Helping a Friend......

Just want to relate a recent and on going experience with a 4-stroke build I'm working on for a co-worker and friend Katrina. She bought a decent 4-stroke bike off craigslist (Kent aluminum frame, huasheng 49cc engine with a cheap pocketbike 5:1 single chain tranny) for $300. Not too bad except for the cheap tranny which failed shortly after she bought the bike.

I trouble shot and replaced the failed tranny with a good 4G that I had laying around. It is the tapered shaft version and her clutch was in fine shape so all was well at that point.

The person she bought the bike from was definitely not an experienced builder and I am the lucky guy that gets to dial this thing in for her.

Gotta go.......to be continued......

Sorry about that....didn't mean to be rude starting a thread this way

Anyhow, the shape this bike was in as she bought it wasn't too bad at all for what she paid. The real issues were poorly adjusted front and rear brakes with worn out brake pads, the crappy pocketbike tranny that took a dump and the bb spindle/crank combo that didn't properly clear the engine and tranny while you pedaled.

OK, so I fixed those probs without too much cost or trouble and then I get a text a couple days later saying......." My bike stopped working on the middle of me riding it".

Umm.......I'm thinking of what may be wrong that it stopped working all of the sudden and then asked her what the symptoms were before the engine quit. She said it just started losing power gradually and then just quit.

Long story short, looks kike the connecting rod cap came loose and broke one side of the rod off about the size of a cc and stripped the other bolt threads out and became completely detached. The piston stayed up in the TDC position in the cylinder with the rod still connected and before I took the side cover off, when you pulled on the recoil starter it made no noise whatsoever. It just felt like there was no compression at all (because there wasn't any when the piston is staying put lol).

The engine looks very new inside an I haven'y found any damage as of yet. The cam looks fine with virtually no wear, push rods fine and straight, engine oil was fine and full. The only damage so far I see is the broken rod and the oil slinger got a bit bent.

Much more to come when I remove the engine and split the case........def looks like a case of over revving the engine from brand new, really over revving it........

ajoh said:

eek that sucks......... well scotto she's in good hands now so i'm sure you'll have her up an good asap..........


btw so since her bike is down i guess she's riding your race bike around..........damn your a nice guy mate




(awaiting scotto to tell me where to get off )

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You're absolutely right mate, I'm a very nice guy.........but not that nice The race bike only gets ridden on the streets around here by me...... don't want innocent people gettin hurt around here if monsta bike goes bad and reeks havoc on the community

Here's a pic of the loaner engine I'll install while I rebuild her engine......

ajoh said:

hey scotto what's with the big ass hole in the sprocket?


yea that's what i like about these HS50's all the spare parts are easily available an cheap
an you are a good man for helping her out........

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That hole is one of eight that will be joined by several smaller holes to lighten up that 2lb. hunk of steel sprocket (boat anchor ).

That sprocket is going on my 212 or 99cc bike.....I don't think the 49cc could even turn it

Here it is a couple months later and I finally got a chance to work on her bike again.....just got the donor engine installed and now have to dial everything in.

A couple pics....







More to come later...

Got the bike up and running today, no issues....runs great! All it needs now is a little black paint on the engine shroud and the top tube converted to a fuel tank (toss the peanut). It did have a chrome exhaust when she got it. One good burn on the leg and she opted for the quiet stocker.

Today's pics.....

I rode Katrina's bike to work today and it ran just fine. She was really excited when she showed up to work and her bike was there and running again.

We got off at 9:30 PM and she had to take it for a spin around the parking lot...she was stoked! It's got really good take-off with the 4G and the rather large rear sprocket, no need to pedal on the starts.

I've got to repair the 4G black plastic tranny cover but other than that it's running great.

NunyaBidness said:

Wish I had a friend like you that lived near me. Dude, you rock and I am sure that she thinks the same thing.

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Up and running once again

Thanks Nunya.....I think you're right. This is a pic of her after riding to work yesterday. Finally I think she's happy with a MAB.....who wouldn't be? She said the ride was cold.....65 degrees?

Alrighty then, here's the updates to Katrina's bike and what happened to her engine.

I repaired the 4G tranny cover with aluminum straps riveted and epoxied to the cover where the 3 mounting screws are located. I didn't take pics of the repair.

Tonight I finally got around to splitting the crankcase of this failed Huasheng and things don't look nearly as bad as you would expect. All in all it is going to be a really cheap repair as all that is needed to be replaced is the connecting rod and the cap. Less than $20 in parts.

I'm uploading the pics now for show-n-tell......stay tuned...

I'm still trying to upload the pics from my phone and things aren't going like they normally do....technical difficulties I guess? Still working on it.....

Pics of the aftermath...









aluminum off the rod journal fused to the crank


next...

the rest of the pics...

aluminum fused to the crank and threads in con-rod cap bolt


snap!




piston & rings unscathed...


cylinder and combustion chamber are just fine


The damage was very minimal for this type of failure......a new rod and cap will be all that's needed to make this engine good as new. A very cheap fix!