Anyone swap out pilot jets ...

These Max X's have 35's stock.
I happen to have a say dozen or so 37.5's lying about. (GS500 come stock with 37.5 and I have done so many GS carbs and the first thing I do is drop in 40's) ...
Now mine had 1 blocked and 1 partially blocked and still ran OK. I also am planning on knocking out the air screw caps. Is it worth trying 37.5's. Any one else has so far ??? TIA.
Cool.
Srinath.

 

I don't understand why you would want to do this? Wouldn't turning the mixture screw out give you essentially the same effect?

I understand that the mixture screw on the Mikuni's is an air-fuel mix, so this is not 100% true. But don't our bikes run a little rich while idling anyway? So why make it richer?

 

Air screws are idle mainly. To 2K. Pilots are 0-1/8th throttle ... aka gentle take off from a dead stop and some very low gear putting around. The GS500 had 37.5's for US bound bikes and 40's in all other countries to cheat the epa. Even canada got 40's. The single biggest thing for rideability in that is the 40's. I'd put 40/125 1 #4 under needle and 3 turns out on mix screws on stock bikes (1 size up on everything). Runs like a charm.
The Max X pilot bump up ... well the jury still is out ... :lol:
Cool.
Srinath.

 

Well, if it works, then I would be very happy to buy some of those jets from you!

 

Upsizing the pilot depends on whether you've upsized the main jet or not. Apparently the tried and tested method is incresase pilot jet by 1 size for every three size increase in the Main Jet.

Three sizes main/1 pilot is extreme but is the recommended increase going from standard exhaust/filter to Pods and 4-1 exhaust for a four cylinder bike engine.

 

That's a bit drastic I think.
Pods and pipe dont have much (not nothing, but not a whole lot) to do with pilots. The pilots are in the under 1/8th throttle range. Pipe and pod are over 1/2 throttle mainly ... now on a GS I'd put in 1 up on pilot for 7 up on main with pipe and pod. Going to 2 up from stock on pilots are disaster. I know cos mine came that way from previous owner, and I'd stall at traffic lights taking off till I figured out and fixed it.
I swap pilots only in cases where they put better jets in other countries. I tried 1 larger pilots on my eli 1000 as well and it was horrible. In fact other than a GS I dont have another bike where pilots had to be upped.
Maxim X the jury is still out ... :lol: ...
In any case its suffereing from airfilteritis ... and srinathisacheapstakeitis ... where I cut foam and put it in place of the paper in a stock filter frame. Too thick foam now I believe.
Cool.
Srinath.

 

Sorry Srinath but I have to disagree with some of your logic. Pilot size works more than just the lower range. It works to feed all the way to full throttle. A quick check of the gallery between the main jet/emulsiontube and the pilot gallery shows a 2mm(approx) connecting gallery between the two. So the two work together all the way.

Pods and pipes therefore have a lot to do with pilots as they allow far more air thru. Small pilot plus more air equals lean running compensated by large main to richen it up.
Going 7 up in main jet size is probably just compensating for too small a pilot jet.

IMO, going 7 up main is not nessecerily giving more power it just means your pouring more fuel in that is not being burned because the pilot is not letting enough fuel/air in. Hard to tell at full throttle but maybe wasting gas.

The following is a quote from Bulldog @ Barons. It is a bit long and hard to read but well worth two reads to come to grips with how carbys work.

This is my carby tuning bible from the people who really know carbs.

Following illustration illustrates where each jet works most.

Cheers
HG

 

Yea I know pilots add fuel all the way across. However going up in pilots to richen the top 1/2 will destroy your low end.
I also know more gas isn't more power ... in fact leaner bikes make more power. I like to jet it to run without needing adjustments from the coldest day to the hottest day in the area I live in as well as elevation changes I am likely to use it in. I have done 1000's of runs with an oxygen sensor screwed into the pipe on a GS500. Your carb diagram while its true its a bit confusing. Look at mikuni's instructions that come with every factory jet kit.
Richening up one area will invariably richen everywhere else, just to what extent is what matters. Put a bigger main in and it will give you a richer low end too. For a stock GS 1 do 1 size up mains and 1 up on pilots and 1 washer under needle and 3 screws out on mix screws.
The write up has a couple points where they disagree with mikuni/factory instructions. They say you need to get mains right first before trying the idle/pilot circuit.
I'll also tell you one other thing ... there is no way pods and pipe included ... other than motor internal mods (flowing, high compression pistons, head work) ... that a Max X will need 2 sizes larger pilot. It may need a 6 sizes larger mains with pods and pipe ... easy. 105's in it stock I dont see holding up to any mod at all. Put a filter and its gone. The 35's for pilots are plenty ... 37.5 is all you'd possibly need.
Stock pipe and filter flow just fine at low rpm. Not just on a Maxim, even on the GS500. I am not compensating for the pilots with too big mains ... no way to do that without getting the top end so rich it will barely run. Look for the factory guide to jetting, its much better. Lemme see if I find a link.
Cool.
Srinath.

 

http://www.factorypro.com/tech/carbtune ... gines.html

That was what I was reading eons ago ... I have since graduated to doing runs with a O2 sensor and precisely know where what is rich or lean ...
Cool.
Srinath.

 

Now I know it seems like I'm nitpicking but I prefer this discussion to be correct for reference of the people who read this later for advice.

The write up states

And the article in the link states do it in reverse which I personally think is incorrect.

Setting a high main jet is no good if the low end is inadequate to get it to WOT.

Damn, carby's have to be the most confusing part of any bike to modify. :wink:

 

Oddly I prefer to do it bottom up too ... however it may take you a while to get it revved up over 1/4 throttle (will prolly not unless you're starting with somehting sooooo far off ... which you wont cos you're starting with stock set up ... ) but once you're there you'll not have a problem.
Setting up the low rpm first may mean you'd have to do it twice.
I'd say if starting with stock ... do high then see if you need to do low ...
If starting with a modded motor and new carbs ... do low end first ... maybe that's the way to interpret these semi conflicting write up's.
Cool.
Srinath.