The latest stage in my 900SS rebuild is to takcle the carbs. As with everything else on this bike, there has been a bodged job at some point. I know the carbs have been apart at some point as some of the bolts holding on the float bowls have been replaced. Others were rounded off, and as with every other bolt on this bike they were way overtightened. The bike has an open airbox and race cans fitted, so I really expected to find a Dynojet kit in there. However, the jets are 140's which I believe are the stock items. It's a possibility that a Dynojet kit is fitted but the previous owner found the 140's worked best, but I doubt it. I suspect that they've just opened the airbox and bolted the cans on and put up with rough running. I'm going to be fitting a stage 2 Dynojet kit but my question is this. I know that the carbs for a 600 and 900 are basically the same, but could I take a set off a 600 and fit a 900 Stage 2 kit, or is there anything left over from the 600's which will make this not work? I've been offered a set of very low mileage carbs off a '98 600 and would rather fit them than use the ones off my bike. My carbs must have been replaced at some point as they have the carb heaters which I don't think were fitted to the early SS's, but I've got no idea how old they actually are or what mileage they have really covered.
Full instructions & sizes etc for any of their jet kits can be found on dynojet.com. Just find your jet kit and click on the little PDF symbol.
Post a pic of the needle and the spring....I can tell by looking at them if they are Dynojet or not.... You could also look and see if there are any numbers on the needle....DJ needles don't have numbers. Also, the jet. photo the number or tell us exactly what there is on it....DJ jets aren't the same as OEM jets even if the number is the same.......The OEM jet has a little square motif near the number...in fact all the OEM parts have the same motif. DJ jets have nothing but a number. And you could use the 600 carbs, but you will need to swap a few things over.....I know exactly what you need to change etc etc etc, so don't go buying new parts just yet..... In fact, I just found this pic I took a few weeks ago........might tell you summmat...... AL
That's helpful ta. i had been looking on the UK site and I couldn't find any of that info. Why does the 900 Monster and the 900SS have different jet sizes for the same model year? I know they put smaller valves in to the later 900 engines but I thought the early stuff was all the same.
I have got pdf files for both Stage 1 and Stage 2 Dynojet kits......It tells you what you get in each kit (including jet sizes), plus fitting destructions......You normally get needles, springs and a selection of jets, plus a load of tiny washers, but as I said earlier, do not confuse the OEM jet sizes with the DJ jet sizes, the flows are measured differently, so you could have an OEM 140 and a DJ 140, but they won't be the same. AL
... and the answer is, my carbs are fitted with standard jets and needles, in short they are stock. The bike has an open airbox and race cans and I can only assume must have been running lean and like a dog. No wonder when I ran it up briefly before pulling it apart that I couldn't get a steady tickover. The previous owner reckons that it pulled like a train, was faster than his mates Fireblade, and thought it must have a 944 kit fitted (which it doesn't) as it went so well. He'd get a shock if he rode after it's been properly set up then. I reckon it's going to be faster than a Busa on Nitrous. No wonder the valves were in a bit of a mess. So it looks like the carbs are getting a total overhaul, new emulsion tubes and a Dynojet stage 2 kit.
FYI....Mine was running OK with a Stage 2 DJ kit, Laser zorsts from a 750IE (straight through...and not that loud), and the airbox trumpets removed..... ...OK for 2.5 years until I had some rough running at low revs which I have partly cured, but I am still suspicious of the manifold rubbers. But at least I can spot a DJ kit by just looking at the needles, jets and springs now..... OEM emulsion tubes can be got from Allens, but you might want to consider getting them from the US as the DJ kit needles are very hard and will wear the OEM tubes.... ...you might have trouble getting float assemblies (they have been out of stock for some time)...... If you have a carb component that you are not sure if it is Mikuni or otherwise (jets, needles etc), the OEM Mikuni stuff has a little square motif on them....I think I said that before. AL.
yes, was well aware of your running set up AL as you document it on here so frequently :smile: quite a steep recent learning curve for you I believe - did you get any friendly help with that? :wink:
Oh yes, thanks.....and DJ filled in the missing bits :wink: Send your old needles to DJ for free replacements......750 & 900 ones are identical (but the springs aren't). AL.
The only thing is I can't recall which way round the jet sizes are measured....the guy at DJ seemed to contradict what I initially gleaned....But you can be fairly certain that a 140 OEM jet isn't the same as a 140 DJ jet.......I don't suppose it really matters because the clue will be the square motif. I also have the pukka DJ Stage 1 & Stage 2 kit instructions in pdf form. What I can't bl**dy well find is an alternative to Ducati manifold rubbers....Allens have a reasonable selection, but unfortunately the nearest ones aren't quite right. AL
I only have a new stage 1 on the shelf now as stage 2 is in Monster so cannot help by back to back measuring at the mo. I know we're off topic here but I saw your request for rubbers* and was a bit mystified as like me i'm sure you would use secondhand if available and good ones seem to be plentiful? If you are really stuck then I will have a check through mine. I think overall they last well unlike the early moulded-in type on the 650's and it's only assembler error that seems to give them an early grave - main two (MOO) are that all faces should be 'dry' (or very lightly lubricated if you must) and that jubilee clips are tightened with sympathy as if these two are not adhered to then 'squirming' (and usually damage) is unavoidable.
Sorry Chris....when I referred to jet sizes, I meant 'flow rate' as opposed to 'hole dimension'....I think DJ are measured by flow and OEM are measured by dimension. Regarding the rubbers, yes I would use 'good secondhand', but as yet I haven't found any really good ones......I have a few pairs now, but unfortunately some the seal ribs have chunks out of them so although I have built up the missing bit of rib with silicone, I'm not convinced they are sealing properly....that means I'm ultimately having to screw them up bl**dy tight, which of course causes distortion. (Don't forget I'm an ex Guzzi owner, so I'm fully aware of rubber manifold connectors....which can be bought brand new for £8........!!.....pity they don't fit). I always used to give them a 'dry wipe' of WD40 before fitting....never caused a problem. AL
just for reference re: Dynojet, here's my airbox mod that I tried when I got water entering carbs via usual, fully cut down lid a few weeks ago :-
That's clever, Chris.....Fortunately, I just have the trumpets removed from mine, so water isn't a problem (so far), but I am intrigued by your rearward facing ones...... .....If you recall the days of car mods and bonnet scoops, the correct thing was to have an 'Out' but not an 'In'......but I guess with yours you have clean cool air passing through the airbox......It would probably be even better if the front trumpets were relocated lower down and more forward (blanking off the OEM holes)....that way the air would pass right over the whole of the filter. Next job, maybe? AL
Interesting suggestion AL but it was always going to be a compromise rather than an aerodynamics/windtunnel venture as there are hardly any places where you can site additional trumpets (this is shrek 2 btw) - correction, I think this is the only place you can site additional trumpets without more modifying. It's a personal thing , and I guess most people wouldn't even bother fitting the additional trumpets.At the end of the day I only posted it because it works. I tried one trumpet to begin with but that was starving engine of air at top end but two really work a treat. If engine had far more mods then I'd look at it again but meanwhile very happy with result.
I meant keep the rearward facing ones...seem like a brilliant idea, but possibly move the front ones down, unless there is not any room to do so...but I suppose they could end up being exposed to water again if they were lower. However, your idea does lend itself to a much simpler mod than hacking the top of the airbox as others have done....and thats cut the airbox straight across the back about 1"+ above the bottom (roughly where the bottom your rear trumpets are) and cut the side curves back to the line of where the front trumpets dished areas are. Then cut another 1" off the curve in line with the cross cut you already made and junk the offcut......That way you have a flap which can be raised slightly....add a couple of infill bits to the sides with glue (or pop rivets) and you have a full width rearward facing scoop. Just an idea. AL.
A quick update on Dynojet stuff......... I found it necessary to talk to their technical department again today........It appears that some of the information I was given earlier in the year was incorrect. I am now told there are slight differences between the 900 and 750 Stage 2 needles, but probably not noticeable if accidently fitted in the wrong bike; unless the engine and carbs are in tip top condition.....The difference (if noticeable) could probably be cured by inserting one or two of the tiny washers or raising / dropping the needle one notch. However, I wish I had been told the following earlier......apparently the 900 and 750 slide springs should be the same length......104mm uncompressed without the plastic end insert......That means for some unknown reason, the springs in my carbs are short by about 12mm, which the techy thinks could be causing flutter and rough running at low revs (lucky I have some spare springs the correct length). Why they are short, I have no idea.....they were in the bike when I dismantled the carbs having suddenly developed a misfire after three years without problems. Maybe the age of the springs has caused mine to compress a bit, although I can't see it. AL.
