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Blown head.
Discussion at Motorized Bicycle Engine Kit Forum in the 2 Stroke Bicycle Engines & Kits forum. So I just got my new head gaskets today. Put one in. Torqued down to 20 Ft-lb and fired ...  | | 
09-15-2009, 01:18 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| |  Blown head.
So I just got my new head gaskets today. Put one in. Torqued down to 20 Ft-lb and fired her up. Immediately it sounded like my head gasket was blown again. WTF?!?! And I could feel gas blowing out of the front of the head. Upon closer inspection I noticed that where the head gasket blew out before the head is very slightly warped. Maybe 1/10th of a mm. But enough to make it not work 
So now I have my non-slant head back on. Which sucks. I really want my slant back.
What can I do? Can I have a machine shop grind it down so it will seal again?? I'm really upset about this  |
09-15-2009, 02:07 PM
|  | Motorized Bicycle Elite Member | | Join Date: May 2008 Location: Fountain Hills, Arizona
Posts: 890
| | Re: Blown head.
can you lap the head (sand it on a piece of glass until flat)???
after seeing the old gasket picture, it looks like you have a ton of compression happeneing tho !!! |
09-15-2009, 02:39 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| | Re: Blown head.
Right now I'm very carefully filing it down. We'll see how it works. If I make it worse, so be it. I can get another one for less than $20 shipped. I just don't want to wait more!! |
09-15-2009, 03:55 PM
|  | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: Mi
Posts: 646
| | Re: Blown head.
Finish it off with some #300 wet/dry on a piece of glass. I think having a machine shop do it may be a bit too aggressive. Last time I had a head ground at a machine shop they just slapped it on this big inverted belt sander for a few seconds then charged me $30. |
09-15-2009, 03:59 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| | Re: Blown head.
So I filed it down so that it is all flat. Then I lapped it on glass to make it shiny. But now the piston interferes with the head
I think this emoticon is a pretty accurate depiction of what I looked like when I slowly turned the engine over only to find it interfered.
good thing I was turning it over from the magnet and not actually started it!! |
09-15-2009, 04:05 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| | Re: Blown head.
And to top it all off my car has a blown wheel bearing, so it probably has 100 miles before leaving my stranded. And my mountain bike is broken. Both of which I'm waiting on parts that will be here next week. So my MB is my only form of transportation unless I want to walk 6 miles to work. Which I don't. But it is looking like it isn't looking good... |
09-15-2009, 04:08 PM
| | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: Mi
Posts: 646
| | Re: Blown head.
Could be worse, your bike could have broken a chain, TSC is 20 miles away and because you've been riding your MB for two weeks straight your truck has a dead battery from sitting. But it's not like anything like that has happened to me or anything.  |
09-15-2009, 04:46 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| | Re: Blown head.
So I used aluminum foil to make 2 extra head gaskets. No interference any more!!
Except running wicked high compression. I was going up the steep hill to my house and it started running like crap. I could feel it getting hot. I hit the kill button, and it kept running for about 5 seconds, it even let me rev it up a bit!!! Then finally died. And yes, my kill button works fine. So it was basically running completely on pre-detonation. I'll try some high octain and see if that fixes it. If it does, it will probably have a lot of power! |
09-15-2009, 04:47 PM
| | Motorized Bicycle Elite Member | | Join Date: May 2009 Location: Maine
Posts: 193
| | Re: Blown head.
Quote:
Originally Posted by Kevlarr  Could be worse, your bike could have broken a chain, TSC is 20 miles away and because you've been riding your MB for two weeks straight your truck has a dead battery from sitting. But it's not like anything like that has happened to me or anything. | Funny you mention that, some thing happened to me. Chain didn't break, but the master link came apart, and it wasn't worth getting a new 415 link because the chain was in horrible shape. But my car's battery was dead (like usual...). I park it on a hill though, so roll down, pop the clutch, and I'm good  |
09-15-2009, 05:24 PM
| | Motorized Bicycle Elite Member | | Join Date: Jun 2008
Posts: 182
| | Re: Blown head.
Quote:
Originally Posted by chrisme Funny you mention that, some thing happened to me. Chain didn't break, but the master link came apart, and it wasn't worth getting a new 415 link because the chain was in horrible shape. But my car's battery was dead (like usual...). I park it on a hill though, so roll down, pop the clutch, and I'm good | reccommended torque for the head is 10 lbs per inch...20 might pull your head bolts out of the cheap threads....over torqueing can cause warpage...Dennis | | Thread Tools | | | | Display Modes |  Linear Mode | 
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