No Compression when kicking



7 replies to this topic
  • pete_w

Posted February 08, 2004 - 09:16 PM

#1

Hey guys,

I am trying to sell my 99 XR600R.
The last two people to look at the bike have noted that there seems to be very little compression when kicking it over. This being my first bike I have nothing to compare it to, so I would have no idea how hard it should be.

Bottom line is: I have had no problems with the bike since I bought it, it runs fine, doesnt burn oil, starts fairly regularly given 5-10 kicks to prime it, and blows no smoke. I have never really had a need to use the decompression lever to get the bike over TDC, but hold it down while kicking before starting it cold.

Does anyone know what the problem could possibly be?

It seems to be preventing knowledgable people from buying the bike, and honestly I would hate to sell it to someone else and for it to be a problem for them.

One kind bloke on the chat recommended checking the valves, should I check this. Does anyone know the location of any good instructions?

Cheers,

Pete W
Australia.

  • Dutch

Posted February 09, 2004 - 02:14 AM

#2

Try checking the compression after running the bike for a while.
A quick and sloppy way to check the valves is to pull the rocker covers and spark plug,
bring the piston up to top and grab the rocker and feel for clearance. If they feel tight
roll the motor over to tdc again and check it again.
The first thing to try is run the motor first, that seals the rings better.

  • ob1quixote

Posted February 09, 2004 - 04:44 AM

#3

Does the bike have automatic decompression for kicking, and if so, is it adjustable?

Robert :)

  • pete_w

Posted February 09, 2004 - 03:15 PM

#4

Not sure if it has automatic decompression, but I will have to check it tonight (im at work at the moment). Am I simply looking for a cable connected to the kick starter or is it done internally on the XR 600s?

WRT running the bike before checking the compression, would that indicate that the rings are worn and need replacing, or is this just the way it is for these bikes? What sort of time do I need to run the bike before checking this?

Thanks very much for your help,

Cheers,

Pete.

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  • ob1quixote

Posted February 09, 2004 - 03:23 PM

#5

I would check the service manual regarding auto decomp. manual decomp comes from a cable. If the cable bellcrank at the motor moves when kicked, and no manual decomp is used, then it has auto decomp.

Robert :)

  • Dutch

Posted February 09, 2004 - 04:54 PM

#6

The automatic decompression only works if the motor turns backwards,
(if the motor kicks back), which is why you can't turn the motor backwards
during valve adjustment if you go past the tdc mark.
If the engine fires backwards an exhaust valve is lifted.

  • Dutch

Posted February 09, 2004 - 05:01 PM

#7

The rings need lubrication to seal up, it doesn't mean it's worn out.
It's a big piston and the bore gets dry.
I'd say run it 'till you can shut off the choke.

  • pete_w

Posted February 09, 2004 - 10:42 PM

#8

I took the bike for a quick run, 5-10 mins. Just to put a sort of value on the force required to cycle the motor, I tried using my hand. With the bike on the stand, and the other hand steadying it so it didnt tip back on me I was able to turn the motor full cycle using just my hand, obviously at TDC there it was a little more of a struggle, but not so much that I couldnt do it with my hand.]

I dont have the service manual to check. Might be worth having a look at if I can find one.

Aswell today I went to a local bike mechanic and spoke with him about the problem. He indicated that this is a common problem with the 600's of this model, apparently the automatic decompression mechanism inside can get a little sticky and causes the bike to feel this way. He said that they generally recommend to their clients to remove this mechanism if the bike has the head off for another reason. He indicated that this is more commonly the fault of this problem rather than the valves, and that I should not worry about it since the bike starts and runs fine. He did try to explain how this mechanism works but can't say I could accurately repeat it.

I might ask another bike mechanic for a second opinion tomorrow just to be sure.

Thanks again for the help.

Pete.





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