Another 2 stroke revival

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SlowMoFo

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7/17/2012 9:27 AM
Edited Date/Time: 7/17/2012 9:28 AM

I found this 04 YZ125 locally and couln't pass it for the price. The guy couldn't get it started and it had been sitting for a year in his garage so after a few offers and back and forth arm twisting I loaded it on my truck for $400! The bike has low compression but everything else is there. It has an FMF muffler and handguards but other than that, its all stock. I am starting the teardown today so stay tuned, I will update as I make some decent progress. Should be fun!


"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

Flesh206

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7/17/2012 11:11 AM

I've been trying to get my old 01 CR125 back. It has about 3 years of actual use on it been sitting in my buddies garage ever since. Offered him $800 a few months ago nothing has turned up yet but I'm still waiting him out. Anyways it looks like you got a steal for $400 man!

headache

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7/17/2012 11:12 AM

Dang I wish i could find a deal like that! Good score

If you aren't premixing, then your just pretending!

Leader of the 2stroke Taliban (Northeast Arkansas Chapter)

Lawrence929

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7/17/2012 11:43 AM

This guy just brought a 2003 rm125 into our shop. Looks pretty damn ok. Paid $500. Of course he won't sell it. i rode the damn thing, like a moron, now my 2011 RmZ 450 is for sale. I was thinking, hmm, i ride for fun. Let's drop $2000 total and have a pimped out 125 and just see who I can run with. Built in excuse for when I suck just as bad as before.

rallendude

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Location: Adger, AL USA

7/17/2012 11:53 AM

I'm going to be having a two stroke "revival" over the next couple of weeks. My '09 Service Honda went bang at Monster Mountain this past Saturday. Not looking forward to finding out what let go.

Mr. Ted

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7/17/2012 12:12 PM

Nice find for $400 bucks. That'll clean up nice!

Indecision is a choice

dboivin

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7/17/2012 12:13 PM
Edited Date/Time: 7/17/2012 12:14 PM

prolly have to pull top end and send out cylinder for recoat. i've had to do it like 3 times in last 4 months on yz125s around here that were brought to me. the bridge on the exhaust port gets rubbed raw and eventually eats the front of the piston/rings...and they lose compression.

newmann

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7/17/2012 12:28 PM

I like those steel framed YZ's. Like those RM125's too Mr. Lawrence. Fun bikes.

SlowMoFo

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7/17/2012 12:41 PM
Edited Date/Time: 8/2/2012 9:58 PM

dboivin wrote:

prolly have to pull top end and send out cylinder for recoat. i've had to do it like 3 times in last 4 months on yz125s around here that were brought to me. the bridge on the exhaust port gets rubbed raw and eventually eats the front of the piston/rings...and they lose compression.

I am hoping for the best. I have done 2 myself and one was mint, the other needed to be replaced. Im tearing it down right now. Should have pictures soon.

"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

Lawrence929

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7/17/2012 12:42 PM

newmann wrote:

I like those steel framed YZ's. Like those RM125's too Mr. Lawrence. Fun bikes.

newmann it was so freakin fun to wind it out! It wasn't even on the track, just in a field by the shop. I forgot how they only go about 10 feet in each gear then you shift. Oh, and how they feel really good up in the revs. I'm so used to a 450 that you lug and short shift that it's insanely neat to have these flashbacks! Why the Fack don't they make these bikes still? It's crazy.

Katoom72

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7/17/2012 2:05 PM

Is the seller nuts or something?

SlowMoFo

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7/17/2012 3:16 PM

Katoom72 wrote:

Is the seller nuts or something?

The guy is a physician assistant and has lots of toys. I guess he didn't wanted to pay for the rebuild.

"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

Katoom72

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7/17/2012 3:19 PM

Katoom72 wrote:

Is the seller nuts or something?

SlowMoFo wrote:

The guy is a physician assistant and has lots of toys. I guess he didn't wanted to pay for the rebuild.

So nuts it is

SlowMoFo

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7/17/2012 3:33 PM
Edited Date/Time: 8/2/2012 9:59 PM

So the bike is all apart and this is what I found out. The piston hit the top of the exhaust port and broke the ring. The piston messed up the sleeve so now comes the debate on how to proceed. Should I fix this one or should I get a new jug? Heck, I might go with a big bore kit. We'll see, I have to do some research. The rod has a little of play side to side but its not too much and if I remember correct, it should have a little. Anybody can verify this?



"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

andymoto

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7/17/2012 4:00 PM
Edited Date/Time: 7/17/2012 4:05 PM

I'd recommend splitting the cases and replacing the rod w/bearing, crank seals/bearings, gaskets and check the tranny thoroughly for any excessive wear without a second thought.

NeWskoolmxer

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7/17/2012 4:12 PM
Edited Date/Time: 7/17/2012 4:14 PM

144 kit all the way .

" To hell with them. When history is written they will be the sons of bitches - not I. "
Harry S. Truman

rallendude

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7/17/2012 4:30 PM

Either stock or over size send it to Millenium Technologies and have them fix it. 144 would be cool. Side to side you should have a little play but no up and down.

newmann

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7/17/2012 4:49 PM

Millenium Tech for the cylinder repair/replate if you are keeping it a 125. Don't know too much about the big bore kits on those. A complete factory replacement crank is sometimes less expensive that parts and labor to rebuild a crank. Compare first.

reded

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7/17/2012 4:55 PM

newmann wrote:

Millenium Tech for the cylinder repair/replate if you are keeping it a 125. Don't know too much about the big bore kits on those. A complete factory replacement crank is sometimes less expensive that parts and labor to rebuild a crank. Compare first.

Agreed, Millenium does top notch work!

PRM31

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7/17/2012 5:46 PM

144 kit!

mx5471

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7/17/2012 6:07 PM

It's an older bike. You don't know what hasn't been done to it. Do it right once and it will save you money. Millenium is great. But please, don't waste your money on an Athena 144 kit. Many shops can do that for you, for less, with better results. They are junk,from personal experience. Others here will agree. You should redo the cylinder, and Millenium will do it for less than a new one, and 144 it while you're there. Go with an OEM crank. About $75 more than aftermarket, but is rock solid. You will have to grind the cases for the 144, but it's easy, because you're splitting the case anyway. Do it right and you got a sweet ride, and tons of fun. On a side note, some the YZ125's like 95 or higher octane, and higher is better. They like to do the detonation thing with low octane gas.

Saltybrad

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7/17/2012 6:14 PM

Buy a new jug, a piston kit and put it back together. Don't bother with the cases for no reason.

machine

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7/17/2012 6:23 PM

Call Eric Gorr, he does a good 144 kit and he has different porting options depending on the type of power you want. I believe he uses Millenium too. All for around 450.00

.

Katoom72

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7/17/2012 6:24 PM
Edited Date/Time: 7/17/2012 6:26 PM

If it has no lateral play (up and down) on the rod and crank then you're good. Aixal play (left to right) is normal if it's not to mutch. look for the tolerance and measure it Get the cilinder fixed or a 144kit and haul ass. If you realy want to be sure you can pull the cases but i would do the top-end first and see how it goes. You can still split the cases after the top-end rebuild if you are not satisfied. The only thing you lose from it if u got to do the case afterall is a gasket.

SlowMoFo

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7/17/2012 6:47 PM

Katoom72 wrote:

If it has no lateral play (up and down) on the rod and crank then you're good. Aixal play (left to right) is normal if it's not to mutch. look for the tolerance and measure it Get the cilinder fixed or a 144kit and haul ass. If you realy want to be sure you can pull the cases but i would do the top-end first and see how it goes. You can still split the cases after the top-end rebuild if you are not satisfied. The only thing you lose from it if u got to do the case afterall is a gasket.

There is no play up and down on the rod. I am going to send the jug in to millenium for a repair (Thanks newman). I already ordered new plastics and some touch up paint from colorrite.com. I will get in touch with Millenium tomorrow to get the jug going! I also need to go through the carb and clean it and put some elbow grease on the muffler. Will update sometime during the week.

"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

NP301

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7/17/2012 8:26 PM

Use this guy STR Performance Engines

I love the 153 he made me, simply amazing.

SlowMoFo

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7/21/2012 5:09 PM

Little update:

The cylinder went out to Millenium to get it opened up a little. I went with a 56mm bore because I didn't want to split the cases this time. That will give me some room for expanding later. I also cleaned up the FMF muffler and painted the expansion. In addidion, I received the front wheel bearings and will be installing those tomorrow. I am waiting on the paint so I can touch up the frame. Plastics and graphics are also on their way. More to follow.



Exhaust all cleaned up

"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

Hando

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7/21/2012 7:32 PM

if you're a big guy go wit the 144

if you're a 125 size rider

KEEP WORKING, MILLIONS ON WELFARE DEPEND ON YOU!

SlowMoFo

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7/21/2012 7:56 PM

Hando wrote:

if you're a big guy go wit the 144

if you're a 125 size rider

I am 190 lbs but this will just be a play bike to ride in the woods. I have a 450f for the "try to go fast days"!

"Don't allow native morons to breed and keep foreign ones out" -Dr. Henry K. Goddard-

loftyair

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7/22/2012 12:10 AM

ALWAYS send new piston to MT for correct clearance. If not, make sure the finish has the right tolerance to the piston you end up getting BEFORE putting it together!