What kind of oil do you use? What ratio do u run and what kind of bike do u have???

Ktm 150sx 2010. Castor 927 and it's at 42:1 right now.

I use castor 927 to but I heard it's not to good for the power valve....

Power valve was cleaned out during top end rebuild. I just need help in figuring what isn't causing the bike to even turn over. It won't even try. It's like there's no spark but I chk the spark and see it

I had the same problem with my buddies bike. I am assuming you replaced piston and rings? And possibly/hopefully replated the cylinder? My buddy replaced piston and rings without replating the cylinder and the cylinder walls were too wide for the new piston and rings from wear. This caused the piston to catch a port in the cylinder and rip everything to hell. after 10 minutes of break in time. The bike also took an hour to start due to the low compression caused by the blow by. The reason your bike is not turning over is either too low of compression, or simply a jetting/carb problem. set everything on your carb back to stock settings (idle, air mixture, etc...) Hope this helps!

Jarrod thanks for input:) finaly something we didn't check! Ima call my friend mechanic that helps me and see what he says bout ur input. BUT the bike did start SECOND kick after the new top end.

Hey we r going to strip the bike down to te piston and pull out the calipers to measure the piston. Why would te cylinder need to be replated? I didn't think that was necessary for a top end change?

Depending on the model and year of the bike, the cylinder may or may not have a chrome(nickleplated) like lining in the cylinder due to better wear characteristics. a nickleplated lining CAN NOT be bored it must be sent to powerseal or millennium technologies to be chemically and electrically replated. older cylinders typically do not have nicleplated cylinders and can be bored. its complicated but just google or look in your bikes service manual to determine the cylinder type. My 2001 RM 250 is nickleplated if that helps at all.

. I'm definitely not to confident in understanding that but I do know that I the manual I have it says the displacement is 66mm an the top end I got is 55.95 mm. Idk if that's right. .05 mm doesn't seem like it would cause it not to start. But my friend said it was pretty easy getting that top end in the cylinder so maybe I just have Wrong top end. Will find out tonight though. Thanks for all the I put

Ur buddy had a bike u said? What was it he had?

My buddy had the bike i currently have in my profile picture. It is an 01 Rm250 and he used a hone in the cylinder to fix the small scratches in the cylinder rather than having the cylinder sent out and replated. new bikes have plated cylinders because they are supposedly more durable. your 2010 150SX more than likely has a plated cylinder and if you or someone else mistakenly used a hone on it, you scraped off some of the plating. this will make the cylinder larger than the new piston and cause blow by which will reduce compression and make the bike hard to start. My advice, go to any hardware store and buy a 20 dollar compression tester and test your bikes compression. if it is anywhere near 150 psi your piston is fine and the problem is somewhere in the carb. sometimes it is as simple as an idle screw that is causing the bike to flood as it begins to start. Sorry to get off topic bourquerippa, but I run amsoil either the yellow or red oil at 32:1 in every 2 stroke i have ever owned whether it is in a snowmobile, bike, or even a quad. too much oil is always a better problem to have than having too little oil. A spark plug is a lot cheaper and more convenient to replace than a top or bottom end.

Yeah I been reading and 40:1 is whT this bike likes. We honed it...

Te hone was used on a rm125 thought so it's not AS BAD but it's still bad I take it and that prolly cause the problem

With some quick googling of your bike it appears the cylinder needs plating rather than honing. Your best bet in my opinion is to take the cylinder off and send it to powerseal or millennium technologies with the new piston for sizing purposes. The turn around time is between a  week and two weeks depending on work load. I personally use powerseal and have had great results. They are a bit cheaper than millennium and their rates are on their website. If you don't get the cylinder replated and run it with a honed cylinder your piston will look like my buddies did after a short run time. It is a bummer that you honed it but at least you didn't make my buddies mistake by running it with a honed cylinder! 




I flex honed. Sorry not actual Hone. We make the cross hatches in the cylinder every top end job. So I'm sure the ppl before me never had it sent off

32-1 91 octane maxima super m

Thanks. That oil looks good

I thought this was a pretty interesting oil test on youtube where you can actually see the where a better oil reduces engine wear in a 2 stroke.


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