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Some interesting RMZ450 internal engine shots.
(Click here to view the original thread with full colors/images)

Posted by: Rich Rohrich---------------------

While we were working on a local expert rider's RMZ450 I took some pictures I thought were worth sharing.

The RMZ450 exhaust cam below has less than 20 hours on it :

http://www.ericgorr.com/images/drn/..._exh_lobe_1.jpg
http://www.ericgorr.com/images/drn/...exh_lobe_1b.jpg
http://www.ericgorr.com/images/drn/...exh_lobe_2a.jpg
http://www.ericgorr.com/images/drn/...sing%20side.jpg

The RMZ's intake cam looked almost exactly the same, but oddly enough the intake valves were in fairly decent shape. The rings and piston were completely shagged. It smoked like a two-stroke when it came in.

As a comparison, the CRF 450 cam below has 2 seasons on it :

http://www.ericgorr.com/images/drn/...%20on%20cam.jpg

Forensic work on engines sure is interesting.

All pictures are of the closing ramp side of the cams.

Posted by: dirt bike dave---------------------

Thanks for the pics, Rich. Very interesting.

What oil was the RMZ rider using and at what change intervals?

Assuming good maintenance practicies, any guesses on how many hours a novice or amatuer rider could expect to get before his lobes looked like that?

Posted by: john3_16---------------------

Wow....I've been totally reamed for saying that Honda has a superior build quality than some of the other brands...A traind eye can see the difference easily.

Those pictures totally ruin the idea of "pic a color, there's no difference in quality" that's for sure.

Posted by: bigred455---------------------

I have 70 hrs on my 05 RMZ 450,B rider here,my cams look in excellent shape.I do however drop oil every 4 hrs(2 rides) and top off in-between.DELO 400 15/40 Change oil filter every 4th ride (8hrs).
I will take pics.

Posted by: Matt Fisher---------------------

It looks like there was valve float on the RMZ, no?

What caused the engine's death, according to your autopsy? Is the RMZ450 going to be relegated to crap (aka RMZ250) status?

Posted by: steve125---------------------

Good pics Rich. I guess my only question would be, did he ever change his oil? Even though the valves were floating, seems the oil was not doing its job.

Posted by: biglou---------------------

Looks like the journal is badly galled in that last photo, too? Did this thing come in with the factory oil in it?!

Posted by: bclapham---------------------

Quote:

Originally Posted by john3_16

Wow....I've been totally reamed for saying that Honda has a superior build quality than some of the other brands...A traind eye can see the difference easily..

one worn out engine bike is hardly proof now is it?

Posted by: XRpredator---------------------

you don't see pics like that from the inside of a KTM

Posted by: Chili---------------------

Quote:

Originally Posted by XRpredator

you don't see pics like that from the inside of a KTM

The KTM's grenade all physical evidence, nothing left to show

Now before all you pumpkin patchers get worked up I'm kidding!

Posted by: Vic---------------------

Quote:

Originally Posted by Rich Rohrich

All pictures are of the closing ramp side of the cams.

What do the opening sides look like?

Was the engine run with no oil? That would explain the death of the piston and rings, also.

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by biglou

Looks like the journal is badly galled in that last photo, too? Did this thing come in with the factory oil in it?!

Quote:

Originally Posted by Vic

What do the opening sides look like?

Was the engine run with no oil? That would explain the death of the piston and rings, also.

The cam cap/bearing in the head has a full circle groove , so the area in the center of the bearing that looks galled is just the space where the groove sits.

At first glance it's easy to think this was an oil related issue , but when you get the parts in your hands is easy to tell it's not likely to be the case. The area of greater pressure on the cam (and the place where the oil has to work the hardest) is the nose of the cam . There is no real indication of excessive wear on the nose (I'll take some new pics tonight). If the oil was the root cause the nose would show signs of it. My guess is the bucket is lofted over the nose at high rpm rather than staying in contact with it. The ridges on the closing ramp aren't galled like you would see in a normal oil breakdown situation, they feel very consistent and evenly spaced, like you see in harmonic patterns. A high zinc oil might have helped, but there are no oils in existence that can cure oddball cam dynamics.

This is a rider who revs the bike hard, and it looks like the valvetrain just isn't up to it, even when new. For the average rider it seems unlikely this is going to prove to be an issue. I guess time will tell.

The rings being worn out after 15+ hours in the hands of a pro level rider is nothing strange. Single compression ring pistons start losing measurable power after just a few hours when ridden hard, even with good maintenance practices. When fast racers start closing in on the 20 hour mark, the rings are just along for the ride. Any hope of good sealing is just a distant memory.

Posted by: Vic---------------------

Interesting stuff.

Thanks, Rich.

Posted by: Pete Payne---------------------

Some of the darker area's of the cams in Rich's pics look like tooling marks ????
Do ya have a close up of a new OEM cam ???
Looks like somebody speeded up the ol CNC a little too fast.

Posted by: john3_16---------------------

Looks good BigRed....You can't go wrong with Delo 400 thats for sure!

Posted by: Yamadad---------------------

Quote:

Originally Posted by Pete Payne

Some of the darker area's of the cams in Rich's pics look like tooling marks ????
Do ya have a close up of a new OEM cam ???
Looks like somebody speeded up the ol CNC a little too fast.

That's what I was thinking too, although Rich is THE man.

Posted by: Rich Rohrich---------------------

Those aren't machining marks.

Those are "I'm a wicked fast rider who can ride a 450 like a 125" marks.

I'm trying to get a hold of a set of fresh RMZ450 cams so I can run a Cam Doctor analysis on them and compare them to some of the other OEM 450 cams.

Posted by: steve125---------------------

If you look close you can see the same chatter marks forming on big reds455 EX cam. Definitely not factory machining marks on either examples.

Posted by: nephron---------------------

Not exactly a properly-powered prospective, double-blind crossover trial, now is it Rich....

So I think you're saying the RMZ simply had an aggressive pilot? Who piloted the CRF?

Now if somebody took 10 of each bike, 20 riders of mixed skill levels with precise 'time-sharing' of the bikes, and rode them for a certain time period with similar service parameters, .....we might be getting there....

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by nephron

Not exactly a properly-powered prospective, double-blind crossover trial, now is it Rich....

Clearly not. When I typed the original post I had the following disclaimer:

It's far from scientific, I just thought the comparison was interesting..

The computer locked up before I posted and I forgot to put it back in when I retyped it.

The CRF was ridden by a normal vet rider, but the cam we pulled out of Tyler Smulder's CRF450 after a 1/2 season didn't look much different than the CRF cam pictured. Tyler got his AMA Pro card this season and has an insane revver style like the RMZ450 rider, with Tyler being a LOT faster. So this is just an interesting contrast, nothing more should be read into it. I should have made that clearer from the start.

Tyler is going to be on an 06 KXF250 and an 06 KXF450 this season, so it should be interesting to see how they fair.

For the record, Tyler has managed to hatchet the cases apart on his 2003 CRF450 practice bike (rod fatigued and broke in an elastic failure 40mm below the small end) and he has blown a CRF250 practice bike to pieces as well.

I guess the moral of the story is, everything wears out, and fast guys wear stuff out FASTER

Posted by: Masterphil---------------------

It'll be interesting to see how that poor KXF takes a pro beating on it. Do keep us updated. Pred mentioned KTM, have you had any 250SXF motors come in yet? If they turn out to be reliable, unlike the KXF/RMZ's, they may just get me off that 125 in a couple years...maybe.

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by Masterphil

Pred mentioned KTM, have you had any 250SXF motors come in yet?

There are only a handful of them in the country so I doubt we'll be seeing one any time soon.

Posted by: nephron---------------------

I thought you said you'd never bother to work on one...

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by nephron

I thought you said you'd never bother to work on one...

Should be an easy follow thru ....

Posted by: bclapham---------------------

on the KTM250SX, they are using oil pressure to keep the cam chain tentioned. a guy who holds multiple drag race records tells me its a good thing, since the higher oil pressure at high revs will keep the chain nice and tight when it needs it. the problem i see, is that drag cars see 7 sec runs, and i wonder how well the SX will hold its oil as the season goes by. ... all of the single ring thumpers quickly burn oil from what i can see..

Posted by: Rich Rohrich---------------------

Just a quick followup on this thread.

After getting more info on the rider's maintenance habits the root cause of the problem seems to be related to cam chain tension. The rider didn't keep up with the adjustment (it's a manual adjuster on the RMZ450) and ran too much cam chain slack for too long. Since I originally posted this we've seen a few more RMZ450 cams like this and in each case the riders didn't pay proper attention to the cam chain adjustment.

You can't blame Suzuki for riders who ignore regular maintenance.

The small handful of riders I've talked to who look after the adjustment don't seem to be having the same issues.

Posted by: bigred455---------------------

Good follow up! Adjusting the Cam chain on THE RMZ450 is a big factor.After 3 hrs of use I pulled my cover off and the Cam chain was slightly loose,nothing alarming,but I adjusted anyway.I then put another 10hrs on it then checked again,it was considerbly loose,I will remind anyone with a RMZ,adjust it TDC ON THE COMPRESSION STROKE VERY IMPORTANT.Believe me or not I have 100+ hrs on mine and after the 1st 2 adjustments the 2nd one being the loosest the chain has not budged.I check the valves and cam chain every 10hrs regardless. Alot of riders are not taking the compression stroke serious when adjusting,the manual RMZ system is a good system,WHEN IT IS USED AND CHECKED PROPERLY!

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Some interesting RMZ450 internal engine shots.

This is the text version of DirtRider.Net
Click Here for the Full Version