Yes Johnboy, correct. I found them while trowling through the bay... Someone from Germany sells them from new. Cheers
The Yamaha TRX850 had the same carbs. I once replaced the choke needles on my 900SS carbs as they looked rough, though not as bad as yours. I got a set from a Yamaha breaker for a few quid. Bike ran better after that.
At the moment I just want to get it going. All slow now.. as getting cold, early dark and little time.. Got the new chokes fitted, and set the floats to ~14mm (square side of float). I checked the float height afterwards with the clear tube and it was on both carbs next to the cast feature. So all good. I wasn't sure the setting for the pilot screw. Previous thread I was going through, stats 1.5 rotations to start with. Is that right for a std 900ss, no stage 1 or 2, std exhaust (loud)? Cheers
I know absolutely nothing with regards to this type of thread love threads like this, looking forward to you getting this sorted Alex
Stage 1 and Stage 2 depends on whether you have a Dynojet kit (or similar) fitted in the carbs. As I don't know the answer to that point, I suggest you start with the pilot screws at 2 to 2.5 turns out. With regards to a Dynojet kit, there are a couple of posts on this forum which shows the significant difference between OEM and Dynojet. As you have had the carbs apart quite a bit, hopefully you can recall what you have seen. AL
Will need to look through the dynojet thing, but I doubt anything else than standard, my Dad wasn't a big mechanic, kept it to oil, sparks, battery and fuel. So he wouldn't have fitted anything aftermarket. I had it back together and gave it a squeeze on the starter... So I turned the accelerator cable screw higher and higher, to at least get some idle. Pilot screw is at 2.5turns. Still get misfires from vertical cylinder(nearly had my eyebrows burnt ), or both cylinders. Unplugged one spark after the other and started in-between. Still felt rough, didn't matter which spark was plugged.... So I guess needles next?
When you assembled the carbs, did you pre-balance them before you fitted them? By pre-balance, I mean use a thin piece of wire inserted into the throat at the bottom of each butterfly like a feeler gauge and adjust the balance screw so both carbs are just open at the same time. You can then adjust the balance a bit more once the bike is running, assuming you have a balance gauge.
Thanks for all the feedback. Last night I got a bit of time to check the mechanical balance of the carbs with a feeler gauge. To at least get the basics sorted. I set the vert cyl to 0.2mm between the butterfly and body, so it just gently slid in. Then I adjusted the hor cyl to get the same gap between butterfly and body. I have some screw nipples on order to check the synchronisation later. All new things to me, excited to get them checked But I guess, it needs to run first... I lost the small o-ring in the abyss of the vertical cylinder, but managed to recover it... Had a little finger camera to look a bit deeper
Evening all, After I managed to mechanicly balanced the carbs. (both butterfly's are at same distance) I got it to start, still badly. Idle screw (with the spring) does next to nothing. Only if fully out it holds idle with choke full on. Pilot jet screw set to 2.5 turns. It feels like the hor cyl is lagging. If you look at the first video you can see the slider on the right hesitates. And it makes the throttle sluggish. While the vert cyl feels like more crisp. I swapped the diaphragm right to left, to see if it makes a difference, but no. Pilot screw at 3.4mm (9 half spins = 4.5rot) Bike only runs on choke. As soon as I remove it, it stalls... Got a few little videos: Still fairly early start. Oil needle slightly raised. Pilot jet at 2 turns and here after a bit of fiddling.. Oil at 80degC Pilot jet screw at 4.5 turns (was 5 pre carb strip) Feels like a bit better in the throttle, but still in choke Now I'm able to reduce choke to half, but always close to stalling. Full choke lift idle to 1200 rpm ish. Every attempt to switch off the choke, stalls it...
what size jets are fitted might be idea to check against standard to see if someone has changed them at some point had a gs 550 wouldnt run without choke jets were completly wrong other thought have you ckecked for air leaks around the manifolds possibly cause similar issue
Have you attempted to balance the carbs when it is running with the choke on? Also with the choke fully on, it should run at around 3000rpm. Try turning the throttle stop screw so the idle rpm is higher. BTW....with these carbs you can't expect the pilot screws to be exactly the same number of turns out.
Evening all, gave it another go today. Started the same way as before... difficult to get her going on the choke, as it is really fighting around the 1000rpm mark... After a while she got some temp, it always comes straight back on (only with full choke). Started by looking for some air leaks, mainly around the intake and rubber that connects the carbs. Found that I actually had to tighten the clamps on the rubber a bit tighter, result as seen on video... I used some brake cleaner to see if it had an effect on the idle, but for the moment it feels ok. I build my own carb sync tool, out of 2 milk bottles and some screenwash... I love the beauty of science. Most expensive bit were the 2 screw nipples. First attempt was just to see what was happening, and it showed stronger vac on the right carb/hori cylinder. First I tried to change the pilot screw, but quickly realised that not the right way. So moved onto the sync screw between the carbs. What a pain to get there and look at the gauge.... (note to myself: were helmet when crawling under the bike..... autsch ) Played around with the sync screw and I was able to balance them, but couldn't get a stable condition. After a blib on the throttle it felt it was moving away the other way.... and it was a bit like ping pong top is vertical and bottom is horizontal cyclinder. I will hang the bottles up next time, recording video, adjusting the screw and watching the bottles is difficult to juggle It always feels like the hor cylinder is struggling and misfiring. At the end I just rev'd her up a little to about 3k rpm and put the choke off, but still same (stalling on idle). But the bike feels happy at higher revs, just crisp. Regarding the jets, which one should I check ? 6,7,8? Hope you enjoy my story. Any feedback appreciated. Cheers
The jet number 6 is the main jet....do not confuse jet sizes between OEM/stock and Dynojet jets***.....they are calibrated by the manufacturers using an entirely different method. ***The Mikuni OEM main jet should be 140. A Dynojet main would be between between YJ116 and YJ124 for a Stage One kit......for Stage Two -between YJ140 to YJ150. ***As mentioned The Mikuni 140 is not the same as Dynojet140. All the OEM Mikuni jets and needles will have the size and a little square logo stamped on them. The other two jets will be 70 (starter jet) and 42.5 (pilot jet).....not Dynojet.....Mikuni only. Dynojet jets only have the size marked......the needles have no markings. While you are checking things I assume you have taken the pilot screws right out to see if the spring, tiny washer and O-ring are present and intact.......Lumbux was having trouble with his 750SS which sounds similar to your problem, IIRC we discovered an O-ring was missing from one carb, so the pilot circuit was drawing air through the pilot screw thread even though the screw was in place. Before you start buying new jets check the photo below so you can see what you have in the carbs.....notice the difference in the needles and how much 'flimsier' the Dynojet spring is.
Would it be worth checking valve clearances before trying to balance the carbs? It looks in your video "Ducati 900ss still searching... #1" that the engine is breathing backwards quite heavily out of the rear carb? Could that be a sign of the inlet valve not being closed fully? Please ignore the above if the behaviour shown in the vids is normal.
