Does anyone know what type of jets go in the carbs? I went to the bike shop and they asked.... which ones I needed.... round/oval? large/ small? There are so many posts now that it takes forever to find this info. Any help is appreciated.
Also, anyone have any experiance jetting with stock pipe and kn air filter ( the aftermarket one that replaces the airbox)? Do I really need to get 147.5 mains for it? I ws going to try 140, but that is still quite a few up from 122.5 stock.
Thanks,
C
From the GS500 FAQ: http://gstwins.com/gsboard/index.php?topic=12929.0
The jets are "Large Round".
Don't go 147.5 with a K&N and stock exhaust. Is the K&N the RU-2970 lunchbox style or is it the one that drops in the stock airbox?
If you have a stock exhaust with no holes drilled in it and you put the K&N lunchbox on you will need roughly 130's to 135's. I'd go 135's which will be just a tad fat.
Quote from: V8Pinto on March 08, 2006, 09:52:57 PM
The jets are "Large Round".
Don't go 147.5 with a K&N and stock exhaust. Is the K&N the RU-2970 lunchbox style or is it the one that drops in the stock airbox?
If you have a stock exhaust with no holes drilled in it and you put the K&N lunchbox on you will need roughly 130's to 135's. I'd go 135's which will be just a tad fat.
He's got an '89. 135 is going to be way too big, I bet.
I was going to get a 2970, not the one that goes in the airbox.... that one seems kinda pointless...
Thanks!
135's will be to big, try 127.5's.
Don't know if the old posts are still here but you can search for "race report" (probably also put me as author) and you'll come up with the jetting you're looking for. Srinath did all this too (long before I did and with an O2 sensor IIRCC).
I tuned the jetting through various phases of mods on my 89' by drag racing, making a mod, changing the jetting, then racing again and logging the result. If you put on the RU-2970 as your only mod, 135's are about one step too rich. You would be surprised at how lean the GS is right out of the box. (I don't know what elevation you're at - should consider that)
I would only bother with 127.5's if you're still on the stock airbox or you swap to a Uni or K&N oem replacement (has the restrictor). The RU-2970 flows a TON more air - like, I could fit my sister through it. Granted, you're still flowing through the two ~5/8" holes in the stock can but for the time invested in a first time jet swap, I would just go 135's and probably 40 pilots at the same time and goof with other mods for a while. Drill a few holes in the can and you're up to 140's and dropped a half second on the quarter mile time.
Just my $.02 worth though. YMMV - all bikes are different.