29 smootbores

Russ Jackson wrote:

... put an inline filter in and it sounds and feels like it is starving for gas. When I ran it without a filter it ran correct....

If not already doing, should fit a quality inline filter with sufficient flow capacity such as carried by Z1E and most all motorcycle dealerships/shops. They are relatively inexpensive, and have an arrow showing direction of flow.

The direction of flow is important. And the filter element eventually loads up with whatever crud it's filtering from the fuel, so it should be replaced when necessary or in doubt. I've experimented using compressed air to blow backward through the filter, thinking it might rejuvinate it somewhat, but can't vouch for whether it accomplished anything.

The inline fuel filters designed for small lawnmower engines may not have sufficient flow for use on a motorcycle engine.

Good Luck!

The early VM26s used 2.3 float seats. I can't imagine running out of gas from continuous wide open throttle as I have reached a state of maturity where that no longer seems like a viable riding option bwhahahaha The 29s use 2.5 float seats I think and I don't believe it is possible to use smaller seats because they just are not available for a smoothbore. The smoothbore has filter screens under the seats to keep larger grit out and they are decently effective although a fuel filter is a real stopper of grit. Another common problem I have seen is that folks buy a filter at the autoparts store and it will turn out to be a lawnmower filter which doesn't flow enough fuel for any bike with the throttle open a lot.

Patton wrote:

Russ Jackson wrote:

... ran it without a filter it ran correct. However without the filter float bowl #1 stuck twice causing gas to trickle out of the pod...

Red Flag Alert -- where gas trickled out of the pod, it may well have also flowed the opposite direction into the combustion chamber and down around the pistons/rings into the combustion chamber.

If not already done, would sniff-test oil for any fuel odor and examine condition of oil for any fuel dilution.

Good Luck!

It actually came out of the air vent once. I checked the oil and it is ok. I pulled the carbs and checked them again and discovered the sticking float. The float also had a small dent in it so I ordered a new one. Thats the problem with bikes that sit a long time. I put sea foam in the tank also. Doesnt take much to clog up a carb or cause it to stick...Russ

Thanks for the info about seat sizes.

Per Sudco Mikuni manual, VM29 smoothbore has 2.5 seat size, and a 2.8 seat size was also produced.

Russ Jackson wrote:

... stock petcock angle makes it tough to utilize the reserve side and get a clean flow to the carbs....

Am thinking both KZ900-B1 LTD oem petcock fuel outlet nipples function the same with flow in either ON or RES position. Same way as an oem Z1 petcock functions.

The petcock handle ON position allows fuel passage only through the taller pick-up tube inside the tank. The petcock handle RES position allows fuel passage also through the lowest pick-up inside the tank.

With single fuel inlet 29 smoothbores, the fuel line may be connected to either oem petcock nipple, with the other petcock nipple being capped off (a vacuum cap works nicely).

Some folks use both petcock nipples with dual lines into a tee and a single line from the tee to a single intake carb (such as 29 smoothbores which have a single intake fuel pipe). But imo that isn't needed, is unneccessarily complicated, doesn't increase volume of fuel flow, and crowds space otherwise available for the inline filter.

Good Luck!

Wow, lot of reactions and the same problem :S . The needle valve assemblys and little filters are new, o-rings, jets and gasgets also new. The 2 29mm sets are fully stripped down and cleaned. The Pingel high flow petcock and the tubes are also new.(Z1Enterprices/great shop)Both sets really run great and pick up gas much better than the 28mm. But i put my problem on the forum because i maybe overlooked something. So i think it must be a vacuum problem in the fueltank or, as WG said, something with the advancer. When the cold/wet/windy winter is over here in the Netherlands i absolutely figure this out and let you all know. Patton, was the 2.8 seat size also suitble for smoothbores because the 33mm sets use also 2.5
Thanks
Willem

Sudco 4th Ed shows Needle Valve Assembly for Mikuni VM29 Smoothbore carb as follows:

Mikuni Part No. N122.032 2.5 Order No. 002-503

Mikuni Part No. N122.032 2.8 Order No. 002-504


Am out of my league but guessing the larger size might be needed for a large overbore high performance application with a huge fuel appetite.

Consider -- if the floatbowl drain screws are removed, fuel tank cap partially open, and petcock then turned ON -- it doesn't take very long to drain a full fuel tank.

It's difficult for me to imagine an engine capable of consuming fuel so quickly. So there must be other factors involved.

Meanwhile, am hoping it's not being overlooked that perfect fuel cap venting and perfect petcock and perfect carbs will not prevent fuel starvation caused by impurities inside the fuel tank which may be clogging the petcock pick-up tubes inside the tank. Often a tank flush and cleaning the petcock pickup tube screen will resolve such problem. Tank flush means removing the tank, fast dumping upside down through the filler hole, adding some fresh clean gas, shaking and re-dumping, and repeating as needed until all grit and crud is gone.

Good Luck!

i also have the 29 smbores and they have needed, cleaning a few times this year...(once not well though) i have a "small" z-1 enterprises fuel filter and still it takes up some of the space that my supply line needs to freely bend over to my petcock...it takes exact length on each cut, and a handfull of tiny clamps to get it right and i gotta swivel my petcock a little or i get kinks that would be bad news....it is the first thing i think of when my bike starts to have any stutters while riding...the filter allways looks to have gas but is hard to check at 115 mph...so who knows....new filter...new lines...wiredgeorge mixture crew,,settings tip...correct....i guess mine just gets gummy cuase they were really really snappy and crisp and twenty tanks later not so crisp.....when i was twenty i had a set of 29's and never once cleaned them...or anything else for that matter....i think my new stutter rolling the throttle on out of a corner is a ign advance lubing or a wire problem..still they are not as crisp as before...thats my 29 stories...good luck craig

I have rebuilt a few VM29 assemblies and have never seen 2.8mm float seats; Sudco.com lists a lot of parts but you need to go to the price list to see if it is actually for sale. 33s use the same 2.5mm float seats, as you have noted. Larger float seats won't fix this issue as the 2.5s are plenty big enough.

trianglelaguna wrote:

i also have the 29 smbores and they have needed, cleaning a few times this year...(once not well though) i have a "small" z-1 enterprises fuel filter and still it takes up some of the space that my supply line needs to freely bend over to my petcock...it takes exact length on each cut, and a handfull of tiny clamps to get it right and i gotta swivel my petcock a little or i get kinks that would be bad news....it is the first thing i think of when my bike starts to have any stutters while riding...the filter allways looks to have gas but is hard to check at 115 mph...so who knows....new filter...new lines...wiredgeorge mixture crew,,settings tip...correct....i guess mine just gets gummy cuase they were really really snappy and crisp and twenty tanks later not so crisp.....when i was twenty i had a set of 29's and never once cleaned them...or anything else for that matter....i think my new stutter rolling the throttle on out of a corner is a ign advance lubing or a wire problem..still they are not as crisp as before...thats my 29 stories...good luck craig

Great reply. I have tried 3 or 4 different methods and do not like any of them. I think I am going to cap off one of the petcock lines and run it straight. I would still like to see a couple pictures if possible. Thanks ...Russ

Am successively posting three photos of the fuel line routing on my Z1 with 29 smoothbores, oem petcock, and inline filter.

This routing easily avoids the two bulky oil cooler lines and affords ample space for the inline filter.

Using relatively pricey ultra-flexible non-kink type grey fuel line.

Only one hose clamp is used (as shown).

Good Luck!

[Click on image to enlarge view]

[Click on image to enlarge view]