1977 Z1000 4into1 Yoshi with Pods Carb work

Hi All,

Ive recently picked up an australian delviered '77 Z1000. Its been restored and in very good conidtion however, it has a flat boggy spot at 2000-4000RPM that Im looking to fix. Im also looking to remove exhaust baffle and give pods filter a go at the same time. The previous owner was good at keeping record of what jetting went into the carbs. If I post here what setup its currently running and then what changes Im going to make, it would be great if those with the same or very similar set ups can give me some advise on whether current jetting will suit with a bit of a tune or whether new jets are required.

Currently Running
- Standard Bore
- Yoshimura 4into1 with baffle
- Standard air box
- VM26SS carbs with below settings
- Currently has a boggy flat spot at 2000-4000RPM and leaky bowls (gaskets seem good)VM26SS X 4CurrentMAIN JET112.5RNEEDLE JET0-6JET NEEDLEY78 (5CN8)CLIP3PILOT JET17.5CUT AWAY1.5NEEDLE SEAT2.0FUEL LEVEL3-4mmAIR SCREW2 turns out  

Want to Run
- Standard Bore
- Yoshi 4into1 without baffle
- Pod filters
- Same Carbs

Note, my VM26's are the ones with a fuel mixture screw rather than an air screw on the air side of the carbs.

After a bit of reading, Im also going to buy some of these air correctors jets that Im told are a must if you want any hope of the pods working. 
www.z1spares.com.au/online-store/Mikuni-...ctor-Jets-p593149812

Any advise is greatly appreciated. 

All you need is those air corrector jets ( which are made by me and supplied to Z1 AUS) .
You should leave ALL other jetting and needle position etc stock and simply increase the mains a couple of sizes from stock and make sure you use quality free flowing pods and not cheap chinese rubbish..

jamcamz1000 wrote:

- Currently has a boggy flat spot at 2000-4000RPM and leaky bowls (gaskets seem good)

Check the bowls with a straight edge, they have probably been over tightened in the past which bends the corners and means there is no pressure on the gasket

Bowls almost Never warp, it's the carb castings that warp downward at the 4-screw corners. This leads to weeping parallel to venturi section where bowl meets carb casting. This is why i oring the bowls and haven't used paper gaskets in years. One pinch-point is way better then trying to smash a flat gasket where it can't be smashed. Nessium Loves when i talk about this haha.

zed1015 wrote:

All you need is those air corrector jets ( which are made by me and supplied to Z1 AUS) .
You should leave ALL other jetting and needle position etc stock and simply increase the mains a couple of sizes from stock and make sure you use quality free flowing pods and not cheap chinese rubbish..

Thanks a lot zed1015,

Sorry, I put all of the current jetting specs in the body of the thread but the formatting stuffed it up a little. Ive attached a comparrsion against whats in them against the apparent standard specs for U.S and Non-U.S models. Its look like main and pilot jets have gone up a size already as you suggest. Does anything else look untoward?

Regrding purchase of quality pods, noted.

Thanks
James

 

 

Wookie58 wrote:

jamcamz1000 wrote:

- Currently has a boggy flat spot at 2000-4000RPM and leaky bowls (gaskets seem good)

Check the bowls with a straight edge, they have probably been over tightened in the past which bends the corners and means there is no pressure on the gasket

Thanks for the pointer. Ill have a look. 
 

jamcamz1000 wrote:

 Its look like main and pilot jets have gone up a size already as you suggest. Does anything else look untoward?

It's only the mains that should be increased when using air correctors.
The pilots must remain stock.

Hi zed1015 wrote:

jamcamz1000 wrote:

 Its look like main and pilot jets have gone up a size already as you suggest. Does anything else look untoward?

It's only the mains that should be increased when using air correctors.
The pilots must remain stock.

HI zed1015,

Looking for a bit of advice. 

Ive installed the air correctors and it seems to have resolved the isolated boggy spot I was getting at 2500rpm but I seem to have a different issue. 

Idle is ok and a slightly open throttle is fine but when I try to bring on the power i just get a constant fluttering. When I didnt have the air correctors or pods in, it used to pass through the boggy spot and then would pull hard up to high RPM. It seems to be a constant flutter no matter the throttle position or RPM when above idle. 

I did tap the 5mm holes a little deep the air correctors sit about 4mm in from the bore but didnt think this would be an issue. Note: my carbs are the fuel screw type so I have them installed on the opposite to blanked out air screw side. See attached photo.

I took the pilot jet back to stock. I have the main jet a couple of sizes up. From the the table in my above message, it appears the needle and needle jet are not stock. I thought I might get away with this but perhaps not?

To remind:
Setup was - standard air box, yoshi 4into1 baffle in. Symptoms were: uncomfrtable idle, boggy @ 2500rpm and then hard pull to high rpm
Set up is now: pod filters, yoshi 4into1 baffle in. Air correctors: Symptoms are now: good idle and take off, fluttering through remainder of rev range


Any help appreciated




 

The jets are in the correct position and the depth won't affect their function.
They are designed to cure the off idle bogging /hesitation which they have and also allow a smaller main jet size increase.
The fluttering is not normal though and is likely connected to the wrong needle and needle jet which appear to be supplying a richer mix along with the 1.5 slide cutaway which is also richer.
I would suggest dropping the needle a notch to weaken the mix and see if that improves things.
As an aside the choke / enrichener can be used as a quick and dirty diagnostic tool with bogging issues when riding the bike.
Feathering the choke at the point of the fluttering can help confirm which way the mixture strength needs to go.
If the fluttering worsens the mix is too rich and if it improves the mix is too weak.