Throttle hesitation, air/fuel mix, spark plug gap By rosiemoto (Read 624 times)

[rosiemoto]

I think my bike is running a little rough, could you all help me out? I'm going to list the symptoms below. Please read them all before posting your conclusions. I ask of this because I currently believe it's all air/fuel and spark plug gap issues, but you experts may find something else wrong judging the symptoms.

It just occurred to me after measuring my original spark plug's gap that my bike has NEVER run according to spec! The original spark plug is measuring somewhere slightly OVER 0.8mm (higher than my feeler gauge can go). My bike spec says 0.6-0.7mm. Why does it give a range? Should I be averaging the gap out to 0.65mm then? I have about a half year old spark plug in now but never did the gap.

With my air/fuel ratio, the screw seems VERY loose, meaning even bumping it with a screwdriver turns it. It has no resistance like screws normally do. I could probably spin it with my pinky finger. Not sure if that's normal? I looked to see if it was spinning around during idle, but it doesn't seem to be, so that's super confusing me.

Here's my bike's SYMPTOMS. I think it's running lean, but maybe there's more to it. What do you think?

- Starting the bike usually takes a few tries or requires giving it throttle. It always starts up quick, but it gives a couple puffs of air then dies... this repeats until I give it a little gas during startup and nurse it for the first 3-5 seconds, and then it's able to hold itself together. (Cause: Spark plug gap issue?)

- If the bike is fully warmed up and I stop the engine at a long traffic light, it's a 50/50% chance that it'll be really hard to start it up again when the light is turning green. (Cause: No idea?)

- Before my bike is fully warmed up, it has very noticeable points in the throttle that cause hesitation. After warmed up, the throttle is improved, but I still feel it hesitates a little, and backing off the throttle a little from those points makes the engine smoother, yet doesn't change speed. I use Ethanol-free gas to help with this, as any grade of ethanol gas 87-93 makes it feels like I'm riding uphill all the time. (Cause: Air/fuel mix too lean? Needle mix?)

- It's been hot out and we suddenly had a cold day, and on that cold day I started up the bike and noticed it sounded different, maybe louder, like more "air pressure" was coming out or something. I also noticed the RPMs were higher than usual for the first 5-10 minutes of riding. I always have let my bike sit for at least 1-2 minutes before I take off, but I've never noticed this before. It was revving 500-1000 rpm higher than usual at the speeds I was going. It went back to normal after bike was fully warmed up. (Cause: A/f mix too lean?)

- (Possibly related) This one's WEIRD. 6 years ago during my bike's first winter (36-45F temps), I'd start it up, let it idle for 3-5 minutes, then try to drive off, but it wouldn't go ANYWHERE. A very tiny amount of throttle was all it would take (as in 5mph), but soon as I gave it more, it just returned back to idle as if I wasn't giving it any gas. It never stalled. Even WOT it did nothing but idle. As it warmed up more, I could give it more and more gas until eventually it ran normally. These days it doesn't seem to do this anymore but instead has that throttle position hesitation I mentioned before.

[cyborg]

Sounds like a slightly lean condition to me

[Alleyoop]

- If the bike is fully warmed up and I stop the engine at a long traffic light, it's a 50/50% chance that it'll be really hard to start it up again when the light is turning green. (Cause: No idea?)

That is caused by tight valves which means it is loosing compression and the motor is having trouble holding low idle when hot. So before you go and adjust the mixture ADJUST your valves set them both to .004 inchs that will make a big difference.

Then you can adjust your carbs fuel ratio mixture.

scooterdoc.proboards.com/thread/1499/4ts-carb-tuning

Alleyoop

[rosiemoto]

I was secretly afraid of that Alleyoop. The problem is I can't get my valve cover off because the right bottom bolt I can't seem to get to no matter what. Trying to remember why.. I think the bike's frame was in the way, and that emissions thing attached to it was in the way too. I'll take the bike all apart again soon and take pictures this time as to why I can't get to that bolt because I seem to be the only one with that problem!

I did try to adjust the A/F mix but it didn't seem to affect anything, which I think meant valves need adjusted, so guess I gotta figure out how to get that cover off first. Funny because I know how to do the rest, but I'm stuck at step 1, undoing the BOLTS. lol

[Alleyoop]

One thing you can try is move the scoot off the center stand and see if then you can get at the bottom bolt by doing that it will change the angle the motor sits in the frame. But until you do adjust them their is nothing you can do to compensate for loosing compression and running rough.

But do take pictures of the front of the motor, if it is that close to the frame the only other option would be to drop the front of the motor down. But I had another guy with the same problem and by taking the motor off the center stand it gave enough room to get at the bottom bolt. Also when you do finally take the cover off I WOULD suggest to take the PAIR system completely off and block the PAIR inlet with one of these. That would remove the chrome pipe in front of the valve cover and take hoses out and a canister and a Vacuum Hose out of the motor area and less things to go wrong.
Alleyoop

[rosiemoto]

I just went out there and did the spark plug gap to 0.65mm. Was pretty little tricky to bend the metal such a small amount without the right tools but I got it. This spark plug (Autolite copper 4194) was factory set somewhere under 0.6mm, maybe close to 0.5mm, so it was too short of a gap. So far the first 4 starts have done good without giving any throttle.

Here's some pictures of my valve stuff. I know normally you gotta take the bike's plastics off to get in there, but this is just demonstration pics as I was only out there for spark plug today. I figured out what the problem is; my ratchet is too fat and is hitting that chrome PAIR cover. So I put my ratchet extension on it and now it's too long and hits the frame. If I get a smaller extension like half as long, it might work!

Or is it possible to take off that PAIR chrome cover temporarily, get that annoying bolt off, then put PAIR back on?

I don't want to kill the emissions stuff just yet. If I do something wrong with the valves I won't know which one was the problem if I also removed a bunch of stuff! I'll get back to you on that later though. By the way my bike shows "Exhaust Emission Control System: TWC, PAIR"

[Alleyoop]

If you take the bucket out I think you will get at the bolt no problem many have the same type and do not have that problem but they do take the bucket out to get at the front of the motor.
Alleyoop

Taking the Pair system out will not effect squat hundreds on here have done it.


HOW TO REMOVE IT:

[rosiemoto]

Yeah I had all the plastics off completely before... it seems doable after seeing it again today with more experience than I had last time/3 months ago, but I think I just need a small ratchet extension, because mine is too long and can't fit between the frame and the bolt. Without extension, the ratchet hits the chrome plate and goes diagonal/halfway onto the bolt. Harbor Freight here I come I guess!

I will most likely remove the PAIR some time afterwards if you think I should. It's just when I'm working in new territory for my own sanity I have to keep it one thing at a time because I get really nervous until I'm familiar with it. Though, after removing PAIR, is the bike street legal? That video in description says "for racing only, don't do it for public roadways. Emissions blahblah" Not that the cops are going to open up my bike to check of the PAIR is there..probably last thing they care about lol. Just wondering what the big deal about removing the PAIR is too... does it change your A/F mix?

[Alleyoop]

Yep you need a short extension even I have to use a short extension.
Alleyoop