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Discussion Starter · #1 ·
Last Sunday I took my 625 SMC on a 900KM ride. This would take it to 4000KM since last service, The valve train got noisy and I was planning on servicing it today. On my way back from work for a few minutes my bike started surging then I lost m most of my power. The bike does not rev over 4000-4500RPM and it feels like a vespa. It does however and start idle perfectly.

Considering the behavior the main culprit would be that the carb main jet clogged. The no name gas stations along the back roads don't always have the best fuel.

On the other hand I have been reading about valve train components seizing on these bikes. Could something from the valve train cause this?

Im not sure where to start now. The carb or the valve train?
 

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why not both? it's not like it takes a lot of work to clean the carb and have a look at the head. if you say you heard noises coming from the valve train then I'd put my money on that.

if the bearing on either the intake or the exhaust rocker arm is shot (ie radial play) this will have an effect on engine timing. when the cam lobe hits the rocker arm bearing it will first press until the play is gone and only then will the rocker arm open your valves. so your valves are opening later then they normaly would, which can cause a drop in power.
 

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Intake roller rocker seized. Mine has twice. Power drops as the roller and cam lobe flatten. I'd start there, then when you are waiting for parts go through the carb.
 

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Discussion Starter · #4 · (Edited)
I cant tell anything by just taking off the valve covers. I guess I have to take off the whole cylinder head top section. The engine manual asks me to drain the coolant. Is that really necessary?

OOOOH daaamn after being very confused from looking at the engine, pics and the manual I realize that the rockers are attached to the cover.
 

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Discussion Starter · #5 · (Edited)
So the intake roller actually lost it's bearings. It's not seized, it moves freely with a lot of play because of the missing bearings (wonder where those went).

The cam is mostly OK. The intake is slightly ground on the inner edge. Otherwise it's smooth. I wonder if I have to replace it...

The rocker has a scratch in it. It's not too deep. I wonder if I also have the to replace it.

How do I pull the rollers out of the rocker?

Damn this has to be the worst case scenario :(







Good times, this bike is really growing on me...

 

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Grab a beer and try to relax. I've been through this twice as have others. Some have been lucky and not had this issue ever, go figure, we're the lucky ones.

The bolts you pulled to remove the cover are not all equal, so be sure to keep them in order. The main 4 are of different lengths, the outer small bolts are the same(I think).

Did you get it to TDC before you started the process? This makes the water pump removal/replacement possible.

Yes, replace the cam. No, you can't just get new bearings for the roller. Once it started grinding and losing the bearings the roller started becoming un-round and wallowed out on the inside. The roller and bearing is relitively cheap, less than $30.

The cam is about $160. Now would be a great time to get the rally cam. ( I'll look up the P/N) Found it :)8536010044

To press out the old pin from the rocker arm; get a bench vice and a small(smaller than the pin) socket or piece of something that size that is a little longer than the rocker is wide. Does that make sense? with the vice and probably a third had, put a larger deep socket on one side, the rocker in the middle and the small socket on the other. use the vice to press the pin out.

New pin and roller will slide right in. Then you will need a good punch and hammer, that third hand would come in handy again, then peen the rocker and pin where they meet each other. Peen well and deep on both sides at least 4 times to hold the pin in place.

Sorry this is spotty, When you take the rocker shaft out there are shims on both sides, #23


This img is from Munn Racing, if you don't already have a parts supplier this is my go to guy. Chip will treat you right! If you take the time to sign up over at KTMTalk you'll get a discount from Munn's.

Back to #23, there are 3 thicknesses of #23. On one side you need to have the 1mm shim. In your pic above, 4th down, that would be the shim at the top of the pic. On the other side you use a combo of shims to cet the lateral play down to ??

Do you have a real service manual? I've one at home that I'll bring to work so I can ref specs for you.

I could probably do the work faster than I can type all this out but....you probably don't live in NW Florida.

I'm gonna go search up some links to my woes here and over on ADVrider.

Anyway, you can do this!

The bearings and pieces are up on top of the cyl under the cam in all that oil. And of course in the bottom of the sump, you'll find those when you drain the oil.

BRB
 

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Lots of good info in here especially the parts about rebuilding the water pump and making a bolt to lock the crank @ TDC


ADVrider pic of how to push out the pin with a vice

Pic of peened roller shafts from KTMTalk thanks WRK2SURF!


Here is the link to my post over at KTMTalk.

There is a lot more on ADVrider, it'll take me a bit to search for it all. This should give you a good starting point.
 

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Discussion Starter · #8 ·
Whenever I encounter unequal bolts I poke them in a piece of cardboard at their relevant location.

The roller pin is just pressed out, got it.

Regarding the shims, I kept them in order. I will look through the manual if my current set up is within specs.

Regarding all the metal shavings, I will drain the oil. Then I will get some rotella to flush it twice.

Did you see the scratch on the rocker? Should I replace it too?

Is the water pump another common problem?

I dont think I will go with the rally cam. I like my low end too much.

I have the KTM 400-660 LC4 1998-2005 service manual. The manual is a bit hard to follow since it strips the whole engine down then it addresses individual parts. I am quite uneasy working on this engine since they are so rare. It's not like I can get one off ebay for $500 if I screw up.
 

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Discussion Starter · #9 · (Edited)
Is it really necessary to lock the crank at TDCC?

Can I just unbolt the camshaft bolt by putting the bike in 1ST and holding the rear brake?
 

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Mine had a scratch like that, didn't appear to me to prevent the part from operating correctly. On my second go around I ended up replacing both rocker assemblies and rebuilding the originals. Now I have a second set on hand.

No, you don't have to lock the crank. It's just a good idea so that the motor doesn't get spun while all the timing components are apart. My 3yo son came out in the garage the first time and rolled the back wheel while it was still in first from removing cam. He did it in front of me but if I hadn't known, things might not have gone back together so well.

Read closely the part about the cam chain tensioner when reinstalling it, the alignment of the water pump(see it has a little locating pin) and the lock ring for the cam can come out while reinstalling.

I wish I could get another off ebay. Take your time, look at the manual and the web, it's easy enough.

I hope you plan to replace those cam bearings while your in there?
 

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So are the two red-circled areas showing factory machining flash? If so, shouldn't those be removed (carefully so as not to drop them into the engine) so they don't get knocked off accidentally and... well... dropped into the engine?

Bryan
 

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Yep, that's what it looks like, good eye. As far as dropping into the engine, that's on the rocker cover. Only way to see that is off the bike. So unless they are removed and thrown into the engine or left in the cover when it's put back on, they wont find there way into the motor. Besides, those two little flecks are nothing compared to the roller bearings floating around somewhere in his motor:D
 

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Discussion Starter · #13 · (Edited)
Thanks everyone.

The bearing you are talking about, I supose it's



23 0625060040 GROOVED BALL BEARING TMB004
25 58036097000 NEEDLE BEARING BK 2012 (Should I add this one too?)

Otherwise this is my shopping list. I decided to get the whole rocker just to be safe. The groove is quite deep. Hopefully I have everything.

58336061090 ROCKER ARM ROLLER CPL. EXHAUST $30.39
58336010144 CAMSHAFT 249/ CPL. $142.05
58536060144 ROCKER ARM INTAKE CPL. 2005 $125.75
58338045100 SCREW TYPE FILTER $23.21
58038005100 OIL FILTER LONG $8.60
59039093100 SPARK PLUG NGK DCPR8E 03 $3.80
Your Total $333.80

Hondabong HT to seal the cover.
 

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Yes and yes to the bearings. If any bearings saw metal shavings it'd be those.

I assume you gave thought to the water pump and decided to pass.

List looks good, minimal but good. Some go all out for new crush seals and gaskets. Heck, some will have a complete rebuild from such and episode.

By the way my last roller bearing failure was at 32k mi. I'm currently sitting at 62k+
 

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Discussion Starter · #15 ·
I barely got to ride this thing, and after my last trip with it, I am ITCHING to take it out asap.

I am reconsidering the Honda HT sealant. Removing the cover was quite difficult with what the dealer used. I didn't want to pry or hammer it so I put the bike in gear and moved it forward. That popped it right off. Would that work again with the Honda HT?

I am surprised you dont replace those rollers every 15 000KM. I told myself I would do that before I even got this bike. I was going to do it this weekend as my oil change was up. What a bummer.

I was out riding with the owner of http://www.pannonsports.com/performance.php I am considering coating my camshaft with his "dry film lubricants", and if it's possible my rollers.
 

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Discussion Starter · #16 ·
Oke weird moment. I just found a hex nut around my valves. You can see it in the third picture to the right of the cam bearing. It's from one of the intake valves. The other one is also missing. I never removed these. Someone really screwed up here. Judging by the gouge in the rocker and the lateral damage to the cam I bet the other one had something to do with it. We will see when I find it.
 

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... I just found a hex nut ... from one of the intake valves. The other one is also missing...
Holy crap, it's lucky something didn't get seriously bent (assuming it hasn't).

You're talking about the intake valve adjuster locknuts, right? Sure hope you find the other one before you button it back up.

Bryan
 

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Nice write up Tim ,very detailed...again:thumbup:
 

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was planning on picking up a 625 next weekend, because i have heard about the great reliability. Then I see a thread like this. How common is this problem? (sry for the high jack just thought that's a relevant question)
 

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It seems one of the flaws of the LC4 motor, is lack of lubrication to the valvetrain. Like Tim explains, keeping the oil at the upper level, changing frequently with quality oils, prolongs life of the rocker bearings. I would say go for the 625. It's still one of the most reliable big bore thumpers out there. Tim has like 60K on his! But I'm planning on doing a tear down, and swapping in a rally cam at 8,000 miles and replacing those bearings, yada, yada. So I'll tell you then. Only 5,000 more miles to go! At my rate thats four years from now.
 
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