tuning stock carbs/best after market carb
Moderator: rztom
tuning stock carbs/best after market carb
I am having trouble with a stock carbs,very hard to start and after it gets hot then it starts without problem so I tune it to work at the idle 1200rpm,after some time when it get cold it is almost impossible to start it.Now i have air screw at 2 turns float hight at 21mm.What are the factory seetings?And what is the best aftermarket carb for the stock motor?
Re: tuning stock carbs/best after market carb
I cant say what may be wrong but you have some kind of problem. The stock carbs work fine. My bike always starts 1-3 kicks hot or cold. Many times 1-2. I think for aftermarket carbs the Kehin PWK 28 carbs are the most popular for a mostly stock bike. You can buy them new from yamaha,kawi dealers,maybe others too. They used them on some motocross bikes. You just have to change out the jetting that comes in them. Search this site,there is a lot of posts that will tell you everything you need to know.
1984 Rz350, Wicked Toomey rep pipes, Dynojet kit,Zeel unit,Toomey Y boot filter.
-
- Posts: 601
- Joined: Thu Jun 19, 2014 9:52 pm
Re: tuning stock carbs/best after market carb
I love my Spec II prepped VM 30 round-slides on my RZ. I pulled the infernal EPA carbs twice and after spending 30 minutes to change a needle clip setting decided I had enough of that. My bike starts 1st kick if ridden daily, maybe 2 or 3 kicks if it sets a month and runs clean from idle to 10.5K
I love the smell of Blue Marble in the morning!
Tim Steele in Front Royal, VA
Tim Steele in Front Royal, VA
Re: tuning stock carbs/best after market carb
I went to PWK28 a few years ago and the bike runs better across the board. The only thing that was slightly better with the stock (non EPA) Mikunis was cold starting.
- Questo vecchio rz
- Posts: 1116
- Joined: Sun Aug 16, 2015 5:55 pm
- Location: Reconquista of California
Re: tuning stock carbs/best after market carb
There are a lot of variables in your question how many miles are on your carbs what is your location altitude and the honest assessment of the condition of your machine
Assuming your bike is completley stock and equipped with the stock airbox.
There is nothing with the stock carbs that cuase it from running correctly, unless there is something wrong , usually it is just dirty or has been altered from factory specs horn simply worn parts you will have to rebuild it
Recommend a complete teardown & cleaning,perhaps do a ulrasonic cleaning or service.
Jet it all to stock factory specs.
Inspect your floats and set them perfectly.
Inspect your floatbowls, ensure there on the correct carb.
There is no "best replacement" carb. Honestly they all work well. Mikuni round or flatslides, and Kehien PWKs. Be forewarned PWKs are NOT a simple bolt on. Theres alot of little details involved in doing it the right way. But once done they are a great option.
Assuming your bike is completley stock and equipped with the stock airbox.
There is nothing with the stock carbs that cuase it from running correctly, unless there is something wrong , usually it is just dirty or has been altered from factory specs horn simply worn parts you will have to rebuild it
Recommend a complete teardown & cleaning,perhaps do a ulrasonic cleaning or service.
Jet it all to stock factory specs.
Inspect your floats and set them perfectly.
Inspect your floatbowls, ensure there on the correct carb.
There is no "best replacement" carb. Honestly they all work well. Mikuni round or flatslides, and Kehien PWKs. Be forewarned PWKs are NOT a simple bolt on. Theres alot of little details involved in doing it the right way. But once done they are a great option.
Banshee (Baja) race bike,+ 2 A Arms,L.E.Ds, Toomey, +4 stroker IMS tank, run flats.
96 GSXR SRAD, Future Yoshimura rep.
85 custom Tri-Z
RZ/YZR bike(project)
86 VFR750 RC24 Merkel replica (project)
Royal Enfield Bullet 500
96 GSXR SRAD, Future Yoshimura rep.
85 custom Tri-Z
RZ/YZR bike(project)
86 VFR750 RC24 Merkel replica (project)
Royal Enfield Bullet 500
-
- Posts: 1368
- Joined: Tue Nov 12, 2013 2:34 am
Re: tuning stock carbs/best after market carb
That sounds a lot more like bad compression than a carb issue. Difficulty cold starting was always a dead giveaway on a dirt bike the rings were toast.
Re: tuning stock carbs/best after market carb
I agree with Evan, poor starting is usually a clue to low compression on an older motor.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid
Like Watches? www.PloProf.com & www.DeskDivers.com
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid
Like Watches? www.PloProf.com & www.DeskDivers.com
Re: tuning stock carbs/best after market carb
Like Questo said, where is the bike from? US has a different carb from most other locations. ...and yes, hard start could mean other issues. Could be a combination of both, due to age.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine
Re: tuning stock carbs/best after market carb
Jettings are too lean. PWKs typically start first kickRuZty wrote:I went to PWK28 a few years ago and the bike runs better across the board. The only thing that was slightly better with the stock (non EPA) Mikunis was cold starting.
Re: tuning stock carbs/best after market carb
Starts fine most of the time, only struggles when the temps get into single digit cold. Conveniently I seem to have lost interest in riding in those conditions in the last year or so.Bare wrote:Jettings are too lean. PWKs typically start first kickRuZty wrote:I went to PWK28 a few years ago and the bike runs better across the board. The only thing that was slightly better with the stock (non EPA) Mikunis was cold starting.
- pushstartrearset
- -----
- Posts: 1339
- Joined: Thu Mar 17, 2011 4:20 pm
- Location: Vancouver, WA
Re: tuning stock carbs/best after market carb
3rd.JonW wrote:I agree with Evan, poor starting is usually a clue to low compression on an older motor.
Both our RZs have close to 30k miles. One would take about 50 kicks to start. The other about 15. Cold starting. When warm about 3 kicks. Very tired motors that need complete rebuilds.
What is the mileage? Running pipes? what pipes? Airbox? Is it modded? If no airbox, what are you running? Single filters? Y-boot? Aftermarket or stock ignition? What is set @ or are you running the default tunings?
I think if i had to pick a PWK, it would be over 28mm (simply not as great a needle selection for PWK28s as i have spent time fiddling w/ them w/ the daytona). Like a PWK 32 (much larger selection of needles to really fine tune). More likely, i would want to stick w/ Mikuni TM28~32? carbs and do the Dave Freist (R.I.P.) treatment to them.
1984 RZ350L (U.S.) Old Toomeys, oil injected!, Y-boot K&N. loctite throttle cable holder on left carb!! , 410 mains, Dynojet needles 2.0 clip, #20 pilot @ 1.5 turn a.s., 240/512 p.v.
Re: tuning stock carbs/best after market carb
I highly recommend PWK 28 for a stock to mildly modded motor. There is a build process to install them but it is not difficult. Follow this thread and you will end up eith a really sweet running RZ.
viewtopic.php?f=1&t=9667&hilit=PWK&start=0" onclick="window.open(this.href);return false;
viewtopic.php?f=1&t=9667&hilit=PWK&start=0" onclick="window.open(this.href);return false;
85 Y/B, Toomey pipes, PWK 28's, JJH Needle #2, 45 pilot jet, 145 main, Pods, VForce 4 reed blocks, +3 ignition, Milled head 1.1mm squish, R6 Shock, Progressive
Many Vintage MX Bikes, 03 ZRX1200R, 86 Moto Guzzi 1000 Le Mans MK IV, 86 VFR 750, 74 GT 550
Many Vintage MX Bikes, 03 ZRX1200R, 86 Moto Guzzi 1000 Le Mans MK IV, 86 VFR 750, 74 GT 550
Re: tuning stock carbs/best after market carb
Im my world poor cold starting is usually a result from jerks throwing all the parts in one box and then swap left/right float bowl on reassembly.
By this mod you successfully disabled the cold start enrichment as the choke jet is only in the right float bowl.
By this mod you successfully disabled the cold start enrichment as the choke jet is only in the right float bowl.
Bye
Martin
Martin
Re: tuning stock carbs/best after market carb
PWKS feature Individual choke assemblies.. parts mixup /bungle unlikely to be relevant here.
Re: tuning stock carbs/best after market carb
Starts / runs fine after warm ?
Gotta be rings.
If it were carbs, heat wouldn't affect much.
Rings though ? Definitely!!!
Compression test first, then leak down test. Then carbs.
I run the pwk's and they're great. The mic's were good too though.
Gotta be rings.
If it were carbs, heat wouldn't affect much.
Rings though ? Definitely!!!
Compression test first, then leak down test. Then carbs.
I run the pwk's and they're great. The mic's were good too though.
84 RZ350 Spec II boost ports shaved head
Y boot 29mm PWKs billet manifold TDR Reeds Spec II pipes
Fox twin clicker JMC Braced swing arm
Tarozzi fork brace
Brembo 19 RCS Master ss lines blue spots EBC Vees
Spec 2 Full Fairing factory Solo Cowl
Y boot 29mm PWKs billet manifold TDR Reeds Spec II pipes
Fox twin clicker JMC Braced swing arm
Tarozzi fork brace
Brembo 19 RCS Master ss lines blue spots EBC Vees
Spec 2 Full Fairing factory Solo Cowl