1200cc engine, VM29 carbs, Pods, what jetting?

Helping out a fellow member, who will remain unnamed, unless he wants to chime in here.

The engine has some aftermarket cams, lobes look "big", big overbore, pod air filters, but exhaust is undecided.  Maybe a header, maybe some repop 4 into 4's.  

I'm doing the carb clean job.  There are no main or pilot jets installed.  

Looking for suggestions on a good starting point.  Also, I need jet block gaskets, and most common sources are showing out of stock, so if anyone has a suggestion there, please share as well.

 

Ed, first there is this from ebay regarding the jet block gaskets, ( item 376490546198).  Also this which shows all the gaskets as well as the jet block ones  www.joescarbshop.com/product-page/vm29-s...n-float-bowl-gaskets

As to a starting point for jetting instead of my attempting to make a suggestion, as I have not worked on a set of 29s in a very long time and it is rather hard to jet over the internet I will pass on some lists I have pulled down in the past. You may have already see these but below are lists from Sudco (some notes from wired George regarding them) and Z1 ent. Will also say there are, at least in my mind others here who have jetted them and may well be able to provide more than I can.


From Sudco
Application Carb 
Model Main Jet Air Jet Pilot Jet Jet Needle Jet Float Throttle Valve N100.604 BS30/97 VM22/210 Needle #261 Series Height VM29/15
Honda CB750 (SOHC) -1978 VM29-A2 #115 .9 #17.5 #5DL31-3 0-8 23mm 1.5
Kawasaki KZ650 (77-79) VM29-A7 #120 .9 #25 #5DL31-3 0-6 23mm 1.5
Kawasaki KZ900 (76-77) VM29-A7 #120 .9 #25 #5DL31-3 0-6 23mm 1.5
Kawasaki KZ1000 (77-80) VM29-A7 #120 .9 #25 #5DL31-3 0-6 23mm 1.5
Suzuki GS750 2-Valve (77-79) VM29-A12 #115 .9 #25 #5DL31-3 0-6 23mm 2.0
Suzuki GS1000 2-Valve (78-79) VM29-A12 #115 .9 #25 #5DL31-3 0-6 23mm 2.0
Float Height
All sizes 17mm


from wiredgeorge 
If you are looking for a good laugh, find Sudco's VM29 jetting recommendations and try them out. HUGE main jets, HUGE pilot jets and the air screws cranked out way too far.  When I first started jetting 29s, I tried following these guidelines but guess what? hehe

The 29s are VERY VERY similar to the 76/77 KZ900A/B VM26s... same needle jet size, same jet needle size, same slide cut out and the main and pilot jets should be REAL close.  The 76/77 VM26 was a bit too rich when back in the good ol' days, the EPA didn't notice.  Those carbs will allow a bike to start with little or no choke and you can change to most any pipe without a flat spot.   

Air screws on 29s don't behave the same way as on other VM series carbs because of the hole in the screw towards the tip.  1/8 turn out is about right for #17 pilot jets. If you are not fouling plugs then you are not too rich... (pilot circuit)

Ive been thru Sudcos jetting , that why I ended up where I was but it didnt seem right with that idle mixture screw setting. Sure glad you straightened me out on it. I noticed that you could put an open 4-1 on a stock set of 76 carbs. To me they run as good or better then the Z1 28 VMs. Thats what I had on the bike before I got the smoothbores back in the day when you could buy a set for $100. Thanks again for the help. 

z1 enterpirse jetting guide from www.z1enterprises.com/reference/z1-carb-guide.aspx

Below is a reference of jet settings for the 29mm carb on Z1 / KZ engines.  This is a good starting point for a bike with 4-1 exhaust, after market cams (up to 0.410" lift) and high compression pistons (approx 10.5:1).  Each bike setup is different, so actual settings will vary.

We have included the Honda CB750 settings as a reference.  You will notice the similarity of setup - so.... if you can find a set of 29mm carbs off a CB750, they should work on a Z1.  The same is not so true with smoothbores setup for the Suzuki GS range.  The slide cutaway is different (2mm) - yes, you can still buy new slides, but they are expensive.


28mm (VM28SC)  Z1 & early Z1-A 
 Main Jet  112.5 
 Air Jet  1.0 
 Needle Jet  P-8 
 Jet Needle  5J9-3 - last number is the clip position where 1 is at the top of the needle (leanest) and 5 is at the bottom (richest) 
 Throttle valve (slide)  2.5mm cutaway 
 Pilot Jet   20.0 
 Air Screw setting  1 1/2 turns out 
    
 28mm (VM28SC) Late Z1-A & all Z1-B 
 Main Jet  112.5 
 Air Jet  1.0 
 Needle Jet  O-8 
 Jet Needle  5J9-2 (last number is the clip position) 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   17.5 
 Air Screw setting  1 1/4 turns out 
    
 26mm (VM26SS) KZ900A4 & A5 
 Main Jet  115 
 Air Jet  1.0 
 Needle Jet  O-6 
 Jet Needle  5DL31-3 (last number is the clip position) 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   17.5 
 Air Screw setting  1 3/8 turns out 
    
 29mm smoothbores  Z1 / KZ900 / KZ1000 
 Main Jet  120 
 Air Jet  0.9 
 Needle Jet  O-6 
 Jet Needle  5DL31-3 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   17.5 or 20.0 (or 25 in the later versions) 
 Air Screw setting  1 1/2 turns out 
    
 29mm smoothbores  CB750 
 Main Jet  115 
 Air Jet  0.9 
 Needle Jet  O-6 
 Jet Needle  5DL31-3 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   17.5 or 20.0 (or 25 in the later versions) 
 Air Screw setting  1 1/2 turns out 
    
 29mm smoothbores  KZ650 
 Main Jet  105 
 Air Jet  0.9 
 Needle Jet  O-4 
 Jet Needle  5DL31-3 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   15 
 Air Screw setting  1 1/2 turns out 








 

I am sure you have seen this before but thought I would post it just in case :

 

I believe this jetting assumes a pipe/pods (race)

What they don't give you there is the pilot air jet setting but that depends if it has the stock air screws, which have a tiny hole in the tip ends that lead to a cross drilled hole. Some owners replace those with normal VM air screws or solder up the holes. With the stock air screws you will find 1/8 turn out as a good start up point, I think max adjustment is 1/4 turn out (not like regular VM)

As for the jetting it may be safer to start it with a #125 main then do a plug chop.

How to know if these carbs are "the later version?"  

Digging through my jet bag, I found both 20 and 25 pilots.

For mains, I have 120 or 122, the later of which are in better condition, but generic brand, not Mikuni.  

I'm thinking to just use what we have, and then tune as needed.  Open to fine tuning suggestions...

BTW, I broke out the pail of Berrymans's Professional Carb dip for these carbs, and holy hell, does that crap stink!!!  How many explanation points can I use to make the point?  When that crap dries up and becomes ineffective, I won't repurchase.  

Ed, again as I understand it there should be markings on the carbs that would indicate what jetting they had from Mikuni, intended to be placed on certain machines.  As I  understand it indicates what jets both air and fuel came on them.As I understand the following markings . A2, A7 and A12 were noted. In the past those 29s I have held the marking were on the outside of # 4 carb. I will not claim that is the only place they could be stamped.

Start with the 25 pilot and a 130 main which should put it on the safe side of the ball park.
Also these 29's come with 0.9 main air jet ( air corrector jet ) as stock which will likely end up being closer to 0.6 once set up..