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XR650R Cam Install Issues

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HI. I just replaced the badly worn (destroyed) cam & rockers in my 2000 XR650R with good (?) used parts off of ebay. After re-assembly I now have an intermittent problem during startup. Sometimes I can kick it through several times before it seems like it's getting any compression. Also, when this happens I will sometimes give it a full boot without pulling in the compression release lever and it will feel like it builds compression mid-kick but then lets go with a feeling of stripped gears or something catchiing and then letting go. I'm thinking there might be something goofy happening with the auto compression release on the newer cam that is causing this. I've also had the engine randomly die if the idle falls below a fast idle which did not happen before I swapped the cam.

 

Any ideas?  TIA

Edited by flowrider

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Valves and chain are properly adjusted. Just adjusted the valves again this morning to verify they are correct after a weekend of riding. Bike runs fantastic except for this intermittent problem at start-up

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I had the same problem just recently, I installed an old cam with autodecompression system, it did exactly the same thing you describe, I thought the valves were tight but no, they were good, so I installed a Hotcam stage 1 back and it was starting first kick hot and cold again, don't knot what's causing this though  :excuseme:

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If MCVL had the issue and it was fixed by installing a Hotcam it's kinda obvious what's wrong..The auto decomp

mechanism on the Cam is malfunctioning. Hotcams don't have the auto decomp on them afaik..

The bike also stalling out at a low idle is another sign of the issue,,read the below,,XR600 but it's the same chit happening.

His fix is there for the stalling,,wouldn't know if it'd fix the other issue. If you remove the auto from the cam it'll

no doubt cure both,,You then use only the manual decomp lever to start the bike. Should you choose to remove the auto

mechanism from the cam also pull the spring and plunger which works in conjunction with the cam mechanism from the head.

 

http://www.advrider.com/forums/showthread.php?p=16753137

Edited by Horri

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Thanks guys that's exactly what I was thinking too. After installing the rocker cover this morning with all the cam lobes facing down I noticed the exhaust valve by the auto decomp was tight while the other rocker had some play in it. After a slow crank through I heaard a snap and suddenly had clearance on both exh valves.

I think I'm going to remove the whole mechanism until I eventually get a hotcams stage 1. My next question was going to be if I could or should remove the plunger and spring as well. Thanks for the info.

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When removing a decomp on the 650R the pin mechanism hole will need to be welded closed in order to keep oil going to where it should..

 

I was having your same issues a few years ago,,now I run a stage one and have tried the stage two for a year or so (still have it in a box).With the stage two the intake(?) valves were touching the piston very slightly. Now I have a (oem) piston with a bit of relief in the pockets just in case I want to run the stage two for a while.

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I was wondering if it need to be blocked off. Is that standard procedure to weld that hole shut when installing a hotcams cam or do they offer a different solution? It's no big deal for me to weld it up, that's what I do for a living but I was under the impression the hotcams cam was sold as a simple drop in replacement. If blocking it off is necessary I would probably press something in there and tack it in place. Maybe turn down a piece of alum, spot drill the end and weld around carefully to keep a center point in case I wanted to remove it.

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Think you're confused over the hole to weld shut..Scalejockey is actually talking about how if you were just removing the auto decomp

mechanism from the stock cam then there's a hole that needs blocking on the actual cam body so oil doesn't flow down it and cause some

sort of lack of lube up there. I should have mentioned it in my other post. If you were putting in a hotcam there's no welding or blocking of

things required. It'd pay to post a picture of your stock cam here once you have removed the mechanism and someone with more knowledge

on the 650R can point out the hole to block off..The same deal applies to any stock cam where you remove the mechanism. I whacked a half

a copper nail into mine when I removed it,,no welding.,it's still in there.. Coppers good,,soft and forms to the hole..Others may freak out and

think it'll fall out and do some damage,,it hasn't..

Edited by Horri

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OK. Here is a pic of the old cam after pulling off the auto decomposition shtuff and the tool I just made to pull it.

Anybody know Which hole needs to plugged?

cam.jpg

cam puller.jpg

Edited by flowrider

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Maybe I'll just weld the both shut and tack in place everything else that looks like it would have been captured by the mechanism.

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Might be the idea..I was just going to have a look around the net and see if I can find the answer..I'll post back if

I find some relevant info..650R owners are few on the ground here as far as I can see..

 

Here,,about the second post ..I'd assume the guy knows his stuff..

 

http://www.thumpertalk.com/topic/113144-decompressor-failed-what-next/

Edited by Horri

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Yes, I think I saw somewhere people pluged both holes that were under the autodecompressor mechanism and didn't touch the rest

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I just replaced the badly worn (destroyed) cam & rockers in my 2000 XR650R 

Did you find a reason of that wear? It can only be the lack of lubrication. If your bike demands a valve adjustments after about 200miles you didn't solve it  :)

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Loaned my bike to a friend that rode it for like two months with no oil. First time I went to ride it it sounded like hammers hitting rhe rocker covers. I'll post a pic of what's left of the rockers next day or two.

I'm actually at the weld shop now, cam on workbench gettin ready to pull the decomp mech off the cam...

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Just wanted to thank everyone for all the help. Got the bike back together tonight. It now starts predictably and no more random stalling.

I did notice that when I checked th oil at the shop there was none showing on the dipstick and took about .5 quart to get it midrange on the dipstick. I changed the oil 2 weeks ago and put about 500 miles on it as it has been my only transportation while my truck is being fixed. Gonna be keeping a closer eye on that for sure.

Edited by flowrider

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