Thanks Steve, i'll contact him for a look if possible, cheers, Chris.
Pm your email again and i'll send em across.
I would like a look too... you guys have my e-mail address...
OK, so I couldn't wait 'til the weekend I made a plate that extends further into the carb' intake horn, 12.5mm total, compared to the 3mm protrusion of the first one I made. 12.5mm looks to be the closest you can safely go to the slide, without risking actually touching it. I'll ride it tomorrow after work and see if it's any different, and post the results, cheers, Chris.
Man the extent of this info is great--detais, extra details.
OK I gotta ask, where do you guys get all this spare time to jack around with your bikes--come up with these inventions, etc?? I am hitched with yung'uns and there is NEVER enough time for the REAL needs, like this!!!
I applied at the You-Don't-Have-to-Work-to-Get-Paid company where I suspect many of you are employed, but could'nt get an interview.
I never sleep :D
OK, probably my last concern, let's see how fast you can answer this!!!
OK Chris, since I KNOW you are awake, no matter what time zone you are in, here goes...
Did you, or better yet, should you re-jet the bike for this mod? Is it going to run lean and fry the thing on the first ride or is it simply redirecting the airflow so there is really no adjustment needed?
Has anyone pulled their plug before and after to make any comparisons?
Hey, sorry I took so long to reply, I'm watching SX, the 250's at Bank One are on cable. (Yeah, I know, we're a little behind) I haven't re-jetted, and don't plan to, as it's running great, showing no signs of a lean condition. I haven't checked my plug recently, but also don't think plug reading always tells you much either. It can, but I often take a screwdriver with me, and adjust the fuel screw a little while i'm out riding. Sometimes tinkering on the side of a track brings good results.
Good job on the home grown PN. Someone posted this link from the 250F side. I also noticed that in your original design the plate was too short 3mm - glad you fixed the problem!
In the pics of the PN that I have (in my sig below), you can see that the plate goes much further towards the carb's slider than in your original design (12.5mm sounds reasonable) - the shorter plate will NOT work right if that plate doesn't go right up against the carb's slider. The reason is because the shorter plate will leave a gaping hole between it and the carb's slider, hence the air can travel through the top side of the plate in the venturi as well as the bottom side to get to the carb's intake which is pretty much what it does stock without the PN. The PN forces more air into the bottom side of the plate (i.e. cutting out the top side) at low RPM, this smaller opening creates more air flow into the carb using the same pressure (since it's going into a smaller opening as in a jet engine) therefore creating better low end and resisting stalls better - kind of like a turbo boost without all the complicated mechanics involved, not as strong as a real turbo unit of course but the design makes sense and it definitely helps my 250F. The 4xxF bikes may show less gains than the 250Fs since your power plants already have much more torque at low RPM but this mod should help with starting and stalling for the bigger engines.
If you guys are going to make your home grown PN, try something radical and add another plate between 0-1/2 throttle (i.e. in the bottom area of the venturi), this should help with the 0-1/4 throttle response - let us know how it works...
OK, I just got back from a decent ride with the longer plate fitted, and didn't notice any further gains over what I originally experienced. I rode the same area as before, same corners etc, felt exactly the same as the shorter plate. Having said that, I will be leaving the longer one in, as in theory at least, it should better direct the airflow, it's just that I didn't notice any gain by doing it. Thanks to those who have sent tips regarding the plate, and thanks again to yamaha-dude for offering to update the PDF, as new ideas are appearing daily.
David, just saw the updated PDF, once again excellent. Cheers, Chris.
i think your template is wrong ! Look at it again!
Agreed with BigDesto, the picture of your "cutting template" and its measurements don't match the "actual" plate used in the venturi. The 'T' head is too short, while the body is too long - you must have it backwards?
Yep its still incorrect, or at least one of them is. The template on pg2 is saying its 54mm x 67mm and has a wing 14.5mm x 11mm. The photos on pg2, bottom right shows a larger cutout rather than a wing shown in the template, and the other description from "Chris from Oz" is only 46mm x 40mm with 3mm cutout checks.
Which one is the WR450 one?
I have been getting dimensions from James... and pictures from other people, who have done their own version... The pictures illustrate the principle and the fitting... the template is what James is recommending... I will clarify what his dimensions are and get back to you...
Looking at the "cutting template", my guess would be 54mm x 52.5mm for the main body then goes into the smaller head of 43mm x 12.5mm(?) i.e. the tip that will go right next to the slider.
IIRC, even though the 426F uses the 39mm carb vs. the 250F's 37mm carb, their venturies(sp?) are the same size since the WorldPower PowerNow people sell the same unit for both bikes. Once the template measurements are correct, then that template can be used by both bikes for years 01 & 02.
As for the 03 bikes (250Fs & 450Fs), the air intake venturi is built into the carb, i.e. you can't remove it like the units in the PDF document. I suspect the PN for the 03 models will look similar to the units they're selling for the 2 strokes - it will probably be harder to copy their design for the 03s since you won't have a "removable" venturi to cut and glue into but we'll see (some people on the 250F side will post pictures of their 03 units when they come in). See a picture of the 2 stroke PN at their web page http://www.worldpowerracing.com under the "PRODUCTS" button.
Ok, I don't have the old PDF in front of me, but to me the drawing of the plate measurements seem off. Are those correct?
I have double checked with James... The pictures are of the one Chris From OZ made, and the other two pics are the one ToyRona made... The templates is correct according to James.. who has done a lot of work on this... he has extended it a little to help with airflow... but the dimensions are correct, for the 426 bikes, and seemingly the 250's as well...
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