rebuild problems

2strokeff54 · Mar 25, 2009

me and a friend rebuilt his 97 i think kdx 220r started it up in a few kicks afterwards and broke it in for a whole day. at the end of the day the bike shut off on the way out to the truck and lost alot of its compression. we took it home and washed it off and started messin with it and he can jump start it down his driveway but cant kickstart it and it has very low compression. he didnt have the engine honed(spl?) or bored out when we re built it. do you think it blew up again?

IndyMX · Mar 25, 2009

Sounds like it.

Take the cylinder off and see what's up.

glad2ride · Mar 26, 2009

Take it apart and inspect it.

2strokeff54 · Mar 26, 2009

i am not new to riding but i am new to rebuilds(cash is tight learn to do it myself or scrap the bike) what will i be looking for to tell if its blown or not. thanks fellas

IndyMX · Mar 26, 2009

2strokeff54 said:
i am not new to riding but i am new to rebuilds(cash is tight learn to do it myself or scrap the bike) what will i be looking for to tell if its **** or not. thanks fellas

I'd say your best bet is to tear it down, take some CLEAR, IN FOCUS pictures of the various parts.. Cylinder, piston, rings, rod, bearings, crank & head.. And post them on here.

Make sure they are clear. And show different angles.

Also, just to make it a lot easier for people on here to help you diagnose the problem, make sure the pics are clear and in focus..

I stress this, cause it seems so many people post pics asking for help but can't seem to grasp that simple concept.

2strokeff54 · Mar 26, 2009

ok thanks indy. ill tell him and se eif he will let me tear it down

liven07 · Mar 30, 2009

Well man i dont know what u call a rebuild if u did not bore the cylinder. If you are spending the time doing a rebuild you should have the cylinder
bore, if it did not need to be bore it most likely did not need a rebuild. If it did not run do to no compression it should have been bored with a over sized piston. Check for nicks inside the cylinder, this could mean a blown lower rod or main bearing blowing chunks of crap in your piston and cylinder. These parts could seem to turn fine when turn by hand when you got the cylinder off, but could be out if you did not replace them. It is most likely your cylinder just needs to be bored with a new piston kit and gaskets. Hope this helps.

KIWI KDX · Mar 30, 2009

liven07 said:
Well man i dont know what u call a rebuild if u did not bore the cylinder. If you are spending the time doing a rebuild you should have the cylinder
bore, if it did not need to be bore it most likely did not need a rebuild. If it did not run do to no compression it should have been bored with a over sized piston. Check for nicks inside the cylinder, this could mean a blown lower rod or main bearing blowing chunks of crap in your piston and cylinder. These parts could seem to turn fine when turn by hand when you got the cylinder off, but could be out if you did not replace them. It is most likely your cylinder just needs to be bored with a new piston kit and gaskets. Hope this helps.

mate thats CRAZY!!! u dont have to rebore every time you do a rebuild, i have been putting new piston and rings in old cylinders without even a hone for years.

and to say "if it doesn't need to be bored, it dosen't need a rebuild" thats just stupid!

IndyMX · Mar 30, 2009

liven07 said:
Well man i dont know what u call a rebuild if u did not bore the cylinder. If you are spending the time doing a rebuild you should have the cylinder
bore, if it did not need to be bore it most likely did not need a rebuild. If it did not run do to no compression it should have been bored with a over sized piston. Check for nicks inside the cylinder, this could mean a blown lower rod or main bearing blowing chunks of crap in your piston and cylinder. These parts could seem to turn fine when turn by hand when you got the cylinder off, but could be out if you did not replace them. It is most likely your cylinder just needs to be bored with a new piston kit and gaskets. Hope this helps.

More bad advice, by someone with limited knowledge and little life experience.

mudpack · Mar 30, 2009

TO THE OP: first thing: pull the piston, and check it and the rings. If they look good, measure ring end gap.

liven07 · Mar 30, 2009

My limited knowledge has gotten threw the better part of almost a 100 engine rebuilds of cars, bikes, sleds ect. . I am going to stand by my advice and say that a piston and rings kit is not going to completely fix a compression problem.If your engine had enough wear that you had to replace your piston and rings, the chances are your cylinder has wear also, and putting piston and ring kit in a good running engine (if this is the case)is a waste of time and money. Also when you buy a piston the machine shop waits for the piston to come in first because, lets say you bore a cylinder .010 over the piston is sometimes almost .002 of a inch off and they size the cylinder to the piston. So just throwing in a new piston in a old jug is is kind of half assed.

julien_d · Mar 30, 2009

My limited knowledge has gotten threw the better part of almost a 100 engine rebuilds of cars, bikes, sleds ect.

Yikes. I must wonder about the poor saps that trusted your judgement when you told all of them their cylinder had to be bored over to replace the rings. A simple re-ring job suddenly turns into boring and replating the cylinder and purchasing an oversize piston and ring set. OUCH.

Keep in mind, a 2 stroke motorcycle engine is NOT a car engine. The rings are the wear item, followed by the piston. A well maintained top end can carry the stock plating and bore size for a very long time.

KIWI KDX · Mar 30, 2009

liven07 said:
My limited knowledge has gotten threw the better part of almost a 100 engine rebuilds

well if you rebored every engine, of those 100 rebuilds, i could have rebiult 1000 engines and still spent less than you.

"juilen_d" said it rite, it starts to get real expensive when you start re-boring, re-plating and buying oversized top ends, especially when you could just put a standard piston and set of rings in!

it mite be time to admit that you are wrong mate!

liven07 · Mar 31, 2009

I would not turn a simple re ring job into a bore for one but i have read what i wrote in the first place and i got to admit i did not word that for sh-t. I would not want any to believe you have to bore the engine every time you are doing some internal work or want to freshen the motor , im sure they are plenty of examples but i was basing the information on the fact he already replaced his piston/rings and lost compression after a day of riding and he may or may not have gave it a rebuild in the first place do to the engine being blown. I think a guy up the line here is right you just have to take it apart and see whats up. Im sorry if i gave misleading advice.

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