another bad mileage thread for you pontificators (and gurus) out there

[indianboy7]

a little history: I bought my '05 600 a couple years ago. It has been running great with no problems. When I bought it, it had an OEM type K&N air filter in it, with a yoshi slip on. My gas mileage averaged between 30 and 35 MPG. I recently replaced the air filter with a stock one. The bike did run better, but the gas mileage dropped to around 25 MPG. I took off the carbs, and reset the mixture screws (which were at more than 3 turns out, I'm assuming for the k&n). Didn't want to mess with too much of anything because it was still running. After that, the mileage came up slightly and now hovers just below 30 MPG...still not as good as before.

The oil doesn't smell like gas and the float needles don't pass air when I try to blow on the fuel line. The petcock works fine and I've recently adjusted the valves and replaced the spark plugs.

I already have a set of carbs from Arsenic ready to go on, but I'm just curious if anyone could think of a reason for the mileage to drop so drastically with just an air filter change.

[05RedKat600]

Had o say without knowing what jets are in the carbs. I don't suppose you resynced them after the new air filter either? That might help a bit. Either way, your mileage is still low. I get 4-50 out of mine with a Delk slip on depending on how I ride it. Willing to be the PO made a mess of the jets trying to get it to run right with the K&N

[indianboy7]

Had o say without knowing what jets are in the carbs. I don't suppose you resynced them after the new air filter either? That might help a bit. Either way, your mileage is still low. I get 4-50 out of mine with a Delk slip on depending on how I ride it. Willing to be the PO made a mess of the jets trying to get it to run right with the K&N

Could be...and yes, the valves and carb sync were done when I put the new filter in.

[arsenic]

Yeah, he's going to be sending said carbs to me now as a core. That's gonna be fun to figure that out. I'll probably just put the stock jetting back in. I can pretty much guarantee it's DJ. I also guarantee the numbnutz PO put the DJ diaphragm springs in too.
Here's the set he has now BTW

[gsx]

so clean and shiny

[indianboy7]

so clean and shiny

that's what I said....

and Arsenic...what's the difference between the oem and dynojet diaphragm springs?

[arsenic]

I DJ one is longer, it provides more resistance so it takes more vacuum to raise the slide and the slide drops faster. If you read the DJ instructions it even says you don't have to use them. They are only provided in case the stock ones are misplaced. You're much better off with the stock ones.

[indianboy7]

I DJ one is longer, it provides more resistance so it takes more vacuum to raise the slide and the slide drops faster. If you read the DJ instructions it even says you don't have to use them. They are only provided in case the stock ones are misplaced. You're much better off with the stock ones.

Interesting. I think you might be spot on with the DJ assumption. The shop that did all the maintenance for the PO does a lot of stuff with Dynojet products....

Does anyone have mileage figures with stock jetting and a factory pro jet kit installed?

[gsx]

i think it all depends on how u ride. Iv gotten 60 mpg with my kat, but i was really wussyfooting it. Normal mpg is 45-50. Don't know about jetted, never did. I figure if i need my kat to get any faster, ill just buy a gixxer for the days i feel like "shaking hands with danger" (bet most of u wont get the reference)

[arsenic]

A jet kit isn't only to make your Katana faster. It smooth out the RPM range. Helps throttle response. It's just overall better. Not that their is anything wrong with stock jetting. A jet kit is just better. Oh, and BTW, that diaphragm spring is only with 98-06 Katanas. DJ doesn't include them with pre 98 jet kits. Well 90-97 600 and 89-97 750 anyway. I honestly don't know about 88-89 600.