Don't overtighten float bowl drain screws, otherwise you will be looking for another float bowl.
Thanks for that Arquebus. I can confirm from your pictures that my needle and spring is the Dynojet kind. Your tips are spot on. The bike wasn't starting well at all, and the tank and carbs were very dirty. I have them well on the way to clean now, and parts ordered as necessary. I noticed the plugs seemed rich. I can't trust the pilot jet setting, so will start from scratch - I guess at two turns out.
For Dynojet Stage 2..........2.5 turns out is what they suggest. Have you got an OEM zorst / can; or is it aftermarket / straight through? If OEM, then Dynojet 144 main jets should be in there. NB....With these carbs, the float / fuel level forms part of the pilot circuit............ If you want to check the float height, take the float bowls off, turn them round the other way and use two of the screws to hold the overhanging bowl on backwards, so it keeps the float assembly in it's place. Then gently tip the carbs at a sideways angle so you can see the little sprung loaded plunger in the float needle just touches the float arm without depressng the plunger. Then measure the distance between the gasket face and the bottom (it's upside down) of the larger float......Make a note of the dimensions so you can always return to them. Ignore the 14mm dimension thet gets talked about......It's just a starting point but IMO it is too weak............You will probably find 12mm is nearer. I made a float gauge from credit cards stuck together.....see pic.
i believe its the oem, its not straight through, but shall check. that pointer is just the kind of check i need . john
Is your air box top cut out? If it doesn't run too well this could help, that might be why it was running a bit rich if it was not cut. Just for future info, the carbs on my 400 are the same as my 750, so would say the carbs are the same across the range.
Yes the air box is cut away, so that should be OK. They may have been rich purely due to fouling on repeated attempts at col;d starting, whilst the carbs were dirty. I think the cables were sticking a little too. So, I'll wait until I start her up and observe the mixture then. Shouldn't be too long, may be a week for parts on order, and I don't want to rush into it. No point getting in a foul mood with a flat battery, god forbid The weather's warming up nicely, I'll enjoy the process and make careful observations. I may need to switch to a 144 main jet. One more thing I have to do is repair a thread on a carb body which takes the float bowl - worn no doubt to the fitting of stainless screws without the lock washers. I prefer the originals with those washers - they work well. Perhaps I'll do a helicoil, what do you think? WHere might I go for such Mikuni parts? I also need the rubber seal for the lift up part of the fuel cap (about 43mm diameter on a taper - not the large green one or vanity seal for the holder); I was told by motorapido that they are not available to order. Any ideas? @Desmoquattro I guess you mean the carbs were jetted differently. Cheers for the great pointers and advice. Very much appreciated at this time. My manual came today as well, so that's fairly useful.
Allens Performance for Mikuni parts.......but there are other places on ebay....and Yam TDM carbs are roughly the same. I managed to deal with a damaged thread by using an M6 instead of an M5........... Only use a 144 jet if the zorst is OEM/stock.........It's easy to tell if you have an OEM zorst....post a pic. PS...When starting, don't touch the throttle if the choke is on.......
THanks, I did wonder; it's nice to know that's how it's supposed to be. (It's generally the way I operate on any vehicle). I'll get the picture posted. It takes me a while to get that ready to upload - mind you if ducatiforum.co.uk is on 'tapatalk' forums app, I can do it instantly from my mobile - though I couldn't find it on there when searching.
Here are the photos as promised, of my exhaust - one gives the stamped on details. It's a ducati exhaust.
I'm assuming it is the original one......it looks like the stock item..........perhaps someone can confirm. If so, I reckon you need to drop down to the Dynojet 144 size jets.......With the 148s that can may be making it run rich like you said it was. But, leave things as they are for the time being..........You need to get the bike out on the road for a good run and then check the plugs. PS....Dynojet jets are not the same sizes as the OEM Mikuni ones; IE a Mikuni 144 or 148 is not the same as a Dynojet 144 or 148. However, if your main needles are worn, Dynojet will exchange them free of charge.
That sounds like the right thing to do; I will, and make my considerations at that time, bearing in mind the whole configuration as you've laid out - as it stands and might be altered to suit. Appreciated. Won't be so long now, parts have arrived. Only this this carb bowl and stripped thread bothers me - I know it will work the 5mm screw will work, possibly for a good long time, with later strip down too, but I might be better to start with another carb body. Reason is, if I screw in a 5mm screw, then it won't so easily be refashioned with a helical at some other time, because it would need reaming to 4.1mm with a drill bit proir to trapping for a helical. @Desmoquattro If you are willing to part with one of your spare sets, or just one carb, could you let me know how much you would want for it? Thanks.
Carbs are back on, cleaned and helicoiled. Due to try and start her up shortly... probably need a can of fuel, maybe some easy start... ~Feel quite excited. Ready for disappointment too. I attempted to prime the carbs today, after making all the fuel and electrical connections good. Pump worked even with my repair to a broken wire on the pump post - fixed by simply cleaning and soldering. I noticed with the little (1/4 gallon) fuel I had put in the tank, that a little fuel got to my externalised glass sided filter when turning her over (without plugs fitted), but it is not full and no more fuel seems to be pumping into her. The tap is open, and tubes correctly fitted, so I guess not enough fuel. Or perhaps could it be something else.
