KTM rebuild - Sportbike Addicts

***carl_g*** · 05-15-2008, 08:42 AM

I know it is not a sportbike, but nonetheless it is my bike and 2 weekends ago I blew up the bottom end during a race.
I need to split the cases and replace the crank. I will also replace the piston and rings while I have it all apart.
Here is my progress so far of taking off the top end.

Head (needs to be cleaned up)

Engine

Cylinder & top of piston

Power valve actuating arm

Cylinder - doesn't look bad at all!

Another cylinder shot.

This weekend I will split the cases so stay tuned for more..
oh yeah wish me luck

ronin_01r1 · 05-15-2008, 08:55 AM

take lots of pics! GL.

NYCSTRIPES · 05-15-2008, 11:14 AM

What controls the power valve?

The head gasket design is very similar to the TZ50 I have. Personally I wish it was something more substantal than these little o-rings.

bondo · 05-16-2008, 08:39 AM

Looks good Carl.
I guess you could consider it a little "unplanned maintenance"
There's a lot of hours on that bottom end and a fresh engine will be nice to have next time you are 20-30miles into the woods.

I think I might start carrying a buddy tow rope too.

The guy who parked next to us at the Curly Fern was the owner of powerseal. They did my cylinder.

Behold

bondo · 05-16-2008, 08:44 AM

Quote:

Originally Posted by NYCSTRIPES

What controls the power valve?

The head gasket design is very similar to the TZ50 I have. Personally I wish it was something more substantal than these little o-rings.

Hey Ken,
Centrifugal force and 3 different springs with a screw adjuster. You can adjust the power/exhaust valve to operate any way you'd like. Tune the power so it's just right.

O-rings are simple and it's all you need with relatively low cylinder pressure/heat. I like 'em! If it was a turbo I-4 drag bike, then some nice copper/bronze head gaskets with metal o-rings machined into the block are necessary.

NYCSTRIPES · 05-16-2008, 01:43 PM

Quote:

Originally Posted by bondo

Looks good Carl.
I guess you could consider it a little "unplanned maintenance"
There's a lot of hours on that bottom end and a fresh engine will be nice to have next time you are 20-30miles into the woods.

I think I might start carrying a buddy tow rope too.

The guy who parked next to us at the Curly Fern was the owner of powerseal. They did my cylinder.

Behold

Powerseal does nice work. They replated the barrels on my TZ250 this spring. I am pretty happy with the quality of the work.
Ken

Ant · 05-19-2008, 10:06 PM

Yeah Carl!

***carl_g*** · 06-06-2008, 08:44 AM

I have been sort of lagging on this project while waiting for parts to come.
I made some good progress last night.

Here you can see I took off the main clutch case cover and took apart my autoclutch.

I also pulled the flywheel and stator off..

I will have an impact wrench tonight to get the primary gear off and then I will finally be able to split the cases and send out the crank to be rebuilt.
Thank god for friends having extra bikes with the willingness to let you beat on them

NYCSTRIPES · 06-06-2008, 11:30 AM

who's rebuilding your crank? Local?

With the TZ250, all you need to do is wedge a penny into the primary gear and you can use standard tools to loosen the nut. From the angle of the picture I can't tell if that's possible with your bike.

Ken

***carl_g*** · 06-07-2008, 12:37 AM

Quote:

Originally Posted by NYCSTRIPES

who's rebuilding your crank? Local?

With the TZ250, all you need to do is wedge a penny into the primary gear and you can use standard tools to loosen the nut. From the angle of the picture I can't tell if that's possible with your bike.

Ken

The crank is getting sent out to this guy in KY. He goes by the name of Mr Crankshaft and he has been super helpful and there has been excellent communication.

Here are some pics of my progress tonight.. finally the cases are split!

Engine out of the frame..

another engine pic...

Make sure you read the shop manual

BAM! Split cases.

Inside of left half of engine.

The reason for all this work..bad crank.

Inside of the right half of engine.

NYCSTRIPES · 06-07-2008, 10:39 AM

looks like you're on your way. the mr. crankshaft website claims a quick turn around...hopefully you'll be back in business quickly. Question..the green stuff on the engine case...is that a rubberized or paper gasket ? or is that silicone?

Ken

***carl_g*** · 06-07-2008, 10:58 AM

Quote:

Originally Posted by NYCSTRIPES

looks like you're on your way. the mr. crankshaft website claims a quick turn around...hopefully you'll be back in business quickly. Question..the green stuff on the engine case...is that a rubberized or paper gasket ? or is that silicone?

Ken

paper gasket..

**John712** · 06-07-2008, 10:52 PM

oh man, and i though my bike was in pieces!

Ant · 06-09-2008, 09:49 PM

why are the rear cylinder bolts corroded?

NYCSTRIPES · 06-09-2008, 09:54 PM

probably from a coolant leak..just a guess.
Ken