I had a breakdown today...

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CTripps

CTripps

Active Member
Aug 22, 2011
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killercanuck said:
Aside from some foreign crud like GearNut pointed out(which may or may not have done any harming damage), it looks like you've had a substantial leak on your head gasket too.

Look at your head-gasket seal from one side to the other, and the trail of leaking sludge out of the exhaust side:



Your head and jug will need a good lapping.

You should pull the jug to make sure theirs no nicks in your rings that match the groove that GearNut pointed out too.


If you don't know what lapping is, get a wettable sheet of 300+ paper on a piece of glass(flattest surface readily available, don't use wood or steel, too many hidden imperfections) to lightly flatten out your mating surfaces. on the head, as well as the jug.

Pro-Tip: the more you take off after a proper "true surface" only raises your compression, but don't go nuts your first time around.

gl.
Click to expand...
I thought that looked like a leak, the underside of the head shows it too between my hand and the plug.



I was expecting a heavier deposit or more sludge than what's there.

Okay, sounds like I have a plan for tomorrow then... pull the jug, inspect it, examine the piston and rings, clean the head surfaces and lap them, reassemble if everything's good...
I have some (red) gasketmaker, is that a bad thing when reassembling one of these? I can pull a (factory) head gasket out but am without access to any other resources right now, except for stuff from the recycling bin.
 
CTripps

CTripps

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Aug 22, 2011
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The weather's supposed to be a bit better tomorrow, might not rain much at all, so should be able to work without leaks in my motor or on my head. I may even take the laptop up there, makes for fewer trips down just to pick everyone's brains and do searches. ;)
 
CTripps

CTripps

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Aug 22, 2011
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Okay, here we go.... Laptop live in the garage today. :)

In have pulled the head and jug, and the news isn't good. The lower piston ring was broken,and there's a large fragment unaccounted for.. it quite likely dropped into the crankcase, I see no sign of it around the work area.

On top of that, the piston and cylinder are both pretty badly scored from the second ring down in a couple of places. Here's pics pf the piston:

Intake @ right:

102_2362.JPG

..@ Bottom:

102_2364.JPG

..@ Top:

102_2368.JPG

...@ Left:

102_2369.JPG

Pics of the cylinder next post.
 
CTripps

CTripps

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Aug 22, 2011
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Here we go.....

These should be in the same order going around. Looking up from the bottom of the cylinder, since the upper half is nice and smooth.

102_2371.JPG

102_2372.JPG

102_2374.JPG

102_2375.JPG

So What I'm seeing makes me think that I need to replace the cylinder, piston and rings. Or (more likely) swap motors and set this one aside for a full tear down.

Your ideas are welcome, I would really like to have things running for the trip to work Monday but I suspect it might not work out that way.
 
CTripps

CTripps

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Aug 22, 2011
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So, what would you recommend? I could replace the parts, but that would leave me wondering about the fragment that might be in the crank case. It doesn't look like it'll be easy to get down into there.
 
N

nightcruiser

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Mar 25, 2011
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CTripps said:
Here we go.....

These should be in the same order going around. Looking up from the bottom of the cylinder, since the upper half is nice and smooth.

View attachment 42132

View attachment 42133

View attachment 42134

View attachment 42135

So What I'm seeing makes me think that I need to replace the cylinder, piston and rings. Or (more likely) swap motors and set this one aside for a full tear down.

Your ideas are welcome, I would really like to have things running for the trip to work Monday but I suspect it might not work out that way.
Click to expand...
I am also interested in what the more experienced riders have to say about this, I would guess you need to replace the top end as you suggested. Personally I would probably follow your second path if possible, swap out the motor and set this one aside for a complete rebuild.
Still I wonder, with all the damage to the piston being below the rings, and all the major damage to the cylinder below the ports, might she still run if you just replace the broken ring(s)? Seems she would still get compression as long as the damage is below the ports and rings???
 
N

nightcruiser

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Mar 25, 2011
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CTripps said:
So, what would you recommend? I could replace the parts, but that would leave me wondering about the fragment that might be in the crank case. It doesn't look like it'll be easy to get down into there.
Click to expand...
The crankcase is easier than you might think to get into, the two halves split apart fairly easy. I was surprised the first time I ripped one appart....
 
CTripps

CTripps

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Aug 22, 2011
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nightcruiser said:
I am also interested in what the more experienced riders have to say about this, I would guess you need to replace the top end as you suggested. Personally I would probably follow your second path if possible, swap out the motor and set this one aside for a complete rebuild.
Still I wonder, with all the damage to the piston being below the rings, and all the major damage to the cylinder below the ports, might she still run if you just replace the broken ring(s)? Seems she would still get compression as long as the damage is below the ports and rings???
Click to expand...
I'm wondering that too. Too bad I can't live stream a 'Skype' style conference call.. it would be interesting to have a few 'armchair mechanics' watching and able to comment in realtime.
 
Ibedayank

Ibedayank

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Oct 29, 2011
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trust me these cylinders do NOT clean up with honing stone in a boring machine...already tried that
bfg=boygofast on Ebay sells just the motor for $85 last time I checked
by the time you order a topend kit and gaskets plus take the time to tear it all down
your in it to the $85 or allmost anyway
 
CTripps

CTripps

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Aug 22, 2011
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Sounds like I have a new pencil cup for the workbench.

Just breaking into a motor kit and am about to see about a change-out.

Follow-up, I'm just waiting for a Logitech update and I should have a (slightly) mobile cam for Skype.

I just created c..tripps as an account. The connection might not be smooth, only 35-55% to the house from here.
 
N

nightcruiser

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CTripps said:
I'm wondering that too. Too bad I can't live stream a 'Skype' style conference call.. it would be interesting to have a few 'armchair mechanics' watching and able to comment in realtime.
Click to expand...
I would guess even if the gauges in the cylinder are below the compression point, just being there will probably be rough on the new rings and could probably make them fail prematurely? I would guess at least a new jug would be in order, at least that way your rings have a smoother ride up and down.
 
V

vincent713

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Jun 2, 2010
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I would definitely change out the jug, it looks damaged enough to lose compression. These engines have very limited horse power and you certainly don't want anything to rob from it. I would check online and see how much it would cost for the top kit with piston & rings and see if it's feasible to replace vs. ordering a bare bone engine.
 
N

nightcruiser

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vincent713 said:
I would definitely change out the jug, it looks damaged enough to lose compression. These engines have very limited horse power and you certainly don't want anything to rob from it. I would check online and see how much it would cost for the top kit with piston & rings and see if it's feasible to replace vs. ordering a bare bone engine.
Click to expand...
Top end kit for 66cc is about $60 before shipping, $74 shipped to my location (from Gasbike.net). BGF on ebay has it listed for $37 with free delivery, and the BGF motor only seems to be selling at $98 delivered....
 
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CTripps

CTripps

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Aug 22, 2011
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Sorry, no pics this time, the camera eats batteries.
Well, it wasn't as quick as I was hoping for (it never is) but before breaking for dinner I got the replacement motor mounted up. It took some time to lap the head and top of the jug, but I'm satisfied with the result. Some red gasket maker and it should be good. Getting the piston back in to the cylinder was tricky, but worked reasonably well for me this time.
Now I should just need to double check my work, add a drop more oil to my tank to bring it in closer to a break in mix, and give it a try. If everything works out, I have a few more minutes ahead after that making the magneto and wiring water tight.
Thanks for doing the legwork for me nightcruiser, I'll probably take a closer look a bit later. Got to get back at it, I ran out of daylight quite a while ago, and I'm not done yet.
 
rustycase

rustycase

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May 26, 2011
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Gosh I'm sry to see how ur motor went south, CT.
How much time did you have on it?

As GN, forst thing I noticed was a lot of ash on the dome, and the little nicks/dings... something was bangin around in there.

I see u got a new motor now... and I'm hopin u follow Alf's new motor page...

...Would someone post a link for this 'red gasketmaker' stuff?
I dunno what it is, and I still don't like it! lol
I just can't see any goop to be as good as a metal gasket on properly lapped surfaces. I'd like to read the specs the producer is claiming for the stuff.

IMO u should run 32:1 for the first 1/2 tank, then go to 50:1 using quality oil.
...but let it cool down after it warms up on a run...
Heck! ur gonna be an ace wrench pretty soon... I'd try Opti2 in the new motor!
It's the newest and bestest with great testimonials here on the forum from competent guys!

Best
rc
 
V

vincent713

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Jun 2, 2010
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Dallas
nightcruiser said:
Top end kit for 66cc is about $60 before shipping, $74 shipped to my location (from Gasbike.net). BGF on ebay has it listed for $37 with free delivery, and the BGF motor only seems to be selling at $98 delivered....
Click to expand...
$37 for the head kit compared to $98 for the bare bone engine hmm that's a big difference to me. I would split the crank case and see if it's still salvageable and get the head kit. This is just my thoughts, what would you guys do?
 
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