mykul
Scoot Junior
Posts: 7
|
Post by mykul on Nov 1, 2011 7:37:44 GMT -5
Okay, my 50cc has almost 500 miles on it, I changed the oil, adjusted the valves which were tight, set the clearances. Had tried raising the needle, fixed needle so used an O ring but that was then too rich so not a problem.
Before the valve job it would reach 30 and a bit more now it won't go past 20 before iit sounds as if its slowing down. on the stand it will run full rpm happily and sounds fine. Under load, not.
Tried sort of forcing it past that flat spot by using WOT and it picked up a bit but sounded unhappy about it (sorry, cant explain that better) and if I was content to go 20 it would probaly be quite happy!
Okay the air filter is clean, if it has a fuel filter at all I havent managed to find it. I cant make sense of the tubes, theres a lot under there because I cant see well enough to track them from one end to the other.
I'm getting ready to ride it to the dealers and throw money at it which is not the preferred option but I've run out of ideas. This seems to me to be a break in issue, trouble is I cannot think what else to try.
The needle raising got me a wet plug so its obviously getting fuel, the air supply is adequate therefore it must be spark related is my best guess. The plug is an NGK and therefore not a suspect.
But why would a good running machine suddenly develop a fault with no apparent reason for it?
|
|
|
|
Post by Fox on Nov 1, 2011 7:42:17 GMT -5
Vacuum leak (crack) at the intake or possibly a torn carb. diaphragm.
|
|
mykul
Scoot Junior
Posts: 7
|
Post by mykul on Nov 1, 2011 7:49:23 GMT -5
Vacuum leak (crack) at the intake or possibly a torn carb. diaphragm. Thanks Fox but the carb diaphragm is perfect and there appears to be no issues with the intake manifold. |
|
|
|
Post by speedy1125 on Nov 1, 2011 7:53:40 GMT -5
bad CDI maybe, ignition timing not advancing? sounds like it. this sounds like what happens when an old vacuum advance distributor is unhooked from its vacuum source.
|
|
|
|
Post by 90GTVert on Nov 1, 2011 7:58:17 GMT -5
If it started immediately after the valve adjustment, I'd start by re-checking the valves.
If it has no fuel filter (just trace the line from the tank to the carb), you should add one. It will help prevent little debris from getting into the carb and clogging things up, which can cause all sorts of issues. If the main jet becomes partially clogged it can cause problems like this, especially at 3/4 to WOT.
If it runs well and nothing seems wrong before 20MPH, like a lack of acceleration for example, it could be a CVT issue.
|
|
|
|
Post by speedy1125 on Nov 1, 2011 8:06:47 GMT -5
yeah im with Brent on that part make sure the fuel line isnt kinked somewhere and verify that the main doesnt have something in it like he said first. make sure to put a fuel filter on it. might be a fuel starvation issue. i know you said a higher needle gave you a wet plug but a clogged main jet will still give you this problem under load because it uses the idle jet to a certain point. once all that is addressed i would suspect a timing advance issue which is rare but still a possibility in my mind. i have seen the exact problem you describe when an old 80s vacuum advance line broke or came unhooked giving no timing advance.
|
|
mykul
Scoot Junior
Posts: 7
|
Post by mykul on Nov 1, 2011 8:16:28 GMT -5
Thanking you all for your prompt and helpful suggestions. Damn I was hoping for a quick fix! I guess it means some more laborious contortions trying to locate whats what and frankly the remarks about kinks in tubes or air leaks does sound the most logical source. However the dealer obviously replaced crap tubes with good ones and conscientiously clipped and fastened each one. I, on the other hand, did move the tubes about quite roughly as I fumbled to find the hidden valve cover bolts and come to think of it I did - just recalled this error - cut a few zip ties and left the tubing to flop freely which might very well be all it took.
I'll investigate and let you know because its not much help for anyone else when a fix isnt reported on, not to mention its rather rude not to respond to those who try to help you.
|
|
|
|
Post by Fox on Nov 1, 2011 8:31:57 GMT -5
Could be all of the above but after what I've read I'd try first checking all the vacuum lines that go to everything and then a CDI in that order and move deeper from there.
|
|
|
|
Post by 2strokd on Nov 1, 2011 9:47:36 GMT -5
Take the airbox tube off the carb and while your scooter is on the centerstand and the engine is warm, rev it up and look in the carb inlet while doing so. You should see the slide move up with vacuum when it under WOT for sure. If not, the diaphragm is messed up and its not visible with the eye.
Only reason i mentioning this after you said its fine is because ive had two of them now that looked fine but were defective. Sometimes you just have to look.
Another "freebie" is too unhook your airbox tube (mostly 2T,s here) and without your engine running twist the throttle to WOT position and look to see if the slide is ALL the way up into the carb? If not, its out of adjustment. Those with cable driven oil pumps can be mislead by the feel because the oil pump is going WO but the carb is not. That is why they both (carb and oil pump) have adjustments on them. Ive fixed more than one "slow scooter" just by adjusting the throttle cable. I think the factory did this on some as another way to restrict them?..
|
|
|
|
Post by Reign on Nov 1, 2011 10:12:49 GMT -5
My Triton was starting to bog past 30 this summer. 30 was literally top speed. And I'm 100% certain it was because of mulitple air leaks. One at the intake (one of the four intake threads were stripped) and at least one other at the base of the cylinder. I've got it in the basement currently and I'm rebuilding it from the ground up. Seems like I have to rebuild that thing at least once a year. I'm gonna do it right this time, though, and I shouldn't have anymore issues.
|
|
