Drop in K&N+slip-on+stock jets?? advice please

[cheddle]

Hullo! I have a k9 gs500 - i purchased it with a K&N drop in and I am soon to fit an after-market slipon. the can is a straight thru almost the same size as stock but has a larger internal diameter.

Currently when cold the bike requries a resonable ammount of choke to get going and runs a bit sluggish untill warm.

I am concerned that with the conservative stock jetting that I will run into real problems with the can fitted... I intend on goign for 20/62.5/145's however this will likley be a good month or two after I fit the can...

I want to know if I am going to cause any harm (melted pistons, pitted head, burnt valves etc...) from running the bike with the drop in, a straight thru can and stock jetting...

Thanks in advance.

[Big Rich]

Why so long after you fit the exhaust? Jets are relatively cheap, and it doesn't take long to change them out.

[cheddle]

I have half a mind to tackle them myself however the bike is going in for its 6,000km service in about 4-6 weeks so I was going to have the jets done at the same time by the workshop...

SO... I am trying to gauge if putting the can on 800km's prior to the jets is going to be a problem for the engine (i know it might run poorly but I am concerned with damage) or if I should do the jets myself OR if I should wait to put the can on and do it all at once... the problem is the shop that will fit my pipe (its not a gs slip on) is some distance from the shop that will do the service... Pipe is ready to go now, service isn't due yet...

I dont have the confidence to tackle the jets myself, this thing about drilling and tapping my carbs really puts me off... If I pay a shop to do it and they damage the carbs its their problem to fix... not mine.

[Big Rich]

Drilling and tapping? I've never tapped anything when rejetting...... and only drilled the plugs over the mixture screws. But you have to work within your comfort zone.

I won't say you will or will not harm your engine by installing the exhaust first - but there is a possibility, yes. Actually, your air filter alone has the possibility as well. But if you are that concerned with it, why not just wait to install the muffler? Assuming you have the stock one on now, it won't hurt to leave it there.

[radodrill]

Changing the jets is actually quite easy.  I just bought the same bike and put in a K&N drop-in (without the restrictor); even with just the filter change I am benefiting a lot from rejeting the carbs.  ATM I have 17.5/62.5/142.5 jets in it; the mid-high range is vastly improved (over stock) with a lot more pull and acceleration  I now just have to fine tune the low end and idle performance.

[cheddle]

sorry, I was reffering to the drilling and ez-out process... the mixture screws.  I might get a mate to give me a hand with that part.

I guess what I am trying to do here is to either validate or disprove my concerns about possible engine damage and am hoping to hear from someone who may have attempted this in the past (maybe no one has and everyone has just done it propperly and had the jets/pipe/filter done at the same time lol). I appreciate the advice Big Rich 

I have read that 20/62.5/145 is a good combination for slip-on/drop-in

hmm... I am off to research changing these jets in a little more detial. I have asked my dealer to source me the jets.

I am still interested to hear how the bike reacts to stock jetting with pipe/filter installed...

[radodrill]

I haven't tried it with the drop-in and stock jetting.  With more airflow and stock jetting, the A/F mixture will be leaner resulting in a hotter burn.  The best is always to rejet when installing less restrictive intake/exhaust components.  Though there are apparently a lot of videos on youtube who put on a performance exhaust without rejetting; even so this will probably result in a loss of performance.

Changing jets is quite straightforward.  Once you've removed the carbs, you remove the float bowls and the jets are right there; just unscrew and put in the new ones.

[cheddle]

thanks Radodrill - so do i need to remove the top of the carb at all?? or just the float bowl from the bottom?

[007brendan]

Only possible damage I can think of would be your engine running hotter from being leaner.  I would imagine you would see smoking before any damage could be done though.

Yes, just take the carbs off, remove the bottoms of the float bowls, and unscrew the jets and replace them with larger ones.  You need to remove the tops if you're planning on shimming the needle jet with another washer, or if you want to do some serious carb cleaning so you don't get any solvents on the plastics and rubber diaphram.

The brass plugs over the mixture screws pop out pretty easy, as long as you don't use a drill bit that's too big, there's really not much chance of causing any damage.

[radodrill]

so do i need to remove the top of the carb at all?? or just the float bowl from the bottom?

The needle height (as well as the mid-main jet) affect the mid-range performance.  You can get close with just the jetting, but for the most optimum performance you'll have to open the top and put in small washers to raise the needles. Just be careful not to lose the springs.

I currently have 3 additional washers under the needles; if I bought a 65 mid-main I might not need any.

I bought several main jets so I was able to test a few options to see which gave me the best performance then am going from there for fine tuning.  BTW, I can do a complete jet change (including removing/installing the tank etc) in about 45 min.

[cheddle]

thanks very much - you have essentially made my question null as I am now going to rejet (myself) prior to getting the exaughst fitted.

I will rejet to 20/62.5/145 - Radodrill what mid-main do you currently have?

My carbs are only a few thou kms old so I would assume they woudnt need cleaning.

[The Buddha]

Slip on and drop in (you mean K&N in the air box) is 135 mains 20 and you can leave the 60 pilots in there. 145 is far too big.
147.5 is for K&N instead of the air box.
Use mikuni jets, do not use the DJ garbage.

Cool.
Buddha.

[radodrill]

Radodrill what mid-main do you currently have?

As I said earlier; at the moment I have 17.5 pilot, 62.5 mid-main, 142.5 main, 3 washers, and 2.5 turns.  This is using stock exhaust and a K&N drop-in without the restricter on the filter.

[The Buddha]

Radodrill what mid-main do you currently have?

As I said earlier; at the moment I have 17.5 pilot, 62.5 mid-main, 142.5 main, 3 washers, and 2.5 turns.  This is using stock exhaust and a K&N drop-in without the restricter on the filter.

3 washers and 142.5 mains - you sure ? You may be very rich up top.
The 62.5 is fine, the 17.5 is OK, especially since you're super rich on the mains.
That 3 washers and 142.5 - IMHO is atleast 2 washers and 2-3 jet sizes too much.

How is top end response - 1/2 throttle and up.

Cool.
Buddha.

[cheddle]

cheers budda - the interwebs told me that people tend to run lean up top with 142.5s, k&n dropin and a slip on? Maybe it was teh lunchbox that caused this problem and I misread...

Staring at the http://beergarage.com/GSMatrix.aspx leads me to think that there are a few people out there with fat mains - I see a few running lunchboxes/slip-ons with 147.5's and 150's

taken from http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Rejetting
"
A conservative Starting Point for upgraded Jetting (Pilots/Mid Main/Main) for a:
Stock GS500 = 20/60/135
Drop in K&N Air Filter Only = 20/62.5/140
K&N Pod or Lunchbox Air Filter Only = 20/65/142.5
Drop in K&N Air Filter + Sports Exhaust = 20/62.5/142.5
K&N Pod or Lunchbox Air Filter + Sports Exhaust = 20/65/145
"
Maybe I should try a 140... hmm

Looking for advice here Budda

[radodrill]

3 washers and 142.5 mains - you sure ? You may be very rich up top.
The 62.5 is fine, the 17.5 is OK, especially since you're super rich on the mains.
That 3 washers and 142.5 - IMHO is atleast 2 washers and 2-3 jet sizes too much.

How is top end response - 1/2 throttle and up.

Cool.
Buddha.

The top end is actually quite good with a smooth hard pull from ~3-4K all the way up to red line.  If I use a 145 main then with WOT it'll stutter a bit around 6-7K with less pull; with the 140 main it has a dead spot at 6-6.5K.
Using the 142.5 main and 2 washers (62.5 mid) with WOT it had good pull in the mid range with a small noticeable increase at 7K rpm.

The GStwin wiki actually listed 20/62.5/140 as a conservative starting point for a K&N drop-in and stock exhaust.  With those jets and 1 washer I had less top end pull and rich idle, which is why I went back to the stock 17.5 pilots.  Note: I did not install the flow restrictor that came with the K&N drop in filter.

The only complaints I have with the current jetting is that there's a slight jerk going from closed throttle to slight throttle (and vice verse) and that if I go >1/2 throttle at <3K rpm it spits a bit (rich low end).

I was also reading Factory Pro's CV carb tuning procedure and they also list slight adjustments to the float height as an effective means of leaning out the low end.

[The Buddha]

Cheddle - I dunno those numbers you got from -  http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Rejetting  - I dunno they are outdated.

I have an Pipe but stock air box/filter GS - its a 95 with 04 carbs on it. It runs 20/132.5 + 1 washer. Runs perfect, except my air screws @ 4 not 3.
Essentially its jetted +1 over stock all the way across. I sell this setup, and its worked well for lots of people. I get feedback, and never had an issue with this setup.

I've recomended 20/147.5 on the K&N and pipe 01+ GS. This however isn't always a slam dunk. Some guys have moved richer from there (beergarage being one of em). But I was unable to get mine to run without spitting and sputtering when I tried it with even 150 past 3/4 throttle - It may be better in winter, I tested it when it was dry and warm, not cold and wet.  With 147.5 it behaved well enough when hot and dry to let me assume it will work well even in january in NC.

The K&N in airbox with restrictor is +1 over the stock. So 135.
No restrictor is +2 over stock - 137.5. However these 2 setup's I never run on my bike - I probably should ... I have airbox K&N somewhere round here ... let me start being able to walk and I'll do it.

Radodrill - If it runs fine run it. Just keep an eye on it and get a trial run on very cold and humid days. However I think you're rich, so you would probably have no issues.

I think that 3 jet system has thrown another wrench in things, and essentially for nearly no gain. I dont feel its better than the 2 jet 89-00 ... its not worse, but not better either. I guess they had to throw in some new crap into the GS when the rest of the bikes went FI. It appears we were too happy with our old 2 jet carbs and buddha kits were making life miserable for them to sell parts ... he he, though I started selling jets only after they changed the carbs.

Cool.
Buddha.

[radodrill]

Radodrill - If it runs fine run it. Just keep an eye on it and get a trial run on very cold and humid days. However I think you're rich, so you would probably have no issues.

It runs great and IMO way better than stock.  With the stock 17.5/60/130 and stock air filter, it had good low-mid range performance but not much on the top end and didn't pull hard for WOT acceleration.
Right now the low end is rich and still needs some adjusting; but other than that she runs good.

Around here in Morgantown, WV the winters are generally quite mild and I ride to school most of the year; so I'll definitely be keeping an eye on it.

[BockinBboy]

Everything I've read on the forum points to much difficulty correctly jetting radodrill's setup ... I don't think I've come across anyone on the forum who has gotten tried and true results with the K&N drop-in, using no restrictor ring, and a stock exhaust.   They always get mixed results with rich at one end and lean at the other end and vice versa... first example that comes to my mind is bombsquad's '93 refresh' build thread... had a heck of a time dialing that in, kept stepping it up here, dropping it there... couldn't land anything too good, and finally just went back to stock setup... said that he rather spend time riding than fiddling.  I also think of the many jet threads started with K&N drop-in, first couple questions are if they are using the ring or not, first suggestion is always to use the ring with it if they aren't.. and if that didn't solve it, it was switched jets or float height/needle issue...

Rado, please let us know when you land on it, if you continue to work with it.  But as Buddha says, if it runs then fine. The only thing odd is that it is rich low-end with stock 17.5 pilot, which is known to be lean even using a stock air filter. Kind of goes against general logical thinking when you use a freer flowing intake. 



- Bboy

[The Buddha]

Rado, please let us know when you land on it, if you continue to work with it.  But as Buddha says, if it runs then fine. The only thing odd is that it is rich low-end with stock 17.5 pilot, which is known to be lean even using a stock air filter. Kind of goes against general logical thinking when you use a freer flowing intake. 



- Bboy

That's cos the mains and needle also make the low end rich. If the low end is too rich, you will have a horrible time with warm re-starts. I set them rich all the way across, except @ idle. You need it to be a shade lean @ idle.
Pilots control the idle-1/8th thtottle, you cant switch to 15's, it will make it too lean down low.

I've had jetting advice say "get the mains right before fiddling with the lower end" ... except on all those bikes ... every one of em, the pilots are never changed. GSXR's, Kawi's etc etc all of em dont react well to a pilot jet change. On a GS, you will have to get the pilots sorted out before you try the mains. Your choices of pilots are very limited. On a 89-00 GS, 42.5 is death to take off's. 40 is ideal, 37.5 is looooong warm up's with misfiring etc etc.

Cool.
Buddha.