Z1 Classic converted to BS34

I'm finally ready to spend and work on at least one of my bikes. I bought my 1981 Z1 Classic a couple years ago for an amazing $600. The bike had been stolen and returned to the original owner years latter and the stock fuel injection had been replaced with a set of Mikuni BS34s. When I got the bike it didn't run. I replaced the valve cover gasket, cleaned the carbs, and did some minor tunning. I adjusted the fuel level and Jet Needle height (no extra slot so slipped in some washers). I never bought any new Carb parts. In the end, the bike runs OK, definitely not perfect but pretty good for $600 if you ask me.

Aaccording to the factory manual for a 1981 Kawi with Mikuni BS34 carbs:
Main Jet: 127.5
Pilot Jet: 37.5
Jet Needle: 5FLZ49
Needle Jet: Y-6

Here is what is currently in my carbs:
Main Jet: 127
Pilot Jet: ?
Jet Needle: 4D30
Needle Jet: Y-7

Two questions:
1) If I keep using Emgo pods and the stock exhaust (4 into 2) and I buy new Main, Pilot, Jet Needle, and Needle Jet what sizes should I start with?

2) If I change to a 4 into 1 exhaust and I buy new Main, Pilot, Jet Needle, and Needle Jet what sizes should I start with?

I doubt new needle jet and jet needles will be needed. Start with #40 pilot type Mik BS30/96 and #140 Mik large mains. Try www.z1enterprises.com for the jets.

Thanks for the sizes and the part number WG. Based on all the other posts I have seen, the #40 and #140 seem to be a pretty safe starting point.

No luck on z1enterprises finding BS parts? The best match I can find is a kit (KL18-2436) for an 81-83 KZ1000. No details on what is actually included, that actual carb, or the size of the jets? I sent a email, I'll see what they say.

If I don't hear from Z1 it looks like I could try one of the following:
www.motorcyclecarbs.com/index.cfm
www.bikebandit.com/partsbandit/

DennisKirk.com has the mains and pilots for the BS carbs available in 2 packs for 5.99. if you spend over a hundred bucks you get free shipping

It has been a while but since I got new jets (I went with the recommended #40 and #140) but haven't had a chance to fine tune and really ride until this week. The top-end (4k-6k rpm) is really nice with the new jets but I am having trouble getting a good idle.

Yesterday I put in new spark plugs and made two test runs with the following fuel/mix screw settings and results:

.75 turns out:
Idle hanging fairly consistently at 3k-4k rpm for about 4 sec. Great power from 3k-5k rpm.

1.75 turns out:
Idle hanging around 3k rpm for about 1 sec. but rpm is really slow to return to idle (1k rpm). Good power at 4.5k-5k rpm but regular stumble at 4k-4.5k rpm.


Then today I did two more test runs with the following fuel/mix screw settings and results.

2.25 Turns out:
Idle hanging around 3k rpm for less than 1 sec. but rpm really slow to return to idle (1k rpm). Hanging idle not as bad with mild acceleration but very consistent following a hard, full-throttle acceleration. Slight stumble around 4k-5k but still good power.

.75 Turns out (same setting as first run yesterday):
Minimal idle hanging, nothing like yesterday's test at this setting. Great power at 4k-6k rpm. Slight, inconsistent stumble at 3.5k rpm. Very rough idle (lots of popping in carbs) and wants to die after about 30sec. Also lots of popping at low speed/low rpm (1.5k -2k rpm).


Very annoying that a run yesterday and today are so different but there you have it. I think my next step will be to drop the fuel level about 1mm and repeat.

Let me know if you have any thoughts.

Just an idea but have you synchronized your carbs? Do this to achieve smooth and more controllable idle. Very bad sync can make rev hanging. Another reason for revs not dropping is air leak. This is usually caused by bad carb boots. As I understand from your writings it´s been sitting for a while so get new carb boots. Z1 ent has them and they will not ruin your budget.

A/F screw should not be adjusted like from ,75 turns directly up to 1.75 turns. Go with 1/4 turns at the time. A/F screw has some affect on running only on idle to 1/4 throttle. Then it´s up to needle/needle jet and around 1/2 throttle up it´s the main jet. And top end is not 4-6krevs; it´s 6-9krevs.

Go slow and start with syching the carbs. Lots of discussion about how to do it here, make a search on this forum. And make shure the carb boots are not leaking air. How to test this is mentioned in many topics here. One way is to just get new ones.

Good luck!