Carburetor Jets with Vance and Hines Exhaust and Octane Question

[bergj1986]

My bike came with a Vance and Hines exhaust and I don't think the carb jets were changed to make the air/fuel mixture richer (slow warm up, backfiring, white and black spark plugs).  I've been checking around online and haven't found anything definite on the jet size for my bike with this exhaust system.  This is the only mod on the bike, the air filter is stock.  If anyone has this setup, could you please tell me what jet sizes you used?  Also, I just filled up with 87 octane and noticed some knocking/pinging during acceleration.  Is this due to the lean mixture or the low octane gas?  I have no problem buying 93 octane gas if needed.

Thanks,
Josh

[scottpA_GS]

Search "jetting Matrix" or Jetting.. This thread may be helpful

http://gstwins.com/gsboard/index.php?topic=35237.0

As far as the fuel... It seems that jetting is your main problem and possibly valves, as the GS can run on low octane fuel with no trouble at all 

[kml.krk]

if you are going to change the jets (which you should) you should also consider changing the air filter to something with better air flow (stock air filter is very restrictive), since it may not be easy to choose correct jets sizes with stock air filter and high flowing exhaust. I'm not saying it can't be done, but I don't think it's the best option to have poor air intake and high air output.

basically you have 2 ways to go:

1. keep the bike louder (V&H exhaust) get the K&N lunchbox filter (K&N RU-2970) and rejet with appropriate size jets

2. make bike quieter (little bit less powerfull) get the stock muffler, put it on and leave everything stock (but eventually you will want to change the jets anyway to shorten the warmup times and get rid of factory leaniness)

good luck

KaMeL

[bergj1986]

I've checked out a few online retailers and found the K&N filter for about $35.  Now, as for the jets, would a DynoJet Stage 1 Jet Kit work?  I found one on eBay for about $73 (which seems rather expensive to me).  Is this kit designed for what I'd be doing to my GS?  Buying jets separately seems rather time intensive.

http://cgi.ebay.com/ebaymotors/New-DynoJet-Stage-1-Jet-Kit-Suzuki-GS500-GS-500-F_W0QQcmdZViewItemQQcategoryZ35597QQihZ013QQitemZ230174210547QQrdZ1QQsspagenameZWD1VQQtrksidZp1638Q2em118Q2el1247

[ohgood]

I've checked out a few online retailers and found the K&N filter for about $35.  Now, as for the jets, would a DynoJet Stage 1 Jet Kit work?  I found one on eBay for about $73 (which seems rather expensive to me).  Is this kit designed for what I'd be doing to my GS?  Buying jets separately seems rather time intensive.

http://cgi.ebay.com/ebaymotors/New-DynoJet-Stage-1-Jet-Kit-Suzuki-GS500-GS-500-F_W0QQcmdZViewItemQQcategoryZ35597QQihZ013QQitemZ230174210547QQrdZ1QQsspagenameZWD1VQQtrksidZp1638Q2em118Q2el1247

One of the members likely has a few jets laying around. Most folks here will roast you for paying for a DynoJet kit. Oh, I have a V&H, with a K&N filter, it runs fine. My plugs are ok, etc. 

The K&N filter is cool because you can re-use it. There seems to be a difference in the filter's performance to me between clean and dirty also.

I haven't rusted through the V&H yet, and it pops -sometimes-.

So, anyone have any jets  laying around ?

[bergj1986]

So you're running the K&N Filter and V&H exhaust and are running stock jetting with no problems? 

I thought the DynoJet Kit was WAY overpriced for what it is, I've purchased jets for previous bikes and they're usually a couple bucks per jet, I just don't wanna be guessing and buying.

I'll put up a pic of my plugs

[bergj1986]

Plug from the right cylinder looks ok, the plug on the left cylinder has a an ivory white electrode and electrode tip, flat surrounding the electrode of flat black (makes me think one cylinder is running lean and the other isn't).  Could this be caused by non-synched carbs?

[kml.krk]

you will be better off if you buy jets separatelly, you didn't mention year of your bike, but pre 04 bike's carburetors jet kits from Dynojet require you to drill slides and other stuff, you probably don't wanna mess with that. it's simpler and easier to buy jets, use stock needles (shim them a little using $0.02 washers) and you're ready to go.

ask forum user:   seshadri_srinath    if he still have any "home made jet kits" available. he used to have them

good luck

[kml.krk]

also: you may want to get the carburetors apart and give them a good wash!! piece by piece, jet by jet. one of your jets may be cloged - it may result in white spark plug.

hope this helps a little

[bergj1986]

Thanks for the help, I'm gonna take the carbs off the bike and check the jets when I have some free time.  You might be right about the diagnosis, I would think if the jets in both carbs are too small, both plugs would show a lean running condition.  I'm gonna clean the carbs first and see what happens, if the plugs continue to look the same, I'll get larger jets. 

My bike is a 2001 with about 7500 miles, when should I adjust the valves?  Like I said earlier, I do hear some knocking/pinging during acceleration.

Thanks,
Josh

[kml.krk]

here is the maintenance schedule for GS500:  http://gstwin.com/maintenance_info.htm

based on this web site you should check valves every 4000 miles -> you should definitely check them now! The pinging may actually be the valves, NOT the low octane fuel. People run GSes on 83 and 85 octanes without a problem, you should run higher octane fule if comprssion of your bike has been increased or if you messed with time advancer.

good luck

KaMeL

[ohgood]

So you're running the K&N Filter and V&H exhaust and are running stock jetting with no problems? 

I thought the DynoJet Kit was WAY overpriced for what it is, I've purchased jets for previous bikes and they're usually a couple bucks per jet, I just don't wanna be guessing and buying.

I'll put up a pic of my plugs

I should have specified. No, whatever is on the matrix is what I'm using. I don't really remember what it is anymore, and actually afraid to look since it runs ok right now

sorry for the confusion. v&h + _______ = rejet
v&h + k&n = rejet
k&n + ___________= rejet

[kml.krk]

how about   STOCK = REJET   

[bergj1986]

I ordered larger jets from motorcyclecarbs.com, I'll let you guys know how it turns out.