KTM 300 2-stroke bottom end engine rebuild

[KTMphil]

It was about time for a new piston for the KTM 300 2-stroke, so off to Nung to get it installed


11066754_529790373829450_1447448317_o by Triangle Golden 007, on Flickr



Looked like it was really about time by the state of it when it came out

11064235_520159574792530_1419508683_o by Triangle Golden 007, on Flickr



Lots of carbon and the needle bearing was almost destroyed


11065032_520163154792172_1703856077_o by Triangle Golden 007, on Flickr





It had become really hard to start cold, you can see the blow-by around the rings


11067582_520160598125761_1240347549_o by Triangle Golden 007, on Flickr

 

[KTMphil]

With the cylinder head off, Nung was horrified how much sideways play there was in the conrod and advised new conrod and big end bearings


11069411_520161548125666_345387408_o by Triangle Golden 007, on Flickr




11045902_520162674792220_2068831032_o by Triangle Golden 007, on Flickr





As you can imagine none of this was going to be cheap .... quickly from Singapore it all came to USD$ 650


11072315_10153731018928345_1447526163_n by Triangle Golden 007, on Flickr




Conrod, beautiful bearings, gaskets and oil seal kit







2 days and it was here


11063145_10153730862698345_1319140204_n by Triangle Golden 007, on Flickr




So now time for major surgery, everything apart


11070592_520157324792755_1024607887_o by Triangle Golden 007, on Flickr

 

[KTMphil]

Cases split pushing out the old bearings

11153445_529389520536202_264829217_o by Triangle Golden 007, on Flickr


e by Triangle Golden 007, on Flickr





d by Triangle Golden 007, on Flickr



The old stuff


f by Triangle Golden 007, on Flickr







New conrod

11088017_529389577202863_301561313_o by Triangle Golden 007, on Flickr




New bearings, the roller bearing to the right is an industrial work of art

11100878_529389440536210_831228157_o by Triangle Golden 007, on Flickr




New conrod


a by Triangle Golden 007, on Flickr

 

[KTMphil]

A successful day


11132441_529389363869551_879085639_o by Triangle Golden 007, on Flickr



Celebrations


11144692_529442143864273_2096801694_o by Triangle Golden 007, on Flickr




Reed exhaust valve is chipped and will need repairing


11141643_528566140618540_665791107_o by Triangle Golden 007, on Flickr




Barrel before a clean


11070315_520157554792732_264336497_o by Triangle Golden 007, on Flickr




Now


11148284_529439140531240_1060794355_o by Triangle Golden 007, on Flickr




Piston kit


c by Triangle Golden 007, on Flickr





Nung looking relaxed, no left over bits yet


11137441_529391437202677_1305784374_o by Triangle Golden 007, on Flickr




11147896_529448620530292_1389712782_o by Triangle Golden 007, on Flickr





New gaskets


11065353_529392313869256_204218632_o by Triangle Golden 007, on Flickr





Torque wrench in Thailand !!!!


11069768_529397023868785_2138537570_o by Triangle Golden 007, on Flickr





11130971_529453717196449_571818906_o by Triangle Golden 007, on Flickr





Head back on


11132414_529453593863128_1911056728_o by Triangle Golden 007, on Flickr





Carb gets a douching


11132103_529912363817251_306338145_o by Triangle Golden 007, on Flickr





Get the exhaust back on and we're almost there

11137699_529881647153656_801027088_o by Triangle Golden 007, on Flickr




11132332_529886103819877_544378491_o by Triangle Golden 007, on Flickr



Hopefully tomorrow running all fresh with air filter oiled




air by Triangle Golden 007, on Flickr

 

[KTMphil]

Bike is back and running good, some people have said use the "hot run in method"


Ride bike at a moderate RPM level until its at full operating temp. Dont hold it wide open. Dont just sputter either.

Let motor cool all the way down.

Repeat X3.

Mix it with the good stuff Motorex, Motul Etc...

I use 60:1.

No issues




Nung thinks its been run to lean at 15ml per liter of 2 -stroke mix, advises going to 18-20 ml per liter. He also swears by PTT fully synthetic 2 -stroke oil, which is a 1/3rd of the price of imported Motorex








http://pttweb2.pttplc.com/weblub/en/products-01.aspx?id=3&lub_id=141&lub_sub=19

 

[Matt]

Just for information, it may be useful to someone - you can get a hot rods bottom end rebuild kit that comes with a new crank assembly and everything you need to rebuild the motor. The crank is factory balanced and mine feels smoother than the one it replaced. >100 hours on the rebuilt motor and it's running great.

I paid $250 usd for the complete kit and had a friend bring it over for me.

Here is an example link - http://www.amazon.com/Hot-Rods-CBK0...1428845607&sr=8-1&keywords=ktm+300+bottom+end

 

[KTMphil]

That is very cheap, I wonder if there's any quality difference or just paying for the KTM badged parts with the original KTM stuff?

 

[Loop]

That is very cheap, I wonder if there's any quality difference or just paying for the KTM badged parts with the original OEM stuff?

I've used and read of guys using Hot Rods stuff without any bad reports about them.

 

[bill]

Phil
Thanks for the informative write-up.
Always interesting to see details of major engine work done in this region.

I fitted a Hotrods crank to my DRZ at ~20,000miles. Same time as the big bore kit. No issues or unpleasant noises yet, at 43,000miles.
Maybe not a great comparison to the KTM300, since the DRZ motor is an over engineered near on unbreakable lump.

I believe the Hotrods stuff is generally considered good quality though.

 

[LUFC]

Bike is back and running good, some people have said use the "hot run in method"


Ride bike at a moderate RPM level until its at full operating temp. Dont hold it wide open. Dont just sputter either.

Let motor cool all the way down.

Repeat X3.

Mix it with the good stuff Motorex, Motul Etc...

I use 60:1.

No issues




Nung thinks its been run to lean at 15ml per liter of 2 -stroke mix, advises going to 18-20 ml per liter. He also swears by PTT fully synthetic 2 -stroke oil, which is a 1/3rd of the price of imported Motorex








PTT LUBRICANTS : Products

He's wrong about it running too lean!

It is not lean on these bikes with Motorex. If it were lean you would have had serious drama the last few years.

I've always run 66:1 (15 mls per litre) and never had any sort of problem in hundreds of hours.
Many run 80:1 and Motorex themselves recommend 100:1.

A lot of people seem to think you need to add 2 stroke oil like was necessary 20+ years ago, It's simply not true with modern hi-tech 2 stroke oils in warm climates like Thailand.

 

[KTMphil]

1,000 hours would probably have shown not enough lube mix by now, tend to agree with you.