One thing I have learnt working on a few Suzuki slingshot carbs which are effectively the same as ours is to check the diapragms for tiny tears , best to take them off the slide top and strech to have a look all around
those little monkeys get everywhere don't they? Seriously, totally agree - I hear that it's a constant problem where temperature constantly high.
Well I've stripped down my Carbs today , engine has high comp pistons fitted, ported head, full spaghetti system, dual oil cooler and lightened flywheel, its got Dynojet needles and springs fitted but low and behold Mikuni 140 mains, and theve been in there a long long time, I wonder if back in the day some tuning shops kept the Mik std jets in for a reason? I'm thinking of putting FCR41's on mine to complement the rest of the tune
Are you sure they are Mikuni main jets? the Mikuni OEM jet will have a small square motif by they number.....Dynojet mains will have either just the number or the number and a dot. AL.
Al yes there Mikunis all right, very strange as they have been in there a very long time and this is the second instence of someone having Std jets with DJ needles and springs. The Mikuni logo for those who dont know looks like this and usally apppears on all jets needles etc. Mikuni Logo as Stamped on Jets etc View attachment 5724
Are the springs 104-105mm long? You can easily identify the needles from the standard ones.....the DJ needle is quite a fine pointed item, usually with no marking; whereas the OEM one is pretty thick like a nail with a slight taper, plus the size and the motif (for the 750 & 900ss it is '5C19'). The OEM emulsion tubes should be marked 'Y6' for the 750 and 'Y2' for the 900. AL.
The worst thing about the OEM Mikunis is adjusting the float height / fuel level....... .........There doesn't appear to be a definitive basic setting for them....and the variety of dimensions advised are contradicted by each other......Even Factory Pro contradict themselves. AL
OK Al, enlighten me. I put a DJ stage 2 kit in the carbs, fitted new emulsion tubes, mixture screws, spent a few hours in a sonic bath, and the bloody things just wont get steady tickover or balance up right. Possibly a sticking float valve. Anyway, I have acquired the 600 carbs and plan on fitting the DJ kit in to those, but what else do I need to change/swap over? Thanks Paul
This might help...........you can ignore the 900s. Also, if you look in the inlet throat you will see an air jet which may need changing over and there is also one where the diaphragm is. You may also need to change over the air cut-off valve diaphragms. The main thing about these carbs is getting the float / fuel height correct...........There is no specific dimension, but 14mm is apparently a starting point.........mine are at approx 13mm.....the smaller the figure, the richer the idle mixture. With the carbs off, take the float bowls off and with the carbs upside down, turn the float bowls around and re-rix with two crews so they hold the flaot assemblies in place. Tip the carbs slightly sideways so the needle is just shut (you don't want the floats compressing the spring in the needles) and measure the distance between the carb 'gasket' face and the rectangular float corner). AL
Just read this, wow so much info. Mines not running too well, idles not great. Cleaned the carbs twice, still pinks a bit on the front cylinder. I've been putting it down to needs a good run after standing for 12 years but I may be wrong. It dose rev fine standing still, hope its ok under load. Hope to go for MOT in a couple of weeks so will see then.
could be so many things considering how many galleries there are just concerned with the idle circuit. How many turns out are your idle mixture screws set at? also are they in good nick at the business end with good sealing grommets? Just got my 900 Elefant running after 8 years standing (also with Dynojet needles plus 140 mains) and an increase from 21/2 turns out to 31/2 turns out made the idle settle down and start responding normally. As said, the air bleeds are sometimes different (600/900) but also the progression hole diameters.
Note the point I made in about float level in conjunction with Chris' point about the pilot screw number of turns..........if the float was set above 14mm, then you will probably find the pilot screws need to be out about 6 turns....IE nearly falling out... Dynojet Stage 2 pilot screw setting is 3.5 turns out (for a 750SS)
Gilps I've got a set of 900 Carbs - just need the front plate (they were donors for the carb heater kit) which should be interchangable Let me know if you want to play with them to help find a solution and I can drop them over to you.
That's my problem I reckon, my are on 2 1/2 turns out. Will adjust tomorrow and hope that helps. Will I need to rebalanced the carbs after this, that bl##by screew is a sod to get at!!??
Cheers mate, that's real generous. I think I should be ok now though. I'm going to Louigo Moto with both sets on wednesday and hopefully will end up with something that works.
you shouldn't have to re-balance, no but you might find that idle speed will be increased by a few 100 rpm. EDIT All our engines and set-ups can be subtly different so you will be using above as a guideline for your particular tuning and it could be that 3 turns out will make enough of a difference. Don't forget to allow for the possibilty that yours could be worse at 3 1/2 turns out but equally as AL said, it could be that you need to adjust even further depending on the state/tune of your engine.
