Is it worth fixing?

GoldenMotor.com

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
Hello everyone, I'm still very new here. Here is my situation. I decided to put a motor on my old mountain bike a few months ago. Unfortunately, I got a cheap 66cc/80cc 2 stroke China special ( http://www.ebay.com/itm/BRAND-NEW-6...7086035?pt=LH_DefaultDomain_0&hash=item35b867 efd3 ) It was the only 2 stroke engine I could find that would ship to CA. I have driven it only 500 miles and today while I was coming home it totally lost power and started backfiring. I adjusted the idle screw to get it to stop backfiring but it just has lost its power, I limped it home at about 11mph. I figured it was a fuel problem so I took apart the carb but everything looked to be working fine. I then thought the problem could be that the muffler might be starving it because I could hear loose parts inside so I took apart the muffler and tightened the screws that had become loose. However when I took the muffler apart I found several small medal balls that look like ball bearings. It is clear that these small balls have gone through the cylinder and out the exaust and got stuck in the pipe.

First: I took a picture of the small balls and pieces of metal that I found in the exhaust pipe. I took the picture next to a tape measure so you could see how big they are (see picture 2251). Anyone know what they are from??

Second: I took the engine off my bike and took the head screws off to check for damage to the piston and the cylinder. I noticed some nicks in the piston from when the medal pieces went through the engine. There are 2 on one side (see pictures 2254-2256) and 1 on the other (see picture 2262). You can see scratches down the side of the piston too. Does this piston look too damaged to use or are those scratches and nicks no big deal? The piston seems very loose. I can turn it about 25 degrees or so. I took a picture of it (see picture 2255), then turned it as far as I could and took another pic (see picture 2256). Also, the up and down has a lot of play in it too. Is this normal or is there something wrong? I should say that I had to zoom in with my camera to get the pictures of the nicks and scratches on the piston, they are actually very small (less than 2 mm wide) and less than (1 mm deep). The largest one (picture 2262) is about 2mm wide and at just over 1mm deep. They might look larger in the pictures than they actually are. Also, the cylinder surprisingly has no scratches or grooves, it only has one very slight nick that is so small I can barely feel with my finger. How this can be, I don't know.

I haven't taken the rest of the motor apart yet but before I do I was hoping someone could give me an idea of what I might be dealing with and what could have happened. Any recommendations on what I should do next? I'm not really a mechanic and I'm a total rookie taking engines apart. Is this really worth fixing or should I just get a new engine? It is only a $100 engine.
 

Attachments

Ibedayank

New Member
Oct 29, 2011
1,171
0
0
Columbia Tennessee
if theres groves in the piston there will be matching groves in the cylinder
either buy a new piston and cylinder plus gaskets and piston rings or a new motor
 

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
The piston and cylinder are toast. The bearings bits look like one of the crank bearings has failed. It would cost about the same to replace all the parts as it would to replace the entire engine.
Take off the mag cover and clutch cover and check the crank ends for up and down/ side to side play. I bet you will find alot on one end.
If you want to learn alot more about these engines, on a new engine replace all the cheap bearings with quality ones before installing it in a bike.
There are plenty of threads concerning this mod.
 

Al.Fisherman

New Member
Sep 9, 2009
1,966
5
0
Calera, Alabama
Those sure look like "balls" from a bearing. How they got there is beyond me, as the only place "balls" are used is on the shafts, in this case the crankshaft. Could they be sucked up from the case, it appears that they did. Repair?,, new cylinder, piston, rings and bearings. Since the engine is off the bike, remove the jug, wash out and take a pencil magnet and explorer the case. How is the head?

All these engines are about the same, cost isn't a factor unless you buy a $500,00 engine some sell. I don't see any difference, if you do some of the mods they over charge you for. (my opinion).

If you decide to repair, here is a picture tutorial of breaking a HT down.
http://s982.photobucket.com/albums/ae309/Ron-Becker/Chinese HT breakdown/

Installing...you might want to read this.
https://docs.google.com/document/d/1GcesQihc7-mm3hJGf7UPiqOaRXZ8ekUT99QUZq2qXXE/edit

GearNut from Mexiifornia :>), is on the right track. Maybe with a new engine, you'd be better off, depending on your mechanical experience.
 
Last edited:

rustycase

Gutter Rider
May 26, 2011
2,746
5
0
Left coast
Well, I don't disagree with the other fellows very often... :-0

Send the pics and a copy of what u wrote to the seller and ask him to warrant it.
NICELY

They should do it.

...Now they are curious sort of fellows... they likes to get in there and find out what makes things tick, and how to make 'em better and stuff...

At first glance, (in this price range), I woulda just called it scrap and gone for a replacement unit.

...but that's kinda where they ended up at anyway, right? :)

I'd volunteer to pay the seller shipping cost to send you a replacement motor, I think...
I'm sure they don't want the blown up parts...

Good luck
rc
 
Last edited:

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
All these engines are about the same, cost isn't a factor unless you buy a $500,00 engine some sell. I don't see any difference, if you do some of the mods they over charge you for. (my opinion).

Al.Fisherman
Are you saying that the $150 Grubee http://www.kingsmotorbikes.com/grub...bike-motor-only-standard-finish_2909_prd1.htm is really not any better made than my $100 T-80 http://www.ebay.com/itm/BRAND-NEW-6...7086035?pt=LH_DefaultDomain_0&hash=item35b867 ? Or maybe this $76 one http://www.ebay.com/itm/Motorized-B...4404436?pt=LH_DefaultDomain_0&hash=item27bd95 ? Would both these engines probably last the same amount of time and built with similar quality parts? I want to thank you for posting and giving your opinion on these things. Maybe I should just buy 2 cheap ones, haha.
 

Al.Fisherman

New Member
Sep 9, 2009
1,966
5
0
Calera, Alabama
Are you saying that the $150 Grubee http://www.kingsmotorbikes.com/grub...bike-motor-only-standard-finish_2909_prd1.htm is really not any better made than my $100 T-80 http://www.ebay.com/itm/BRAND-NEW-6...7086035?pt=LH_DefaultDomain_0&hash=item35b867 ? Or maybe this $76 one http://www.ebay.com/itm/Motorized-B...4404436?pt=LH_DefaultDomain_0&hash=item27bd95 ? Would both these engines probably last the same amount of time and built with similar quality parts? I want to thank you for posting and giving your opinion on these things. Maybe I should just buy 2 cheap ones, haha.
My first 5 of 6 (6th bought from a member) engines were bought on ebay...the CHEAPEST I could find. I have my first engine not running, due to a bad aftermarket head gasket, and it trashed both the piston and cylinder. All others run great and this is what I do right after removing from the box. I make no exceptions.
https://docs.google.com/document/d/1GcesQihc7-mm3hJGf7UPiqOaRXZ8ekUT99QUZq2qXXE/edit
Some say you don't need to but I do.
My first and only engine I bought was from luckyearlybird, wife of BGF. The only issue I had was a bad magneto after 3 days, so since they treated me like chit after I purchased both a replacement magneto and CDI, I refuse to purchase ANYTHING from them. All over a $10.00 item. It wasn't the ten bucks, it was how they treated me.
 
Last edited:

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
The PK-80 I have sitting in a box will be getting new 6202 Japanese Nachi Bearings on it's crank, new SKF Nitrile seals in the case and a KBK upper bearing, I may go ahead and replace the bearings on the clutch shaft with the the better ones also, gonna make sure all gaskest are bullet proof best as possible and I plan on making my jug to case gasket from 12 mil. Alum.

Ordered 4 of these bearings tonight.

http://www.amazon.com/6202-2NSE-Nachi-Bearing-15x35x11-Bearings/dp/B0045DWDPI


Peace, Map
 

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
Those sure look like "balls" from a bearing. How they got there is beyond me, as the only place "balls" are used is on the shafts, in this case the crankshaft. Could they be sucked up from the case, it appears that they did. Repair?,, new cylinder, piston, rings and bearings. Since the engine is off the bike, remove the jug, wash out and take a pencil magnet and explorer the case. How is the head?

All these engines are about the same, cost isn't a factor unless you buy a $500,00 engine some sell. I don't see any difference, if you do some of the mods they over charge you for. (my opinion).

If you decide to repair, here is a picture tutorial of breaking a HT down.
http://s982.photobucket.com/albums/ae309/Ron-Becker/Chinese HT breakdown/

Installing...you might want to read this.
https://docs.google.com/document/d/1GcesQihc7-mm3hJGf7UPiqOaRXZ8ekUT99QUZq2qXXE/edit

GearNut from Mexiifornia :>), is on the right track. Maybe with a new engine, you'd be better off, depending on your mechanical experience.
Okay, I have gotten to step 29-30 where you take the 10 tooth gear off. It says:

"The 10 tooth gear is keyed with a woodruff key (1/2 moon) and gear removal should/can be done with the gear multi tool. Proper tools (box wrenches) and method of using the multi tool. When using the tool, back out the threaded center. Thread the tool into the 10 tooth gear and tighten till it bottoms out. This is important as there are not that many threads and can either strip the threads on the gear, tool, or both if not installed correctly. Hold tool and turn the threaded pin. This should slide the gear off the shaft."
I don't think I have this tool. Is there any way to get it off without that tool or do I have to buy one? What exactly is it called? A "gear multi tool"? Where do I go? Home Depot??

Thanks!
 

Tyler6357

Well-Known Member
Mar 15, 2012
1,293
294
83
Santa Barbara, CA
I'm sure that the only place you can acquire the gear puller is from a 2 cycle HT vendor (sometimes included in the kit.. mine was), or borrow one.

I hate the thought of suggesting this vendor to you, but it was easy to find,
http://www.ebay.com/itm/motorized-g...494?pt=LH_DefaultDomain_0&hash=item20c1eeba96
Really the cheapest you will find.

There might be another way, I haven't done so yet. Last resort.
Removing the clutch shaft:
1)Remove both clutch covers.
2)Remove flower retaining machine screw.
3)Remove flower nut.
4)Remove flywheel.
5)Remove clutch gear assembly (gear puller is required, pictures in this album). It is possible to skip this step.
6)Remove both bucking bar and ball bearing, set aside.
7) Screw (2) 6mm nuts on to the flower shaft threads, making sure that the threads are not exposed on the outboard end of the shaft.
8)Take a block of wood, I use brass, and drive shaft out of the assembly. The shaft will come out without removing the drive sprocket. The seal and bearing will come out with it. To remove the bearing on the clutch side, insert a drift punch in the sprocket side and punch out the bearing. These bearings seldom go bad.

Keep in mind this is a possibility, I know I can do it, can you accomplish it??? Best thing is buy the gear removal tool.

.
Al, Thank you so much for the quick reply.

I think I will just order the tool, I know you don't like the vendor but it's only $7 including shipping. I will order that now and finish this when I get the tool in the mail.
Thank you thank you thank you
You're the man!!
 

Al.Fisherman

New Member
Sep 9, 2009
1,966
5
0
Calera, Alabama
That's best. The way I described removing the clutch gear, you need to do it slow, and as soon as the clutch gear is loose, remove it and remove the key, there isn't much room before the key hits the bearing if any at all.. Yea...I don't like them, but I wanted you to know the tool is not expensive. One more thing when the tool arrives ensure that the threads are clean and install the puller all the way in before you attempt removing the sprocket or clutch gear, as the teeth can strip. Also tighten the center bolt pretty tight, and strike with a hammer...repeat until the part is loose.
 
Last edited:

vermhot

New Member
Jan 19, 2012
28
0
0
Wisconsin
The PK-80 I have sitting in a box will be getting new 6202 Japanese Nachi Bearings on it's crank, new SKF Nitrile seals in the case and a KBK upper bearing, I may go ahead and replace the bearings on the clutch shaft with the the better ones also, gonna make sure all gaskest are bullet proof best as possible and I plan on making my jug to case gasket from 12 mil. Alum.

Ordered 4 of these bearings tonight.

http://www.amazon.com/6202-2NSE-Nachi-Bearing-15x35x11-Bearings/dp/B0045DWDPI


Peace, Map
Was wondering where you ordered that upper bearing from ??!!