xr600 cam swap, how long



17 replies to this topic
  • Matt96xr6

Posted December 11, 2001 - 11:58 AM

#1

Hey, how long does it take? Also do you have to pull the motor from the frame as the cylmer manual states?

  • LP

Posted December 12, 2001 - 05:07 PM

#2

Hi Matt,

I am afraid the donk has to come out. The 250 has enough clearence to take the rocker cover off but the 600 doesn't.

You might be able to take the main bolts out and rotate the donk slightly to get at them. It is an easy job after that(30mins). Try to get an aftermarket Cam that has all the Auto decomp gear on it. Some shops do a modification with your cam gear.

Mine doesn't, so the kicker likes to come back real quick. Nothing is funnier than watching my friends trying to start the bike!

You might want to go to heavier valve springs if the cam is designed to work up the rev range and you will be revving it harder than before.

  • Fastdirt

Posted December 12, 2001 - 05:46 PM

#3

I had a 92 xr600 and was able to do a thumper 660 kit with the engine in the frame, this involved removing the rocker cover, the head, and the cylinder. I had no problems with clearance between the rocker cover and the frame

fastdirt
00 XR650R

  • LP

Posted December 13, 2001 - 02:19 PM

#4

G'day again,

I am been told by several people (inc feedback@thumper) it is possible to do it in the frame.

Last time I even asked the local Honda Mechanic and he said pull the donk. Matt when you pop the top off your xr6 let me know how you go!

Seeya
LP

  • Moredesert

Posted December 14, 2001 - 02:46 PM

#5

I've done tons of work on a XR600. If you have any questions I'll be glad to help.

moredesert@aol.com

  • Matt96xr6

Posted December 15, 2001 - 03:37 PM

#6

Thanks, I will if I get in a tight spot.

Anyone have any tips on swapping this out with the auto chain tensioner?

I will start tearing it down tomorrow nite, get the cam Monday or Tuesday and be done with it!

  • Matt96xr6

Posted December 21, 2001 - 08:04 PM

#7

Well I got the engine basically out of the frame. PIA to say the least. Got the cam out. The auto tensioner looks to be a PIA the to get back installed. But looks like I need to press the decompression sprocket off. I am going to leave the rest of the auto decompression off.

So that is where I stand now.

  • Moredesert

Posted December 21, 2001 - 08:26 PM

#8

Keep a clean rag over the engine to keep the dirt out. You might even stick rags in the engine during assembly. You can't afford to drop a cam bolt or the scerw that holds the tentioner tight.

Even being carful I droped the little pin from the decompression cam down the hole. Talk about PIA. When installing the rocker cover put the long bolts in the cover before you put it in place. There too long and hit the frame. I had to remove the carb rubber mount (the dong) and go in from that angle. Its not really that hard if you do it right.

  • Matt96xr6

Posted December 22, 2001 - 04:37 PM

#9

the motor is wrapped up in a garbage bag and sealed presently.

Question, can you use a gear puller to get the cam sprocket off the cam?

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  • Matt96xr6

Posted December 24, 2001 - 01:55 PM

#10

help!

I got everything installed. It is a MOTHER to kick over now without the autodecompression. Plus there is a loud racket from the motor and the power bogs like crazy. I am thinking I got the cam installed 180* the wrong way. thoughts? My friend is the one that got it to top dead center, but I am thinking he was 1 rotation from the true TDC with all the valves slack.

But then the bike would not fire. I checked the valves again tonight and they were slack. That cut a TON of the noise down. I am thinking that I just need to let the cam break in for a while and then adjust the valves and time the motor.

Any pointers on how to time the motor? I have timed cars, not a XR

[ December 24, 2001: Message edited by: Matt96xr6 ]

  • Moredesert

Posted December 24, 2001 - 10:02 PM

#11

Well it is hard to say but I would go back to basics. There is a little peek hole for the timing on the left side cover. Using an allen wrench and pull the plug and find the "T" mark on the fly wheel. Align it up with the fixed line or pointer. Us the kick starter so you might have to pull the spark plug. Only go one direction don't back up. If there is any slack in the chain you could set the timing wrong.

Now you need to have the valve cover off. The cam gear will have the timing marks and will algin with the top of the head or gasket serface at 3 and 9 o'clock. Double check everything

Once your sure the timing is right put the valve cover back on kick it over a couple of times and set the valves. Intake .004" ex .005"

I didn't want to ask why you removed the decomp cam but what the heck "why"

  • Matt96xr6

Posted December 25, 2001 - 06:06 AM

#12

more low end.

I checked the valves again last night and they were a bit loose. See what happens today

  • Matt96xr6

Posted December 25, 2001 - 01:00 PM

#13

check the valves again, that was good. So I tore the motor out again. Looks like the cam jumped 3 links. Back up and running great now.

There is a bit of a cough to the bike that I am going to have to sort out here after I get the cam broken in, oil changed, new throttle cables (found them frayed) and washed!

Thanks for the help! the tip on the timing marks helped a ton!

  • ossagp

Posted December 25, 2001 - 03:33 PM

#14

Depending on your cam, the cough may come from being a little lean. If you had taken the vacuum reading off of the old cam setup and compared it to the new one you could tell whether you needed to go up or down on jetting. (some cams will increase vac and some decrease it). More vac means leaner jetting etc. FYI the XR fires on each rotation almost like a 2 stroke.

  • Moredesert

Posted December 26, 2001 - 02:46 PM

#15

Glad I was able to help. I've lost sleep over things like that so I know where you were coming from.

"The XR fires each stroke" I didn't know that. See you learn something everyday.

You might want to raise the needle one notch, make the low end richer.

  • Matt96xr6

Posted December 26, 2001 - 04:39 PM

#16

after some running time it is running better. The top end seems a bit flat, so I may install my old CR main in there (178) which I had tried earlier with no improvment from a 165, so I went back.

I am going to tear down the carb, do a total clean and rebuild on it when I get the new throttle cables.

A friend suggested I go a bit leaner on the pilot and needle jet. Reason being the motor is getting more fuel in it since the cam has more lift and duration. Sounds logical. Time to read up on the Eric Gores carb tuning page.

  • ossagp

Posted December 26, 2001 - 06:47 PM

#17

I am with more desert on the jetting. If your cam has increased lift and duration you likely have less vacuum. With less vacuum there is less pull on the jets in your carburetor hence your bike runs leaner. Virtually every performance cam I have put in anything from one to 8 cylinders has decreased low speed vacuum, and required richer jetting. Now,,does any of that sound 'logical' or applicable.

  • Matt96xr6

Posted December 26, 2001 - 07:00 PM

#18

well I hear you, more power more air/fuel.

The bike is running better. I need to clean the plug and clean the carb. check all the vent hoses also.

But I got my guides. I am going to start with the main jet up, and the needle jet down one notch. Go from there.





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