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General => General Discussion => Topic started by: Iahawk on March 14, 2021, 06:55:20 PM
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Hey guys, I was hoping this issue would go away on its own but it hasn't. Starting with my first start this season (2 weeks ago) my scooter is idling much rougher than it did previously. I'm used to some normal vibration at idle but my current vibration is about double what it used to be. It runs fine and I don't notice anything different when riding, just when idling. I've done about 4 rides and 75 miles this month. Scooter sat in garage for past 2 1/2 months from last ride last season to start of this season.
Fresh oil change last December, level full. I checked valve clearances but they were all in spec so i changed nothing. Carb seems to be working fine, although I do have a new carb bowl gasket on order and am planning on taking out carb and giving it its first thorough clean in its life. Still on same tank of ethanol free fuel with stabilizer that I filled it up with in December.
Scooter is 2010 People S200, 2 valve, air cooled 163cc with carb. 3100 miles. Iridium plug was installed around 1100 miles ago. Scooter fires right up but idles a lot rougher than it used to.
In diagnosing this I can only think of a few things that could cause a rough idle...
ignition coil and plug (potential ignition issue causing misfire?)
carb
engine mounts (will look closer but don't see anything that appears off/broken/loose)
something in the CVT (haven't pulled cover, yet)
Any other suggestions or places to look to diagnose the rough idle? It seems like this should be an easy one to fix..
Thanks for any help.
IaHawk
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@lahawk,
for me the first suspect would be my carburator. (for it sat and didn't have any symptoms before)
Is it surging or just limping on idle?
Surging would mean, IMHO, lack of fuel and stuttering
I would put to an air leak somewhere or just a speck of dirt in an bypass.
Or, if this roughness comes from your CVT section, rollers and plate could be a little bit corroded too.
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If all its doing is vibrating but running steady, not missing, look for an air leak. What you describe is a too lean situation.
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Only 3000 miles in 11 yrs. I would suspect carb needs cleaning....
Are you using a Denso or NGK, Iridium plug?
I found my 163 engine preferred the NGK...giving a stronger idle RPM.
Look for air leak, if OK... then run a shot of that cleaner.... Chevron Techron.. Stuff got my old Jetta through its last E-Check.
Good luck.
Stig
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good ideas for me to investigate, thanks! Stig - it's an NGK iridium plug ..
so air/vacuum leaks or dirty carb...2 things I can definitely do. My carb bowl gasket should be in this week so I can pull it apart and do a full clean and I'll also look for any air leaks. I'm off work this week to coincide with my kids' Spring Break so I will have plenty of time.
Doesn't seem to be missing...just vibrates a whole lot more while idling. Thanks, again, for the quick responses.
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Has your idle speed decreased? That might cause vibration.
That said, I prefer the carb as the culprit.
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Has your idle speed decreased? That might cause vibration.
That said, I prefer the carb as the culprit.
+1
Stig
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First 11 year old scooter with no miles----bound to have some fuel system problems- Me, I would change spark plug to proper NGK heat range standard plug, making sure plug outer is clean (so doesn't fire around), fresh tank of corn free fuel, some fuel system cleaner in tank-----go out, run tank of gas thru in one day---refuel, set idle correctly. Might be ok. Bike that sits as much as this one does, should be parked only with full tank of fuel, something like Staybil added.
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Great advice from all. I'll look for any intake or vacuum leaks and still plan on giving the carb a full clean. I don't think the idle has changed significantly but I'll get a tach on it and confirm.
It's funny..I think I have a pretty good handle on most things mechanical and then something as simple as a much rougher idle initially stumps me. Thanks for all the input and I'll report back later in the week with what I come up with.
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to follow up...removed carb and fully disassembled it and gave it a good clean. Also replaced carb bowl gasket, as old one was squashed very flat. Replaced fuel line while i was in there. No change to the idle roughness. I initially looked for an intake leak using one of the methods suggested by many online...hitting it with a small propane cylinder...didn't find any leaks. The other method suggested is to hit the various connections with carb cleaner, looking for a change in idle...will probably give that a try, too.
Put a tach on the scoot and got the idle adjusted to roughly 1700. It's been years since I've had a tach on it..interesting to see the idle speed fluctuate by up to 150 rpm.
Drained fuel tank, replaced with fresh, non ethanol fuel, added marine stabil and some techron.
Will try to get in a ride this week. Last week the weather was beyond awful around here and then I had to travel out of town for the funeral of the husband of a young lady who works for me. She is 33, he was 38. Very sad week.
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I would look for a vacuum hose leak. There is a couple of house going to the fuel petcock and the emissions smog pump. If one of those is cracked/split it will cause a rough idle .
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thanks, Kansas Kymco, I don't see any clear cracks or breaks but the vacuum lines are all original and kind of stiff. I went ahead and ordered new vacuum line (in red, should look good!), a package of T, Y and straight connectors and package of assorted spring clamps, since the ones on there are a pain to take off and put back on...and I even broke one pulling the carb and doing the fuel line.
Shouldn't be difficult replacing the vacuum lines, just kind of a pain. Must be an age thing because man my back gets sore leaning over to work on the motor from the top!
So the journey continues and I'll update later in the week. Amazon shipment will arrive on Wednesday.
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thanks, Kansas Kymco, I don't see any clear cracks or breaks but the vacuum lines are all original and kind of stiff. I went ahead and ordered new vacuum line (in red, should look good!), a package of T, Y and straight connectors and package of assorted spring clamps, since the ones on there are a pain to take off and put back on...and I even broke one pulling the carb and doing the fuel line.
Shouldn't be difficult replacing the vacuum lines, just kind of a pain. Must be an age thing because man my back gets sore leaning over to work on the motor from the top!
So the journey continues and I'll update later in the week. Amazon shipment will arrive on Wednesday.
As Dad use to say it sucks to get old but sure beats the alternative. Probably would be good to have a motorcycle lift to work on scooters. Good luck getting the issue resolved. I will ask my local dealer owner next time I visit with him. He has 40 years mechanic experience on motorcycles.
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@lahawk, just as a shot....
if you take your CVT cover off, please check your drivebelt whether its knocking at its housing on idle.
Then spray kind of WD40 or similar on your clutch-shoes, trough the openings. Revv up a little
(on mainstand and rear wheel in air !!!) and then, what does it do on idle again?
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Ruffus - your suggestion may be the winner. I have clearly visible black belt marks inside my cvt case on top and bottom. The belt also shows a clear mark on the back side where it's been rubbing.
I'm still waiting for a new belt and also ordered a new contra/torque spring for rear driven pulley. i disassembled both my existing rear clutch/pulley and my spare..(practiced on the spare, first)...cleaned out old grease, re greased and also measured length of spring. Both were quite a bit below minimum length, per manual.
So to attempt to fix vibration at idle I went through the following things:
cleaned carb
checked for intake or vacuum line leaks (replaced about half the vacuum lines, wasn't necessary but looks better)
checked for belt hitting inside of cvt case.
more to come..
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@Iahawk,
good to see you're tracking it. Pls compare old/new belt by lenght. In my case the old one (same brand Bando, same numbers on, same width, etc.) was 15 mm longer than identic new one. Was whipping and caused a rough ride-off.
Best bet IMHO is to change the whole part strain (rollers, belt, spring-coil, clutch) at once and from one brand, for me Malossi. Running, accelerating and decelerating smooth since then.
Only with the belt I did not stick to Malossis Kevlar item, for I read somewhere about rare cases of disintegrating (could have been an instaling issue too) after a while.
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all right, thought I'd provide an update on my attempts to cure my rough vibration.
Scooter has been idling with much more vibration than it used to. It also seems quite a bit louder, both exhaust and motor.
after some suggestions from the members, here, I did the following:
-pulled the carb, fully disassembled and cleaned everything, twice
-replaced about half of my vacuum lines with new silicone ones
-replaced my fuel line and added an inline fuel filter
-replaced my intake manifold O ring (old one was completely flat but still appeared to seal)
-replaced belt with new OEM..appeared same length as old belt but was difficult to measure exactly
-replaced OEM rollers with Dr Pulley sliders, 13 gram
-disassembled, cleaned and regreased rear driven puley
-replaced contra spring in rear pulley
-cleaned and scuffed inside of clutch bell and sanded clutch pads
-cleaned and scuffed front drive pulley faces
-new NGK plug
-new air filter
-checked valves earlier, all in spec
reassembled everything, set idle, checked for any intake or vacuum leaks multiple times using both propane and starter fluid, spraying on all connections...no change to idle with any of these
adjusted air/fuel mixture screw to try to get the smoothest idle. Even reset the throttle position sensor (TPS) on the scoot using info from an old post.
After all this? no change. Idle is just as rough and vibrating. It kind of feels like my scoot is turning into an old Harley.
The upside is that with the changes it accelerates faster than ever from a stop and my top speed seems to be back where it was.
So I've checked the main suspects - carb, intake leaks, vacuum leaks and cvt. Nothing. Still vibrates a lot. Oh, well, at least I had a lot of fun tearing into things.
added a few pics of the carb and the new vacuum lines (red)
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@Iahawk, seeing you did all possible, only one more question.
Did you check the axial play on your front boss-pulley?
(pls see pics).
If there is any up-down play, might cause this vibrations. Had this in my Mallossi drive.
Wait a couple of hundred miles with Dr.P's. They improve gradually.
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Ruffus, thanks for the suggestion but there was no play in the front boss and pulley. I made sure to clean them up and used a little metal polish on the boss to make it as smooth as possible. It slides in and out but does not have any other movement.
It's vibrating enough that yesterday the front plastics were resonating...something I haven't noticed before..and that was after the idle had settled down after it was warm. I guess the mystery continues...
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Sadly this is a area where Kymco USA is lacking in help troubleshooting. I've had this comment from my Kymco dealer. I will ask him if he has any ideas next time I'm down to his shop.
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@Iahawk, one of my last straws:
-could you check the rubber motor mountings?
This two or four rubber bullets on that teeterboard.
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Ruffus, yes, that was one area I checked. Both rubber bumpers are still in place on the engine hanger.
One last thing..my exhaust is a lot louder than it used to be. I can't imagine that an exhaust (possibly rusted or broken internally?) could contribute to a strong vibration at idle?
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@Iahawk, I see at this below
https://www.kymcoforum.com/index.php?action=dlattach;topic=30858.0;attach=19776
that you have an kick-start option. Is this assambly properly fixed within its CVT housing?
For the muffler I would simply take a piece of let's say 12mm / 1/2 inch reinforced plastic airhose, put it from behind into the COLD silencer and start shortly the scoot, to see whether there is any significant change in vibration or idle. But pull it out quickly, might give an strange odor when melting.
But reading all over, I still think the crux is somewhere in an airhose or carb.(pls see pics)
I read and know you did all this checking on your carb and airsystem, but watching following pics might give you an additional idea where to look at.
Pics are from a125 ccm LIKE, but your carb should look similar.
As for sparkplugs, I had sometimes, if nothing else helped anymore (particularely on early BMW 1100 oilhead motors) good success with BRISK 4-pronged plugs.(pls see pic)
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.just two more pics to this subject
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Wanted to update with some thoughts on my rough idle issue after a season of riding (edit - the idle is very smooth, it's the scoot that vibrates like an old Harley). After eliminating all of the usual suspects (carb, air leaks, cvt) I'm leaning toward Kansas Kymco's suggestion of an out of balance crank. The scoot still idles like a Harley but runs great.
After looking at more youtube videos of other scoots with bad vibrations...and many commenting about out of balance cranks causing these issues...and hearing from (who I thought was) Kansas Kymco's friend/bike shop owner..this may be the culprit.
It seems my (our) single cylinder Kymco motor has a 1 piece connecting rod on a pressed together crank (as opposed to a forged crank with a 2 piece connecting rod). It's possible for these to come unbalanced. When they do they will shake like a..well..shake a lot.
Not sure about the long term implications of riding it like this...may just be an irritating vibration...or it may eventually shake the scoot apart. I see that it is possible to remove and rebalance a crank but if I went to the trouble of removing the crank i'd just replace it with a new one ($145 USD).
I currently have no desire to pull the motor, crack it open and replace the crank. I'm not even sure I have the skills to properly do this. I sure don't want to pay anyone to do this as the cost would likely far exceed the value of the scoot.
I've had the scoot for 6 years and have put under 2000 miles on it..as I have 2 other bikes to ride.
I can continue to ride it as is...I only feel the vibration at idle, not when riding. Wondering what you guys think about this or what you might do in my situation?
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Only 2000 miles??
Vibrations shaking the scooter.....?
some pasta on the kitchen walls then.....:
wheel bearings
engine mount bushings
rear axle bearings
broken frame weld
screwy roller weights
clutch spring broken
stretched belt / wrong belt
Problem here is that measly 2,000 miles - can't see any of the above parts failing on a Kymco in only 2000 miles - including an internal engine part.
As an old medic - we liked to work sometimes by "ruling out" things.....can we rule out O.C.D.? :)
Stig
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@hawk, I do have a crank here in my storage, will check it tomorrow and so some pics, how and where and if, such a rod exists...
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This is possibly not what you want to hear, but these are not really smooth-idling scooters, especially when cold. My suggestion would be to simply ride it until you can't stand it any more, and then have another look at the various tunable items.
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scoot has about 3800 miles..I meant that I'd only put about 2000 miles on it since I've owned it. 2010 model.
Earlier this spring I'd isolated it to the motor...I removed the variator, ran the scoot.. and the vibration was still there.
It seemed to occur with the first start up of the year this past Spring. Much stronger vibration at idle than ever before. that's when I went through it and cleaned, inspected and replaced about everything I could.
I'd never even heard of an out of balance crank until KK mentioned it as a possibility.
The scoot looks brand new, rides well, is nice and quick (with the Dr Pulley sliders) and runs great...except for the 'Harley like' vibration.
So I may do as JJ suggests..and just live with it! (unless Ruffus comes up with a secret solution!)
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You mentioned that the carb has been cleaned but depending how the carb has been cleaned, I still think the problem has something to do with the carb. Or maybe an air leak in the intake system.
Maybe you should have a look whether the carb has been mounted properly, and make sure the bolts are tight. Again, make sure there is no air leaks in the intake system.
Depending on how the carb has been cleaned, I would remove the carb, remove the main jet, and submerge everything except the needle and seat spring in white vinegar for about 24 hous. Just make sure the seat spring does not get submerged in vinegar - because the vinegar could destroy the seat spring and then you will be sitting wit a bigger problem. I’ve had such an experience on another application before, and due to that mistake the coplete carb had to be replaced.
After about 24 hours in vinegar you can just blow out the the main jet and carb channels with an air compressor if you have one. Just make 100% sure the main jet channels are clean.
Side note - I cleaned my son’s electric generator’s carb this way two weeks ago. My son was at the brink of buying a new carb, but since the carb has been cleaned properly the engine now runs like new.
Good luck, maybe this helps.
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@hawk, as said some pics from a non drop forged Kymco LIKE 125 crank. As far I can see there is, as mentioned, a conn. rod holds/keeps it together. From marks it has been machined after completing, so I assume its heatshrunk together. No welding marks to be seen.
The likelyhood to turn is given, but IMO not very high.This motor was a complete piston/ cylinder wreck, and those bearings are still in good order, so I would exclude a bearing fault on your ride.
Btw, this 4-slot special nut on the generator side is LEFT HAND threaded.
@scooterfan, you might be on a good track too.
Forgot to mention in my carburator issue that, when I replaced my vacuum lines with silicone hoses, I had an intermitting surging.
It came out, those silicone vacuum hoses were after a while not airtight anymore. Became a pudding-like consistency. Got a patch which softened in contact with oil and fuel.
Changed them to simple black rubber fuel lines, new clamps on it and vacuum was established again.
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thanks for all the replies, guys.
Scooterfan - I pulled my carb twice and completely disassembled, cleaned all passages with a spray can of carb cleaner and replaced pilot and main jet. I 'think' I have it perfectly cleaned but I can always do it again. I thought I did a thorough job of checking for any air or intake leaks. I replaced my intake manifold O ring..and checked for leaks using both starter fluid and propane gas (from a small cylinder) sprayed around all connections...no change in idle with any of these (and I didn't blow myself up, either, which was a win!)
Ruffus - thanks for pictures of the crank..that's likely my exact crank as the 163cc motor is a bored out Kymco 125cc.
I can always redo my vacuum lines and clean carb for a winter project. I hadn't heard of silicone vacuum line issues (I don't believe mine did that as the problem existed before I changed my vacuum lines to silicone and persisted after)
I watched a GY6 crankshaft replacement video on youtube and the person made a point of pointing out the left hand thread you're referencing..important point!
So I guess the simplest explanation is usually the correct one...which would be carb or intake or vacuum leaks. All things that can keep me busy during the off season.
I appreciate everyone's input.
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submerge everything except the needle and seat spring in white vinegar for about 24 [hours].
Vinegar is corrosive, so use sparingly. I've always used toluene, an excellent, non-destructive carb-cleaner solvent. You can buy it in auto-parts stores as "carb cleaner", but also cheaper as "lacquer thinner" in Home Depot, occasionally mixed with acetone. Either works well for soaking carb components.
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thanks, JJJ, looks like a serious carb cleaning is in my future.
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Maybe it's just the gas going bad. How about riding it until the tank is empty and see how it idles with a fresh tank of fuel?
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Stuo - thanks for the suggestion but I've run multiple tanks of gas through the scoot this season. I always use ethanol free gas with stabil marine added and I've even been dosing it with techron this season in hopes of cleaning something in the carb that I may had missed. I also added a fuel filter this year (did not have one, previously).
I've put 650 +/- miles on the scoot this season.