Hi Folks,
I've been searching around the forum but have not found any info on later post 2001, 3 jet carb diaphragm spring length. Is there a spec on this? If not, could any folks with an open carb measure their spring length, hopefully, a standard length will soon appear after a few samples.
Let's do this for earlier pre-2001 2-jet carbs too:
1. Type of carb
2. Free Spring length
3. Number of turns of wire
Also has anyone managed to find a way lower the needle height. Possibly replace the big plastic doughnut spacer with something thinner?
Just some ideas I am thinking of experimenting with while playing with my AF sensor on the bike.
Cheers
BMF
Sure, you could replace the nylon doughnut with some #4 washers. Or whatever size that translates to in your region. If you have access to a lathe you could cut a new groove in the needle or just shave the doughnut. I suspect if you could do that you'd have just done it instead of asking so just go with the washers. :)
I can't help with the spring length. Mine is the older 2 jet type. Though they are probably the same.
Hi Kilted, thanks for the input. Have you done this before? The reason I ask is that I understood that the reason for the doughnut was to keep the needle in position and reduce wear on the needle jet. If that's true then just using washers might lead to premature wear.
I'm open to any confirmation or dissuasion ;)
Cheers.
I haven't done it and I'm no expert. I just recently got my carbs dialed in with more or less stock settings. #4 washers are commonly used to raise the needle height when added to the "donut" so if you're looking to lower the needle, I don't see why you couldn't simply replace the donut with washers. Two potential issues come up to my mind though. First is the metal washers are going to weigh more than the nylon (or delrin, or whatever) donut. Maybe not enough to make a significant difference but it seems to me that more weight on the vacuum operated sliders would result in a lower position and ultimately leaner system (which it sounds like what you're after anyway.) The second is that once the needles are all the way down to the point of seating in the emulsion tube, they're not going to go any lower. I don't know how close to that point their nominal height is.
Not sure why you're wanting it to run even leaner than the factory lean but good luck with your experiment!
Just read your other thread about the 6K flat spot and I get it. I recently had issues with an over-rich system and eventually fixed it by lowering the fuel level (raising the floats). It's just a tad outside spec and running great. But reading your thread makes me want to check my air filter. It's clean but is it the right one?...
Anyway, I think Mr.72 has the right idea of putting everything back the way it SHOULD be, starting with a complete tear down/rebuild to eliminate potential leaks, and fine tune from there. If you have a non-standard intake and/or exhaust, that can be accounted for in the initial setup as documented in the wiki and forums.
FYI re: the first question, you know these springs don't likely suffer any meaningful fatigue. They are not ever in a high-heat (>400C or so) condition, they are not loaded beyond their elastic limit. But even so, they are not a precision choice for this application. Furthermore, considering the relatively huge amount of preload on these springs, free length variances wouldn't be meaningful anyway. The spring *rate* won't change unless you change the diameter of wire, number of turns, or the spring material.
A lot of things lead to the rate at which the slide rises and the spring rate is only one of those things. Elasticity of the diaphragm has as much effect and is much more likely to degrade. Friction in the slide guide has probably more of an effect and is also far more likely to change or degrade over time. None of these things tend to come up as causes of GS500 carb issues so I wouldn't really worry about it. If the slide is not coming up or is coming up too fast then the problem is almost 100% guaranteed to be primarily vacuum since that's the root cause of slide movement to begin with. The force of it being pulled up via vacuum should be much more than the spring tension, the spring is probably mostly there to make sure it returns to bottom, overcoming any friction in the slide guide and making it work at an angle (in my estimation).
Anyway, I think you may have been barking up the wrong tree. And I think the right plan again is to try to return to stock at least as a starting point of tuning. It should run like a stock bike if everything is stock: potentially slightly lean, but otherwise functional. At least this allows you to rule out jet/needle/etc. as the cause of whatever problems and focus on finding other root cause. But a change from stock component specification in the carbs is not going to be required to get it to run properly. If you are doing that, then you may be trying to compensate for some other problem (or modification).
Thanks for the input Josh, the reason I'm looking for STD spring info is to make sure they are stock. The Harley crowd love to cut springs and then stretch them back to stock length (hard to beleive but Google it...). I've also read that the springs have primarily a damping effect on the slide oscilation, but also a non-negligible effect an needle height.
So a quick bump.
If anyone can provide the following info that will be great to build up a little same set!
Carb type: 2 or 3 jet type.
Spring length in mm
No of turns.
Hi Folks,
Looked into the carbs today and here is a first data sample.
3 Jet carb
Spring has 15 turns
Spring length is 101 mm
bump :2guns: ;)
weekly bump :dunno_black:
Does anyone know why the US spec ones don't have the 5 notches for adjustment on the needles?
Or was that aftermarket even over here?
It seems like this would solve many needle adjustment issues?
Probably because they don't want the user "adjusting" the needles. This is for smog, after all.
Non-US spec OEM needles were adjustable. Installing a set with the clip in the 4th position (from the top) does wonders to cure the EPA mandated part throttle lean areas, adding power and livening up the bike.
Regards,
Derek