compression
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compression
i was just out on the ped and i felt somthing give and then it just died. it now has no compression is there a way to fix this besides buying a new moter?
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Pygmaelion
- Goped
- Posts: 63
- Joined: Sat Dec 31, 2005 7:00 pm
- Location: Poughkeepsie NY
Depends on what's happening...
I lost a "kind" of compression when my reed valve snapped. This meant that any fuel I sucked thru the carb, got shoved back out thru it when the piston moved down (instead of pushing it to the top of the cylinder).
This was an easy fix.. fish out the busted bit of reed valve, and replace it.
The other time I lost compression, I had melted my piston, shoved the rings into the side of it, and generally made a big mess.
This required me purchasing a replacement piston and rings (don't forget to get an expansion ring for underneath the regular one), taking off the cylinder, piston, wrist pin, head... do the acid cleanup thing for the cylinder (Noiseguy put that in the Tech FAQ's)...
in the worst case, you have f*ed up your crank bearings, which shot up into your piston, which deeply scored the side of your cylinder... At that point, you may wish to find a new engine... I have yet to successfully replace crank bearings (mostly because I don't have proper tools, and the one I'm doing now isn't a success yet).
Find out what's busted, take off the head (just the head, don't pull the cylinder off the piston right away), then the carb and feeder neck to the lower engine... Look for nasty black scorch marks where the cylinder touches the crank case, or where the head touches the cylinder (Maybe you lucked out, and it's just a seal)...
Most of all, go slow... if you feel like you're gonna huck a wrench in frustration, walk away for a few weeks until you cool off... It's no good trying to fix a frelled engine when you're *.
I lost a "kind" of compression when my reed valve snapped. This meant that any fuel I sucked thru the carb, got shoved back out thru it when the piston moved down (instead of pushing it to the top of the cylinder).
This was an easy fix.. fish out the busted bit of reed valve, and replace it.
The other time I lost compression, I had melted my piston, shoved the rings into the side of it, and generally made a big mess.
This required me purchasing a replacement piston and rings (don't forget to get an expansion ring for underneath the regular one), taking off the cylinder, piston, wrist pin, head... do the acid cleanup thing for the cylinder (Noiseguy put that in the Tech FAQ's)...
in the worst case, you have f*ed up your crank bearings, which shot up into your piston, which deeply scored the side of your cylinder... At that point, you may wish to find a new engine... I have yet to successfully replace crank bearings (mostly because I don't have proper tools, and the one I'm doing now isn't a success yet).
Find out what's busted, take off the head (just the head, don't pull the cylinder off the piston right away), then the carb and feeder neck to the lower engine... Look for nasty black scorch marks where the cylinder touches the crank case, or where the head touches the cylinder (Maybe you lucked out, and it's just a seal)...
Most of all, go slow... if you feel like you're gonna huck a wrench in frustration, walk away for a few weeks until you cool off... It's no good trying to fix a frelled engine when you're *.
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Pygmaelion
- Goped
- Posts: 63
- Joined: Sat Dec 31, 2005 7:00 pm
- Location: Poughkeepsie NY
The top of your piston is scratched/dented?
Did you find the "offending" particle that's doing all this damage? If it's managed to drop back down into your crank housing, you may end up just coughing it back up on top of it another time.
Is there a dent in your head (cylinder head, not your head) where "whatever' it was smacked between the piston and it? Did your piston smack ito your spark plug?
If you find the offending particle (maybe in your exhaust pipe by now), and you get it out... pull off the whole cylinder, inspect the piston and rings for wear/warp/melt. If your cylinder is unscratched, clean it out really well, and re use it.
Even if the piston is still usable, you may wish to replace it and the rings... you now have just a little more surface area on top of it. If it was running full tilt, and then smacked dead on into the bottom of your plug/mystery particle, it probably damaged it enough to make it no good.
I picked up a cylinder, wrist pin, and new rings for around 25 bucks from VT Cycles (2 of 'em, in fact).
Check for scoring on the side of the cylinder too... could be you snapped a ring, and part of it is hiding... only way to know is to check the rings.
Did you find the "offending" particle that's doing all this damage? If it's managed to drop back down into your crank housing, you may end up just coughing it back up on top of it another time.
Is there a dent in your head (cylinder head, not your head) where "whatever' it was smacked between the piston and it? Did your piston smack ito your spark plug?
If you find the offending particle (maybe in your exhaust pipe by now), and you get it out... pull off the whole cylinder, inspect the piston and rings for wear/warp/melt. If your cylinder is unscratched, clean it out really well, and re use it.
Even if the piston is still usable, you may wish to replace it and the rings... you now have just a little more surface area on top of it. If it was running full tilt, and then smacked dead on into the bottom of your plug/mystery particle, it probably damaged it enough to make it no good.
I picked up a cylinder, wrist pin, and new rings for around 25 bucks from VT Cycles (2 of 'em, in fact).
Check for scoring on the side of the cylinder too... could be you snapped a ring, and part of it is hiding... only way to know is to check the rings.
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Pygmaelion
- Goped
- Posts: 63
- Joined: Sat Dec 31, 2005 7:00 pm
- Location: Poughkeepsie NY
Cool... easy enough then. Replace clip, check rings, clean every surface as if you were going to eat off it. Lube the rings and the cylinder insides. Seat the gasket, insert piston into cylinder, add head, insert bolts and torque to setting (see your owner's manual). check, gap, and insert plug, connect coil to plug.
Kick start it slowly and listen for grinding or clunking... If you hear any, take it all apart again...
If everything's mellow, hit the 'lectric start and see how she flies.
Kick start it slowly and listen for grinding or clunking... If you hear any, take it all apart again...
If everything's mellow, hit the 'lectric start and see how she flies.