lost compression

peezy

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well, i am going to change the subject from the title. (sorry about that)


is there a way i can learn how to re build a 2 stroke 125 engine? a guide of some sort?

also what does it mean if the engine lost compression?
 

bomber

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I'm not an expert, but a decrease in compression can mean a couple of things. It could be from the piston rings and cylinder wall wearing each other so there is slight gaps, could be a hole in the piston head, could be a gasket leak, or even a mechanical problem with the exhaust valve (I think this one is not likely tho).

Eric Gorr has a great site that is very helpful and full of info. His main site - http://www.eric-gorr.com/ and his 2 stroke rebuild guide - http://www.eric-gorr.com/2 stroke top end and performance.pdf
 

Dezertpilot

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A 2-stroke is the easiest thing in the world to rebuild. And cheap!!!!
 

kenaroo

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[video=youtube;-FFIWtqU5Zc]http://www.youtube.com/watch?v=-FFIWtqU5Zc[/video]
 

rmracer09

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when i rebuilt my cr250, me and my dad just followed the owners manuel when we needed guidence.
 

kenaroo

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Humm.. just rebuilt and got bad compression.... sounds a little strange....

I'd ask him a few things like what oil mixture and brand of oil was he using? how was he mixing the gas? some time people get lazy and mix oil in gas tank and it doesn't mix well or too much oil will seize a bike too.

does the bike crank over? could be more like the lower end going(crank bearings) or crank seal bad letting air in

could be the guy is just mechanically inept and didn't rebuild it correctly or mixed the gas wrong

regardless. if he's selling that cheap.. you really can't complain. a total engine rebuild for that bike would be pretty cheap (bearings, seals, crank, piston less than $600)
 

cosmo

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You can easily get into a world of trouble. Wrist pin clip falls into the crank,wrong parts (A, B, piston?)Catching a ring on a port. Get the manual and READ it. Get GOOD tools, go and work with some one who IS experienced . Seems like you have asked this same type question(s) before?
 

peezy

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the dude wont email me back.
 

cosmo

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He's maybe read all of this and has second thoughts. If I were you, you're young,anxious to buy "something". WAIT. Save up some money,do your homework, buy a bike either new, or from someone that won't take advantage of you. How can you trust someone? You can't, but, you can try and buy from someone local, and bring along a buddy who can spot trash from a a good bike.Ask, if you can take the bike to a shop (dealer) for an inspection. If they balk, say thanks and walk away. Don't be in a rush to buy. There's lot's of bikes for sale. Shoot, hire me to come and look at a bike for you. I have either bought new or from someone I knew and trusted.
 

kenaroo

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He's maybe read all of this and has second thoughts. If I were you, you're young,anxious to buy "something". WAIT. Save up some money,do your homework, buy a bike either new, or from someone that won't take advantage of you. How can you trust someone? You can't, but, you can try and buy from someone local, and bring along a buddy who can spot trash from a a good bike.Ask, if you can take the bike to a shop (dealer) for an inspection. If they balk, say thanks and walk away. Don't be in a rush to buy. There's lot's of bikes for sale. Shoot, hire me to come and look at a bike for you. I have either bought new or from someone I knew and trusted.
Ditto: you deserve to get a good bike for the money.. not someones crap.. there are deals out there.. keep looking...
 

peezy

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i got a bike, so i am happy =D
 

Vtr_Racing

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Have someone check the cylinder and make sure its within specs. Sleeve it/bore it or whatever you have to do. Change the crank seal while your at it just to be safe. Run good oil and you should get plenty of use from it. May have your mechanic check the rod while your at it and have the cylinder off.
 

peezy

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well, the guy changed the oil the day i went to look at it, you had paper work on when you took the engine to get rebuild (new transmission or something) he broke the 3rd gear or something like that. it runs and sounds awesome, i will be checking some stuff too.Sleeve it/bore ? how much would that cost me?
 

cosmo

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well, the guy changed the oil the day i went to look at it, you had paper work on when you took the engine to get rebuild (new transmission or something) he broke the 3rd gear or something like that. it runs and sounds awesome, i will be checking some stuff too.Sleeve it/bore ? how much would that cost me?
Good luck with your purchase.
 

peezy

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instead of posting an other thread, i will just ask it here.

1. i bought the bike, for 1000. the sprocket teeth are not to bad, but can need a new one later one. if i did get another one, how many teeth should i get for dezert?

2. what are some good front tires?

3. whats a brand of a bike stand (like the ones that use the foot to lift it?)

4. he gave me 2 headers one, for a 2005/2006 he said, stoke i would think but i am not sure, if i plan on to sell it how much can i sell it for?

thanks, for all the help. i know this is not a bike place, so where is a good forum for yzf's?
 
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