KTM 85cc compression test...

[toddb3]

I've already searched for this but cant find any info, does anyone know what the compression should be for a KTM85? My bosses son just got one and we want to make sure all is right with it before his next race.

Thanks in advance
Todd

 

[robwbright]

From what I understand, it should be a minimum 150 psi in 85s/125s.

Perhaps someone will correct me, but that's pretty much what I recall seeing on here . . .

 

[toddb3]

Do you know if thats 150psi testing the engine cold or warmed up?

 

[Oldman125]

I've already searched for this but cant find any info, does anyone know what the compression should be for a KTM85? My bosses son just got one and we want to make sure all is right with it before his next race.

Thanks in advance
Todd

I'm wont tell you I know what the cranking pressure should be. However somewhere over 150 sounds good. Thats vague I know. Try KTMTalk for some better info on that. The mini section is full of, among other things, good info and folks who know what they are doing.

As for testing the compression, warm the engine, ground the spark plug wire to the frame. Then with the test gauge in place hold the throttle open and kick the starter over like you mean it until the needle doesn't climb any higher. There you go...thats it.

More critical is jetting. Make sure its on or the bike will run like krapola. Mix at 32:1 with a high quality oil like Motul 800.

Good luck, hope this helps.

 

[toddb3]

Thanks for your help, I'm very familiar with the testing procedure as I've ridden 2 strokes for almost 20 years. I just dont know anything about KTM's other than they are great bikes. I was really impressed thumbing through the owner manual, it actually has parts diagrams and numbers for almost every part on the bike.

Thanks again,
Todd

 

[gwcrim]

How's come ya ground the sparkplug wire?

 

[Oldman125]

How's come ya ground the sparkplug wire?

In a nutshell, one needs to keep the charge from building up in the ignition system. The voltage can find a way out thru the components or the wire if not sent directly to a ground source. Any ignition should be grounded at the wire or plug when testing involves cranking the engine with power to the coil.