KZ400 Stock F/R Sprocket Size / Proper Pod Size

Hi Everyone,

I'm back for more help, and yes, I'm asking for both in one to minimize the posts. First, I can't do much test riding cause its 30+ ºF in NYC, so this is for winter working that I won't be able to test much until I have a warm weekend.

So, on with it:

1.
My bike seems to have a low top speed for the bike, Usually max out at 70 with the bike screaming at top rpms (i have no tach, just speedo). I'm curious what the stock front and rear sprocket sizes are and if anyone has messed with putting a bigger front, smaller rear on a bike to get a better top speed. I don't need a ton of speed, living in NYC, but I'd like to be comfortable cruising around 65-75 and not feel like the bike is about to explode.
2.
I want to dump my airbox. It's just too clunky and the replacement filters are way too much $$$. What size pods fits the bike? I've heard conflicting info 48mm, 52mm...Just want to make sure I get the right set.

Thanks for the help!

-Ryan

According to Kawasaki.com the stock sprockets for the 1976 KZ400-D3 are 15 / 45. Ed

Thank you Ed. You've been a lot of help in the past and again here. I always have an issue sifting through schematics. Would you recommend getting a larger front / smaller rear to give better cruising speeds? I think for the city it might be better to have longer gears. Wouldn't have to shift nearly as much since I'm constantly going 0-35 unless I'm on the highway.

Sorry, but I don't know what sprocket sizes would be best. You may want to compare what's on the bike now to the stock sizes to see if it currently is running at normal or higher than normal rpm for a given speed. I understand that the first link below can be used to calculate rpm for different sprockets, but I've not used it myself, so I'm not sure how it works. One thing to consider is the bike's power at various rpm. If you take a look at page 7 in the second link you can see the power curve. It's not a big engine, so it may need fairly high rpm to develop the horsepower necessary to run at highway speeds. If you don't get a satisfactory answer here you may want to ask on the website in the third link. Ed

www.gearingcommander.com/

home.online.no/~ivbekkel/Workshop%20manual/1974-1977%20Kawasaki

www.kz400.com

Like Ed said, I wonder if you are running stock, or higher than stock?

I am curious as to what the best combo would be for slightly higher top speed as well. I have the same issue with my 79 KZ400. Even though mine is a 6 speed I still feel like it's screaming at 65-70 mph. Like you, I also don't have a tach, so maybe it's not as bad off as I think. Wouldn't mind bumping it a little with a new sprocket on the front or back.

handtius wrote: , , , seems to have a low top speed . . . Usually max out at 70 with the bike screaming at top rpms (i have no tach, just speedo). . . I'd like to be comfortable cruising around 65-75 and not feel like the bike is about to explode. . . .

With stock gearing 15/45 sprockets, attainable top speed should exceed 70 mph.

Taller overall gearing with larger front sprocket and/or smaller rear sprocket would be expected to produce a more relaxed cruising speed with less rpm at any given road speed, would also reduce acceleration, and likely not result in higher fuel mileage.

Good Fortune!

I plan on checking out my sprockets as soon as I have a weekend day where I can feel my fingers. I have a feeling they were changed in the past. Once I figure that out, I'll at least have an idea where to go with it. I know the top speed on the bike is closer to 90, so I know I'm loosing power somewhere. I think at 70, I should be somewhere in the 3500 rpm range and i can tell it's not there.bike doesn't want to do more then 70-75, maxed out.
I've been trying out gearing commander. The issue is, they don't have the bike on the list. I've put in the numbers that I understand, but I'm not sure if there's some info I'm missing to properly calculate. What I've deduced is that I should got +3 front / -1 rear. Not sure yet, but that's where I am,

I'll keep this post updated on my findings. If I figure out the best gearing, I'll be sure to share.

Thanks. With a 400cc bike, I'm not to worried about gas mileage, just having a little more comfort on the ride. We will see. Got to start counting them sprockets!

The stock gearing of 15/45 is best unless there has been some serious engine work done.
First gear becomes sluggish the taller the gearing gets. First and top gears in both the
early 400 5 speed and the late 400/440 6 speed are virtually identical. Top speed will be
over 90 m.p.h. between 8-9k r.p.m..


.

handtius wrote: . . . I know the top speed on the bike is closer to 90, so I know I'm loosing power somewhere. I think at 70, I should be somewhere in the 3500 rpm range and i can tell it's not there.bike doesn't want to do more then 70-75, maxed out. . . What I've deduced is that I should got +3 front / -1 rear. Not sure yet, but that's where I am,

To confirm, the small "front" sprocket is also known as the "countershaft" sprocket.

The large "rear" sprocket is also known as the "rear wheel" sprocket.

Changing the number of teeth on either sprocket will result in different overall gearing.

Adding or subtracting a tooth from the front (countershaft) sprocket effects a significantly greater difference in overall gearing than does adding or subtracting a tooth from the rear (rear wheel) sprocket.

An 18 tooth front sprocket -- +3 to the stock 15 tooth -- if it will even fit into the space provided, would be expected to produce an enormous (impractical) increase in overall gearing.
Perhaps so high that the bike's normal engine power would be unable to push the bike past 70 mph regardless of whatever the rpm happened to be at maximum achievable road speed.

Large Kaw fours are typically in the 4000 rpm range at road speeds of 60-65 mph with stock gearing that permits roughly touching red line at maximum achievable road speed.

Would suspect that the stock KZ450 would normally pull considerably more than 4000 rpm at 60-65 mph.

Good Fortune!