V6Jon Posted June 18, 2012 Report Share Posted June 18, 2012 Sorry for staring another thread about this, but I really need a responsible adult to confirm I am not just clutching at straws here !! Stock jetting on my '96 750 SRAD is : 127.5 Mains on pots 1 & 4 125 Mains on pots 2 & 3 12.5 Pilots all round. While fitting the new exhaust on mine I sent the carbs to Kin Useless of these parts who ultrasonically cleaned and rebuilt them for me (and a wonderful job he did too) with the following jets : 130 Mains on pots 1 & 4 127.5 Mains on pots 2 & 3 15 Pilots all round. Everything else (float height, air screw etc) is set to stock. Having ridden the bike for a while now there is clearly something wrong with the low down fueling : Starts from cold without the choke Difficult to hold a constant throttle below 5-6k rpm Feels like its going to bog down, then lurches away after holding constant throttle Sometimes I get a hic-up as it seems to miss going up through the revs at about 6K My expert* opinion** is that it is running rich, so I have gradually dropped the needles and they are now on the top groove, which has improved things a bit, but not enought. So I am thinking my next step is to put smaller pilot jets in and move the needles back to the middle of the adjustment range, and see what that feels like. So am I barking up the wrong tree entirely, or does this sound like the way to go ? Presuming I do need smaller jets, is there a size between 12.5 and 15, or should I just go back to the stock jets ? And lastly, how do I change them ? do I just remove the slide and carefully unscrew them from there ? or do I have to removed them from insde the float bowl ?? Cheers Jon *This is a lie ** This is actually pronounced 'G-U-E-S-S' Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 18, 2012 Report Share Posted June 18, 2012 Do you have anything fitted? Exhaust,k&N ect? My bike (ZX6r) has a full SS remus exhaust and runs stock jets. It sounds to me like you have upped the jet sizes too much mate. The number (130,125 ect) is how much fuel it allows through at a given rate. Too much fuel and you will bog down or be hesitant, which is what it sounds like your bike is doing (IMO). If i were you i would revert all the jets back to stock and see how it runs..I bet it will run better. Edit:- I have TimboS2's race bike here and that is a 96 Gsxr Srad 750.. His carbs have stock jets in them.(i just rebuilt them) Tims also running a full Akra system on the bike with a K&N as well. Link to comment Share on other sites More sharing options...
V6Jon Posted June 18, 2012 Author Report Share Posted June 18, 2012 I have a K&N in the stock airbox, and GSXR1000 K3 Ti headers with the butterfly valve removed and an Arrow race can with the baffle out. Lorenzo (I think, I am crap with names !) had a similar setup on is and it wouldnt run on stock jetting, and after some fannying about he settled on what I fitted when the carbs were cleaned. Once the bike is above 5K it runs beautifull and howls (literaly) all the way up to the red line, its just below there it's (I think) too rich. Jon Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 18, 2012 Report Share Posted June 18, 2012 Ok then... Try putting standard pilots back in and see if that helps.The fact that it starts from cold with no chock tell you the pilots are wrong..lol (Too rich) Put these back to standard and see how it goes.(lean it out) It's trial and error im afraid,,unless you get it dyno'd If 5000rpm upwards is ok then it has to be your pilot jets that need altering.. Link to comment Share on other sites More sharing options...
V6Jon Posted June 18, 2012 Author Report Share Posted June 18, 2012 Cheers BudgetBoy ! Any ideas on if there is a jet size between 12.5 and 15 ? I presume not. And do I need to remove the carbs / float bowls to change them or do the screw in from the needle side ? Thanks Jon Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 18, 2012 Report Share Posted June 18, 2012 Cheers BudgetBoy ! Any ideas on if there is a jet size between 12.5 and 15 ? I presume not. And do I need to remove the carbs / float bowls to change them or do the screw in from the needle side ? Thanks Jon No i dont think there is another size between the two.I could ask my supplier but i don't think there is.. And yes you need to take off the fuel bowls which are underneath the carbs.Be careful when you undo the jets as they are brass and you can very easily ruin them.. Take your time. Link to comment Share on other sites More sharing options...
V6Jon Posted June 18, 2012 Author Report Share Posted June 18, 2012 Cheers, I didnt think there was an in-between size either, might phone Allens when I get five minutes just to double check though. Thats a pain the arse, was kinda hoping I could do this without disconecting the throttle cables etc to remove the carbs, might leave it a few days then and do it the next time the sun buggers off again Thanks Jon Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 18, 2012 Report Share Posted June 18, 2012 Cheers, I didnt think there was an in-between size either, might phone Allens when I get five minutes just to double check though. Thats a pain the arse, was kinda hoping I could do this without disconecting the throttle cables etc to remove the carbs, might leave it a few days then and do it the next time the sun buggers off again Thanks Jon you dont have to disconnect the cables mate, put a towel over the inlets/engine and flip the carbs over with cables attached if you dont wanna take em off. Undo 1 bowl at a time and replace the part then do it all up and move to the next. Not ideal and not how i would do it, but that another way.Remember to keep it (work area) CLEAN. Link to comment Share on other sites More sharing options...
scooby601 Posted June 18, 2012 Report Share Posted June 18, 2012 What about the needles, are they stock or DJ? I am running 12.5 pilots, 132/134 main jets, slide holes drilled and standard needles. Runs really strong with either the stock exhaust or a straight through can on (k&n filter too). I changed to DJ needles (had 2 different sets with different profiles), no 15 pilots and various different mains. Had an absolute nightmare and couldn't get the fuelling right. In the upper revs it was really good but down low it was shocking, couldn't even pull away when up to temperature. Reverted back to what I had before and decided to wait until its on the dyno to play some more!! Link to comment Share on other sites More sharing options...
dansp1 Posted June 18, 2012 Report Share Posted June 18, 2012 Is the use of gixxer 1000 headers an accepted mod? i would have thought oversize headers a good recipie for a fluffy bottom end! Link to comment Share on other sites More sharing options...
V6Jon Posted June 18, 2012 Author Report Share Posted June 18, 2012 What about the needles, are they stock or DJ? I am running 12.5 pilots, 132/134 main jets, slide holes drilled and standard needles. Runs really strong with either the stock exhaust or a straight through can on (k&n filter too). I changed to DJ needles (had 2 different sets with different profiles), no 15 pilots and various different mains. Had an absolute nightmare and couldn't get the fuelling right. In the upper revs it was really good but down low it was shocking, couldn't even pull away when up to temperature. Reverted back to what I had before and decided to wait until its on the dyno to play some more!! Cheers for that, the needles are DJ so I will bear that in mind. At the moment I can't get it on a dyno so I am just trying to ge it more rideable. Is the use of gixxer 1000 headers an accepted mod? i would have thought oversize headers a good recipie for a fluffy bottom end! It seems to be a mod lots of people mention, but Lorenzo is the only person i have found who actually seems to have done it, everyone else just seems to know of someone else who did it ! It is clearly (to me) running rich low down, so I will start with changing the jets and lifting the needles again an see how we go. And BudgetBoy, having thought about it a bit I will probably remove the carbs and do them on the bench, it will be easier, probably quicker and removes the possibility of me dropping a stray jet down the inlet ! Even if I cover the engine with a rag I am sure I can still manage it ! Jon Link to comment Share on other sites More sharing options...
scooby601 Posted June 18, 2012 Report Share Posted June 18, 2012 It seems to be a mod lots of people mention, but Lorenzo is the only person i have found who actually seems to have done it, everyone else just seems to know of someone else who did it ! I know someone who has done it too, me! But thats on the FI bike so no worries with jets and the like.......... Link to comment Share on other sites More sharing options...
sennidott Posted June 18, 2012 Report Share Posted June 18, 2012 This may help John. I ran this set up on my WT SRAD750 with full system and K&N filter. Stock pilots jets were used so I would suggest trying that. Try the needles in the middle setting and 132 / 134 mains as a start point. Link to comment Share on other sites More sharing options...
V6Jon Posted June 19, 2012 Author Report Share Posted June 19, 2012 This may help John. I ran this set up on my WT SRAD750 with full system and K&N filter. Stock pilots jets were used so I would suggest trying that. Try the needles in the middle setting and 132 / 134 mains as a start point. That muddies the water further When I bought the bike (the carb rebuild revealed) it was running 132 / 134 mains, with stock pilots, unknown needles, and a high level race system ! Given that I now have all the DJ parts and high flowing headers, maybe this is the way to go ? Link to comment Share on other sites More sharing options...
lorenzo Posted June 19, 2012 Report Share Posted June 19, 2012 Yep, it was me. I can't remember what the jets were that I used but if that's what I've told you then it was probably right. I think it was factory pro needles I used though, so that could make a difference I suppose. I do remember that when it was on the original jetting, especially before I swapped the pilot, it was really lurchy from a closed throttle, I'd often end up stalling it trying to pull away and getting back on the gas from a bend was also a slightly nervy affair. My thoughts on the whole swapping to the thou exhaust are that it'd be worthwhile if you could do some serious dyno time on it, mine was dynod just the once and I amended if from there so there's a slight questionmark on if was was fuelling spot on. Saying that, it's not that far off, Stewbie is riding it at the moment, and as far as I'm aware he's fine without making any fuelling changes. I did a couple of track days on it afterwards too, had no complaints at all. The thing that prompted me to do the swap was that my stock exhaust was corroded to hell round a few of the welds and the titanium set up off a thou was too good to turn my nose up at. If I'd had gone for a stainless system off another srad I'd have paid more for it and still had to do all the jetting etc anyway. Assuming no typos on jetting my bike was the same set-up as yours, with the same headers etc, Akra can, K&N filter, factorypro needles. I'm not saying it was perfect, but it was 90% of the way there, certainly very usable. I'd stick some stock needles in there before drilling the slides, it's easy to swap back, which you can't do when you've got the drill out. What you'll probably find with the smaller pilots is that it'll feel very wheezy and weak over the first few thousand revs, just generally a bit shit. It's nigh on impossible to swap the jets without at least pulling the carbs off the engine and flipping them over, taking them off completely isn't necessary though. The hardest bit to do is to get the airbox back on, I found. Also, when comparing jet sizes, bear in mind that Mikuni sizes do not correspond to DJ sizes at all, and for what it's worth, they're different to kehin sizes too! Link to comment Share on other sites More sharing options...
ronenige Posted June 19, 2012 Report Share Posted June 19, 2012 Before you faff about too much try screwing the pilot screws in 1 turn and try it again , I used to do a similar mod pilot wise on the facelift bandit , it worked well but had to reduce the ps opening by 50% added bonus is it's easy and cost's nowt Link to comment Share on other sites More sharing options...
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