Gouged cylinder-replace it or ride it?

Huffathump · #1 03-31-2009, 11:22 AM

Yesterday I noticed that my bike was running a bit too well. Too much power and too much revs. I should have stopped, but I was a long way from home. On the way back I noticed a fairly randon "PING!" every few minutes.

When I got home I locked the clutch on and let the bike idle while I looked for some starter fluid to check for an air leak. The motor gave one last ping, which was enough to stall it.

worried about doing any more damage, i pulled the motor and stripped it down.

What I found... the head bolts were loose and the cylinder walls had numerous shallow gouges- but the rings were intact and did not show any signs of "burn through". Also, the piston cycles freely enough to spin the motor with thump and forefinger. Basically, it did not look great but it did look like it should run.

Then I opened the clutch cover. FULL of rubber.... and when I blew out the rubber I found a loose hunk of metal about 1/8" by 1/2" that had been bouncing around in there. It appears to have torn up the friction plates as well as having caught in between the gears several times (the loud ping!)

My question is thus- should I trash this motor, rebuild it or just put it back together and see if it runs? It was running right up until I took it apart, but i wonder if the cylinder was on its way out? How much of a gouge can the cylinder wall take?

wildemere · #2 03-31-2009, 02:12 PM

Clean it up and run it unless its mission critical.

Otherwise keep it for spares.

Huffathump · #3 03-31-2009, 02:42 PM

Well, I was about to chuck the motor in the parts bin- then my curiosity got the best of me. I have the thing cleaned up, put back together and ready to test- as soon as the silicone dries.

I think it would be fun sometime to start a race with completely disassembled motors. Each team starts with an equal pile of parts & tools and an identical bike- the object is to be the first to assemble the MB from scratch and make fifty laps on a one mile track!

Huffathump · #4 03-31-2009, 04:21 PM

OK- file that under "waste of time"- I should have checked the compression before I remounted the motor. I have NONE!

Also, the bit of metal in my clutch case appears to have been the woodruff key- so now the small gear spins freely of the motor.

How did all this happen at once? Perhaps the real question is, how did I make it three miles home like this!?

Is it possible that running it lean (and fast) for a few miles could have caused all this?

toytime · #5 03-31-2009, 05:40 PM

I'm still trying to figure out what that "rubber" was that you mentioned. I guess it may have been a puck from the clutch?
The key breaking seems logical, you said the gears got rammed with that "rubber" and the key did it's job.
I think it's time to get a $100 engine and keep the other for parts.
Your at 19 posts, was this a new engine?

robin · #6 03-31-2009, 11:59 PM

Hey the race idea is great but it takes me a day to assemble !! LOL

Huffathump · #7 04-01-2009, 12:27 PM

Robin:
not to brag- but I tore down and reassembled one motor, mounted it, gave it a test drive, pulled it off the bike, stripped it down again (dead) tore a motor off another bike and did a partial strip down/ rebuild, installed it on the original cruiser, and was still able to get in some riding before dark.

On the other hand, my first build took me three weeks.

Huffathump · #8 04-01-2009, 12:38 PM

Quote:

Originally Posted by toytime

I'm still trying to figure out what that "rubber" was that you mentioned. I guess it may have been a puck from the clutch?
The key breaking seems logical, you said the gears got rammed with that "rubber" and the key did it's job.
I think it's time to get a $100 engine and keep the other for parts.
Your at 19 posts, was this a new engine?

The engine was my newest one, but BGF gives no warranty.

I think the ground up rubber was just left over from clutch slippage- I tend to overuse the clutch, letting it slip a bit on takeoff. It seemed like a lot, but I checked and my other BGF motor is the same. All the pucks were in place- I checked.

Also, it was definitely the chunk of steel (not rubber) that got caught in the gears- the teeth are clearly gouged by something very hard. Now, I am not completely certain that it IS the woodruff key- but the key was missing and the chunk of metal was about the right size. It is so mangled though, that it could have been anything.

**Norman** · #9 04-01-2009, 02:13 PM

one thing that is a sort of rubber in there is the engine crank shaft seal( combination of rubber and metal) under the small gear on the engine if its gone the engine will not run right and will leak the fuel mix out into the gear case of the engine. The engne may run but not for long with out a seal there it will soon go bang.

**2door** · #10 04-01-2009, 10:03 PM

I think it would be fun sometime to start a race with completely disassembled motors. Each team starts with an equal pile of parts & tools and an identical bike- the object is to be the first to assemble the MB from scratch and make fifty laps on a one mile track![/QUOTE]

I once was envolved in stock car racing and one event we did was that all the drivers had to put their shoes in a pile before the start of the race. When the flag dropped the drivers had to run to the pile of shoes, find theirs, put them on and tie the laces then run to their cars, start their engines and make one lap of the race track. The first one over the finish line was the winner. Your idea reminded me of that. LoL, thanks, haven;t thought of that in years.
Tom