What to expect from a eBay 80cc Engine

[Boosted]

I scanned through the "noob" stickies and just had a few questions that I didn't see directly answered that I thought i'd ask.

I am looking into purchasing a 80cc Chinese engine kit off eBay and am going to put it on a older 26" mountain bike, or I may possibly buy a 700c singlespeed road bike from walmart, I haven't decided yet. I was curious from a reliability / lifespan standpoint what I should realistically expect out of this engine. Obviously, even with good maintenance I won't get a ton of miles, but would it be unrealistic to see 1 year / 2-3K miles from one? Does the engine drastically add wear to the rear tire faster than you would see from normal riding? I'm pretty set on getting the eBay $120 kit, especially because I like the clutch / no pull start, and $120 is about all I really want to spend on this.

I'm just trying to get an idea what owning one of these kits is going to be like long term over something like a 1 year / 2-3K mile period. Can these engines last even more miles when they're used regularly?

Thanks!

 

[Fabian]

I was curious from a reliability / lifespan standpoint what I should realistically expect out of this engine.

With a Jaguar CDI, and using 25:1 oil ratio and keeping the engine under 4,800 max rpm (with 4,200 max cruise rpm), you can reasonably expect to get around 4,000 kilometers (2,500 miles) out of a piston and cylinder and around 10,000 kilometers (6,200 miles) out of a bottom end.

 

[bluegoatwoods]

My own feeling is that Fabian is essentially correct in his estimate. But I'd regard it as an average or a 'mean'. Individual results will definitely vary.

But even if you get one that doesn't last all that long, a new one is cheap.

My experience is that the rear tire does wear a bit more quickly than on a pedal bike. But the difference isn't huge. And it might be nearly zero if one keeps a good eye on tire pressure.

 

[Fabian]

My situation is a little different in that i do a lot of heavy haul, but typically i get 3,000 kilometers (1,900 miles) out of a front tyre (at 20 psi) and 1,500 kilometers (950 miles) out of a rear tyre (at 26 psi), using a open tread pattern found on most mountain bike tyres.

At one time i used a smooth faced Maxxis Hookworm style tyre and it lasted 10,000 kilometers on the rear wheel with the sidewall failing before the tread was completely worn down, which can be seen if doing a Google search for "Macgyver-ing It"

 

[HeadSmess]

getting up to near 5 years and 10,000km on one old girl now... with out having opened it.

other hand, ive had a cheap fleabay one die on the first ride.

sometimes it pays to spend just a little bit more.

while essentially all the same, different factory, different tolerance, different machines, different quality...different price.


fleabay has one issue. you leave good feedback when you receive engine, but cant follow up two weeks later when you find the exhaust studs have been epoxied into stripped holes from the factory.

tyre wear is about the same as putting on an extra few kg...not a big issue.

 

[074KU]

getting up to near 5 years and 10,000km on one old girl now... with out having opened it.

My first engine did about 8000ish km over about 5 years before it really needed rebuilding (I am a 97kg bloke!) Now I run a little bike computer to help me keep a track of distances and such for my own amusement, my current engine is up to 3057km in 2 years and is only just now getting a little noisy in the clutch bearing.
I would agree with the previous statements as to life expectancy of these engines (I am a bit heavy and tend to ride like hounds of hell are on my heels)

As for the rubber, I run Marathon Extreme (the green guards are apparently better) tires in the 26 x 1.75 @ 60psi (5psi below max rating) and find them to last about 1.5-2 years (and still to this day not a single puncture) where as "normal" non-touring tiers I have had sidewall failure inside 100km.

 

[PDUB]

I just put on 4000 miles before mine died crank bearing issue. Had very few problems to overcome. Grey 66 cc best bicycle engine I ever had.

 

[Anime2019Master]

It's luck of the draw tbh. You might get a decent engine, you might get junk. I only have bought one off ebay, about a year ago, had to be returned. It was assembled with too large a piston, wouldn't fully cycle. By the time I figured out what was wrong, it had stripped the wingnut and scattered the bearings all over. Took a month to get my refund, they tried to say they hadn't received it, but I was smart about it, I had tracking on the package, and told them I knew they had it. Got refunded within 5h of that email. Took me until now to gt the nerver to try again, thins time ive done my research vey thoroughly. This is the kit I will buy in another day or two.

PK80 by Runwell Kit with Upgrades | Bicycle Motor Works

Amazing Performing Engine Kit with UPGRADES!!!! Runwell PK80’s are the real deal! 40mm Stroke, short rod, type A piston, M8 mounting studs, and Allen-head hardware all around - not to mention their well balanced crank that’s machined to near perfection and is oh-so much fatter than the others...

bicyclemotorworks.com

This site seems that have a good rep, andother on this forum usually have good things to say about bicycle motor works, check out their other kits, you may find something in your price range you like here.

 

[willis617]

It's luck of the draw tbh. You might get a decent engine, you might get junk. I only have bought one off ebay, about a year ago, had to be returned. It was assembled with too large a piston, wouldn't fully cycle. By the time I figured out what was wrong, it had stripped the wingnut and scattered the bearings all over. Took a month to get my refund, they tried to say they hadn't received it, but I was smart about it, I had tracking on the package, and told them I knew they had it. Got refunded within 5h of that email. Took me until now to gt the nerver to try again, thins time ive done my research vey thoroughly. This is the kit I will buy in another day or two.

PK80 by Runwell Kit with Upgrades | Bicycle Motor Works

Amazing Performing Engine Kit with UPGRADES!!!! Runwell PK80’s are the real deal! 40mm Stroke, short rod, type A piston, M8 mounting studs, and Allen-head hardware all around - not to mention their well balanced crank that’s machined to near perfection and is oh-so much fatter than the others...

bicyclemotorworks.com

This site seems that have a good rep, andother on this forum usually have good things to say about bicycle motor works, check out their other kits, you may find something in your price range you like here.

That a good kit you linked to, the 2 rear sprockets will allow a gearing change, the engine mounted chain tensioner is a plus, I bought an engine from BMW last November and had a good experience, he also sells a basic zeda kit for $129, and you won't find cheaper shipping

 

[JerboaJohn]

even if you get a good one (75-80% chance) youll find out quick all bolts and nuts are garbage and strip if you stare at them too hard