Pulling the TZ250 motor
 

I have decided to send out my TZ250 motor to MCE racing in CA for a full rebuild. Despite the mechanical downtime on the 250, it is still worth riding it. I have a full rebuild kit on order and when it arrives, I will pull the motor and send it out to Kevin Murray.
Upon its return it will have a new crank shaft, new pistons, new heads, bearings, seals and other related items. I expect that with a professional rebuild like this, I should have an easier time keeping it running properly. I just got frustrated with the unexpected items crapping out on my 1995 motor and going fresh with all new parts.
Should prove to be a good thing for the bike anyway. After this I should be able to keep up with scheduled maintenance a whole lot easier.
Ken

Cool stuff Ken. Lots of pics. Need any help let me know, be cool to check it out.

Be assured I will take plenty of pictures...it's the Japanese tourist gene I have... can't be helped. LOL

Ken

Nice dude!

Is that typical? Seems like a huge labor of love. Either way you're doing it right for sure.

Not typical, but needed. Mine is a 1995 and I know it was never professionally serviced. I am still a 2 stroke newbie and my aim is to get this thing back into shape and make it reliable. Replacing all of the expendible parts at once and having qualified hands get a look inside at the same time will be something that will give me the confidence I need to run it for 2008.
It will also give me a solid timetable to run with leaving me near zero surprises. So, at 300 mile intervals I can change top ends and at 1200-1500 miles I can change out the crank. That should be the only things I need to worry about next season other than tires and fuel.

Ken

just jet it fat and you should not blow it up!

Ken,

There are a few things you need to know / do when you get your motor back.

1. power valve cable setup
2. Timing
3. Break-in Procedure...Oil ratio change, Heat Cycles and run time.
4. 95' Carbs?...Well then you need to rebuild your carbs if you not already done so. The parts in the carbs wear and you would not believe how much difference it makes. Your motor will not work / run as hard and you gain HP.

He owns a TL so hes used to it:lol:

Tom

Thanks, I will keep that in mind. + Welcome aboard. Are you a member at www.tz250racing.com? Here are some pics from Summit Shenandoah over Labor Day.
Ken
http://i20.photobucket.com/albums/b2...0/TPMS8066.jpg
http://i20.photobucket.com/albums/b2...0/TPMS6615.jpg
http://i20.photobucket.com/albums/b2...0/IMG_3013.jpg

Very True...LOL

Nice bike!

Thanks for the welcome!...Yes, I'm a member of that site as well. I've been building and racing 250's for 15 years and they're AWESOME bikes to race on.

There a few little tricks you can do to gain more reliable power. Let me know if need some help.

I also make parts for Yamaha TZ 250's...pegs, fairing ears, brembo master cyl replacement washers and knobs, cush drive etc.

Sounds good, I will probably drop you a line when the motor comes back. I am just waiting for RSCYCLES to return before I can get my rebuild kit and new crank on the way.
I may have some gearing/jetting questions for you. I am trying to put together the gearing/jetting for different tracks so I can run the longer tracks as well as the smaller ones effectively.
I may be interested in getting some spare pegs..just in case.
Ken

Sure no problem...Glad to help out. I also sell DZUS 1/4 Fasteners if you need any.

Ken,
don't listen to Carl.
Jet it as lean as you want, especially in 40 degree weather and skip that stinky oil. Custom welded pistons are the HOT setup!


Seriously, glad to see th TZ getting some TLC. Looking forward to seeing it in the spring. :nod2:


This piston was the result of too little oil (spilled some in the wind mixing in the tank) and a little too lean at 1/4 throttle. Bigger main was not enough. It ran PERFECT, plug was nice and brown. Rolled off after a bonzi fireroad blast and she locked up tight.

Looks like a cylinder repair will be in the works. What bike is this?

Drop me a PM with prices for a set of pegs.
thanks
Ken

2007 KTM 300 XCw.. I told him to go up one size on the pilot jet! :doh:

I could be wrong but it looks like there is a cracked port. If the port cracks then it will suck in air and seize on off throttle.

Millenium Technologies fixes cylinders really good.

I don't really think it was the jetting... even the manual recommends a 35 pilot at 30 degrees F. I put a 42 in it in Sept.... I don't think raising the needle 1 click would have prevented melting my piston.

Also, the main is a 165, stock is a 162. My jetting is richer than the exact same motor I has running next to, but he runs more oil in the gas. I had 50:1 to start with and probably screwed up at the gas station, running it even leaner.

guess I was due for one :nopity:
I haven't blown up a bike since 1990 and even that was just experimenting with base gasket changes and squish rings.

I think what you saw was casting flash. I'm going to clean that off before the I send out the cylinder.
I wish I could blame it on that... right now, I'm blaming myself :wtf: :lol:

Planning to send it to powerseal as soon as my head and piston come back.

Ken,
Are you doing a "factory" rebuild or making any changes while it's opened up?
I hear the TZs are pretty hot as-is.

More than likely it will be kept to stock specs. I may opt to have some head work done on one of my older sets of heads. I have one NEW set of OEM heads going into the motor and I would like to have a spare set machined to match them as a backup. While the motor is there, I will more than likely be needing at least one of my cylinder sets to be replated before the start of next season.
Its gets expensive pretty quickly. I am quite happy with the power to weight ratio of the TZ250 as is. I can only expect it to run better just with the simple rebuild. I don't plan on doing much actual racing, so the extra engine mods are not going to be cost effective for me. If I were to race one, i would probably opt to purchase a newer version of the bike.

Ken

Motor is out, now I have to find a suitable shipping container.
Ken

Ken how big is the motor? Find a plastic container barrel that they use to ship stuff in.

Something like this http://images.google.com/imgres?imgu...n%26safe%3Doff

The motor is pretty small. I was going to try Home Depot and grab a plastic storage bin and pad the motor inside of one of those if I can find one that will hold up to the trip in both directions.
I will probably use that foam insulating spray inside a plastic trash bag to make a custom fit pad to protect the motor. I ordered a replacement rim for my Explorer once and the new rim came sandwiched between two trash bags filled with foam insulation. The bags contained the foam, but the foam formed perectly around the part and once it hardened, it protected the new wheel. The same should work great with the motor.
My only concern is finding a container that will stand up to the round trip.
Ken

A square container would probably work better.
Ken

Alot of people use a cooler.:ride:

Just got the TZ250 cylinders back from re-plating. Should be getting the motor back together in a week or so.
New heads too..should be good to go for my first track day in April.
Ken
http://i20.photobucket.com/albums/b2.../TZ250/006.jpg
http://i20.photobucket.com/albums/b2.../TZ250/005.jpg
http://i20.photobucket.com/albums/b2.../TZ250/007.jpg

They look pretty.

Cool pics..you can see the cross hatches from the honing.. looks good man!

Nice Ken - Be certain that the port edges are not sharp.
They look like they are good to go but verify that just to be sure.
It's hard to tell from the pictures.

I made that mistake once and had a piston ring shatter
on the sharp edge of a transfer port after building up an
entire Kawasaki 100 from scavenged parts back when I
was about 12...I remember thinking:
"What the hell just happened? oh well, it's still running so it can't be that bad."
:doh::lol::doh:

Rob
it was the first thing I checked when the barrels came back. They did a good job of dressing the edges of the ports.
thanks
Ken
http://i20.photobucket.com/albums/b2.../TZ250/009.jpg
http://i20.photobucket.com/albums/b2.../TZ250/005.jpg

Ay,
You start puttin her back together yet?:ride:

today it begins..

Got the motor completed today, just have to pressure test it. I put in a new clutch cover, new heads, replated cylinders, new pistons, bearings and some other stuff.
If I get the pressure testing done soon, I will fire it up and get it ready for the next track day.
Ken

Update.
I just got finished pressure testing the motor.
I have the left cylinder holding pressure at 6PSI. THe intake manifold was leaking air and it took a little while to find the leak. Now its A-OK.
The right one (forward cylinder) is leaking air into the cooling system. I pulled the head and re-sealed everything and checked the o-rings. Everything looked OK, but it still leaks. I have to pull the barrel now and check the base gasket to see that there is adequate sealant on the case/underside of the barrel.

I was also sent the wrong heads and I had to return them to RSCYCLES.com for an exchange. While I was at it, I ordered the replacements to be from a 2000 TZ125 and I am having Roland Cushway machine them for the TZ250. Looking forward to getting those installed on the motor at the next top end rebuild.

Tomorrow morning, I will be pulling the barrels again and re-checking the base gaskets and applying a little more Yamabond to everything. Sucks that I ran out of time today I have to head into work now. I am hoping that this takes care of the air leak. I would like to get the motor back into the bike this week so I can have my 250cc lawn mower back on the track soon.

Ken

It will be all worth it in the end!
I am pulling mine apart tonight... new bottom end is needed I fear.

Turned out to be my front cylinder base gasket. Some high heat silicone and that was it.
All buttoned up and ready to re-install.
Ken