200cc Shineray(VM26, 110/20, no idle, bogs

[thedakotakid]

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?

[TominMO]

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.

[Megadan]

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

[BrokeAss]

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.

[thedakotakid]

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 ?

[XLsior]

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

[Magician16]

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.

[thedakotakid]

Originally Posted by Magician16

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 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

[Megadan]

Originally Posted by thedakotakid

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 ?

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?

[thedakotakid]

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!

[thedakotakid]

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?

[XLsior]

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.

[Magician16]

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.

[Magician16]

I don't remember who wrote this carb tuning procedure. It was shared with me many years ago when tuning snowmobiles. I would have given credit.