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Post by dexameth on Mar 19, 2020 10:01:43 GMT -5
So... I'm curious as to any other tuners that has run into this issue:
70cc Minarelli with a 21mm, 26mm, 28mm PWK carb - whenever I get past 1/4 turn out on the idle screw I get a hanging idle. I know the PWK carburetor idle mix screw adjusts the air into the idle circuit when the CVK carbs are opposite and adjust the fuel flow.
So, with all three size carburetors and on two different machines, I turn the idle all the way in closed (gently) and they idle fine but tend to richen up a bit; turn out 1/2 turn and blip the throttle a few times and the idle hangs bad. Only a half turn? Seems weird.
I used a 46 idle in the 21mm AND the 26mm, the 28mm used a 48 idle jet.
If I'm sitting at a light for a while at the current setup, she bogs when I try to take off like she's idling way too rich. If I open up that needle the slightest bit, the idle hangs.
My only idea is to use an absolutely HUGE idle jet, and maybe I'll be able to adjust the needle better? Just seems weird. I know a 180cc 4t guy that had to do the same with is 28mm carb...
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Post by repherence2 on Mar 19, 2020 10:53:58 GMT -5
When you say "idle" screw, are you referring to the screw that is knurled (with the spring) that raises the carb slide?
Or are you referring to the screw that is recessed into the side of the carb?
A lot of times, here in Honolulu, i see guys on modified Hondas always fiddling with their carbs while at a stoplight. It appears that they are adjusting the knurled screw on the 28mm OKOs. Add to that, they continuously blip the throttle while at a stoplight to clear it out.
This may be an inherent issue with the PWK carbs.
Have you tried up jetting the pilot and readjusting the air screw in conjunction with idle screw?
I can't recall that issue with any of the OKOs I've run. However, i know that i did change out my emulsion tube to a different rating than what the OKO came with from the factory. I do run a venturi divider on my carb. And i have changed out the pilot jet from what came with the carb.
For my situation, it may be a combination of different pilot jet, different emulsion tube, and venturi divider. I dont have issues with hanging idle. The OKO is smooth throughout the whole trottle range and unlike the Honda guys, i never had to fiddle with my carb at stoplights.
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Post by dexameth on Mar 23, 2020 8:59:11 GMT -5
No, not the idle speed screw that those guys are fiddling with, I'm talking about the mixture screw. The 21mm carb had a 42 idle, I went all the way up to 48 with no change, the same idling as the other. Crack that mixture screw open to a full turn out and the idle hangs when I blip the throttle.
Funny you say those guys have to keep blipping the throttle to clear it out, I do the same. If I sit there, it will idle throughout and entire stop light (4-5 minutes) but when I take off it's so boggy. If I blip the throttle a few times before taking off it's 100% better.
I have known about the emulsion tube (or atomizer) being different between 4t and 2t but I haven't bothered with removing it to verify what is installed. My guess is 4t and that could be effecting it. I may need to lower my float a little as well; I was playing around with it again yesterday and got her idling really nice when upright, but I lean over on the kickstand and she sputters out and dies. Restart, idling upwards, lean over and she sputters but I upright her quickly and she's fine. I've noticed with doing sharp uturns and leaning hard there's a good bog when under throttle until I upright again. Funky carb, I tell ya.
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Post by repherence2 on Mar 23, 2020 10:04:51 GMT -5
Got it.
Very interesting details. Now that you confirmed that clearing the throttle helps, it makes sense as to why the wide-open-OKO-hondas are bliping their throttles at stop lights.
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Post by dexameth on Mar 23, 2020 10:10:00 GMT -5
I do have my oil injector zip-tied to pump max at all times - it injects to the intake manifold so it's not messing with jetting but I think this is why I have to blip it to clear it out. If it idles for a while, when I do clear it out it smokes a LOT. I think I need to just swap to premix, get rid of the pump.
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Post by repherence2 on Mar 23, 2020 10:13:35 GMT -5
What kind of intake manifold are you using?
The CT forward facing one?
Or the 360° type that faces the carb backwards and angled upward?
I use the CT chrome manifolds.
And when you describe the transition from the bike leaning and then going upright as well as making u-turns, that sounds like a float issue.
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Post by repherence2 on Mar 23, 2020 10:16:59 GMT -5
I do have my oil injector zip-tied to pump max at all times - it injects to the intake manifold so it's not messing with jetting but I think this is why I have to blip it to clear it out. If it idles for a while, when I do clear it out it smokes a LOT. I think I need to just swap to premix, get rid of the pump. Now it all makes sense. I agree, you should try premix in that case. But if you go premix, you gotta rejet. In my situation, i run injection pumps because my cable assembly is still good.
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Post by dexameth on Mar 23, 2020 10:43:55 GMT -5
What kind of intake manifold are you using? The CT forward facing one? Or the 360° type that faces the carb backwards and angled upward? I use the CT chrome manifolds. And when you describe the transition from the bike leaning and then going upright as well as making u-turns, that sounds like a float issue. It's a Minarelli 70cc 2t with the typical chrome performance intake manifold and Polini reeds, one thick and one thin for that dual-stage feeling. So, the carb sits pretty much in the factory position.
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Post by jackrides on Mar 23, 2020 11:25:09 GMT -5
Would your injection pump have a cable connection? A lot of older MC pumps did, and the quantity of oil was determined by both throttle pull (courtesy of a cable 'splitter') and rpm. So a lot less oil injected at idle.
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Post by repherence2 on Mar 23, 2020 20:10:21 GMT -5
What kind of intake manifold are you using? The CT forward facing one? Or the 360° type that faces the carb backwards and angled upward? I use the CT chrome manifolds. And when you describe the transition from the bike leaning and then going upright as well as making u-turns, that sounds like a float issue. It's a Minarelli 70cc 2t with the typical chrome performance intake manifold and Polini reeds, one thick and one thin for that dual-stage feeling. So, the carb sits pretty much in the factory position. The instructions that came with my Boyesen (dual stage reeds) mentioned that the jetting should be set differently from a normal set of reeds.
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Post by pete130 on Mar 24, 2020 3:04:11 GMT -5
I have had same trouble buy I fixed it, i use a pwk 30mm power jet so a little more jetting involved,I found if you jetting isnt spot on it will hang or no hold idle after 5 seconds at lights I used to have to keep flipping it at lights and running a bit rich is way better than lean but once I got the jetting right it's working a lot better I had trouble because I run a rear facing carb set up and runs nearly 40° off horizontal so I changes to side manifold and works even better and smoother just my thought but you get good advice here most know what there talking about
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Post by pete130 on Mar 24, 2020 3:04:47 GMT -5
It's a Minarelli 70cc 2t with the typical chrome performance intake manifold and Polini reeds, one thick and one thin for that dual-stage feeling. So, the carb sits pretty much in the factory position. The instructions that came with my Boyesen (dual stage reeds) mentioned that the jetting should be set differently from a normal set of reeds.
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Post by pete130 on Mar 24, 2020 3:06:02 GMT -5
I run the same power reeds work very well I would recamend to all nice having a 2 stage power band sort of if I hit it they just open up fully at same time
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Post by dexameth on Mar 24, 2020 8:40:25 GMT -5
I love the feel of Boyesen on my Stella, thanks Lee! I actually just emailed Boyesen to find out EXACTLY which reeds worked with Minarelli... seems the older model Zumas had a bigger reed than the newer. This is their reply: "Hello Tyler, We list Boyesen dual-stage Power Reeds, part # 711 to fit the 2001 and earlier year model Yamaha Zuma 50, and we list dual-stage reed # 712 to fit the 2002-2011 Yamaha Zuma 50. Attached are pictures of both reeds. The reed dimensions for reed # 711 are: length = 39.2mm and width = 39mm. The reed dimensions for reed # 712 are: length = 38.2 and width = 32mm. We do not a reed to fit the Genuine Stella 150 2t engine. If possible, please send us a tracing or photo of the stock reed in that engine, including the reed dimensions." Here's their attached pictures: Older 711 Newer 712 The reason I was asking was because my friend has a Genuine Buddy, and they use the Minarelli reed pedals on their own block. It's a flat reed surface, so they can easily be used on the Buddy. But, if you guys are familiar with the Minarelli reed block in the later models, they have a raised lip edge on the reed petal surface. So, if you cut out the center bar to allow the extra airflow with the Boyesen reed, you'll lose a seal right near the middle bottom/top. Best to leave the middle bar in the later model Minarelli. But, it looks like the earlier model 711 is what fits the aftermarket reed blocks... at least our SSP-G reed block. If I remember right, the Polini reed is 39mmx39mm as well, so they'd even fit in there. Looks like I'll be buying a couple sets soon to try... 712 for the Buddy, and 711 for myself. But, side note - look at their response to me asking about what part number fit the LML/Stella 2t engine! Haha the RD350 bolt right on, but their website was down so I couldn't find the part number and just emailed them. That gave me a laugh. drc174 do you remember what part number they were?
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Post by dexameth on Mar 25, 2020 10:54:23 GMT -5
I pulled the trigger. Ordered a set of each 711 & 712, will report back...
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