110cc Engine Slamming, wont start
 

Hello! I am new to rebuilding ATV's and I'm on my third one with these Chinese 110cc's with my kids. I have a current one that is stumping me if anyone can help....

I bought one from a guy who says the Stator caught fire, and then he disassembled it. I bought it with the engine emptied of oil and sitting in a bucket (inside).

I have since tore it apart, cleaned it out, all new gaskets, and then put it back together making sure timing was correct.

I assembled the ATV with new battery, new stator, all new wiring, new starter, new spark plug, new oil, new carb, new gas tank.

When I go to start the engine, I get spark and it turns over, but there is a loud slam from the engine (sounds like metal grinding maybe?) and the engine kicks once, then goes back to just turning over. Every time I press the starter it does this kick/slam/grinding once and then keeps turning over.

I can't find anything online helpful, and since I don't have a lot of engine experience I'm not sure what to think or what to do next. Can anyone offer some advice?

It’s pretty hard to diagnose any sound going by someone’s written description ,you might want to make a YouTube video of the problems .

Good point, here's a video:

https://www.youtube.com/watch?v=KbOAhFHPIhY

Transmission or clutch assembly error?

I saw that chain kick when it stalled.

I mean, you can crank it, without the wheels turning, but once it starts to turn a real RPM, it looks like the chain is engaging for a split second. That’s definitely down to transmission or clutch in my opinion. Probably clutch.

Hmm, I only took off the covers and then replaced them when I took apart the engine. Could I have done something wrong without actually taking the transmission/clutch apart?

Well, it did come used in a bucket, so who knows what may have happened to it previously.

As a matter of fact, looking at the video one more time, I see the chain moving even when you crank it. Is it definitely in neutral while you are starting it? If so, something is engaging it.

It’s definitely not free turning. There is certainly some problem there after the engine in the transmission or centrifugal clutch area.

I'm not sure about the neutral factor as there is no shifter or anything. So what would that mean?

I’m sure you already tried raising the rear wheels off the ground and with a fresh charged battery try again? This would determine if there was at least a clutch malfunction?:hmm:

This battery is new and was on a charger before this, also starter is working and I'm getting spark.

I have not tried with the wheels up actually. Would that make it start though if it were a clutch issue?

That may define the difference. If it starts with the wheels in the air…clutch. If not back to engine…my thoughts as I noticed the chain jerk too!

I elevated the wheels, new video:

https://youtu.be/sqvwQL5nvco

It’s looking like to me the clutch system may be the problem. The starter can’t spin fast enough to start trying to turn the wheels too?

Another thought, take the chain off and try to start again. This too will give you the clue where the problem lies.

So regardless it sounds like I'll have to open the engine back up? What do I look for in the engine/clutch?

What we do is eliminate the easy things first then go from there! If with the chain off and it wouldn’t start, then engine and clutch. I don’t know your engine, just pointing too the problem.:tup:

If you look real hard at the video, the chain starts to run backwards when the "event" happens... sure your timings not too far advanced?

We’ll it started without the chain! Sounds like it wants to run away and then after I killed the power it smelled like something burning…. Thoughts?

https://youtu.be/bd9KtYScAEs

I see this as a clue. There should be a shifter. It's usually located on the left side. It seems that you are starting the in gear. Also, it's normal that you have to engage the rear brake to turn it over.

Other observations... the exhaust is off and something is dripping out when you shut it off. Fuel? It's revving too high. Check the throttle. Is it stuck all the way open?

I have no idea where there should be a shifter. Since these small ones don’t have reverse I just figured they are automatic or a clutch that doesn’t need a shifter?

Good eye, I didn’t see the drip at first! After inspection it looks like one of the head bolts is missing a washer and I think that’s where the oil came out….


As for the exhaust, it is attached it’s just on the other side from this video. The throttle is not stuck open.

http://www.chinariders.net/blob:http...2-dad11f5545c9Is this where the shifter should go? It doesn’t look like it would connect to anything? Is there supposed the be a shifter? This is on the left side below the sprocket basically.

It's the short shaft sticking out the left side with splines on it.

I don’t think my photo uploaded. There is no shaft sticking out!

I see the exhaust now but it's very loud. Is there a hole in it?

Pull the air filter off and look at the carbs throat. You shouldn't be able to see through the carb; the sleeve should be all the way down. If it's not, then there is something keeping the sleeve up. It could be installed backwards. It's easy to do.

Even small ATVs should have reverse but not all. I'll check tomorrow and see where the shaft comes out on my 125. On the video, it looks like there's a round hole below and rearward of the stator cover. Is there anything there?

It could be a CVT auto trans meant for young beginners. Not meaning to be insulting, but I am supposing you know where a shifter should be from experience with other bikes, correct?

Looks like you're gonna be going inside. Think of it as an adventure! :lol:

Thanks everyone for the replies.

Yea, that hole is where my other 110 shifter is coming out of, but this one doesn’t look like it leads anywhere. I can try to upload the picture again tomorrow but it just looks like a hole. I don’t see it connecting to anything or looks like it’ll move if there were a pedal in it. What should the shifter connect to in there? If there were one, shouldn’t it go all the way through to the clutch?


I can look at the throttle cable tomorrow too, but I have done a bunch of carb work and highly doubt I did it backwards. Although it could be sticking up.

Which way is the sprocket turning in the last video with the chain off?

Hmm not sure, I shut it down quick because I don’t want to damage anything any more. I’m thinking most of you are right with a clutch problem, but idk if there’s suppose to be a shifter there or not. If there is suppose to be something there, that seems like a very obvious fix. If not, I’ll have to open her up again and…. Idk?

Does this link work for the picture of the gap where the shifter normally is? https://ibb.co/cTPFHXb

Yes.

IMO, you really need to get it to idle. Regardless of whether there is a reverse or not, the clutch is the noise you are hearing. It's getting slammed because of the high revs. If you can get it to idle, you'll be able to see which way the sprocket is turning. If it IS going backwards, then this tells you that there is a reverse and you are missing the shaft.

Good point. So maybe check carb throttle/needle first. My gut tells me something is up with the clutch though because it wouldn’t start until I took off the chain. I just don’t see how a shifter shaft would connect to anything in there, via my picture….

It's entirely possible that it just has the automatic clutch that engages with engine RPM. My sons GIO Mini-Beast (110cc I believe) had no shifter or reverse, and I bought it new. It was just gas and go. I never had the clutch side cover off though, so I can't be of much help there. It didn't have a ton of torque though so it wouldn't surprise me if it just had one of those little centrifugal clutches like go karts come with.

knock
 

hello... I had this problem with a motor as well... torn it down could not see any thing.. switch the complete motor from a brand new unit... ( I am a dealer so I can do that )... and it did the same thing... I was stumped.. then I realized I used the carb that was on the one that was making the noise on start up,,.. only when you tried to start it.... the carb was switched with the one that was on the other atv... perfect... the throttle plunger was set to high allowing it to get too much fuel on start up... so I lower the plunger .. ( the one on the cable).. so it would not draw as much fuel on start up... ( PERFECT.. )
WHEN you try to start it and give it throttle as some require it... it would over fuel and KNOCK on start up,... like pre-ignition.. stupid problem.. drove me nuts.. so lower you throttle setting.. and DO NOT GIVE IT FUEL ON START UP.... I am sure lots of atvs have this problem.. I now notice this on some atvs. as people twist the fuel trying to start and it over fuels the motor.. and either you flood the carb and sparkplug... or it knocks too much fuel in motor.. try it and let me know..

Hey everyone, sorry for the delay in replies. I went to put the washer on the head bolt that I forgot to put on, and I found I had stripped the bolt. I ordered new ones and had to wait for them to get in.

After replacing the head bolt, I pulled the carb out, reset the throttle cable, and ran the main sprocket a few times to make sure the clutch was free. She wasn’t happy, but I was able to eventually get it started and idling! It took a couple hours to secure all the wiring harness, attach the body, attach the seat, air up the tires, reattach everything else, and get it ready to ride. I took it for a 60 second spin! It had a weird smell and I need to tune the carb but it seems to be nearing trail ready.


Thanks for all the help!

So new Update; I’ve posted a video but the engine sounds weird, like a “bop bop bop” at idle. It won’t run without the choke on, and the spark plug is pretty dark when I remove it. There also iso a lot of white smoke out of the exhaust. I’ve tried adjusting the carb but can’t get it to stay running without the choke on.

My son was riding it and it died on him, and he couldn’t start it. He hooked it up to a battery charger, then was able to start it later, but it died after a bit of riding again. I went out to try and work on it but couldn’t get it started. It turns over and everything, but there was a loud bang again and lots of smoke from the head.


Any thoughts on what I need to do next to get it running?


https://youtu.be/FG8xx0NBfLY