76 KZ900 LTD Streetfighter build

Thanks for all the nice comments everyone. It's been a lot of fun building this bike.

Now on to riding issues. She runs great everywhere except around 1/2 throttle. Now I'm just guessing at RPM's because I don't have a tach, but seems like she bogs between 1/4 and 1/2 at low RPM, more narrowly close to just 1/2 throttle at high RPM. I can push right through it by twisting harder and the front end gets light in 2nd gear. I taped up the switch gear and put a push pin in the grip, so I'm pretty confident where she's bogging. I would guess lean on the jet needles? Haven't riden it a ton, but the baffle is a bit white on the cone. Pods, RC 4 into 1 with baffle only, no packing, 29mm Smoothbores, valves in spec, Dyna ignition, advancer smooth and lubed, fat blue spark. Not sure on the jet sizes, wrote them down and can't find the piece of paper now.

I bench synched the carbs only, with wire to set the slide heights. Have not put vacuum gages to them. I had the air screws out 1 1/2 turns. Lots of controversy on what's proper. Wouldn't run with the choke on and had to blip the throttle every once in a while till she was warm. Then the idle was a bit high when I would pull up to a stop. Went to 1/2 turn out and it seems a lot better. Drops back to idle like it should now.

Without a tach, I've performed the gist of the Slide Carb Tuning test 1 and 2 from the filebase. Leads me to believe lean condition with the needle. Concurence? Opinions? Don't do anything until I get a tach on her?

Alan

Does it have an issue in the upper range when you're on the throttle hard? I'd say it sounds like the needle for now. Have you done a plug check in this throttle range? Ride it at this range, grab the clutch and turn the key off. Pull the plugs quick and check to see what colour you're burning at.
As for your pilot circuit, have you thought of tuning with a Colortune unit? I picked one up over the winter, and they're a great tool for balancing in your pilot circuits.

A good vacuum synch should also sort any little issues out

Devin

It pulls really hard above 1/2 throttle. I thought the problem was 3/4 throttle before I marked the positions. That throttle tube spins a long ways. No plug chop or colortune for me unfortunately. I'd have to have someone else do it for me as I'm color blind. I can tell if a plug is lean or rich, everything else is a mystery to me.

Alan

Not sure if you said anywhere in the thread if you have a Dynojet kit on the bike. I have a stage 3 kit on my 650, and had somewhat of the same issue as you're having. With my kit, there's a little washer that goes under the needle circlip to do half steps with. Are you able to do this with your needle at all? Last year, I did quick 1 mile runs with the bike, and changed the needle half a step until I had it burning where I wanted. Just a thought, Al

Devin

No, just standard 29 parts as far as I know. I don't see that Dynojet has parts specifically for the 29's, but I didn't look that hard yet. Maybe try a full step first and see what that does. Not looking forward to pulling the linkage, tops and slides out to get to the needles. What a pain. And then washer steps, ack. I read that in the tuning guide and thought, that must be for extreme finess tuning.

Alan

Beautiful looking bike! Congrats on getting it up and running!

Al,

It's a pain in the rear, but if it means you can grab a fistful of throttle and have to hold on tight, it's worth it

When I was tuning my 650 last year, I tuned it in half steps to settle where I wanted. I basically tuned it until it lean popped when letting the throttle off, and went a half step richer.

I just took a look at the Dynojet site, and the closest you can come is a 78-80 kz1000 kit. If you're going that way, give them a call- they're pretty good with stuff like that.

Hope that helps,

Devin

Your bike looks beautiful Alan. A job very very well done. You should be proud of yourself!

Thanks Adam. You must be itching to get on the road to reassembly.

Carbs off and apart. Needles were on the 3rd position. Noticed 1 and 4 have about 0.5mm slop in the slide armature due to tired springs probably. Maybe a little washer inside the brass screw will help out the springs. That could explain the lean condition. Those two carbs would have lagged in lifting the needles. What to do. Leave the clips in the 4th slot or move them back to the 3rd. I have a feeling these carbs are coming off a few times before its right.

Alan

good catch there al.

leon

Haybus wrote: It's about 5" to the tire. I deleted all the 2up stuff. I don't like the plate location but I don't have any other good options. I may crease the plate a little so it doesn't look so straight up and dicular.

Alan

Have you thought about doing a plate bracket that attaches to the rear swinger/axle bolt? I have seen a lot of guys run them that way; have thought about making that change myself.

I would have done something like that, until a few months ago when a guy that works for me got a ticket for obstructed plate. Apparently in Wa state the license plate must be visible from either side of the bike. I'll take a picture later, I think it looks pretty good.

Alan