Broken Chain Guide?

[noahg]

Alright so I have a 2008 Motobravo Paparazzi and it had been working fine up until recently. It started going bad when I had to go full throttle. The engine would just give out and I had to let it sit for a little bit until I could go again. Then when I was riding something broke and it made a horrible banging sound everytime the engine turned over. I got a rebuild kit and was taking it apart and when I took out the chain guide it seemed sharp and lopsided at one end. After I pulled it out and I looked into where the chain is there is a hole in the metal with some metal pieces around it. Is this my problem? Also if it is can I fix it?

[blueboy5000]

First of all, this is EXACTLY why you DO NOT ride at full-throttle, high RPMs are when 90% of fatal engine problems happen. The gy6 engine does have an oil-pump, but it is very much a non-sump oil system. (yes I know the inlet could be technically called a sump) The engines starve for proper lubrication at high RPMs.

As to what possibly you have blown, you won't know until you disassemble the engine. I'd say it is most likely you dropped a valve or blew an engine bearing or rod/rod pin.

[noahg]

I have disassembled the engine up until the actual block. That's what the attached image is. I'm wondering if that hole is suppose to be there? I doubt it though because I see small metal pieces around it. The piston head, rod, and rings are all fine. The sound that it was making sounded like the rod or the piston head was broken but they are in reletively good shape. Is there a way to take the actual block apart without destroying everything? Sometimes I have to go full throttle when my scooters top speed is 45mph... I'm just hoping I can fix it since I've already put like 150-200$ into fixing it already. Thanks for the reply though.

[gitsum]

Originally Posted by blueboy5000

First of all, this is EXACTLY why you DO NOT ride at full-throttle, high RPMs are when 90% of fatal engine problems happen.

Is this specific to GY6 engines or all engines? Is this more likely to happen on a Chinese engine?

Do you have any data to back these numbers up?

I don't have any data, so I'll give my opinion strictly as a guess and from personal experience.

Neglect is probably the number one cause of engine failure. Running low or out of oil, running on dirty and broken down oil, running lean because of a dirty carb/clogged air filter or an air leak, valves out of adjustment etc, will break an engine faster than anything else including running WOT.

I ran my Honda Elite 110, CPI Oliver City 50, SYM DD50, SYM HD200, Yamaha C3, and Tomos Nitro 150 at WOT for extended periods repeatedly with no engine problems.

I noticed in your signature you state the top speed of your scooter is 65 mph GPS verified. What good is that if you are unable or unwilling to use it?

I tentatively question that you may be saying running a Chinese scooter at WOT is not recommended?

[noahg]

Thanks for joining in. I know for a fact I took good care of the engine while I've had it. I'm jot sure about the previous owner but I changed the oil right when I got it, even the brake fluid because the brakes werent working like they should. I cleaned the carb the other day and it was spotless. All passageways were clear and it wasn't dirty at the bottom of the float. The engine would give out sometimes before this as stated before.

[blueboy5000]

Originally Posted by gitsum

Is this specific to GY6 engines or all engines? Is this more likely to happen on a Chinese engine?

Do you have any data to back these numbers up?

I don't have any data, so I'll give my opinion strictly as a guess and from personal experience.

Neglect is probably the number one cause of engine failure. Running low or out of oil, running on dirty and broken down oil, running lean because of a dirty carb/clogged air filter or an air leak, valves out of adjustment etc, will break an engine faster than anything else including running WOT.

I ran my Honda Elite 110, CPI Oliver City 50, SYM DD50, SYM HD200, Yamaha C3, and Tomos Nitro 150 at WOT for extended periods repeatedly with no engine problems.

I noticed in your signature you state the top speed of your scooter is 65 mph GPS verified. What good is that if you are unable or unwilling to use it?

I tentatively question that you may be saying running a Chinese scooter at WOT is not recommended?

17 years as professional automotive technician, and 25 years as a motorcyclist have taught me all about how excessive WOT riding can drop valves, blow head gaskets, seize oil-pumps ect.

Working on my clubs's fleet of 12 current scooters has re-affirmed all of this, as two of my riders INSIST WOT is cool, and routinely waste gy6 engines (not that they care, a whole engine is only $500 or less)

My bike has FUNCTIONAL top-speed of 65 mph, so what I should be saying is "I have ridden my bike at a maximum speed of 65mph gps verified", I hit 65 at about 7800 to 8000 rpm on FLATS, my bike redlines at 8500, and has a MAX rpm of aprox. 10,500 (or whatever I set it to with the adjustable CDI, the CDI limits RPMS to 12,500, I have it SET to 10,500)

As to "what good is it": What good is riding at 65+mph? Why do I need to ride my bike at a faster speed? 150cc are NATIONALLY BANNED from limited access highways in the USA. I see NO logic in running my bike in the higher RPMS, and risking inner damage from OIL STARVATION.

I simply do not understand this logic of people claiming that engines are supposed to run at 100% of their power band routinely. I don't buy this as it is illogical. That's like claiming that because you can run at full-speed, you should never walk. I mean running is cool and all, but find me a doctor who says you should run constantly. You won't. He'd say not to run everywhere as fast as you can as it is BAD for you to do so.

As to my estimate that most engine death occurs at high RPMs, I invite you to ask ANY engine building shop about this.

[blueboy5000]

I fully agree that the gy6 engine should not be run at rpms higher than 8k. So I suppose I should not state "don not run at wot" instead, I should state "do not run at over 8k rpms"

I also tend to agree with JR, he's been a great help, and has taught me very much about the gy6.

http://scootdawg.proboards.com/threa...-wot-longevity

[gitsum]

Maybe a few turnpikes might have different rules, but a 150cc engine is legal on interstate highways.

So if your bike has a functional top speed of 65 GPS, does that mean usable?

You are saying that WOT is bad and running 8000 rpm's on a GY6 is bad. Does that mean one or the other or both together are bad? What if running WOT is below 8000 rpm's, is that bad?

What about a lawnmower, weedeater or chainsaw? Should everyone modify the carb or throttle so it can't run WOT or near the redline? What about a 2-stroke engine that has external lubrication and no valves?

I'll ask again. Is WOT bad on every engine, or just a GY6?

What about millions of small Japanese scooters that are rev-limited at top speed? People ride WOT all of the time, how many of these do you see with a prematurely failed engine?

What about events like the Scooter Cannonball? Does this mean the people that compete and finish are just lucky? And yes, there were some GY6 scooters which finished (nothing Chinese).

What about all of the documented trips of people taking small motorcycles or scooters on long trips? To Alaska, to South America, across the United States, around the world, across Canada, and their little machines make it. I think my favorite was across Canada on a Yamaha C3. They seriously overloaded it by more than 100 lbs and then rode it WOT for 3000 miles, two-up. They continued to ride it for a long time afterwards with no ill effects.

I think a quality well built and designed small engine can run at or near WOT for a good percentage of it's lifetime and still have acceptable reliability and longevity. Not all engines are capable of this, and Chinese GY6 engines seem to have a bad reputation for failing when ridden at high speeds.

But there are many Kymco People 150, Kymco Agility 125, Genuine Buddy 125/150, Lance Cali Classic 125/150, SYM Fiddle II 125 and others running their GY6 engines hard all of the time with no worries.

I just can't accept the generalization that running all engines at or near WOT is bad and will break them...

[blueboy5000]

I have already stated my bike's capabilities. I have also stated why running at WOT is bad.

I cannot supplant my own 3 decades of practical experience with your opinion, as it contradicts my own experiences, as well as the opinions of other technicians I have discussed this issue with.

You are free to believe whatever you want, regardless of whether you wish to acknowledge the proven reality that running a gy6 engine a WOT is a very bad plan. But no amount of you believing so is going to rewind time and magically undamage or fix the several gy6 engines I have seen and replaced because their rider thought they could ride in excess of 8k rpms for extended periods

Believe what you want, but simply put, experience and facts disagree with you, ESPECIALLY when you speak of small engines such as lawn mowers and weed-trimmers which are mechanically limited to be impossible to run at dangerous redline rpms.

[gitsum]

Originally Posted by blueboy5000

I have already stated my bike's capabilities. I have also stated why running at WOT is bad.

I cannot supplant my own 3 decades of practical experience with your opinion, as it contradicts my own experiences, as well as the opinions of other technicians I have discussed this issue with.

You are free to believe whatever you want, regardless of whether you wish to acknowledge the proven reality that running a gy6 engine a WOT is a very bad plan. But no amount of you believing so is going to rewind time and magically undamage or fix the several gy6 engines I have seen and replaced because their rider thought they could ride in excess of 8k rpms for extended periods

Believe what you want, but simply put, experience and facts disagree with you, ESPECIALLY when you speak of small engines such as lawn mowers and weed-trimmers which are mechanically limited to be impossible to run at dangerous redline rpms.

OK, now we are getting somewhere.

First of all "several" GY6 engines is a basis for "all"?

Your experience with GY6 engines must be limited because there are quite a few tuned to be drag limited way before hitting 8000 rpm's at top speed. This can also be considered a way to mechanically limit the GY6 engine to a safe speed, just like lawn mowers and weed-trimmers.

Your argument that WOT is bad for a GY6 engine is based on the incorrect assumption that all of them will approach or exceed 8000 rpm's running flat out (there are quite a few Taiwanese or Japanese 50cc GY6 based scooters that can and do exceed 9000 rpm's regularly without engine damage).

In some of your previous posts this was including "all engines" which is even more incorrect.

There is some validity to your idea that WOT can be bad.

My point being that this cannot be generalized and applied to every type of engine (including a GY6). Someone with your experience should know this.

For the record I just want to make it clear there are plenty of scooters that can be pushed at WOT without automatically assuming eminent engine damage.

[noahg]

... I guess I'll go somewhere else...

[inuyasha]

Originally Posted by noahg

... I guess I'll go somewhere else...

Hi
So sorry about this
Please dont leave /gitsum and blue boy got side tracked but we can and will help if able
Gitsum blueboy start a new thread to hash out your differences dont highjack this persons thread
Take care and ride safely
Yours Hank

[gitsum]

Originally Posted by inuyasha

Hi
So sorry about this
Please dont leave /gitsum and blue boy got side tracked but we can and will help if able
Gitsum blueboy start a new thread to hash out your differences dont highjack this persons thread
Take care and ride safely
Yours Hank

Sorry, I did get caught up in a difference of opinions which did not contribute in any way.

I don't have an answer for the problem, but hopefully someone that does will help out soon.