List of Most Common Breakdowns???

[RonInColorado]

Having just bought my first MB with the fairly standard 'Flying Horse' 66/80cc engine, I just encountered my first breakdown issue, a fairly simple thing, just a broken master link for the drive chain.

What I'm wondering is could some of the more experienced/seasoned riders provide a list of perhaps the 5-10 most common breakdowns that they have encountered as I would like to lay in a stock of spare parts in order to do repairs on the fly rather than having to search for parts whenever my new ride develops issues.

Also, any tips/do and don'ts for first time builders would be appreciated as well since I'm on the threshold of losing my 'builder virginity'.

Thanks and ride safely!!

 

[Alabama Fisherman]

Here are some common problems, some due to the non quality of the Chinese and some brought on by the installer. I have encountered very few as I chose to eliminate the potential problems to start with.

1. Coil..mine went out within 3 days of delivery
2. CDI
3. Head gasket.. Blew one on first bike. Didn't check torque coming out of the box.
4. Broken studs..more on that later
5. Stripped stud/threads..more on that later
6. Running either too rich or too lean.
7. Plug, plug wire and or plug cap.
8. Drive chain

I don't know how many times I've stressed for proper instillation and modifications coming right of the box. ALL of these can avert a breakdown later. I had very minor issues on my first build, but ZERO issues on my last 4.

1. Couldn't do anything about this one. Just buy a new one.
2. Never a problem but they are cheaply made and can go bad any minute.
3. Use proper torque 150-204 inch pounds on 8mm and 50-75 inch pounds on 6mm. I use 150 and 50
3, 4, 5. I recommend that ALL soft Chinese studs are replaced with Grade 5 (Metric grade 8.8) right out of the box. Cylinder head, engine mounts, exhaust.... and intake if desired.
When installing studs use lock tite...I use RED some use Blue. I use nylon locking nuts, or double nut all engine studs.
6 Carburetor adjustment.
7.Replace plug, wire and boot out of the box.

Most important is to mount the engine properly....
MotoredBikes.com: Motorized Bicycle Forum - Al.Fisherman's Album: Proper engine mounting

Make or buy a front mount if needed, do not shim engine mounts. Incorrect mount alignment causes both broken/stripped studs, and broken engine cases.
MotoredBikes.com: Motorized Bicycle Forum - Al.Fisherman's Album: Mike's Cruiser - Picture

Enjoy your ride
Ron

 

[bairdco]

i take the time to "blueprint" my motors before i install them, but on my first build i just slapped the kit on. here's the list of "problems."

*had to bend the exhaust to clear the cranks.
*masterlink disappeared on the first ride, even though i installed it correctly.
*spark plug wire disintegrated.

fixed all these the first day and was off and riding.

on subsequent builds, i've had leaky petcocks and pinholed floats with the NT carbs, and leaky petcocks in the tanks.

i took the head off a brand new motor and there was a fingernail clipping size piece of metal that came off the threads from the spark plug hole sitting on the piston.

all my builds i upgrade all the hardware, change the plug and wire, and throw away the masterlink.

then i just fix the other minor crap as it happens.

 

[Cabinfever1977]

My list of breakdowns:
master link - will break or come off if installed backwards, buy extra.
flat tires - get extra tubes.
buy extra nuts for all mounts/studs - there all the same size, double nut them.
check fuel in tank, the mileage is so good you may forget to check.
buy roll of gasket material (paper not cork) every time you remove something time to change gasket.
Tab on front fender mount may break, secure it.
Buy extra throttle cable, the cable tends to break off in the twist throttle.

 

[Bikeguy Joe]

I ran out of gas twice.

 

[Bill in Oregon]

Where do buy grade 5 metric studs?

 

[bairdco]

bill, look for an "industrial fastener" place in your area. sometimes you can find the stuff at ace hardware, but it's about 5 times as much as a place that specializes in fasteners.

i pay less than 5 bucks to upgrade all my hardware to grade 8, black, allen head cap screws.

 

[RonInColorado]

I want to express my thanks to all my brother/sister riders who have taken the time to respond to my original question about frequent failures and suggestion for first time builders. Some of the problems that I anticipated encountering were confirmed and a few that I hadn't thought of were pointed out. All information quite valuable for helping to ensure solid builds in the future, avoiding potential problems or dealing wiht those that will inevitably arise.

 

[silverbear]

Good thread. I had the clutch cable break on my first build after a couple hundred miles.
SB

 

[Alabama Fisherman]

Where do buy grade 5 metric studs?

Most industrial supply stores sell all thread in a meter stick. Don't worry about a US grade 8. A Metric grade 8.8 (our grade 5) will be more then enough. The cast aluminum in these engines won't even take the max that you can put on a grade 5. Grade is way overkill. Torque 8mm to between 150 inch pounds and a max of 204 inch pounds. For 6mm torque 50 inch pounds to a max of 75 inch pounds. I use 150 and 50. I have never stripped a thread, never broke a mount. Improper engine placement instillation is the #1 cause of both broken studs, and broken engine mounts. If you can't find what you want/need PM me.

http://www.motoredbikes.com/album.php?albumid=1018

For PROPER engine alignment, here is one possible solution to the few. http://www.motoredbikes.com/album.php?albumid=1014&pictureid=6606 DO NOT drill holes in a bike frame...yes you can get away with it but I've had a frame break in two.

 

[2door]

Replace the kit supplied fuel line as soon as possible. In my experience it is the one most certain thing to go bad. Everything else is the luck of the draw. The sub-standard material that the fuel lines are made of will most assuredly harden and crack after a short period of exposure to gasoline. Most auto parts stores, lawn mower and motorcycle repair shops can provide fuel line, 1/4" ID, that will last.
Tom

 

[DOC BOLM]

My only problem is the loose nut driving the bike.

 

[kr632]

I ran out of gas twice.

same here. the damn thing just wouldnt start and i could not figure out why. had her all taken apart then i noticed there was nothing in the tank. SMH.

i would keep extra 41 chain if you can (10 feet for around 15-20 dollars).

 

[Mac]

A few more...
1. Coil/cdi connectors, replace or solder, then heat shrink, yea a bit of a pain when you have to remove the engine, but otherwise carefree
2. Kit sparkplug is junk NGK B5hs or B7hs good replacement
3. kill switch, not IF it will fail, it's when.
4. Stock 415 chain is poor quality, I go right to .41
all of the things said above I concur
Mac

 

[oylavabeer]

throttle cables breaking at carb end, I now carry some alloy rivets with me to crimp on the end to get me home to a more permament fix.

 

[noco]

1. rear hub problems
2. exhaust coming loose from motor
3. flying horse...nut on bottom of exhaust pipe coming off
4. air leak at carb
5. my own stupidity
6. gas lines hardening and falling off tank
7. blowing red lights with a cop behind me
8. gas leaking from carb
9. flat tires
10. the 44 tooth gear is too tall....i want to go faster than that

 

[furament]

grudgen clips small weeak evel bad they wiil break bwwaaaaaaa click then nothing when you pull the head you will see a nice gouge up and down your cilender and a little peice of metal sticking up some times breaks rings replace by aney means

 

[Riderx]

I bought my motor and out of the box the piston were broken. So i bought a 2nd motor while i waited on the new rings. List of issues....
1. Every mounting bolt including exhaust failed and required replacing
2. Carburetor failed twice.
3. Clutch cable broke.
4. Gas tank leaked.
5. The spark plug was stripped and forced out of the head while riding out nowhere. Replaced it and the next day.....
6. The engine siezed out of no where (all of the previous issues were within the first 4 weeks at 16 hours of use).
7. I installed the other motor i had finished building with new rings and replaced every bolt to avoid the same failures i had with with first engine. This time it ran like a top with no issues until at about 4 weeks and 16 hours of use again the engine seized out of no where. Anyone have any ideas? I was running a 20:1 mix which should have been plenty rich. I have no clue why this keeps happening. Any thoughts would be helpful.

 

[Citi-sporter]

The engine's drive chain sprocket, are all machined with the teeth milled out of round to the center of the taper. I've bought 4 of these sprockets and they all come with varying degrees of out of roundness.

Local guy who makes custom motorcycle sprocket sets says it the worst machining he's ever seen in a mass produced product and should be a recall condition. No road legal motorcycle would ever come with such awful sprocket eccentricity.

I don't know what the solution is, as I believe 90% of the chain problems you experience with these bike engines can be tied to the sprocket setting up a bad vibration on the chain, loosening the spoke clamped wheel sprocket and making the chain oscillate from tight to loose rapidly is not doing your bike or drive train any good.

 

[Citi-sporter]

I bought my motor and out of the box the piston were broken. So i bought a 2nd motor while i waited on the new rings. List of issues....
1. Every mounting bolt including exhaust failed and required replacing
2. Carburetor failed twice.
3. Clutch cable broke.
4. Gas tank leaked.
5. The spark plug was stripped and forced out of the head while riding out nowhere. Replaced it and the next day.....
6. The engine siezed out of no where (all of the previous issues were within the first 4 weeks at 16 hours of use).
7. I installed the other motor i had finished building with new rings and replaced every bolt to avoid the same failures i had with with first engine. This time it ran like a top with no issues until at about 4 weeks and 16 hours of use again the engine seized out of no where. Anyone have any ideas? I was running a 20:1 mix which should have been plenty rich. I have no clue why this keeps happening. Any thoughts would be helpful.

I honestly believe that you folks run your engines too hard.

They have low cooling surface areas, thermal mass and running WOT 80% of the time just heat soaks a cylinder and head with limited ability to shed heat. Heat kills lubrication, even when it's present in adequate quantities, using cheap 2 stroke oils, Dino based instead of synthetic, running these engines hard in high summer heat, the fact that the CDI has a poorly designed advance curve, any number of factors.

These are bike assist engines, not motorcycle replacements and frankly running above 25 mph all the time is probably not doing these any good as stock.