Had my little putter for a year now...

[Bohemian_Lady]

Aloha,

As the title states I've had my motorized bike for about a year now, shes a fankin-bike to be sure. I cobbled her together form three diffrent mountain bikes, a poor choice I know but its what I had, and strapped on the cheapest 80cc kit that I could find.

I am currently engaged in a full tear down becasue she made the most aweful noise before loosing power. That heart stopping grinding noise that left me with the inclination that something was terribly wrong in the piston housing. I cracked her open to find metal shavings in the piston chamber, my suspisions were correct. So why the full tear down? Well its a cheap motor and I want to be sure nothing else is wrong with her, I will also be investing in a proper cruiser frame.

 

[wheelbender6]

Welcome to the forum. If your engine is not repairable, you can buy an engines only (no kit items) from online vendors.

 

[Bikeguy Joe]

Mountain bikes are excellent choices for motorized bikes, it just the tires that aren't so great.

 

[Bohemian_Lady]

@wheelbender6: Thanks for the warm wlecome, I acctually got this cheap little motor off ebay. At the time I was ready to buy it was the only motor under $300 so its what I got. Fortunetly the metal shaving swere pretty small, I've got my fingers crossed that I can get her working again. I know the piston is shot and her clutch pads need replacing I'm getting ready to finish inspecting her now. Hopefuly thats all she needs.

@Bikeguy Joe: The only way we could get the motor to work on the Mountian bike was to rig it so that the inital gear stayed on the lowest seting. When you started her up you had to do so in the lowest gear. To engage the motor she needed to be shifted into the highest possible gear or else she would stall. When stopping you had to shift her back to the lowest gear, every time other wise she stalled. I'm curious is there something that we missed in hooking up the gears that coudl have caused undue ware on the piston, or was it just the cheapness of the motor its self?

 

[2door]

I see you do not have a shift kit so what gear the bike is in doesn't have any effect on the engine. It sounds to me as if your clutch cable isn't adjusted correctly. When coming to a stop all you should have to do is squeeze the clutch lever which will disengage the engine from the rear wheel. Just like any manual transmission on a motorcycle or a car.
You'll want little to no slack in the cable where it attaches to the engine and when the handlebar lever is fully compressed the rear wheel should spin free with just a little resistance and some chain noise. The bike gears have no influence on the engine drive side or how the engine idles or pulls the bike.

Tom

 

[Bohemian_Lady]

@2door: Sorry I worded that incorrectly, during use there was no problem using the clutch to disengage the engine from the back wheel as long as I had the bikes manual chain at the highest gear. The problem was that engaging the engine with the manual chain in the lowest gear resulted in the bike not producing enough torque to assist in turning the back wheel and the bike would stall. Shifting the manual gear up fixed this problem, but it also caused the wheel to lock up if the bike was turned off in this mode. Which resulted in the need to shift the bike down again when turning it off for parking. I'm assuming there is some thing we did wrong that caused this but I'm not sure what it is. The next motor is going on a one speed so I can avoid this issue entirely.

On a different note entirely I think she's hosed. I dissembled the Piston housing and found that the piston bar had nicks, along with the wheels that drive the piston. There were also small metal shavings in the piston housing. To top it ll off when I opened the Coil housing I found this...

Apparently my best efforts to keep her dry did no good in this moist environment... Next time WD40 is going to be part of regular maintenance.

 

[2door]

Wow, ma'am, I'm sorry but still not following you. The pedal side chain/gears have no impact on how the engine drives the bike other than when starting the engine. Typically a lower gear makes it easier to pedal up to speed to start the engine but after the engine is running and the clutch is engaged the pedal side chain/gears should have no effect on how the engine pulls the bike. In fact after the engine is running you could essentially remove the pedal chain/gears and the bike would still be propelled by the engine.
In some cases where the engine is not running correctly or producing enough power, you might have to pedal assist it but unless you are ascending steep hills or have a small rear sprocket, pedal assist shouldn't be necessary. If, as I said, if the engine is running right.

The magneto cover and the wire entry point should be sealed with a silicone sealer to prevent moisture from getting to the Magneto. Even in high humidity, if sealed, that area should remain dry. I'd suggest replacing your magneto coil. It looks as if it has seen better days.

Tom

 

[Bohemian_Lady]

Don't worry the problem is very confusing. When my partner tried to explain what he thought was going on, I let him test drive it first you know in case it exploded =P, I didn't understand either. At least not until I got on the bike.

Aside from that, yes the magneto coil does need to be replaced and I'll make sure to use a silicone sealer. This motor came with a little rubber gasket for the wire entry point and the seal that they used for the housing obviously wasn't good enough to keep the moisture out. I need to take some naval jelly to the magneto casing and get that rust off and prevent it from oxidizing further, unless you have a rust remover that you would recommend instead of naval jelly. So the list of things that need replacing grows but the up side is the housing for it all is still in relativly good condition.

 

[Wickedest1]

Ok so for me I use pb blaster, on my chain, cables and any other place rust might appear...plus a wire brush...as 2door said check your clutch cable tension...you want the clutch to disengage with about a quarter pull of the lever...

Did you get your kit from bgf? I bought 2 from him...one died with less than 100 miles and the other about 1700 miles...both had metal shavings in the crank case, the longer miled engine killed itself cuz the screws in the flyweights came undone and ate my piston...

Little advice that was passed to me:
Check everything before you start it...everything

Good luck to you miss...please feel free to ask tons of questions...

 

[Bohemian_Lady]

pb blaster I will put that on my list of things to get. I got my kit from MotorMike on ebay, I admit it was foolish to hook her up with out cracking it open but I was so excited!! Fortunately I wont have that problem this time as I'll be rebuilding her.

I do have a question. I've seen people recommend a full break down and cleaning out of the kits but that was before break in. Since I've wiped the crankshaft case and the piston housing down with a clean cloth to get any possible metal particles after her break in period I'm not sure if I should just run her through break in again or give the housing and crankshaft case a light coating of machine oil then run her through break in. Will just running her through break in again provide enough lubrication? If I do need to machine oil her as I reassemble what weight and brand do you recommend?

 

[Bikeguy Joe]

Any oil will do when you are re-assembling it.

Regular break in will be sufficient. By that I mean 32:1 mixture, take it easy for a few miles and vary the throttle quite a bit.

 

[Bohemian_Lady]

Update.... Question answered here

Finally got money for the parts, got them ordered and they are here!! I'm in the process of wiping down all the parts with an oiled rag. Theres one problem... I'm pretty sure there are metal shavings in the ball bearings of the crank shaft case... I stuck my finger int he hole and turned the bearings manually, I can feel them hitching on something. I'm just not sure how to get them out of there so I can check the bearings then replace or re-grease them, which ever is necessary. I am searching the forums for an answer now... but if any one can chime in that would be greatly welcome.

 

[Master-shake]

Yeah, I had said before to not take apart a new motor but after experiencing 3 different ones, I would suggest anyone with a new motor to take it apart. I found metal shavings in there out of the box! also there was grease in the crank case that looked dirty it had like sand particles in it.

Also, this video series might help you.
http://www.youtube.com/watch?v=p6E0fLlsysk
http://www.youtube.com/watch?v=qRuCvAnl_TM
http://www.youtube.com/watch?v=3jM1iaNBO08
http://www.youtube.com/watch?v=-1qFxuLQXTg

 

[maniac57]

I simply rinse the bottom end with diesel fuel or good solvent like MEK or lacquer thinner while turning the crank until all the grit is gone, draining and refilling often until it drains clean. Once its spotless, I soak it in straight two-stroke oil a couple hours to lube the rod and mains well before draining the oil and assembling the top end. I do this on ALL my new engines just in case. I have never had a bearing or engine failure yet. (knocks on wood)
You should check for proper assembly also while you're inside the engine. Pay special attention to the crank seals and make sure the small drive gear is on straight and not wobbly.

 

[Bohemian_Lady]

So I got her all put back together with the new parts and she still wont turn over... The piston wont even move. So depressing. I'm guessing the problem is a small scratch in the chrome of the Piston chamber. I know of a small motor repair guy that does free diagnostic work... I think I'm going to take the motor to him. Other wise I'm going to have to break her down again and try to figure out what wrong.

Anyone know of some good Youtube tutorials... not getting this thing working has been really discouraging.

 

[Intrepid Wheelwoman]

Welcome to the forum Bohemian_Lady

When you fitted the piston back into the cylinder barrel how did you compress the rings so they would slip nicely into the bore. If you've broken a ring it might be caught in one of the ports in the cylinder barrel.

Are you sure that the new piston you replaced is the same as the old one because there are differences between engines made in different Chinese factories even if the engine is of the same capacity.

 

[Bohemian_Lady]

I'm pretty sure the rings compressed with out breaking, and I'm positive the at the new piston was the same as the old one. I kept all the old parts so that I could compare them with the new ones, just to be sure. I'm kind of hoping that I just mucked something up in the rebuild process. I'm going to order more gaskets and try again, this time I'll have some youtube tuts to help me along...

When I put this thing back together I didn't have electricity, so no computer and no internet. It was guess and hope. Obviously that didn't work or something that I didn't replace is broken.

 

[rustycase]

Greetings from the mainland!
I'm glad to hear you have had a year of fun riding around a beautiful island!

If I had caught your post earlier I would have advised you purchase a completely new kit and swap the motor out in your bicycle.

The extra parts not used are always handy to have, and a complete kit cost is not a whole lot more than a list of individual parts needed... and amended parts lists at additional cost and the associated shipping costs.

Gosh! Freight costs must be high to the island!

There are many vendors who advertise here on the forum. Always nice to patronize them as they help the forum thrive, for benefit of all.
However, unless the vendor is doing a teardown, inspection, and improvement mods on the chinagirl, IMO, they are all the same. An equal chance for significant problems, right out of the box!
But they are fun!

rc

 

[Bohemian_Lady]

Actually in my case it was cheaper to order the individual parts.

The kit I bought was $230 (with shipping)
And the parts were $70 (With shipping)

I didn't get new casings but just about everything else I replaced. If I had ordered new casings as well then yeah I would have just ordered another kit. Since I mucked this up I'm kind of glad I didn't, if something broke during our attempt to rebuild or start it at least I only wasted $70 instead of $230.

Once I get the old baby running again I'm going to order a new kit and shelf it until I need to ravage it for parts. This was always the plan it just took longer than expected ^_^

 

[CrzdCtryRebel]

You don't have to get a new kit you can get just a basic engine for 100 bucks