Upper Cam Chain Guide Missing


13 replies to this topic
  • Dnnap

Posted July 07, 2009 - 08:15 AM

#1

I took my head cover off my '07 YZ450F to check the valves and timing and noticed the cam chain guide was missing. The two pins under the head cover to hold the guide in place has wear on them from the chain rubbing them. The cam chain feels tight and the bike runs and starts fine with no problems other than the lack of bottom and mid power, which is the way the bike has been since I bought it 2 months ago. This low power is why I was checking the timing.
I usually change my oil every 2 hours on my hour meter and noticed on my last oil change that there was a few chunks of very small pieces of rubber in the drained oil.

So, what should I do and what should I be worried about if I can't flush all the rubber pieces out?

Any advice would be greatly appreciated.

  • Dnnap

Posted July 08, 2009 - 10:27 AM

#2

Anyone???

  • bigred455

Posted July 08, 2009 - 12:06 PM

#3

Even though the parts manual show the guide stopper under the valve cover,I do not recall seeing it on my 07.I have had 2 07's and have checked my valve clearances to the point of being silly and I do not recall seeing that rubber stop.I still have 1 07 and my clearances are fine so I did have my cover off a very short time ago and I still do not recall seeing the guide stopper under the cover.Now I am starting to doubt myself

  • Modmotoman

Posted July 08, 2009 - 04:25 PM

#4

Bump you to the top.

  • Dnnap

Posted July 08, 2009 - 05:35 PM

#5

BIGRED I hope you're right, but I'm pretty sure it's supposed to be there.

  • Aka.Goose

Posted July 08, 2009 - 06:03 PM

#6

Yeah man, it's supposed to be there as opposed to coming out in chunks in your oil...
I suppose you're just really going to have to open it up as much as you can to flush it out, all the covers, especially check inside the ignition cover as that's where the guide debris would've went first, I'd even take out the clutch, and make sure you haven't got any more stray pieces in your gearbox)...If there are any kinks or wear on the cam chain (you said it was directly rubbing the pins) you'll want to replace your cam chain, and the cam chain damper guides if worn (the side ones as well as the top missing one), and the tensioner if it seems to not have a smooth spring action (myself and a few other people have had problems with the cam tensioner failing, I think maybe heat makes the internal spring go bad quickly or something)...

BUT, I'm on TT to get advice more than give it...It's just an opinion and not an expert one...But again, at least this will bump you back to the top for more info from someone wiser...

  • Dnnap

Posted July 08, 2009 - 06:19 PM

#7

Goose, thanks alot I really do appreciate it. I will take off all the covers and try to find and remove all the rubber pieces. Hopefully there isn't a big chuck of rubber binding somewhere in the bottom end or blocking an oil port. Is there a way to check if I have any blockage in the oil passages? I beleive there is an oil pressure check bolt, but I don't think that will tell me if there is a blockage in one of the oil ports.

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  • lftdjeep426

Posted July 08, 2009 - 07:07 PM

#8

Now this makes me very curious. I've been having loss in power problems as well on my 07' and I only have 43 hours on it. I have another thread going right now to where my bike won't hardly stay running anymore. I am really low on compression. A buddy of mine also has an 07' and let me do some parts swapping (his bike is not maintained near as analy as I do) but I checked compression on mine and I was down to around 35 psi. I checked his also and it was only around 65psi WOT after 10 hicks. I am starting to wonder if there is something going on with the 07' motor. I believe that it was slightly changed from the 06'? If you can, check your compression, I'm thinking my problem is in the valves and I wonder if yours is the same. :banana:

Day after tomorrow I'm pulling my head to check clearances. Just curious to know if yours is the same problem just not as far along. Mine seemd to be loosing power until one ride where it dide while 3/4 throttle. I have only got it to start back twic and will run for about 5 minutes ad won't start/fire back.

:worthy:

  • Dnnap

Posted July 09, 2009 - 04:51 AM

#9

Well, I just bought my bike from a local pro, and every wear part was replaced. It has a new HC piston and rings, ported and polished, web cams, and I've only put about 10 hours on it so far. I'm new to the 450's so I compared the power of mine to my friends '09 YZ450F and I have no bottom to mid pull compared to his. The pro rider had the carb modified by Tokyo Mods and was running a full DRD exhaust, so I thought the stock exhaust was causing the power loss, that was until I posted the question in the intake and jetting forums and Eddie says it's not the exhaust.
At that point I went and checked the valve clearances and timing and all looks good, so that is when I noticed the upper cam chain guide missing.
The bike starts great and runs fine, it's just it has no pull and revs out fast compared to the '09 YZ450F.
I just completed a dry compression test and I'm getting 35 to 40 psi. This must be wrong or the bike wouldn't start??? Am I correct? I'm thinking the auto de-compressor is causing the inaccuracy in my compression readings.
I'm not sure how to rebuild a 4stroke, so I'm not sure how to do a leak down test to see if it's my valves staying open.

  • grayracer513

Posted July 09, 2009 - 05:45 AM

#10

I just completed a dry compression test and I'm getting 35 to 40 psi. This must be wrong or the bike wouldn't start??? Am I correct? I'm thinking the auto de-compressor is causing the inaccuracy in my compression readings.
I'm not sure how to rebuild a 4stroke, so I'm not sure how to do a leak down test to see if it's my valves staying open.

I think I already pointed out that compression tests on these engines are worthless. A leak down test requires a special tester, which you can buy. Be prepared to spend $70~100+ for one. Most will take the bike to the shop and have it done.

Check your valve clearance and timing first, and consider the fact that your pro racer friend may have a set of cams in the bike that are built for top end power at the expense of low end.

  • Dnnap

Posted July 09, 2009 - 06:03 AM

#11

Thanks greyracer.
I did check the valves and the clearances are within spec. I also checked the timing and the marks on the exhaust cam are at 9 o'clock and 12, and the intake are at 12 o'clock and 3 o'clock as per the manual and research I've done on TT.
But, you may be correct about the cams being for top end power because the pro rider who owned this bike was running a larger rear sprocket. When I bought the bike everything was replaced, valves, chain, sprockets, plastics, tires, top end, ALL bearings, new stock exhaust, ect....
When I first got the bike the clutch cover and ignition cover was leaking oil and the weep hole on the water pump was leaking coolant. The bike also had a misfire at low rpm. The pro's mechanic came and got the bike and fixed these problems at no cost of course and adjusted the carb to eliminate the low end bogging/misfire.
When I replace the upper cam chain guide how do I prevent it from falling off again?

  • grayracer513

Posted July 09, 2009 - 07:07 AM

#12

When I replace the upper cam chain guide how do I prevent it from falling off again?

There are no fasteners, per se, for the upper guide. It basically snaps in place on the pegs in the cam cover. If you say these pegs have been damaged, it may be that they will not properly hold the new guide onto the cover. That would mean would would need a new cam cover (which comes with the guide in place), and they aren't cheap.

If the damage is minor, you may get away with replacing the guide and augmenting the normal fastening system with some 3M Super Weatherstrip Adhesive, or an equivalent product.

It's a little difficult to envision what might have caused the guide to become dislodged in the first place, and also to imagine how it would have gotten down from it's normal position into any other area without causing a major problem. I wonder if it was simply left out at some point.

  • Dnnap

Posted July 09, 2009 - 06:35 PM

#13

It's a little difficult to envision what might have caused the guide to become dislodged in the first place, and also to imagine how it would have gotten down from it's normal position into any other area without causing a major problem. I wonder if it was simply left out at some point.


I hope you're right, but I did find some chucks in the drained oil which resembled and felt like hard rubber. They were about 1/8" cubed in size on average and in the amount of which might be about a quarter of the whole guide. So, if it did fall into the bottom end and I got lucky without any major problem I have no choice but to assume the worse and try to find the remaining pieces of the guide.

As for the lack of bottom and mid power I think I will wait intil I reach 20 to 30 hours before I do a top end rebuild, but for now I'll change my rear sprocket from the current 49 tooth to a 50 or 51 tooth and run a DRD exhaust. I will however check my valve clearances avery 2 hours as I usually do.
I did learn today that one of my friends has a leak-down tester and he will check my valves for me just to make sure this low power isn't due to the piston rings or valves.
One more thing, how many hours do you recomend one should to a top end rebuild?

Again, thanks so much for all your help!!!:worthy:

  • grayracer513

Posted July 09, 2009 - 07:48 PM

#14

One more thing, how many hours do you recomend one should to a top end rebuild?

No set number. I did the rings on my son's at somewhere around 90 because I was doing a head gasket. The old '03 I had ran up over 300 and never did get a new top end, valve adjustment, or need either. If all you do is race MX, you probably can't go that far on one.

Leak down testing will tell you what your rings are like, and your valves need replacement once you have to shim them .08~.10mm or so.





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