8541Hawk

As I've been asked a couple of time and with all the issues I've heard about with carb set up I guess it's time to pass on what I have learned in the last 14yrs of owning a SH (yes I picked mine up in 97)

Note: The following set up works with a stock airbox and stock air filter. If you want to run a aftermarket filter or airbox mods, you are pretty much on your own trying to get it dialed in correctly.


I have arrived at this set up by taking the info I have received from Dan Kyle, Bob Hayashida and HRC. Then by a little experimentation and looking at how HRC did things, I have come up with what I feel is a very good base line set up. As with all tuning, this is just a starting point and you will need to fine tune for your bike.

First lets cover a couple of things. First is the old axiom that the bigger the CV carb, the harder it is to tune. As this bike has the largest CV carbs factory installed, it is no wonder you hear about all the problems getting them "right". I've read many posts where people state that "the bike runs great, except at..... insert low end, mid-range, etc here.
To me this is unacceptable.

Then there is how the aftermarket jet kits (except HRC) deal with the stock set up. They address the low end /mid-range lean condition by running larger mains and a different needle profile and in the case of DynoJet by getting the slides to open sooner & quicker. While these methods work well with most bikes, on a SH there is IMHO a better way.

The HRC kit comes at things a bit differently. Though it is really for a full race set up and if you want to run ram air or a real high flow filter, then their method of plugging the air bleeds and running small jets is the way to go. On a street set up, this really isn't all that good of an idea. I'll just leave it at that for now. It can be discussed later but really doesn't have a lot to do with what this is trying to accomplish.

The main thing a street rider can get from the HRC set up is a modification they have done on the slides and their recommendation to run #48 pilots. The slide mod is useful to widen the power band on a bike with stock velocity stack. It also can be used for racing where the set up is 2 short stacks. This same method is what is needled with stacks like the Dr. Honda units which go rich in the mid-range. Though I am getting ahead of myself, so I'll explain the mod and what it does in a bit.

So back to the stock set up or starting point. The problem with a stock bike is it is a bit lean on the bottom and mid-range and pretty close on the top end by what I have seen. The good part is the stock needles actually are very good. In fact they are some of the best stock needles I have ever seen. Which leave us with how to get the best performance from the bike.

So here we go. The first step is to install a set of #48 pilot jets (per Dan Kyle & HRC). You will here people say they have tried this and it didn't work. The reason for this is that they have done it along with installing a jet kit. As I stated earlier, aftermarket kits install larger mains and different needles. When you change both, you end up too rich with a stock motor. It's a one or the other with this bike. By upping the pilots you cure the low end leanness and also add a little to the top end as the pilot circuit doesn't turn off, so larger mains are not required.

Then you need to shim up the needles. While they have a very good profile, they are a little too long for performance. The question here is how much do you shim them. Around .040" is a good starting point but will need to be tuned to each bike. Also there is more to it than just shimming both needles .040". One of the set up tips from HRC is to use one more shim on the rear needle than you use on the front (this tip might be helpful to try on bikes with an aftermarket kit also). So what I do when setting up a set of carbs is remove the stock thin washer that is under the front needle and leave it in place on the rear. With this method you actually end up with the front needle approx. .030" higher than stock and the rear .040" higher than stock which seems to work well.

So You can stop at this point, put it all back together and start with the pilot screw set at 2 1\4 turns in the front and 2 1\2 turns rear as a start and the bike will work pretty good but it can be better.

This is where the HRC slide mod comes into play. What is this "secret" mod? Well it really is quite simple. We'll start with this hijacked pick once again



The 2 holes are called lift holes. It's where the slide gets the pressure differential signal which causes the slide to open. That is why DynoJet has you drill an extra hole, to cause the slide to open sooner, but that is the wrong way to go IMHO.

Because of the different length velocity stacks what is really going on with the bike is the front cylinder slide opens too quickly causing the front cylinder to go rich in the low to mid-range. FactoryPro even recommended running an emulsion tube from the rear in the front to help cure this problem.

Now the HRC cure for this is to supply a slide with one lift hole. This will lean out the low & mid while not effecting the upper mid-range and top end. So the last step would be to use some epoxy and seal one of the lift holes in the front slide.

This will give you a very good baseline set up. Yes some tuning will be required but all it involves is adjusting the washer stack ( you might need to raise or lower the needles a small amount) and set the pilot jets per the service manual.

The HRC type slide is also the cure for the Dr. Honda stacks which cause the over rich mid-range. The problem here is the stacks create too good of a vacuum signal to the slides causing them to open to quickly. So in this case you would plug one hole in each slide. This will eliminate the rich condition without causing a lean condition on the top end.

Hope this is some help to you guys.

waterbug89

very helpful thank you

nothing

good read and some good advice. I never even noticed those holes but I have been meaning to do some re-jetting in the near future. the OP will come in handy thanks!

mikstr

Good info Mike, and well explained.

FWIW, for bikes being used on the street, Roger Ditchfield (of Revolution Racing in the UK, for those who aren't familiar with him) recommends against drilling the extra hole as called for the in the DJ kit installation procedure.

nothing

So how many holes are on the slides stock?

wyldryce