engine rattle/power loss at 25mph (solved) « Thread Started on Mar 21, 2012, 1:37pm »
hello folks, I own a GY6 engine that has about 1000 miles on it, and recently it's been giving me an issue that seems unsolvable... The engine starts, and idles really well, it accelerates fast too, but a couple months ago it started producing what sounds like a loud metal rattling sound when i hit about 25-27 mph, and wont accelerate past that point.
at first, i thought maybe it was a transmission issue, so I pulled it apart, the belt was worn, rubber dust everywhere, cleaned it out, replaced it, found the variator glides were worn through and contacting the variator plate metal to metal, so I thought maybe that was making the noise, ordered new ones, and some new dr.pulley sliders, put itback together, nice snappy acceleration, but STILL makes the noise.
Next I re-adjusted the valves, they were a little tight, that didnt fix it. Then I looked at the spark plug, nice caramel color, nothing wierd there... Swapped CDI's. Did an Oil change, no metal flakes in oil.. Drained the old fuel out of the tank, put in fresh fuel, ethanol free premium...91 octane. From what I can tell, there is nothing vibrating on the outside, plus that doesnt explain the power loss when it rattles... I have run out of ideas.....and am getting quite frustrated seeing how this moped only has 1000miles on it... If anyone has any ideas, please chime in.... Thank you.
Re: engine rattle/power loss at 25mph « Reply #1 on Mar 21, 2012, 2:00pm »
What is it a 50cc or a 150cc, put it on the center stand and take the CVT cover off and rev it up a little and see if the belt is moving up the variator and listen to where you think the noise is coming from. Make sure there isn't any wobbleing from the CLutch and variator.It could be the Starter Clutch they do make a racket but I would think you would also hear that when it was Idleing. It could also be baffles in the Muffler that broke off inside and blocking the exhaust if you hear a rattleing. Wile
Joined: Jul 2010 Gender: Male Posts: 5,894 Location: Mainely Scooters
Re: engine rattle/power loss at 25mph « Reply #2 on Mar 21, 2012, 2:21pm »
Where is the rattling coming from? It could be detonation. You may need to upjet the carb and adjust the needle position. Normally the engine just loses all power and bogs down. If you don't feel any vibrations when it happens then it is most likely not a drivetrain issue. If it were, you would feel it.
Wile makes a good point. It could be the starter bendix or the kickstart gears. I assume its a 50cc. However, if you opened up the CVT case and the problem re-occurred, then it's something you don't normally touch when installing the case. Check for the receiver bushing for the bendix in the cover. Also look for any worn teeth or gears.
Re: engine rattle/power loss at 25mph « Reply #3 on Mar 21, 2012, 3:35pm »
it's a 50cc...everything is stock. I looked over everything in the CVT case, I see no signs of abnormal wear on anything...
Plus, it's also losing power....as in, when it hits the speed in which the rattle occurs, it also stops accelerating....it rattles for a split second also when I give it full gas from a stop and the RPM's hit that range... how do i start it with the CVT case off? wont the starter bendix rattle around since it isnt being held up on the cover side off the case? I also checked and oiled the starter bendix bushings when i had the CVT apart. there is a bushing on both sides... there is a washer between the engine frame mounts that rattles, but its not the same rattle... found that out by putting it on the stand, holding the loose washer and revving it until it makes the noise...
Re: engine rattle/power loss at 25mph « Reply #4 on Mar 21, 2012, 3:51pm »
A loose baffle in the muffler kinda makes sense, but why would it lose power? i wacked the muffler a few times with a rubber mallet and didnt hear any rattles...
Re: engine rattle/power loss at 25mph « Reply #5 on Mar 21, 2012, 4:28pm »
Well if its a 50cc that Leaves out the Starter Clutch. But if everything looks good to you in the CVT I would then say it is detonation since it is looseing power like Mainpeace said. And it could very well be since it is a new scoot they set those suckers really lean. So first thing is to try 93 octane gas GOOD STUFF do not get gas from those cheap places and see if it goes away. Wile
Re: engine rattle/power loss at 25mph « Reply #6 on Mar 21, 2012, 5:26pm »
I am using premium ethanol-free gas. 91 octane. It's not detonation, something is vibrating badly enough somewhere that its causing the engine not to be able to rev up when it rattles...like something spinning that is out of balance... I used a stethiscope on it and found it's not the muffler either...could it be coming from something under the r-cover? kinda sounds like it, or from the valve cover.. i took off the r-cover, but the flywheel needs somekind of gear puller to get it off... but i dont hear anything loose when i shake it with my hand....where is the oil pump located? could that be it? or the stator? I'm running out of ideas.
Joined: Jul 2010 Gender: Male Posts: 5,894 Location: Mainely Scooters
Re: engine rattle/power loss at 25mph « Reply #7 on Mar 22, 2012, 12:40am »
The oil pump is inside the case. A frozen oil pump would just mean a frozen engine. If the crankshaft were broken or out of balance the entire motor would vibrate. It's *possible* the timing is off by a tooth and the rattling you hear is the valves hitting the piston. Possible valve float, but I think there would be other indications.
Try turning it over slowly by hand and listening closely for any metallic ticking that would indicate the valves hitting something. Possibly the rockers are loose? Hmm, this is really hard to diagnose without hearing the noise.
Also try to look at the valve springs. One may be broken and that is causing the noise and power loss.
Greg
« Last Edit: Mar 22, 2012, 12:41am by mainepeace »
Re: engine rattle/power loss at 25mph « Reply #8 on Mar 22, 2012, 3:06am »
I guess ill take off the valve cover and look everything over, I have an uncle who is a mechanic, maybe after I have the cover off ill him him peek at it to see if anything looks strange... If I still cant locate the issue, what choices do I have here? Is this something I should tear the whole engine down to find? I sure hope not. I hope I'm not missing anything in the drivetrain anywhere... What are symptoms of valve floating?
Re: engine rattle/power loss at 25mph « Reply #12 on Mar 23, 2012, 3:50pm »
YAY! It seems Ive finally found the issue. It was a broken intake valve spring...gonna have my mechanic uncle help me remove the old and install the new one, so i dont drop the valve inside the engine....
I noticed when looking under the valve cover that even when the intake valve was closed, i could still twist the spring around, then i saw the crack..... thanks for everyones input, greatly appreciated...
Mainepeace: I just ordered a new valve spring from your e-store...i was wondering, on your e-store its called an "inner valve spring" that IS the intake spring....right? Also, good call on the 7g sliders, i have a nice improvement on acceleration, and im sure the top end is the same, or better....
Re: engine rattle/power loss at 25mph « Reply #14 on Mar 28, 2012, 5:11pm »
Greg- Sorry to be a bother, but that spring you told me to order was the wrong one... I didnt realize that what was meant by "inner spring" and "outer spring", means exactly that, each valve has an outer, and an inner spring, I ordered the "inner spring" thinking it was the "intake spring", not realizing that there was two springs to each valve... anyways, now i have to order the OUTER spring, and wait ANOTHER 3 business days, and pay ANOTHER 5.00 shipping, what a pain! Also, Iv'e been having to get rides to work since this is my only transportation for the time being... so waiting until.....monday? to get the new spring, is a concern, because I wont have a ride to work this weekend... Is there anyway I can order the inner spring 2-day shipping? I dont see an option on your e-store....
Joined: Jul 2010 Gender: Male Posts: 5,894 Location: Mainely Scooters
Re: engine rattle/power loss at 25mph « Reply #15 on Mar 28, 2012, 7:23pm »
Sorry, I apologize for the confusion. I thought you were asking about the difference between the intake and exhaust spring. I can do 2 day shipping via UPS but that option will cost $28.70 (their cost). If you want to do that let me know. I only make $0.50 on your order so don't think I'm padding the bill or anything.
Re: engine rattle/power loss at 25mph « Reply #16 on Mar 29, 2012, 12:53am »
Ok, I'll just order them standard USPS 3-day then....
I'm surprised theres no option for 2-day shipping via USPS for cheaper than that... its just a little valve spring that fits into standard envelope...
also-any idea what the torque specs are for the 4 nuts that hold the camshaft on? also for the flywheel/stator cover thing, or is there not a spec for those two items?
![[Search This Thread]](http://images.proboards.com/new/buttons/search2.png "[Search This Thread]")
![[Share Topic]](http://images.proboards.com/new/buttons/share.png "[Share Topic]")
![[Print]](http://images.proboards.com/new/buttons/print.png "[Print]")
Author
Logged![[avatar]](http://i1246.photobucket.com/albums/gg605/Wilecoyote0/SMILEYS%20AND/wile-coyote-A.jpg "[avatar]")
![[image]](http://i1246.photobucket.com/albums/gg605/Wilecoyote0/SMILEYS%20AND/1887-1.gif "[image]")
![[avatar]](http://mainelyscooters.com/images/scooter1.png "[avatar]")
![[homepage]](http://images.proboards.com/new/buttons/www_sm.png "[homepage]")
![[image]](http://mainelyscooters.com/images/Facebook.Like.png "[image]")
![[image]](http://mainelyscooters.com/images/Banner.Ad.ScootDawg.600.100.jpg "[image]")
![[Home]](http://images.proboards.com/new/menu/home.png "[Home]")
![[New Topics]](http://images.proboards.com/menu/topics.png "[New Topics]")
![[Help]](http://images.proboards.com/new/menu/help.png "[Help]")
![[Search]](http://images.proboards.com/new/menu/search.png "[Search]")
![[Login]](http://images.proboards.com/new/menu/login.png "[Login]")