The DJ kit comes with a new needle, which is adjustable, and that is really the only thing I liked about the kit.  The adjustable needle will not require you to modify the white spacer but the the kit is about $50, if I remember correctly.  You can accomplish the same thing by modifying the spacer (or replacing it with one about 1/2 to 2/3 the thickness of the original) and getting a couple of $3 main jets.  I bought the DJ kit not knowing any better at the time.  I wouldn't do it again if I had it to do over.

here is what im going to try once i finish rebuilding her... any advice on my set-up would be nice.. also im at right at sea level, well maybe about 30ft up at the moment haha

155 main jet (stock since im rockin an 87)
1/2 spacer
mixture screw i will adjust once i can play with it at idle
k&n pod rc-1250
sporster muffler
and the rest is stock (pilot, etc.)

id love to get as much performance as possible out of this without buying a different carb.. should i do anything to the pilot? how about a 157.5.. is that overkill?

Here's my thing that I can tell so far with what I've done...

It appears the bottom has dropped out of my fuel mileage.  Granted, I expected a little drop due to increasing fuel flow, but my last tank checked out at 41 mpg.  

I'm not heavy handed when I ride, and keep a pretty even throttle hand when out on the highway.  Now, as I said before, the plug when I pulled it the other day seemed a bit sooty -- no wet fouling, just a dry sort of soot.  Tells me it is rich -- correct?

By what I read, the K&N by increasing air flow should serve to lean that back out, right?

If I don't see any leveling out of the mileage, I'm considering backing up one size on the main jet to say, a 150, possibly.

Right now, I'm having a difficult time seeing where everybody is making these mods and still averaging around 50 mpg when mine has tanked.  Kinda aggravating, since the tank on this bike is milk jug sized anyhow...

I'm just trying to pinpoint any area where I may be off a bit, or may need to do additional to level this thing out.  Performance of the bike is great powerwise.  But I'm not impressed at all with what it has done to my fuel economy.

911radioman wrote on 12/31/69 at 16:00:02:


It sounds to me that you are operating your bike in the mid range or even low speed circuit of your carb. That 1/2 spacer mod you did is causing the richness in this zone. It is also likely the cause for lost mpg. It happened to me when I enrichened my slow speed circuit. When making carb modifications, do one change at a time and closely verify your results. Remember your carb has an idle circuit; a slow speed circuit, a mid range, and a high speed circuit. If you want to test your main jet for richness/leaness, do it a wide open throttle.

I would replace the original spacer or if you shaved it, then add a couple of tiny washers. Then readjust your pilot screw and see if it will allow for a half turn in or so.

911radioman wrote on 12/31/69 at 16:00:02:


For optimum performance/mpg I would suggest one or the other. The faster air and fuel get through the engine the more power you're creating, you're just not pushing enough air into the engine for the amount of fuel you're putting in. the choice is yours, but keep in mind more air is going to mean more power, with less filtration. That would be my choice, new K&N rather than screwing with the jets anymore. This should also help with fuel economy since the fuel should burn more thoroughly, thereby creating more power/less waste.

But I'm talking tech, I haven't done these mods myself (garage is too cold right now, but they're coming real soon)

911radioman - I have a 157.5 main jet and 1/2 spacer and last I checked I got 52 mpg. This was on a group ride and I was twisting the throttle quite a bit. You should be getting closer to 55 mpg.

I'm not so sure the white spacer is the problem. I'd check for air leaks and/or exhaust leaks.

I think you'll find everyone here running the half spacer is getting at least 50 mpg.

necropsy wrote on 12/31/69 at 16:00:02:


So if I understand you correctly, the white spacer mod, rejet and MAC muffler upgrade isn't totally correct or complete unless the K&N filter is installed as well?

I just want to make sure I'm understanding all sides of this issue here...