Tuning my 2006 big bore Ruckus --- journal

[Dandy Dan]

turbowagon said:

I forgot to mention, that with the 38 / 85 setting, I still needed to turn the idle adjustment screw all the way in, so maybe I'll need to go back to the stock 35 slow jet???

I'm with ya on this. I tried a 42, 40 and 38 slow jets thinking a small slow jet would prevent the need to turn the idle mix screw all the way but regardless of the slow jet, it always idle's best with the idle mix screw all the way in. Maybe I'm just too rich still and I need to go to a 35 but it's bugging me how with the 38 I still need it 100% of the way in and if I turn it 1/2 turn out then it sucks. You'd think that because it idles okay with a 42 with the IMS all the way in that when I drop to a 38 I wouldn't need it 100% of the way in still. Anyways, I posted up to ask Chanito about the slow jet and IMS relationship here:
battlescooter.proboards27.com/index.cgi?action=display&board=Tuning&thread=1162177572&page=2

Hopefully he can respond to that soon.

[turbowagon]

Glad to hear your results are consistent with mine...

When my dealer gets the bigger main jets in stock, I think I'll move back to a 35 slow jet as well (should be able to test this next week). Maybe Chanito's right... it's all about the main jet.

Unfortunately, the dealer's part lookup was missing the 88 and 90 jets, so I'm going to have to skip directly to a 92 (I ordered the 92, 95, and 98 jets).

With my luck, the ideal main jet for me will be the 88 or 90, so I'll have to get them from Battlescooter, and pay the $15 in shipping.

In other news, I had to send back my Veypor and harness to the manufacturer, since my speed stopped registering all of a sudden.

[Dandy Dan]

Whaddaya mean the 88 and 90 jets were missing? They should be able to type in the part number and get em even if they are back ordered a week or two. The parts numbers are:

99101-zh80880
99101-zh80900

That sucks about your Veypor....hopefully you get that functional soon. They're super cool.

[turbowagon]

Are you sure you have those part numbers right?

Try it yourself at the RonAyers part lookup:

99101-ZH7-0750
99101-ZH7-0780
99101-ZH7-0800
99101-ZH7-0820
99101-ZH7-0850

Are all valid.

99101-ZH7-0880
99101-ZH7-0900

Are missing?


99101-ZH7-0920
99101-ZH7-0950
99101-ZH7-0980

Are there.


My dealer's parts lookup behaved the same

[turbowagon]

What's the difference between the ZH7 and the ZH8 series?

99101-zh8-0880
and
99101-zh8-0900

do seem to work, but the base part number is not what I get when I look through the Ruckus microfiche

[Dandy Dan]

Just use the parts number in your last post....according to HaydenHonda.com, the ZH8 part number just replaced the ZH7 ones. I bought the ZH8 88MJ and it works perfectly. I think the only difference is the lower price.

Check it:
www.haydenhonda.com/fiche_select.asp?mfg=Honda&partnumber=99101-ZH7-0880

[timberwolfmadcat]

One of them the flat slot is embedded in the screws, one of them its on the flat piece

[Dandy Dan]

I don't understand

[Dandy Dan]

I had a look at my jets and I understand now....it's hard to explain but the difference is really just that the threads come up higher so there's no flat section at the top. It's really not a big deal.

Turbo, I rejetting this saturday and was able to reach ideal performance with a 35/88 setup. With the 35 slow jet I was able to reach the ideal idle mix with the screw about 1/2 way out and the 88 MJ is giving me a great top speed and a nice tan plug.

[turbowagon]

OK, I have an update (no graphs since my Veypor is out for service):

My previous jetting was 38/85, and I had to turn the idle mix screw all the way in, and I was fairly sure that I was lean on the top end.

I got the 92, 95, and 98 jets from the dealer, but I'm still waiting on the 88 and 90 ones to arrive. I decided to throw on the 92 main jet for kicks.

Now I know what it's like to be rich... the exhaust note (even on the stock pipe) is noticeably different from when I was lean, and my top end is similarly weak. So now I know the sweet spot is going to be 35/88 or 35/90. I'll probably try both out to see which one I like best.

Here's a neat observation I made, (not sure if it's typical):

When I was running lean, if I quickly went from idling to full throttle (after being warmed up), the engine would sputter and die.

When I was running rich, if I quickly went from idling to full throttle (after being warmed up), the engine would sputter and die, but then restart by itself.

[Dandy Dan]

Once you've done a lot of tuning you can start to tell if you're rich or lean by the exhaust note...especially if you have an aftermarket pipe because then it's a lot easier to tell what's going on. In my experience, a rich engine has a dull, muffled sounded exhaust note whereas a lean one has a sharper, crisper exhaust note. Anyways, I haven't noticed what you mentioned about the rich mix restarting itself but maybe....

[chanito]

I got to congratulate you on your method, i am way too deaf to hear anything with my modify stock muffler, but 90 seems too rich

[Dandy Dan]

I'm back to wondering if a 35 slow jet isn't all that great. With a 35/88 jetting setup my Ruckus idles nice when it's warm but doesn't idle well at all when it's cold but more importantly, my 0-30mph times are around 7.3 seconds and last summer with a 42/82 setup I was able to record quite a few time under 6 seconds...some as low as 5.6 seconds. It just doesn't seem to have the same low end pull any more.

[turbowagon]

Could be your main jet, maybe. Why did you go from an 82 all the way to an 88? At WOT, the main jet should be in charge of most of the fuel, right? Maybe you're rich now.

[Dandy Dan]

I'm actually get a pretty white plug. It was almost white as snow with an 88 MJ when I did a plug chop so I swapped in a 90 and the performance was identical. I tossed in a brand new plug too so I know I'm getting good readings.

Slow jets are always open so if you go to a smaller slow jet you get leaner across the board. Slow jets are a lot smaller than main jets so going up or down a size doesn't have a big effect on your top end mix but my calculations show that going up or down 2 slow jet sizes will affect your mix on the top end like you went up or down 1 main jet size. Does that make sense? So a 35/85 would be very similar up top to a 40/82. Using the area of a circle you can calculate the 'surface area' of the jet holes to determine the total hole area. I realize there's likely a bit more to it than this but slow jets do affect your top end to some extent so it's good to be aware of. Slow jets mainly affect things at 1/4 throttle because at this point the MJ is closed so they are all you've got thus they're very important but they never do close so you can mess up your top end by playing with slow jets.

Anyways, the point is that a 42/82 mix that I had last summer has almost as much top end gas as a 35/88...it actuallly works out like 35/87 has as much flow potential at the top end as the 42/82.

Anyways, it could also be the gas (I still have the gas in it with fuel stabilizer that I put in last fall) or it could just need a bit of time to 'blow the cobwebs' out.

[chanito]

What is wrong with you people, fluid dynamics tell us that flow is a function of area and speed or pressure, yes the area of the slow jet is a little less than half of the main jet BUT the slow jet send the fluid thru a lot of speed reducing passages in order to get into the air stream, and the main jet is just a straight shot into the venturi, so it flows WAY more than twice the slow jet
Anyway i am not an expert on carb, just using my own experience and whatever info i could come up with, also being a inquisitor with people that had experience with car variable venturi carburetors, i have use the stock jet on Katrina with an 85 main jet and it does not run lean, i also have clipped the spring and so far it appears to be running like a champ
Being a tech by trade i am always amaze at the result of most people who just change slow jets and do not worry about idle mixture or accel problems and get away with it, i am not that lucky

[Dandy Dan]

Okay I trust your experience more than my mathamatical calculations. Other than not idling well while cold, my Ruckus does run nicely across the board. I'm getting decent results and a nice tan plug. It's just not as fast as last summer which is why I want to keep messing around to squeeze a bit more ppower out.

[chanito]

Go ahead and experiment by all means, i just post this to help people and let you guys know of my finding, but i certainly look forward to different opinions and results, because that will help us all

[Dandy Dan]

My Ruckus isn't setting any records right now but it's also running reliably (other than the cold idle issue) so I don't want to mess with it too much....I just wanna ride. I am going to spend one more afternoon in the next week or so playing with the jetting though because I wanna try a larger slow jet one more time.

[turbowagon]

plot some before & after veypor curves if possible!