07-27-2022, 11:22 PM | #1 |
Join Date: Jan 2020
Location: NoDak! (Kinda like Red Dawn w/o mountains)
Posts: 69
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200cc Shineray(VM26, 110/20, no idle, bogs
200cc Shineray. Just got a VM26. Pulled the 100 jet, put in 110. Left stock 20 in. Tried 1 1/2 out on air/fuel mix. Needle is in middle position. (If the jet fits, but looks different is an issue? The factory one looked more like a small stove bolt)
Exhaust is decatted, foam air filter. Problems: Starts much better, but will not idle. I can crank in the idle screw and nothing changes. Bogs off the starting line and at about 3/4 throttle. I am guessing the idle jet needs to be a bit bigger. I increased the turns to 2 out and still it seems like it is starving for gas. I am wondering if my fuel filter could be clogged. Suggestions? |
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07-28-2022, 08:53 AM | #2 |
Join Date: Sep 2021
Location: De Soto, MO
Posts: 1,953
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As you said, I'd check the fuel filter first to see if that was the issue. Always do the cheapest and simplest things first. Then if necessary go up a size on the idle jet.
I learned a long time ago with carby cars to keep a spare fuel filter in the car along with the tools to change it out. Saved my butt a couple of times, in between cities on road trips.
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2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Nope, finally retired. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself |
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07-28-2022, 12:44 PM | #3 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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idle circuit could also be blocked up. I never trust the carburetors out of the box and always clean them and blast carb cleaner through all of the passages and then blow them out with air if possible You may need to bump up the pilot jet as well. The CG250's tend to need a 27.5 pilot jet with your level of modifications so it may not be a bad idea to have a 22.5 and 25 on hand
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07-29-2022, 12:31 AM | #4 |
Join Date: Mar 2021
Location: Ohio
Posts: 43
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I had a 20/110 in my VM26 on my Magician before I went Stage 3 big bore with a Nibbi and it ran way rich, even fouled an Iridium plug fired off a Nibbi coil. Can't imagine things working better on a 50cc smaller engine. Bet you never need the choke.
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08-09-2022, 10:56 PM | #5 |
Join Date: Jan 2020
Location: NoDak! (Kinda like Red Dawn w/o mountains)
Posts: 69
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UPDATES:
112 main, 22 idle. Results? Will not idle, pops and farts at WOT, sluggish starting. Air fuel 1 3/4 ~ 2 turns out. Cleaned out all passages. New manifold (other one had cracked threads), changed fuel filter. Starts 'ok', but definitely not a one kick machine\ So... suggestions ? |
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08-10-2022, 02:04 AM | #6 |
Join Date: Aug 2020
Location: Australia
Posts: 1,416
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Considering my issues with trying to adjust a PZ30 and NibbiPE28...
my conclusion ended up being a bad CDI unit. All pops, farts and cutout stall issues in my situation has been a too lean scenario so far. My idle swings between running temp and a hot and cold ambient temp all at the same altitude... So I am just dialing it in on the fat side with a middle clip on the needle and making adjustments with idle on the fly depending on how temperamental my bike feels. I live about 1000ft up a hill...If you're at sea level you might want to keep it on the lean side of things. How any of this information correlates to your VM26 I can't say...I'm just rolling the carby tuning bones for guidance Last edited by XLsior; 08-10-2022 at 03:13 AM. |
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08-10-2022, 09:14 AM | #7 |
Join Date: Aug 2019
Posts: 472
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You're trying too many things at the same time. First get your starting and idle right. In your first post, you stated your jet doesn't look like the one that came out of the carb; it's possible that the needle doesn't fit the new jet.
I use the PZ-30 on both my bikes without issues since tuning. My Magician has the same mods as your ShineRay and uses a 105 Main. My Storm has no mods and a 110 main. Both bikes have 1 size larger than the stock Idle Jet.
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2018 Bashan Storm(sold) 2016 Magician 250 |
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08-10-2022, 06:59 PM | #8 | |
Join Date: Jan 2020
Location: NoDak! (Kinda like Red Dawn w/o mountains)
Posts: 69
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Quote:
I got different main jets and pilot jets. These match the original ones that came with the carb. I went one size bigger in the idle jet (20 to 22) and up 12 in the main jet (100 to 112). I kept the middle needle setting For reference, our altitude is 1959 |
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08-10-2022, 07:33 PM | #9 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Quote:
Stop making multiple jetting changes for starters. As suggested above focus on getting the idle and low throttle sorted then worry about the main jet. As far as the idle mixture... which is it 1 3/4 or 2 turns out? A quarter turn of idle mixture is a decent amount of adjustment range to just pish posh Is the idle speed around 1500rpm? If you try to adjust the idle speed does it respond at all? If you blip the throttle does the idle drop back down quickly or hang up?
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08-10-2022, 08:57 PM | #10 |
Join Date: Jan 2020
Location: NoDak! (Kinda like Red Dawn w/o mountains)
Posts: 69
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Idle screw does not change the idle.
Air/fuel screw is 1 3/4 out. Blip the throttle, idle drops quickly. Starts worse now. So starting all over, back to square one: What size idle jet do you recommend to get the starting and idle sorted out? Tried the 20 originally and it did not idle with that one either (factory jet) Thanks all for help so far! |
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08-10-2022, 09:36 PM | #11 |
Join Date: Jan 2020
Location: NoDak! (Kinda like Red Dawn w/o mountains)
Posts: 69
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Odd... Just walked out to the garage. Would not start at all. I pulled the plug (BLACKKKK) OK... way to rich. Shorted it to check for spark. Got spark. Put it back in. Started right up. So... was that divine intervention or is that coil or CDI module playing games on me too?
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08-10-2022, 10:50 PM | #12 |
Join Date: Aug 2020
Location: Australia
Posts: 1,416
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If the plug is coming out like tar with a a/f mix screw outside the 1 to 2 margin the pilot jet will need to be changed...in your situation a smaller/leaner pilot jet it seems.
The idle screw is basically backed out so the slide is just about move up a crack from seated. Not sure if it has a choke or enrichment circuit...but no point making fine adjustments while the engine is still cold/warming up. Yes i would also get a new CDI and Coil not just for testing but also as spare/backup parts. |
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08-11-2022, 10:32 AM | #13 |
Join Date: Aug 2019
Posts: 472
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Basic Carburetor Tuning Guide
First off, there's 2 basic fuel related problems. You either have a rich mixture, or a lean mixture. A rich mixture is caused by too much fuel compared to the amount of air being used during combustion. Rich conditions can be detected by the engine spitting and sputtering, blurbling, or acting like a rev limiter, rapidly losing and regaining power. In severely rich conditions, you may be seeing black smoke coming from the exhaust. The black smoke you see is actually raw fuel that is not being burnt and is being wasted. By looking at the spark plug, a rich condition can be detected by a black, sooty plug. A lean mixture is caused by too little fuel compared to the amount of air being used during combustion. Lean conditions can be detected by the engine losing power, yet retaining it's engine speed. For instance, the engine sounds to be accelerating to higher RPMs, yet feels as if it has no power. By looking at the spark plug, a lean condition can be detected by a white, blistered plug. Secondly, there are 3 basic carburetor circuits: Pilot Circuit, Mid-range Circuit, and Main Circuit. These 3 carburetor circuits can be troubleshooted by knowing the throttle opening they control. The Pilot circuit is responsible for throttle openings from Idle (0 throttle) - around 1/4 throttle. This circuit consists of pilot air jet(s), the pilot fuel jet(s), a pilot screw (either fuel or air screw), and pilot ports inside the carburetor throat (a.k.a. Venturi). There are 2 types of pilot screws: a fuel screw and an air screw. The fuel screw is located on the engine side of the throttle slide in the carb, and controls the amount of fuel that is drawn into the Venturi by the pilot ports. By turning the fuel screw out, you are allowing more fuel to pass the screw, effectively richening the mixture. By turning the screw in, you are restricting fuel, effectively leaning the mixture. Another way to determine whether it is an air or fuel screw is that a fuel screw has a rubber o-ring to keep air from entering the pilot circuit around the screw. The air screw is located on the airbox side of the throttle slide in the carb, and controls the amount of air that is drawn into the Venturi by the pilot ports. By turning the air screw out, you are allowing more air to pass the screw, effectively leaning the mixture. By turning the air screw in, you are restricting air, effectively en richening the mixture. The air jets are hardly ever changed, so we won't go over that. The pilot fuel jet(s) can be changed to bigger (richer) or smaller (leaner), depending upon your problem. A good rule of thumb to use is that if you have to adjust the pilot screw more than two turns either way if it's stock setting, then you need to accommodate by changing the pilot air or pilot fuel jets accordingly. Remember, the Pilot Circuit is only effective from 0 throttle to around 1/4 throttle. It still functions during the rest of the throttle positions, but it's effect is minimal, and goes un-noticed. The Mid-range circuit is responsible for throttle openings from 1/4 throttle - 3/4 throttle. This circuit is controlled by 2 things: the Jet Needle, and Needle Jet (a.k.a. the Main Jet Holder). The Jet Needle, or needle as many call it, is attached to the throttle slide, and drops into the Needle Jet. All needles are tapered. Either the Jet Needle is adjustable or it is not. If there are more than 1 grooves for the needle clip to sit in, then it is adjustable. By raising the clip on the needle, you are allowing the needle to sit deeper into the needle jet, which restricts fuel, effectively leaning the mixture. By lowering the clip on the needle, you are raising the needle out of the needle jet, which allows more fuel to pass, effectively en richening the mixture. When the slide raises, it raises the needle out of the needle jet, allowing fuel to pass by the needle and into the Venturi. This is where needle taper comes into play. Unless you are extremely fine tuning the carb, you don't need to worry about taper. You change which part of the taper is in the needle jet by the position of the clip. Remember, the Mid-range circuit is only effective from 1/4 throttle - 3/4 throttle. None of the other circuits have a drastic effect on this circuit, so if your problem is in the mid-range circuit, then it can't be the main jet or the pilot jet. The Main circuit is responsible for throttle openings from 3/4 throttle - Wide Open Throttle (you'll see me refer to this at WOT later on). This circuit is controlled by 2 things: the Main Jet, and the main air jet. The Main Jet is the #1 thing that people change in a carburetor when it comes to tuning them. This is often a big mistake, as it only controls 3/4 - WOT, and NOTHING ELSE. Remember that. A larger main jet will allow more fuel to pass through it, effectively en richening the mixture. A smaller main jet will restrict fuel, effective leaning the mixture. With the main air jet, it allows air to premix with fuel as it goes up into the Venturi. The Main Jet only functions at 100% when the slide is open and the jet needle is pulled completely out of the needle jet. At this time, the only thing restricting fuel flow into the Venturi is the size of the Main Jet. Now for tuning. If you read above, you should know the difference in feel of rich and lean mixtures. By knowing at what throttle opening the problem is occurring at, you can figure out what circuit the problem is occurring at. If it's the pilot circuit, there are 3 basic way to tune the circuit. You can adjust the pilot screw, change the pilot air jet, or change the pilot jet. Adjusting the pilot screw is simple. With the engine running at idle, warmed up to normal operating temps, turn the screw in until it starts to idle rough, then turn the screw out until it starts to idle rough, then turn the screw so it's between those two extremes. To check the position of the screw, you can count the number of turns as you turn the screw in until it seats SOFTLY with the carb body. Reason I capitalized SOFTLY is that the screws (especially the fuel screws) are easily damaged if over tightened. So screw them in until they SOFTLY seat the carb body. Compare your counted number of turns to soft seat and compare it to stock settings (stock settings are determined by counting turns until soft seat before you do any adjustments whatsoever). Again, if you had to turn the screw more than 2 turns either way, you need to change pilot jets (air or fuel) accordingly. In the mid-range circuit, there are 2 basic ways to tune the circuit. You can adjust the jet needle, or change the needle jet. Raising the clip will lower the needle, leaning the mid-range. Lowering the clip will raise the needle, en richening the mid-range. You can also change the needle jet, but only if your jet needle adjustments make no difference in the way the mid-range circuit operated. If you are running lean on the mid-range, and you've raised the needle as far as it will go and it doesn't get any better, then you should go up in the needle jet size. Many carb manufactures don't have different sized needle jets, so the aftermarket may offer them, or they may not. In the main circuit, there are 2 basic ways to tune the circuit. You can change the main jet, or change the main air jet. Changing to a larger main jet will effectively en richen the circuit. Changing to a smaller main jet will effectively lean the circuit. You can determine which you need to do by first determining whether you are rich or lean. Changing main air jets, again, is for very fine tuning. Once you have the main circuit functioning properly, you shouldn't have to worry about the main air jet, because the air for the circuit is mostly provided by the air passing through the Venturi. On many carbs, the main air jet is not changeable. They may be pressed in. So there you have it. I basically touched base with carburetor internals and how to adjust them to tune the carb. Every brand carburetor has different ways of accomplishing the same main goal of every carburetor. That goal is to precisely and efficiently mix air and fuel in the right ratios for efficient engine operation. This efficient operation comes from complete combustion, which cannot occur if you are too rich. Whether Mikuni, Keihin, or whatever, they all do the same thing, just in different ways. Hopefully this will help some of you to understand the functions of the carburetors internals.
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2018 Bashan Storm(sold) 2016 Magician 250 |
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