|
|
Post by morgy on Apr 19, 2020 9:26:33 GMT 1
Hi This has probably been ask many times but my search came up with nothing.. My 4L1 bottom end now with 350 barrels stage 2 tune & +4mm crank, I am not starting to look at buying some carbs but wondering what's best. Mikuni Flat side or Kiehn PWK? I plan to run Pre mix but not sure if this makes any differance to the carbs i need to buy. Are there any pro's or con's to one or the other Photo just because...   1EDA3F2F-9C17-4F4A-A1A4-6BE33820C94D by mark morgan, on Flickr |
|
|
|
Post by dusty350 on Apr 19, 2020 9:46:45 GMT 1
Hi Mark The PWK's get a lot of great reviews for these engines. Good up to mid 70's bhp. I bought a pair brand new from Mutts on here - he jetted them to suit my set up too. He can add oil injection spigots as well. Why go with premix ? Dusty  |
|
|
|
Post by morgy on Apr 19, 2020 10:20:40 GMT 1
I got rid of all my oil pumps. So buying new ones plus getting it dialed in for Stroker motor is going to cost!!! I Want less complexity cleaner looking motor and i am used to premixing for my Paramotors.. I always used to be worried on my old MK1 125 about the pumps breaking so always premixed, I guess just habit? Also the way my Rear Brake Pipe setup is running, the Bottle may foul on the Pressure switch pivot area when riding...  IMG_2315 by mark morgan, on Flickr Someone told me a while back flat sides have better Bottom/mid rage pull over PWK or more response? Also flats easier to tune? I need to get my motor set up by someone anyway and get pipes Made so might just go with what they recommend, |
|
|
|
Post by jon on Apr 19, 2020 11:05:16 GMT 1
I’m going to throw a curve ball in.
Have you seen Norbo’s CV manifolds for have PWK 33, 35 or 38 carbs?
I have no experience of these but would love comments on those that own them.
Norbo says they give performance gains at all revs, and with the obvious not needing to balance must run equally on each cylinder.
Just happened to be looking at them myself, then came across this thread next.
Jon
|
|
|
|
Post by muttsnuts on Apr 19, 2020 11:21:24 GMT 1
PWK's are flat side carbs (well to all intents and purposes they are), both Mikuni and Keihin will work fine, it will be more of what size, 28mm, 30mm or bigger, depends what you want from the bike, the pipes will also have a factor to play in this.
If going for all out power then the bigger carbs will give you that, but you'll pay the price at lower RPM, smooth riding on the road, but if just punting it down a track/drag strip then just go big as you don't care about bottom end
Also, it depends what tune has been put on the barrels/ports, if you don't know that then you will also struggle with the exhausts for it as you need that to design a set of pipes to suit your needs, otherwise the pipe maker is going to be guessing.
BTW: What the hell does "Stage 2 tune" actually mean - certain tuners band these words about, but nobody has ever been able to put it into technical terms as to what that is, how does it differ from a Stage 1 or 3 and how many stages are there ?
As regards the 2 into 1 manifold, I've done a few on the big bore stuff, there are compromises, its not all gains as some would have you believe, if it was, everybody would be running them and they aren't !
As I say, it all comes down to what you want, I assume you are running a programmable ignition of some sort as well, this also will play its part in getting everything working as you want
HTH
|
|
|
|
Post by dave1w on Apr 19, 2020 11:25:34 GMT 1
PWK's are flat side carbs (well to all intents and purposes they are), both Mikuni and Keihin will work fine, it will be more of what size, 28mm, 30mm or bigger, depends what you want from the bike, the pipes will also have a factor to play in this. HTH Like for like is a 28mm flatside TM better than the VM28? |
|
|
|
Post by muttsnuts on Apr 19, 2020 11:31:04 GMT 1
PWK's are flat side carbs (well to all intents and purposes they are), both Mikuni and Keihin will work fine, it will be more of what size, 28mm, 30mm or bigger, depends what you want from the bike, the pipes will also have a factor to play in this. HTH Like for like is a 28mm flatside TM better than the VM28? good question, it comes down to a number of factors, I've yet to do a full back to back test on the same bike. but I have to say the TM tends to give a better bottom end (not by much), but does seem to do that, however, that could also be down to the exhausts fitted, I'll get round to doing a back to back test at some point, then I'll be able to tell you for sure ! |
|
|
|
Post by morgy on Apr 19, 2020 11:40:24 GMT 1
PWK's are flat side carbs (well to all intents and purposes they are), both Mikuni and Keihin will work fine, it will be more of what size, 28mm, 30mm or bigger, depends what you want from the bike, the pipes will also have a factor to play in this. If going for all out power then the bigger carbs will give you that, but you'll pay the price at lower RPM, smooth riding on the road, but if just punting it down a track/drag strip then just go big as you don't care about bottom end Also, it depends what tune has been put on the barrels/ports, if you don't know that then you will also struggle with the exhausts for it as you need that to design a set of pipes to suit your needs, otherwise the pipe maker is going to be guessing. BTW: What the hell does "Stage 2 tune" actually mean - certain tuners band these words about, but nobody has ever been able to put it into technical terms as to what that is, how does it differ from a Stage 1 or 3 and how many stages are there ? As regards the 2 into 1 manifold, I've done a few on the big bore stuff, there are compromises, its not all gains as some would have you believe, if it was, everybody would be running them and they aren't ! As I say, it all comes down to what you want, I assume you are running a programmable ignition of some sort as well, this also will play its part in getting everything working as you want HTH Thanks Dave.. I thought the PWK's were cylindrical but having another look they are Fat! The PWK carb on my Paramotor has a round slide so just assumed it was the same for all PWK's The 'tune' or the Barrels were tuned for mid range power that's all i know, I was told Stage two?? ... Would i need to ask them for the port timing profile to be able to build the pipes? Running standard timing gear. As for what i am after is a strong mid range Not Screaming motor all at the top end.. Forgive but tuning isn't my area at all... |
|
|
|
Post by midlifecrisisrd on Apr 19, 2020 11:44:08 GMT 1
Pwk's have a D shaped slide so flat on one side and curved on the other but not enough to be half round
They tend to improve mid range and throttle response over a round slide
Steve
|
|
|
|
Post by nokturnal on Apr 19, 2020 12:05:31 GMT 1
The PWK are known for being more forgiving with jetting. Being off a size is not as big a deal.
Mikunis have more specific needs I have heard.
|
|
|
|
Post by muttsnuts on Apr 19, 2020 13:07:55 GMT 1
To make the pipes suit the tune of the engine, then yes you really need the port mapping/timing etc, so port width, height etc, the stroke will of course be 58mm rather than 54mm, but you also need ther rod length, I'd assume its 115mm rather than 110mm (stock LC), but could be wrong, all these things make a difference I am also assuming John has set the timing to suit the extra stroke etc. If its mid range your after like my 421LC (LC barrels relined to 68mm and 4mm stroked crank) then the pipe design is critical, the first pipe I did worked really well, except it revved way more than I had designed (still not figured out why), so changed the design again and got what I was after, so it wasn't cut n dry for sure  |
|
|
|
Post by tony2stroke on Apr 19, 2020 13:08:48 GMT 1
PWK's are flat side carbs (well to all intents and purposes they are), both Mikuni and Keihin will work fine, it will be more of what size, 28mm, 30mm or bigger, depends what you want from the bike, the pipes will also have a factor to play in this. If going for all out power then the bigger carbs will give you that, but you'll pay the price at lower RPM, smooth riding on the road, but if just punting it down a track/drag strip then just go big as you don't care about bottom end Also, it depends what tune has been put on the barrels/ports, if you don't know that then you will also struggle with the exhausts for it as you need that to design a set of pipes to suit your needs, otherwise the pipe maker is going to be guessing. BTW: What the hell does "Stage 2 tune" actually mean - certain tuners band these words about, but nobody has ever been able to put it into technical terms as to what that is, how does it differ from a Stage 1 or 3 and how many stages are there ? As regards the 2 into 1 manifold, I've done a few on the big bore stuff, there are compromises, its not all gains as some would have you believe, if it was, everybody would be running them and they aren't ! As I say, it all comes down to what you want, I assume you are running a programmable ignition of some sort as well, this also will play its part in getting everything working as you want HTH I have an idea what different stages are, stage 1 would be mostly standard with some blue printing as it should come out the factory, stage 2 would be altered jetting with air filter mods and maybe better reeds and ignition mods, stage 3 would be exhaust mods, stage 4 would be porting to a certain level, stage 5 would be all out porting with bigger carbs too, stage 6 would be bigger bores or stroker crank or both increased capacity should I say, obviously one mod follows on from the last and all settings will need altering along the way including exhausts, as in stage 3 on its own would not be stage 3, you would need the other mods too, that is as I understand it. |
|
|
|
Post by muttsnuts on Apr 19, 2020 13:16:20 GMT 1
LOL - Tony I like your thinking !! the only problem with that is, each tuner who uses the phrase seems to have a different interpretation of it, some of the best tuners I've spoken to just use the term "ported" and will do "X" or "Y" e.g. peaky power high up (high revving) or more mid range (lots of bottom end grunt) I tend to steer clear of such terms, I just say ported or not ported, if ported, what has the ports been altered to, then you have a chance of working out what pipe design to go with Its like "Banshee coils" - no such thing, there are just 12v 6ohm coils in either "Orange" or "Black" - its all about marketing and hype - on my web site I just sell coils in orange or black, both do exactly the same thing in exactly the same way with exactly the same results on the dyno |
|
|
|
Post by tony2stroke on Apr 19, 2020 13:23:32 GMT 1
It is from car tuning I got that long time ago, stuck in my mind, as you say all tuners have their own take on what is what.
I just amended to include ignition mods, I forgot about that, but that would be early on.
Basically more fuel in and more gasses out and better ignition in stages as you go.
No point putting more fuel in if you can't get the gasses out.
Also on a dyno stage 1 would not produce the same output as say stage 6 obviously.
As if you just put a stroker crank in without the rest you would not have the same result on the dyno as you would with all the stages complete, 1 follows the other
|
|
|
|
Post by tony2stroke on Apr 19, 2020 13:54:18 GMT 1
Here is a little RD200 I tuned a couple of years ago
I started with blue printing, then pod filters, then reed cage mods (removing bridge and fitting carbon single reeds cut myself from reed sheet) then carbs RD250LC ones with balance pipes, then ported it, then I had a pair of expansion chambers made, I could not have ignition mods as it had electric start I wanted to keep, I was testing this bike to destruction to see what is what.
Have a look.
So as mutts said not as simple as stage 2 3 written in law.
|
|
|
|
Post by paulincayman on Apr 19, 2020 14:37:17 GMT 1
|
|
|
|
Post by marrcel on Apr 19, 2020 18:47:05 GMT 1
|
|
