XR600R valve adjustment, anybody got any ideas???


13 replies to this topic
  • jclaus98

Posted October 30, 2007 - 04:10 PM

#1

A couple weeks ago, my Dad and I adjusted the valves on my '93 XR600R and 3 of the 4 were perfect, however, for some reason, the left exhaust (non-decompressor) was WAY out of adjustment. I mean, you could have fit two or three quarters in between the tappet and the valve head. We adjusted it to the factory .005in and it ran great. Then, this last weekend at the 49er enduro, I noticed ALOT of noise from the top end. I suspected the same exhaust valve as the culprit, and sure enough, today I went to adjust them, and the same valve had almost the same gap between the tappet and valve head! ***??? :worthy: The lock-nut was still tight, but it was as if we hadn't ever adjusted it! What the heck happened? What does this mean and how can I fix this???

  • creeky

Posted October 30, 2007 - 05:20 PM

#2

Sounds like the cam lobe is wearing off. If so, the associated rocker arm is probably going too. You can make a quick check by taking the slack out of the rocker arm and turning the engine over while watching the rocker arm. If the rocker moves only a little compared to the other exhuast rocker, the cam lobe is probably worn off. Pull the cam cover and visually inspect the cam if you need to confirm suspicion.

  • jclaus98

Posted October 30, 2007 - 06:00 PM

#3

Wow, I acctually witnessed that while I was adjusting them today, it was doing exactly what you are describing. Not exactly what I wanted to hear, but thank you very much for your knowledge and experticse. Looks like its time to rebuild! :-(

  • metisse

Posted October 30, 2007 - 06:05 PM

#4

Agree with Creeky - after two big adjustmens on the left exhaust I pulled the head cover and found all four followers and cam lobes gone - the left exhaust was by far the worst - Now - why did they fail with frequent oil and filter changes? - all the pipes are clean and all the screens are clean - the oil pump is well within the specs in the manual - so I am putting it back together and fitting a brand new oil pump - will assemble with lots of prelube on the cams and find some way to "motor" over the engine with the plug out while I check the oil flow and pressure - after that I am going to run an additive of some kind in the oil - research required on this one! - good luck but it sounds like the same problem

  • cleonard

Posted October 30, 2007 - 07:01 PM

#5

There was a post here about a week ago with a simple method for priming the oil pump using pressurized air. The last time I was into my engine it took over 90 seconds for the oil to reach the head. The way to check is to loosen the top oil tube banjo bolt and look for oil to come out. The Honda manual says to use a thin film of the moly paste on the entire valve train. With the priming method I don't think that I'll use the moly next time, unless I fit a new cam or rockers.

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I also do the loosen the top oil tube banjo bolt check after every oil change just to be sure.

It seems that this is a very common issue on all the RFVC engines.

  • martinfan30

Posted October 30, 2007 - 09:20 PM

#6

cleonard, what you think of this...

just put in my hotcam, and i dont have comp. air at home. i used plenty of good cam lube upon assembly.

i will loosen the banjo at the head and thinking of cranking it over with the starter(ign. off) until i get oil out of the pipe. i also will fill the cyl. head thru the left exhaust valve access cap with new oil.

think this is a good enough priming method without comp. air?

  • martinfan30

Posted October 30, 2007 - 09:22 PM

#7

i also changed the oil and soaked the new filter in new oil...

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  • jclaus98

Posted October 31, 2007 - 05:08 PM

#8

Alright guys, so I'm assuming that if the cam lobes are wearing off, there are other areas in there that are suffering from the same type of wear, so I've decided the only course of action is a complete rebuild. Having decided that, I immediately had the inspiration to bore it out! I'm thinking one of the 630 pistons that XR's only sells??? Here's my question: are there ANY other vendors who would sell a larger piston/rings since XR's only has such a terrible reputation on this site? And, as far as the cam, am I better off staying with the stock cam with a larger bore piston, or do I need to upgrade that if I go bigger??? Any knowledge you guys can share is greatly appreciated.

  • cleonard

Posted October 31, 2007 - 05:46 PM

#9

They are not completely idiots at XR's only, but they are not perfect either. They do great machine work and know the XR engines better than anyone. You do need to have the head looked at to be sure that the valves are OK. I would consider sending the cylinder and head to them for all the work. Get the piston from them and have them do the boring. The rocker arms are just simple assembly and would do that myself. If the valves are not in 100% good condition get some new ones.

When you have the cylinder off take a look at the transmission gears. Look for signs of pitting on the gear faces.

To answer your question, the pistons are standard parts available from Wiseco and I think JE. You can get them on ebay and many other places that sell pistons. Be sure that you use the correct head gasket when reassembling it. The stock XR600 gasket will be 3mm too small. I know that there are aftermarket gaskets, and I think that OEM gaskets for the XL600 or the XR650L should be the right size as well. There are 101 and 102mm oversizes available too, but I think that 100mm is good.

If you are replacing the cam anyway you might as well get one of the stage 1 aftermarket ones.

  • jclaus98

Posted October 31, 2007 - 08:58 PM

#10

Cleonard, you seem to know alot about this subject, so do you mind a few more questions? First, it appears as though the XR's only 100mm piston only comes in the higher compression ratio, is this true? If so, is the higher comp. ratio simply a byproduct of the increased displacement? Or is it possible to get the larger piston in stock comp. ratio trim? Also, if I were to run the higher comp. ratio piston, would I be forced to go with a hotter cam or could I use the stock cam? Basically, I'd like to retain stock compression, but with a greater displacement. This way, I can get more ponies, but still be able to use regular old unleaded 91 octane pump gas. If I go with the higher comp. ratio piston I will need to be using a higher octane fuel, correct? At the end of the day, I'd like to use as many stock parts as possible, so as to retain as much of the stock reliability, with the exception of a few more cc's to send a few more ponies to the rear wheel. Any light you could shed on those questions would be greatly appreciated. Thanks in advance.

  • cleonard

Posted October 31, 2007 - 09:39 PM

#11

Cleonard, you seem to know alot about this subject, so do you mind a few more questions? First, it appears as though the XR's only 100mm piston only comes in the higher compression ratio, is this true? If so, is the higher comp. ratio simply a byproduct of the increased displacement? Or is it possible to get the larger piston in stock comp. ratio trim? Also, if I were to run the higher comp. ratio piston, would I be forced to go with a hotter cam or could I use the stock cam? Basically, I'd like to retain stock compression, but with a greater displacement. This way, I can get more ponies, but still be able to use regular old unleaded 91 octane pump gas. If I go with the higher comp. ratio piston I will need to be using a higher octane fuel, correct? At the end of the day, I'd like to use as many stock parts as possible, so as to retain as much of the stock reliability, with the exception of a few more cc's to send a few more ponies to the rear wheel. Any light you could shed on those questions would be greatly appreciated. Thanks in advance.


The hotter cam is not all that much hotter. Martinfan30 just put one in his XR650L and this is the same cam for the 600. Since the 600 cam is already hotter than the 650L cam the difference is not all that great. While I have not studied the specs on the aftermartket cams, usually gains are achieved with higher lift and faster opening. Both of these put more load on the valve train so they don't extend the life. I don't think that it is all that much though with the rather mild cams that are available. A stage 2 cam has higher lift and puts a lot more load on things.

I really depend on the low end torque. Being able to loft the front end on the trail at whatever speed is critical for me. Even the small loss of low end makes me think that I'll be keeping the stock cam as long as it is in good shape. The aftermarket cams also don't have the automatic decompression system that makes starting easier. I've been on bikes with the aftermarket cams and it does make starting a little more critical. I have my 600 setup so it almost always is a one kick starter. I don't know if the aftermarket cam would mess that up, but I would miss it.

The pistons are available in the stock compression. You can check out the Wiseco website and they have a online catalog. With stock compression you can actually run 87 octane regular. I have been forced to do this and I get light pinging under heavy load. With the high comp piston it should be OK with 91. Many have reported this. There is just less margin with the hi comp piston. The engine does run hotter with the hi comp piston. I do a lot of slow technical riding and my bike gets too hot as it is. My engine is already on the max oversizesize Honda piston. When it's time for a bore job, I think that I'll go with the 100mm 9:1 piston. It depends though. If I have another woods bike at the time, hi comp it is for the desert.

No problem using the stock cam with the larger hi comp or std comp piston. The rest of the system can use some attention as well. With the larger displacement more air will flow. Anything that can be done to assist breathing will help the engine.

For something else to check, take a look at your carb. The choke plate has a little flapper valve/plate on it. It is known to break off and get sucked into the engine and doing a lot of damage. When I checked mine it was hanging by a thread and the whole choke plate had a big crack in it.

  • martinfan30

Posted November 01, 2007 - 08:22 AM

#12

im not too concerned about wear on the valve train now with the hotcam . the lobes are VERY round. the opening and closing face on the lobes are very smooth and dont spike. i really beleive this is a well made cam from billet that was desinged for a 8-10 percent HP gain, while keeping the top end reliable.

i do belevie that a 10.5 to 1 piston will be completely fine(with the hotcam) on 91 octane. the 11.1, might not.

  • zipper600

Posted November 02, 2007 - 12:11 PM

#13

A couple weeks ago, my Dad and I adjusted the valves on my '93 XR600R and 3 of the 4 were perfect, however, for some reason, the left exhaust (non-decompressor) was WAY out of adjustment. I mean, you could have fit two or three quarters in between the tappet and the valve head. We adjusted it to the factory .005in and it ran great. Then, this last weekend at the 49er enduro, I noticed ALOT of noise from the top end. I suspected the same exhaust valve as the culprit, and sure enough, today I went to adjust them, and the same valve had almost the same gap between the tappet and valve head! ***??? :worthy: The lock-nut was still tight, but it was as if we hadn't ever adjusted it! What the heck happened? What does this mean and how can I fix this???


I had the same problem with my XR600. During a valve adjustment i noticed the left exhaust valve too much clearance.But i didnt adjusted like you did.I removed the valve cover and got a RC arm all blue...but the cam was ok.the Cam is way harder than the RC arms.So i just put it a new RC arm and the problem was resolved.But.....for that to happen i supposed oil was not getting up there.So i drained the oil and checked the 3 filters that XR haves.The cartridge one was ok..the metal screen too but the one in the frame was simple totally blocked.Full of metal shaves and catdrige filter little pieces.Put it new oil and filters and better than that i glued little magnets to the 2 drain plugs.Now every time i drain oil i take all the shaves out and they never "play" inside engine....

About checking oil is coming to head at every oil change: i have a stupid but with results way of doing it: i put 1/4 of total capacity of oil on head,fill up the frame and then lay the bike on his left side and fill up the oil filter case with oil with the filter in it.then start the bike and loose a little the banjo bolt on the head and in 4-5 seconds i have oil on the head..Simple...

  • creeky

Posted November 02, 2007 - 04:48 PM

#14

About checking oil is coming to head at every oil change: i have a stupid but with results way of doing it: i put 1/4 of total capacity of oil on head,fill up the frame and then lay the bike on his left side and fill up the oil filter case with oil with the filter in it.then start the bike and loose a little the banjo bolt on the head and in 4-5 seconds i have oil on the head..Simple...


Clever! :worthy:





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