4G HS cruising, heard noise, engine died, won't start

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beauhawk

New Member
Apr 17, 2010
12
0
0
Santa Cruz
I finally took some pictures of my broken machine. Hoping that I can just get the parts, clean it up, and put it back together. Turns out I will need a new piston too. Hoping I don't need a new engine ... can't really aford it right now; especially since I think that I would shovel out the extra dough for a quality genuine Honda engine. I have seen one for $275 ($100 more than the HS); and I believe that the 4G Belt drive will hook right up to it; I think that there may be an extra part or two.

As far as reason this happened, it's hard to say. I wasn't over-revving when it happened, and when I am going downhill, I always ease up on the throttle to avoid over-revs.

Given the pics, do you think that I can re-build? Oh, and there are 2 broken bolts that I have to extract from the case, and fill two holes on the case? Maybe w/epoxy?
 

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MotorBicycleRacing

MotorBicycleRacing

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Jul 28, 2010
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SoCal Baby!!!
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beauhawk said:
I finally took some pictures of my broken machine. Hoping that I can just get the parts, clean it up, and put it back together. Turns out I will need a new piston too. Hoping I don't need a new engine ... can't really aford it right now; especially since I think that I would shovel out the extra dough for a quality genuine Honda engine. I have seen one for $275 ($100 more than the HS); and I believe that the 4G Belt drive will hook right up to it; I think that there may be an extra part or two.

As far as reason this happened, it's hard to say. I wasn't over-revving when it happened, and when I am going downhill, I always ease up on the throttle to avoid over-revs.

Given the pics, do you think that I can re-build? Oh, and there are 2 broken bolts that I have to extract from the case, and fill two holes on the case? Maybe w/epoxy?
Click to expand...
The 4 G gearbox that you have will not work with the Honda motor.
There is another model of the 4 G that works with a 5/8" shaft style motor that sells for $140

Where can you buy the Honda GX 50 for $275? Do you have a link to a website?

What gearing are you running on your 4 G? tire size? front and rear sprocket size?

What is your maximum speed?
Do you have any idea of what RPMs you are hitting?
 
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scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
oooohh, that's pretty bad. You'll need a new piston and rings, a connecting rod and cap, an oil slinger and you could patch the holes in the case with epoxy (if you know what you're doing).

How about the crank journal.....that's where the connecting rod and cap are connected. There were no close-ups of it and it is rather important that it is not scuffed, gouged or abraised if you're thinking of re-using it.....at very least you should mic it and polish it, but I strongly suggest you replace that as well if you want to do it right. Good luck, scotto-
 
Quenton Guenther

Quenton Guenther

Dealer
Feb 21, 2008
686
1
0
Outer Banks of North Carolina
Hi Beauhawk,

Sadly the Honda motors have ended up the same way when run at high RPMs. It won't help to spend the extra money for the Honda.

It is difficult to tell if the motor is running at too high RPM level because the muffler is so quiet. The only way is to use a tachometer to know for sure.

The replacement motor you need is $189.xx from bicycle-engines.com.

If your crankshaft journal is OK, you might be able to rebuild your motor and save some money.

It might be well worth your time to determine the current ratios, and if needed buy a smaller rear sprocket [on the wheel] to keep the RPM level down.

Have fun,
 
MotorBicycleRacing

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
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SoCal Baby!!!
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beauhawk said:
As far as reason this happened, it's hard to say. I wasn't over-revving when it happened, and when I am going downhill, I always ease up on the throttle to avoid over-revs.
Click to expand...
OK, I am going to assume that you had an 11 tooth front to a 50 tooth rear sprocket
and had a 26.5 diameter rear tire with a stock Grubee G 4 gearbox.

At redline which is 7800 rpm = only 27.1 mph
9,000 rpm = 31.2 mph
10,000 rpm = 34.7 mph
When you are riding WOT do you never go faster than 28 mph?
 
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