OzVMX Forum
Clubroom => Tech Talk => Topic started by: shelpi on December 03, 2014, 06:14:20 pm
-
Ive only ever used round slide but what is the best out of flatslide and round, and why? as I am just about to use a flatslide TM38 for the 1st time
-
The early Mikuni flatslides are (in my experience) harder to tune/fussier than a Mikuni roundslide and don't seem to offer a worthwhile improvement in performance or throttle response.
For my money, there's only two carbs that should go onto 2T dirt bikes: the Mikuni VM and the Keihin PWK. I will entertain the Lectron option if you're prepared to get your head around them.
-
I will second Nathan , Shelpi the VM is the best option for simplicity by three lengths of the main straight.
I do have some knowledge of tuning Lectrons (and parts) DON'T Bother.......
-
There is not much in it, nothing wrong with the TM flat slide especialy with a powerjet
-
Damnation Lozza ... I have had SFA to do with them :P ;)
-
What about the keihin pe
Seems very similar to a VM?
-
Too hard to get jets for.
-
lot of punters in the US on old huskys having good results with the Lectrons.
-
There's too much to write on this subject in a post here. There are many things to consider, sure a flat-slide will give a stronger pulse over the needle jet at part throttle but if you want more power at 'part throttle' ..... just open the throttle more.
I like the idea of a VM round slide Mikuni but with a 'slide optimiser' filling the void under the slide giving a stronger pulse at part throttle, plus a more streamlined venturi at full throttle.
I disliked the early Mikuni flatslide I had one on my RM250Z, the vacuum at part throttle use to make the throttle valve hang-up, I think the tiny return spring wasn't powerful enough to push the light plastic slide home; had the same problem with the first model GSXR750's. Loved the wheels on the FCR41 slides on my ZXR750 :-)
Once I get the jetting fine tuned on my Keihin PE38 round slide on my CR500, I'll be happy. Liking the VM38 on the KX400.
-
Like Nathan says, Lectrons are cool & good but a head fu*k, as are EI & Blue Magnum. I've used a few Mikuni TMX's and although people say they are harder to jet than a PWK, I've not found that to be the case. A VM round slide with a power jet works nice too. Bings are unreal till they get worn, even though you have to douse your engine with fuel to start them.
K
-
I have used the good old round slide VM's for years. They were always ok. Just ok, not perfect.
I was having issues with the Husky 390 after I fitted a set of Boysen reeds. Never could get the jetting just right. So I bit the bullet and bought a Lectron. The transformation was incredible. So simple to understand, set up and use. I am now kicking myself for not using one years ago. They are way better than back in the 70's and 80's. The power jet also helps.
I will never go back to a Mikuni now.
The Lectron is very simple to get your head around. Just expensive. But then again, the best always is.
Am I biased now ............. :-)
Yep.
-
thanks eveyone, well thats plain and simple, stay with what I know best ! VM Mikuni, but seem that I have gone to the trouble of doing the initial set up with the TM I will run it 1st then I can do a comparison ;) the lesson here is the one I should already know, do the home work first and dont follow like a sheep :-[
-
I just got off the phone to Ian Williams (Tuneing) had a chat and he seems to think both are fine :o
Any who asked how much for a New VM38 $175.00 was the answer, so in for a penny in for a pound ;)
-
everything runs a distant second to a Dellorto PHBE/PHSB/VHSB ;)
-
everything runs a distant second to a Dellorto PHBE/PHSB/VHSB ;)
What would make you run one of the Dellortos in place of a Keihin PWK Airstriker on a big bore 2 stroke?
-
The reason he loves Dellortos is that he has a pallet of Dellorto needles & seats that he needs to use up .... before lunchtime.
:D
-
The reason he loves Dellortos is that he has a pallet of Dellorto needles & seats that he needs to use up .... before lunchtime.
:D
;D ;D ;D
Everything must go..........Lozza's gone madder sale..........my birthday but you get the presents..................
What would make you run one of the Dellortos in place of a Keihin PWK Airstriker on a big bore 2 stroke?
tunability of a Keihin is not in the same league as a Dellorto
-
I love Bings, Yes they are harder to get right and Yes when they wear there not good. The good bits nothing makes as much power as a Bing and the throttle is light easy action.
-
Never tried A dellofto on a 2 stroke, but its the way To go on a 4 stroke for sure
-
Dellorto on 2 strokes make power, as do Bings!
-
The reason he loves Dellortos is that he has a pallet of Dellorto needles & seats that he needs to use up .... before lunchtime.
:D
LOL.
On the 2 Strokes Downunder 380 KTM/Cagiva project Lozza is singing the praises of a power jet modified PWK.
-
That was a long while a ago and thinking of swapping to a VHSB, plus I had several PWK's lying around :D Keihin are good, mikuni better , Dellorto much much better.
-
I cannot see how one carb can make more power than another, sure one may have better component supplies but they all have similar circuits .... pilot jet, pilot air bleed, slide cutaway, needle, main jet, main air jet. Sure flat slides increase pulse strength at part throttle but they would ALL flow the same at WFO ..... I think you guys are jerking us off ;-)
-
John think real MiKuni vs Chinese copy muckuni looky same....but no goee same not even a wide FkN open. :)
-
I cannot see how one carb can make more power than another, sure one may have better component supplies but they all have similar circuits .... pilot jet, pilot air bleed, slide cutaway, needle, main jet, main air jet. Sure flat slides increase pulse strength at part throttle but they would ALL flow the same at WFO ..... I think you guys are jerking us off ;-)
Not really Mikuni and Keihin are tuned with the main jet ,Dellorto's(maybe Bings ???) and Lectrons are tuned via the needle not so much the main jet. A VHSB dellorto has a pilot to needle transition jet/ atomiser and a needle to main jet transition jet and atomiser
-
I don't doubt the Dellorto is an effective carby, but gee, weight of numbers OE and aftermarket and anecdotal reports give the PWK, PWK Air Striker high marks.
From Google sourced images of Dellorto VHSB34's the internal layout of the carb shows Mikuni/Keihin similar pilot and main circuits with air bleeds/ emulsifier holes on the pilot and main circuit brass ware. I cannot see any obvious design differences to the Jap units.
The Dellorto's slide guide arrangement looks like a conversion of a round type rather than the more sophisticated, to my eye a least, dedicated Keihin design.
-
I guess it doesn't really matter whether the needle or the main jet is metering fuel at a given opening, as long as the air/fuel ratio is correct at any slide opening/rpm.
Having air bleeds ensures the chance of correcting the fuel curve for all rpm's, so, if a given bore size venturi is giving the selected air/fuel at all of its adjustable areas, then they must all make the same power?
-
I don't doubt the Dellorto is an effective carby, but gee, weight of numbers OE and aftermarket and anecdotal reports give the PWK, PWK Air Striker high marks.
From Google sourced images of Dellorto VHSB34's the internal layout of the carb shows Mikuni/Keihin similar pilot and main circuits with air bleeds/ emulsifier holes on the pilot and main circuit brass ware. I cannot see any obvious design differences to the Jap units.
The Dellorto's slide guide arrangement looks like a conversion of a round type rather than the more sophisticated, to my eye a least, dedicated Keihin design.
All those Guzzi's Ducati's Aprillia's Cagiva's and a long line of scooters don't count? Dellorto is a needle carburetor not a main jet depending on set up normaly with a Dellorto the main jet only becomes dominant at around 90% throttle. There is the difference. Just have learn how to use that to your advantage.
-
All those Guzzi's Ducati's Aprillia's Cagiva's and a long line of scooters don't count? Dellorto is a needle carburetor not a main jet depending on set up normaly with a Dellorto the main jet only becomes dominant at around 90% throttle. There is the difference. Just have learn how to use that to your advantage.
I found a decent scale parts diagram in english which was helpful; it showed the separate air bleed and emulsion parts of the pilot and main circuit. I can imagine that the variable, by replacement, main jet 'atomiser' secondary venturi thing when optimised could make for a better mixture preparation than the simple annulus of the Keihin/Mikuni
When I used to play hot up with Alfa Romeo 4 cylinder engines many of these came with Dellortos, and some with Webers. It was reckoned that the Dellortos worked slightly better at part throttle and in transient situations. Slight differences in design resulting in more complete atomisation of the fuel was the reason.