remove auto decompessioner?


17 replies to this topic
  • 650r

Posted March 29, 2007 - 04:50 PM

#1

has anyone done this? what did you do with the whole in the cam? my spring went bad and we pulled it off the cam and the bike seems to start and run better(using just the manual lever now) talked to al baker's and they said to seal the whole in the cam with JB WELD. that doesn't sound safe to me. any ideas. thanks

  • glenn6109

Posted March 29, 2007 - 04:56 PM

#2

I Would Find A Good Welder And Fill It, Jb Weld Works But I Just Cant Do It Cause It Looks Trashy. Glenn

  • Billahjack

Posted March 29, 2007 - 06:08 PM

#3

Welding can distort the cam and cause problems. I would consider the JB weld as long as you thoroughly clean the oil journal (with alcohol or acetone) before hand and thoroughly mix the epoxy.

  • jetski701

Posted March 30, 2007 - 05:15 AM

#4

Welding can distort the cam and cause problems. I would consider the JB weld as long as you thoroughly clean the oil journal (with alcohol or acetone) before hand and thoroughly mix the epoxy.

Replace the cam with a hotcam while it's out, no auto decompression on the new cam, and a little more power for your trouble!

  • XR650L_Dave

Posted March 30, 2007 - 09:20 AM

#5

Even guys who bump up the comp. say it starts fine without the decomp.

Dave

  • Xr650rhonda

Posted March 30, 2007 - 03:06 PM

#6

has anyone done this? what did you do with the whole in the cam? my spring went bad and we pulled it off the cam and the bike seems to start and run better(using just the manual lever now) talked to al baker's and they said to seal the whole in the cam with JB WELD. that doesn't sound safe to me. any ideas. thanks


Ok, I miss Gary's wisdom so much to dig up a old post.

http://www.thumperta...to decompressor

  • Kawabuggy

Posted March 30, 2007 - 03:14 PM

#7

I just pulled my XR600R apart to find that all 4 rockers are wasted, and one of the exhaust valves is hammered. Apparently someone decided to pull the auto-decompressor off and did NOT fill the hole! I have pictures if anyone would like to see where the hole is, and what your cam/rockers will look like if you forget to fill the hole. Needless to say, my Hot-Cam will be going back in, and I will be replacing EVERYTHING in the rocker cover due to this.

  • wickedsprint

Posted March 30, 2007 - 05:33 PM

#8

So when you say put back in your hotcam, what else was there they should have plugged? I am going to slap a hotcams in mine, I heard there was some sort of hole in the head that needs to be plugged as well, is this true, or just swap the cams and call it a day?

  • Billahjack

Posted March 30, 2007 - 11:07 PM

#9

Good post on the old thread using the mig welder to snap a quick tack weld in the hole.


One question about hotcams - Where is the spring pin in the head and what do you plug it with? This is listed on the frequently asked questions on the hotcams website, http://www.hotcamsin...aqcategoryid=27

"Question: Do I use the stock decompression mechanism on the 1004-1, 1009-1, 1010-2 Hot Cams for the XR600, XR650L, and XR650R?

Answer: No, there is a spring and pin located in the head that lubricates the stock decompression mechanism, this also must be removed. "

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  • Kawabuggy

Posted March 31, 2007 - 06:53 AM

#10

This is the way I understand it to work... On the factory cam, the cam core is hollow and oil passes through the center of it. On each cam lobe, and on each journal surface where it touches the head or cam cover, there will be a hold drilled into the cam on the lobe or journal to allow oil to lubricate the contact points. The factory auto-decompressor is pressed onto the cam core right behind the cam gear where the chain rides. If you REMOVE that auto-decompressor, you will see that there is a hole drilled into the cam to allow oil passing through the center of the cam to lubricate the decompressor.

That is the hole that you MUST plug. Because oil feeds into the cam on the RIGHT side of the cam cover, then works it's way towards the left side of the engine, the auto decompressor is the first item to receive pressurized oil moving through the cam. With that hole unplugged, effectively you are bleeding off all of the pressure inside the cam-so nothing else after that hole will receive pressurized oil/lubrication! Well, in truth it "might" receive some oil, but not the quantity that it needs to keep all of the parts alive. Hence, my destroyed cam & rocker arms & followers.

With the Hot-Cam, there is no hole drilled for lubrication for the auto-decompressor, nor is there a way to install an auto-decompressor as the mount for the cam gear is a part of the cam core. So, don't worry about any hole with the Hot-Cam as it simply is not there!

You only need to worry about the hole if you have a factory cam, and you decide to remove the auto-decompressor. Everybody mentioned JB weld, and welding as solutions. I would recommend welding, or tapping the hole, and putting in a small plug or set screw. The JB weld could fall inside the hole and then plug up one of the galleys, or could come off the hole completely once you have it all back together and you would never know until it is too late.

Be safe-weld it, which will NOT distort the cam if done properly!!!! Or, tap the hold and put a set screw or small bolt in it. If you decide to tap the hole, pack the hole with grease first to stop small shavings from going into the cam, then afterwards, you can clean with brake clean or solvent to get all of the old grease out. Blow compressed air through one of the galley holes on the left end (as installed in the bike) of the cam so that you are pushing anything left over back out the big hole in the end of the cam.

  • Xr650rhonda

Posted March 31, 2007 - 12:07 PM

#11

has anyone done this? what did you do with the whole in the cam? my spring went bad and we pulled it off the cam and the bike seems to start and run better(using just the manual lever now) talked to al baker's and they said to seal the whole in the cam with JB WELD. that doesn't sound safe to me. any ideas. thanks


I wish I could talk you into the hot cam stage 1 (no valve springs to change, it's easy), buy a sprocket collar from service honda cheap and push it onto the hot cam with your fingers (some people break the ears off the collar getting it off the stock cam) I went to the hot cam stage 1 after my auto decompresser started to click, after I put it in the bike I could that believe how much of a monster the bike became.

  • blacktdi

Posted April 01, 2007 - 08:54 AM

#12

I removed the decompressor system and mounted a piece of thin aluminium pipe which fitted exactly over the camschaft. The only thing you have to make sure is that it has the corrrect length so the sprocket can be mounted in its original location. I did this about 3000km ago and it works perfectly.

  • Kawabuggy

Posted April 01, 2007 - 05:27 PM

#13

One other thing I forgot to mention... If you remove the auto-decompressor, you need to also remove the plunger & spring that ride in the head under the cam.

  • wickedsprint

Posted April 01, 2007 - 07:30 PM

#14

One other thing I forgot to mention... If you remove the auto-decompressor, you need to also remove the plunger & spring that ride in the head under the cam.



Do you have to plug them?

  • Kawabuggy

Posted April 02, 2007 - 05:13 AM

#15

No, you do not have to plug the hole under the plunger/spring assembly. It is a dead hole-meaning it has a bottom. The purpose of the plunger/spring assembly is to have something to trigger the auto-decompressor in the event that the motor trys to kick-back. In that instance, the plunger activates the auto-decompressor to open the valve and stop kick-back. This is how I "think" it works.

I know the hole is bottomed due to my very scientific testing method. I put an air-gun nozzle in the hole and blew compressed air in it. It comes right back out. I then used a flash light to confirm.

I figured all of this out when I went to put my head back on, with the new cam, and noticed in the service manual that it says to put those pieces in before installing the cam. Well, I looked at my head, and those pieces were missing. I "guessed" that they were part of the auto-decomp system and that I did not need them. I went ahead and verified the hole was bottomed.

I installed my Hot-Cam, and then later read the paper work that came with the cam. There was a small red piece of paper that specifically says to remove the plunger & spring. Whew! Something that finally worked in my favor?

  • wickedsprint

Posted April 02, 2007 - 05:57 AM

#16

Hey thanks alot, startin to get a warm fuzzy for swapping the cam now.

  • Thumpmeister

Posted April 02, 2007 - 07:39 PM

#17

Replace the cam with a hotcam while it's out, no auto decompression on the new cam, and a little more power for your trouble!


Thats what I did. For YEARS my auto decomp would make this tiking sound, even after I did the top-end. Finally, I figured that it must have been the auto decomp, so I bought the HotCam stg1, and the bike never sounded better!

Didn't notice a huge power increase; maybe a little in mid to upper range. But getting rid of the stupid auto decomp was well worth it.

  • Kawabuggy

Posted April 04, 2007 - 05:55 PM

#18

Here is an aftermarket cam that already has the pressure feed hole plugged with a simple pressed in pin.

http://cgi.ebay.com/...1QQcmdZViewItem





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