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Big Rich
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Any updates Pete?
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Guest
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Sorry guys, I've been a bit slack and haven't logged in for ages!
Update wise, I found some velocity stacks to fit the carbs but have had to dodgy up a bit of gutter mesh to go over bell mouth until Unifilter release some new rally pods they have coming which should fit them nicely.
I only got my first run with the stacks on Saturday and I actually overheated her by running too lean, but that was with the needles at the mid point. I have since raised the needles. I think I lucked out and did no damage as she seemed fine once cooled down again. That's the risk you take when the only real testing is the commute... I'd love to have a bit more time for tuning runs.
Jetting wise, I'm now running stock pilots, needles two notches richer than stock, and 132.5 mains.
After lifting the needles there is still crackling on decel so I'm still lean somewhere... I'm beginning to think the 132.5 mains are still a bit small as she feels great at low to mid throttle, but once you get past that I swear she's lacking something. I'll probably get the 137.5's in later this week to check.
Update wise, I found some velocity stacks to fit the carbs but have had to dodgy up a bit of gutter mesh to go over bell mouth until Unifilter release some new rally pods they have coming which should fit them nicely.
I only got my first run with the stacks on Saturday and I actually overheated her by running too lean, but that was with the needles at the mid point. I have since raised the needles. I think I lucked out and did no damage as she seemed fine once cooled down again. That's the risk you take when the only real testing is the commute... I'd love to have a bit more time for tuning runs.
Jetting wise, I'm now running stock pilots, needles two notches richer than stock, and 132.5 mains.
After lifting the needles there is still crackling on decel so I'm still lean somewhere... I'm beginning to think the 132.5 mains are still a bit small as she feels great at low to mid throttle, but once you get past that I swear she's lacking something. I'll probably get the 137.5's in later this week to check.
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Guest
Guest
I should add I haven't put the GS500 camshafts in yet, next service is something like 1000km's away so I'll check the valve clearances and if everything looks good I'll slot them in then.
I'd like to get close with the jetting as is now first though.
I'd like to get close with the jetting as is now first though.
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Big Rich
Guest
Where did you find velocity stacks Pete? I've never seen them for the 500 carbs...
Sorry to hear you're chasing your tail with jetting again. But think of all the experience you'll have after doing it over!
Sorry to hear you're chasing your tail with jetting again. But think of all the experience you'll have after doing it over!
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Guest
Guest
I'm not worried about re-doing jetting Rich, I'm just happy to be moving forward at last after dealing with dodgy diaphragms and then dodgy pods...
I ended up finding two sources of stacks that suit 60mm carb inlet diameter, one locally here in Aus and one place called Speed Moto in the US.
Speed Moto had only one in stock and they don't look as well made as the ones here, only catch being the ones here had no way to mount as they're fairly generic.
http://www.jntperformance.com.au/index_i6515601.html?catId=269035
So I slotted them so I could clamp them down and that did the trick nicely.
They have a huge (for the 450) bell mouth of 99mm which is why the difficulty in finding sock filters to go over the top, but Unifilter have said they're releasing ones to suit up to 100mm. They were supposed to be out in March but have been delayed.
I upped the pilot and main jets last night... 20 and 137.5 respectively. I'll be happy if I end up a bit rich so I know where I'm at with the jetting.
I'll be heading out again Sunday morning so I really need to get some more fuel in there so I can get a proper feel for how she's running now.
Tom, to be honest it's hard to tell right now given it's been so long since I had a good ride with fully functioning carbs, but it is getting better all the time. Saturday was my first ride other than the commute with the stacks on and up to half throttle she felt absolutely awesome.
The biggest difference I have noticed with the stacks is that it has smoothed the throttle out quite a bit, not so jerky from a closed to partially open throttle for example.
Once I get rid of the lean bits I expect even better again.
She's definitely stronger up to that half throttle stage at the moment but I don't really know if it's more power as such or just better throttle response and fueling due to a smoother air flow.
Quite a while ago she was dyno'd and had a bit over 32hp at the rear wheel, so once I get this sorted I hope to get on the dyno again and see where the AFR is and get a new power reading.
Overall I'm happy I put the 500 carbs on and am happy I chose to go with the stacks, despite the need for fiddling with the jetting.
Oh, and the noise... the noise is quite addictive
I ended up finding two sources of stacks that suit 60mm carb inlet diameter, one locally here in Aus and one place called Speed Moto in the US.
Speed Moto had only one in stock and they don't look as well made as the ones here, only catch being the ones here had no way to mount as they're fairly generic.
http://www.jntperformance.com.au/index_i6515601.html?catId=269035
So I slotted them so I could clamp them down and that did the trick nicely.
They have a huge (for the 450) bell mouth of 99mm which is why the difficulty in finding sock filters to go over the top, but Unifilter have said they're releasing ones to suit up to 100mm. They were supposed to be out in March but have been delayed.
I upped the pilot and main jets last night... 20 and 137.5 respectively. I'll be happy if I end up a bit rich so I know where I'm at with the jetting.
I'll be heading out again Sunday morning so I really need to get some more fuel in there so I can get a proper feel for how she's running now.
Tom, to be honest it's hard to tell right now given it's been so long since I had a good ride with fully functioning carbs, but it is getting better all the time. Saturday was my first ride other than the commute with the stacks on and up to half throttle she felt absolutely awesome.
The biggest difference I have noticed with the stacks is that it has smoothed the throttle out quite a bit, not so jerky from a closed to partially open throttle for example.
Once I get rid of the lean bits I expect even better again.
She's definitely stronger up to that half throttle stage at the moment but I don't really know if it's more power as such or just better throttle response and fueling due to a smoother air flow.
Quite a while ago she was dyno'd and had a bit over 32hp at the rear wheel, so once I get this sorted I hope to get on the dyno again and see where the AFR is and get a new power reading.
Overall I'm happy I put the 500 carbs on and am happy I chose to go with the stacks, despite the need for fiddling with the jetting.
Oh, and the noise... the noise is quite addictive
G
Guest
Guest
Question... anyone directly compared the 500 carb boots with the 450 carb boots? Measurement tells me the 500 carbs have a slightly smaller engine side diameter than the 450 carbs and I think this is allowing a slight vacuum leak on the right carb as that plug always seems a little leaner than the left plug no matter what I do nor how many times I sync the carbs.
Just wanna make sure I'm on the right track before shelling out $100 for the 500 carb boots, O rings, and clamps.
Oh, and can anyone confirm they're a bolt on to the 450 head? I can't see why not but thought I should check...
Incidentally I upped the mid mains and mains last night as she still feels lean when I get to probably half throttle and up. I haven't had a chance to do any plug chops lately but I'm hoping to get some done this Saturday. In the meantime I'd much rather be rich than lean...
Just wanna make sure I'm on the right track before shelling out $100 for the 500 carb boots, O rings, and clamps.
Oh, and can anyone confirm they're a bolt on to the 450 head? I can't see why not but thought I should check...
Incidentally I upped the mid mains and mains last night as she still feels lean when I get to probably half throttle and up. I haven't had a chance to do any plug chops lately but I'm hoping to get some done this Saturday. In the meantime I'd much rather be rich than lean...
Pete, have you tried increasing the diameter of the carb temporarily with some of that aluminum tape around the carb?
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Guest
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Nope didn't think of that! Although I'm seriously thinking of swapping the boots regardless... one thing I noticed when i did get them to sit in properly (or the best I could) is that the spring for the butterfly and the vacuum port sit hard up against the rubber boot which doesn't seem right to me.
And looking closer again I reckon the boot is clamped down so much that it is starting to deform and bulging a bit. I'll try to get a photo or two to see if I can demonstrate what I'm trying to explain.
I had a great ride yesterday and she felt strong all through the rev range finally but still popping under decel with a closed throttle and if I held the throttle at say 1/8 or so then cracked it there was a period of nothingness/hesitation before she started to pull again.
In comparison, holding it at around 1/4 throttle then cracking it was a pretty instant increase in acceleration.
Unfortunately despite marking the throttle positions I got so carried away with the fun I forgot to do any plug chops... however that behaviour at closed throttle reaks of being lean still to me... where the rest of it just felt good.
And looking closer again I reckon the boot is clamped down so much that it is starting to deform and bulging a bit. I'll try to get a photo or two to see if I can demonstrate what I'm trying to explain.
I had a great ride yesterday and she felt strong all through the rev range finally but still popping under decel with a closed throttle and if I held the throttle at say 1/8 or so then cracked it there was a period of nothingness/hesitation before she started to pull again.
In comparison, holding it at around 1/4 throttle then cracking it was a pretty instant increase in acceleration.
Unfortunately despite marking the throttle positions I got so carried away with the fun I forgot to do any plug chops... however that behaviour at closed throttle reaks of being lean still to me... where the rest of it just felt good.
Sounds like the bulging boots leaking may be the only problem, or at least the main one. Try the tape.
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Guest
Guest
Certainly could be, I think I only need to make up about a 1mm diameter or so difference. Trying to find some of that locally is the big question...
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Guest
Guest
Actually is this the stuff? If so I can duck out at lunch tomorrow and get some probably:
http://www.jaycar.com.au/Service-Aids/Tapes/Other/Aluminium-Foil-Tape---50mm/p/NM2860
http://www.jaycar.com.au/Service-Aids/Tapes/Other/Aluminium-Foil-Tape---50mm/p/NM2860
Were the carb spacings identical between the original 450 carbs & the gs500,carbs? I was planning to build resleeved cammed built up 502cc GS425 next winter, & running the gs500 carbs (pre-2001 slingshots). Another member I have been chatting with about his similar gs400 449cc wiseco build had just got some early gs500 carbs for his 78 gs400 & sent me a picture of them mouth to mouth, & the gs500 carbs were slightly wider intake boot spacing than the 1978 gs400 carbs. I figured all 400/425/450 carbs would bevthe same spacing, but with the cylinder spacings being slightly different, maybe not so... With a different intake boot setup or potentially altering the linkage/choke setup/fuel tee/etc, maybe the 500 carbs could be narrowed .47" I believe is what he told me.
Any thoughts???? With the 2.8lb slingshot flatslide carbs being far superior to the 6lb stock carbs, the extra work is very tempting!
Any thoughts???? With the 2.8lb slingshot flatslide carbs being far superior to the 6lb stock carbs, the extra work is very tempting!
Looks like it, but I think it comes in thicker versions. Might take quite a few wraps at .04mm to get your required .5mm thickness, but for temporary use I bet it works OK.
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Guest
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Just remembered we're one team member down for the next 2 months, so no chance of me getting out to get some tape and lunch... I think I might stop procrastinating and just bite the bullet and order the new boots/clamps/O rings. The dealer I buy from doesn't have the boots or clamps in stock but it's usually only a day or two delay... if I can get them on before this weekend then hopefully I'll have time to feel it out during the commute and hopefully sync the carbs again on the weekend.
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Big Rich
Guest
Pete, are you planning on getting new GS500 boots? Just want to make sure.....
Chuck, I measured the spacing when I put 500 carbs on my 450 and they were identical as far as I could tell (same spacing on a GR650 as well). I assumed the spacing was the same for the 400 & 425, but have never been near one to measure......
Chuck, I measured the spacing when I put 500 carbs on my 450 and they were identical as far as I could tell (same spacing on a GR650 as well). I assumed the spacing was the same for the 400 & 425, but have never been near one to measure......
Well when the time comes (475cc or 502cc custom pistons & megacycle cams + head work), I think I will buy a set of GS500 carbs & try to adapt them by narrowing them first, 2nd bet is to adapt different boots, although I really don't want to disrupt the path of the airflow by offsetting the carbs outwards almost 1/4". That may gave other performance side effects as best as I can speculate.
G
Guest
Guest
Yep Rich, ordered 01 500 boots, O rings, and clamps yesterday. Not in stock so they're ordered from Suzuki Australia, hopefully there's not too much of a delay.
When I pulled in the drive way yesterday afternoon she was idling a little high which she hadn't done previously... sorta almost like a hanging idle... and we all know what that typically indicates!
As far as spacing goes, with the 01 500 carbs there are two long bolts that go the entire length of the carbs and screw in from the left and there are two T's that join the carbs, one of the overflow at the top and then the fuel T at the rear. There is also another spacer between the carbs at the rear.
So to widen them you would need to sort out 2 T's, a spacer, and maybe get longer bolts depending how far you need to go.
You can just see the head of the long screw underneath the stack in this photo:
The other option would be to get adapter plates made up (or make them yourself).
Bolt the carb boots to some aluminium plate which is rotated 90 degrees or so from the head mounting bolts, then bolt it to the head.
The intake hole in the plate could be cut then slanted towards the carb and engine intake... I don't know any other way to try to describe what I'm thinking... I'm not sure if that would have a negative effect on air flow into the engine or not...
When I pulled in the drive way yesterday afternoon she was idling a little high which she hadn't done previously... sorta almost like a hanging idle... and we all know what that typically indicates!
As far as spacing goes, with the 01 500 carbs there are two long bolts that go the entire length of the carbs and screw in from the left and there are two T's that join the carbs, one of the overflow at the top and then the fuel T at the rear. There is also another spacer between the carbs at the rear.
So to widen them you would need to sort out 2 T's, a spacer, and maybe get longer bolts depending how far you need to go.
You can just see the head of the long screw underneath the stack in this photo:
The other option would be to get adapter plates made up (or make them yourself).
Bolt the carb boots to some aluminium plate which is rotated 90 degrees or so from the head mounting bolts, then bolt it to the head.
The intake hole in the plate could be cut then slanted towards the carb and engine intake... I don't know any other way to try to describe what I'm thinking... I'm not sure if that would have a negative effect on air flow into the engine or not...
I believe the GS500 carbs are too wide for the 1977-1979 gs400/425, not too narrow, so a narrower set of fuel (& vent?) Tees would need to be sourced or made up, about 6mm narrower on each side of the tee if that is possible. So the carbs would need to be made about 12mm closer together if that is possible. Do you mind looking at yours & telling me of any major problems/obstacles you see in attempting that, especially with the throttle linkage & choke setup? Is it a single shared throttle shaft on the butterflies of both carbs???
On the GS425, there are already some thick (9/16"?) Thick adapter spacer pieces boltled between the head and the carb boot. I was wondering what those were on there for. I suppose it would be possible to rework those & maybe even tig weld some extra material onto them (tricky, as it's cast Aluminum) in order to be able to bore them out at an outward angle, outward toward the rear, & use the TIG add-on metal to fill in the inner rear area that the old carbs occupied. I assume these spacers are factory & have some sort of intake boot o-ring groove. Making your own would mean they would have to have a darn goid seal in the form of a gasket capable of handling cylinder head temperatures, unless you had a mchinist capable of maching a nice groove in for intake boit o-rings.
You absolutely would not want to make the new carbs angled down from the boots, as this would mess up the flow of air/fuel mixture. More modern heads like the Chevy vortec/LS series(& our tscc & tdcc Suzuki engines I believe) use a raised intake runner design so the air/fuel mixture has less bends to make as it enters the cylinder with more of a straight shot with less angle than an older head design.
You absolutely would not want to make the new carbs angled down from the boots, as this would mess up the flow of air/fuel mixture. More modern heads like the Chevy vortec/LS series(& our tscc & tdcc Suzuki engines I believe) use a raised intake runner design so the air/fuel mixture has less bends to make as it enters the cylinder with more of a straight shot with less angle than an older head design.
