Hi,
I just finished my build just last month and I was looking at some feedback on some stuff. My bike currently has the following:
-1975 RD350 stock7
-HPI Ignition
-Banshee/RZ intake with crossover tube
-OKO 28mm Carbs
-Y Boot with K&N filter (3D printed adapters)
-Spec II chambers
I am currently loving these OKO 28mm carbs on my build. The throttle response is great and it has been a pretty to tune. I am currently hitting a flat spot (seems rich) around 5k-6k, but when it gets to 7k, the pipe starts to hit. I was wondering if anyone else experienced flat spot and has any suggestions? I know that the stock vm28 had the same issue but the solution was to do the dave modification with the R5 carb parts. Any input on the matter would be appreciated.
Thanks.
what needle us in the carbs?
JJH.
bump?
What's your clip position and have you tried moving it?
Does it still go flat when under full power? Like full throttle from 3k rpm into the power band?
Thanks everyone for your input.
I have tried moving the clip position, currently 2nd position on the needle. It doesn't seem like its doing much.
Bill: Pretty much. Once it enters 6k, it wants to start going at 1/2-3/4 throttle.
So it wont go before 1/2 throttle? You moved the clip up one position from center ( moving needle down) and it didn't help? Might try moving the clip down one position from center, enriching the mixture.
It will go before 1/2. Hell, it will go 1/2~3/4 throttle but it's a sluggish process cause of the flat spot. I am just trying to figure out if I needed to go from a JJH to JJJ needle or or the air filter adapter for the y boot I made is restricting the airflow too much.
(https://i.ibb.co/7Q8C4Pn/carbs.png) (https://ibb.co/9hzgt6b)
temporary image upload (https://imgbb.com/)
ditch the adapters they fuck up airflow. you're probably getting a reversion effect.
Might as suggest getting some Wintergreen oil, acetone or xylene and soaking the ends of the Y boot overnight?
It will expand the rubber to the point where they will fit the carb openings and you can let it dry/shrink in place...
I have some UNI I can test if it helps with the issue or not then purchase some long 5 inch, if it goes away.
AS for the wintergreen oil + alcohol. That solution works great but they swell up and shrink back down.
try the unis. needle may need to be moved
The fair-skinned should use great caution with the methyl salicylate. It can cause serious burns, depending on your skin'd sensetivity to it. It also melts plastic - not like acetone, to make a nice glue, but just into a glob that is useless. In the '60s we used it to clean and soften slot car tires, but had to pick the cars up immediately when stopped and set them upside-down or the residual wintergreen oil would melt the plastic track where the tires touched. One fair-haired friend mistakenly sat on a rag soaked with it, and ended up spending the evening with his rear in a tub of ice water.
Quote from: pidjones on September 11, 2020, 07:03:24 AM
The fair-skinned should use great caution with the methyl salicylate. It can cause serious burns, depending on your skin'd sensetivity to it. It also melts plastic - not like acetone, to make a nice glue, but just into a glob that is useless. In the '60s we used it to clean and soften slot car tires, but had to pick the cars up immediately when stopped and set them upside-down or the residual wintergreen oil would melt the plastic track where the tires touched. One fair-haired friend mistakenly sat on a rag soaked with it, and ended up spending the evening with his rear in a tub of ice water.
Oh I know. But that smell is great :haw: :haw:
**Update**
I was able to test ride the bike without the Y Boot with the single K&N filter. It definitely helped my throttle response with the extra amount of airflow. The flat spot is much better but I will mess around with my needle positioning to see if it improves anything.
**Update**
Changed the needle position to position one and it helped it a bit more with the throttle response but it's still a little rough between that 5-6k gap. I will see what I can do with the transition to my mid range.
this is where reed spacers may help a bit.
Thanks for the tip, Mark. I will look into this. Be cool if I can use some high temp filament and 3D print some.
that, unfortunately, would be a negative. 1/4" aluminum plate or the ones john sells at economy. :twocents:
I was gonna ask my buddy to cut me some with his plasma table, I saw that John was selling 9mm ones but 1/4" (6mm) would would as well?
I was just pulling your leg about the 3D printed parts, still going to try to make those expansion chambers though! :dawg: :dawg:
:dawg: :clap:
Just got some 1/4 inch steel spacers made by my buddy. Simple 2 min cuts from his plasma CNC machine. I will be putting them on my RD tonight.
Any update with the spacers installed?
Sorry, Dino. No major updates. I have been working on my Suzuki T-500.
It seems like it has helped it a bit, but I would need to rejet my carbs. I think I over shot my pilot jet (i went up two steps) when I installed the spacer. Riding season is almost over, so I would need to jump on this.