04 CRF450 Crank replacement

[Dave Hoelcher]

19 hours ago, Shawn_Mc said:

I guess you can over complicate anything if you try hard enough. I'm doing a CB1100F for a customer right now. Is it more work, sure. Are there a completely different set of specs to watch, of course. But saying it's "hard"...I guess that all depends on what's between your ears.

I guess it's 'hard' primarily if you are determined to get it correct... It's certainly not 'easy' to fully assemble the cases on a multi, once with plasti-guage, then disassemble the cases to measure the plasti-guage, then swap out bearings, after having ordered & received the several hundred dollar bearing assortment kit, and then reassemble the cases again...will you plasti-guage it the second time to insure proper clearances or ASSume it 'should' be ok now? I guess you can sometimes use the word 'hard' in place of tedious. Surely would have been nicer, IMHO, if Honda had used plain bearings in the CRFs, at least on the rods. I don't think we'd be seeing all (or any?) of these exploding rods.  The only things left worth using on this 450 engine is the head, cam, gears, & clutch. Makes for LOTS of rolling chassis ripe for transplants. Inexcusable. K.I.S.S.

[Shawn_Mc]

10 hours ago, Dave Hoelcher said:

I guess it's 'hard' primarily if you are determined to get it correct... It's certainly not 'easy' to fully assemble the cases on a multi, once with plasti-guage, then disassemble the cases to measure the plasti-guage, then swap out bearings, after having ordered & received the several hundred dollar bearing assortment kit, and then reassemble the cases again...will you plasti-guage it the second time to insure proper clearances or ASSume it 'should' be ok now? I guess you can sometimes use the word 'hard' in place of tedious. Surely would have been nicer, IMHO, if Honda had used plain bearings in the CRFs, at least on the rods. I don't think we'd be seeing all (or any?) of these exploding rods.  The only things left worth using on this 450 engine is the head, cam, gears, & clutch. Makes for LOTS of rolling chassis ripe for transplants. Inexcusable. K.I.S.S.

The bearing type doesn't have anything to do with why the rods occasionally chucking out. It's got way more to do with the Fender washer...I mean piston skirt, collapsing and allowing the piston to kick over sideways binding up the whole world. The rod ratio isn't overly short on the engine, but the cylinder to crank angle they built in causes an incredibly sharp rod angle on the upstroke that doesn't help in the slightest when that skirt gets even the tiniest bit collapsed.

If you take a close look, that bike was loosing the rod bearing long before the rod broke. Look at the pin...

Plasti-gauge? Really?...ever heard of a bore gauge? I haven't used plastic crap since I did my first bug engine over 40 years ago.

[Dave Hoelcher]

56 minutes ago, Shawn_Mc said:

The bearing type doesn't have anything to do with why the rods occasionally chucking out. It's got way more to do with the Fender washer...I mean piston skirt, collapsing and allowing the piston to kick over sideways binding up the whole world. The rod ratio isn't overly short on the engine, but the cylinder to crank angle they built in causes an incredibly sharp rod angle on the upstroke that doesn't help in the slightest when that skirt gets even the tiniest bit collapsed.

If you take a close look, that bike was loosing the rod bearing long before the rod broke. Look at the pin...

Plasti-gauge? Really?...ever heard of a bore gauge? I haven't used plastic crap since I did my first bug engine over 40 years ago.

The bearing type has EVERYTHING to do with failure of the BOATLOAD of CRFs blowing rods. EVERYTHING. 'Piston skirt collapsing' indeed! RUBISH!!!  I'm not going to waste ONE more minute educating YOU. You've obviously been out from under your shade tree & in the sun WAY TOO LONG. For the others here, I've been a factory trained, certified, Honda Suzuki Yamaha cycle wrench since '76, & service manager of dealerships of same ever since, with state drag racing championships & WORLD Land Speed Records. Plasti-guage is THE ONLY way taught & approved by the factories for a REASON! I'm out. I won't be seeing any more of this grunts rambling yakky yak.

[Dave Hoelcher]

To the rest of you following this topic:

1. There is NO WAY these pistons are flopping over, in ANY way, shape, or form. Does this guy THINK a piston can 'collapse', flop over sideways, then return to PRISTINE condition??? (The piston out of that 450 engine in my  pic is not worn at all & neither was the bore.) Slipper pistons like these have been used for decades. They don't do shapeshifting! NO WAY is his B/S story a remote possibility. Ever.

NOTE: If he was to have said, and he didn't, that the wrist pins are going oval, & seizing into the pin bore, thereby allowing the rod to seize to the piston, THEN a failure occurs, well, I'd have to agree, this HAS happened, in auto racing. But, in the case of the AMC V8s, at extreme power levels, while dusting EVERYTHING Detroit could muster in the SCCA TransAm racing of the late 60s, & early 70s, it wasn't the rods that broke. Due to the outrageously strong rods AMC produced, the 426 Hemi sized 1" pins ripped the bottoms of the pistons right off, pin & all...

2. What IS happening, with the CRFs, IS that all those needle (roller) bearings, trapped within their cage, on the crankpin, on the big end of the rod, can only BE trapped within the DESIGN SPECS of that cheap assed cage so long till the cage goes out of spec, & the bearings begin to get more & more clearance, which means they can become further & further away from each other, meaning they no longer fully encircle the crankpin at distances which can absorb the load. No amount of oil pressure can protect the crank, its all just running out AROUND the bearings, so we see the wear on the crankpin. Some of you may be familiar with the term 'wedge of oil', which is SUPPOSED to be maintained between the bearing & the crankpin, by this point, it's gone, & we have metal to metal contact... Once THIS begins, the fuse is lit & it WILL go bang unless the wrench intervenes. Contributing factors to EARLY destruction include not using moly oil, sucking air & losing lubrication, running excessively on the rev limiter, holding the revs @ limiter in the air with no load. A trail ridden bike MAY survive this wear a bit longer but suffer cam & follower wear from the loss of oil pressure past the self destructing rod bearing. 

What can cure this problem, other than scheduled replacement of the rod, crankpin, & bearing? In MY opinion, as a professional... If it HAD been designed as a two piece rod with plain bearings, there wouldn't necessarily be a problem. R&D would have worked out rod material, rod bolt size & material, and come up with something that could live under the design goal conditions. Just as Honda has done in F1, Indy, etc.

Working with the design, and I'd bet there are teams who do what I'm about to suggest; don't use a caged bearing at all; you can likely get about twice as many rollers/needles in there & have a REAL bulletproof joint. There's no need to 'cage' the bearings, just use high quality thrust washers on each side to force the oil to stay within the rollers as long as practicable.

BTW: another HUGE plus of plain bearings is their ability to allow dirt to embed within them & not destroy the working surfaces. Not so much with metal to metal bearings - HAVE to keep dirt OUT.

I'm not here to debate the issue. I'm explaining what is happening & how to proceed towards a better outcome.

[Smokey450r]

They are a video on YouTube, I’m actually rebuilding an 2002 model today just a cheap selling bike tho.

[Shawn_Mc]

17 hours ago, Dave Hoelcher said:

To the rest of you following this topic:

1. There is NO WAY these pistons are flopping over, in ANY way, shape, or form. Does this guy THINK a piston can 'collapse', flop over sideways, then return to PRISTINE condition??? (The piston out of that 450 engine in my  pic is not worn at all & neither was the bore.) Slipper pistons like these have been used for decades. They don't do shapeshifting! NO WAY is his B/S story a remote possibility. Ever.

NOTE: If he was to have said, and he didn't, that the wrist pins are going oval, & seizing into the pin bore, thereby allowing the rod to seize to the piston, THEN a failure occurs, well, I'd have to agree, this HAS happened, in auto racing. But, in the case of the AMC V8s, at extreme power levels, while dusting EVERYTHING Detroit could muster in the SCCA TransAm racing of the late 60s, & early 70s, it wasn't the rods that broke. Due to the outrageously strong rods AMC produced, the 426 Hemi sized 1" pins ripped the bottoms of the pistons right off, pin & all...

2. What IS happening, with the CRFs, IS that all those needle (roller) bearings, trapped within their cage, on the crankpin, on the big end of the rod, can only BE trapped within the DESIGN SPECS of that cheap assed cage so long till the cage goes out of spec, & the bearings begin to get more & more clearance, which means they can become further & further away from each other, meaning they no longer fully encircle the crankpin at distances which can absorb the load. No amount of oil pressure can protect the crank, its all just running out AROUND the bearings, so we see the wear on the crankpin. Some of you may be familiar with the term 'wedge of oil', which is SUPPOSED to be maintained between the bearing & the crankpin, by this point, it's gone, & we have metal to metal contact... Once THIS begins, the fuse is lit & it WILL go bang unless the wrench intervenes. Contributing factors to EARLY destruction include not using moly oil, sucking air & losing lubrication, running excessively on the rev limiter, holding the revs @ limiter in the air with no load. A trail ridden bike MAY survive this wear a bit longer but suffer cam & follower wear from the loss of oil pressure past the self destructing rod bearing. 

What can cure this problem, other than scheduled replacement of the rod, crankpin, & bearing? In MY opinion, as a professional... If it HAD been designed as a two piece rod with plain bearings, there wouldn't necessarily be a problem. R&D would have worked out rod material, rod bolt size & material, and come up with something that could live under the design goal conditions. Just as Honda has done in F1, Indy, etc.

Working with the design, and I'd bet there are teams who do what I'm about to suggest; don't use a caged bearing at all; you can likely get about twice as many rollers/needles in there & have a REAL bulletproof joint. There's no need to 'cage' the bearings, just use high quality thrust washers on each side to force the oil to stay within the rollers as long as practicable.

BTW: another HUGE plus of plain bearings is their ability to allow dirt to embed within them & not destroy the working surfaces. Not so much with metal to metal bearings - HAVE to keep dirt OUT.

I'm not here to debate the issue. I'm explaining what is happening & how to proceed towards a better outcome.

What ever happened to you going away?

1. Ive got a whole box of pistons that have collapsed.

2. I dont disagree with any of your assertions regarding what happens with a caged roller. I happens constantly, exactly as you described to the left side main bearing. Ive got a whole box of cranks to show you regarding this too, simply because the cost of a new OEM crank isn't that much more than fixing one, and, when you fix it, the only replacement Ive been able to find is the HotRods kit that runs a plastic cage. Is a plain bearing rod more durable, sure. I'm not exact sure why you think you're the only one here that's worked on something other than a motorcycle engine. I've got several 1000+hp boat engines under my belt. Try keeping an L88 alive that runs 7500rpm under load, nonstop for the entire race, and then comes completely unloaded, spins well over 10,000 momentarily and then  gets completely loaded again. By they way, we couldn't even run a damn stud girdle...Oh ya, we had to run stock rods and an OEM crank too.

I'll stand by my bore gauge comment until the end of time. Plastigauge is spec'd exactly for home guys that dont want/need/cant afford $5000 worth of measuring instruments to do one engine, that will never see race abuse. You cant measure to the 10th of 1-1000th with plastigauge.

You realize that KTM uses a plain bearing on a press together crank / rod, right? You know why Honda uses a roller? Because they make money selling it at $275, brand new. Just the rod kit for the KTM costs twice that much, but since you know everything..you probably knew that too...

[Picasso_the_Impaler]

On 6/19/2018 at 2:43 AM, Dave Hoelcher said:

To the rest of you following this topic:

1. There is NO WAY these pistons are flopping over, in ANY way, shape, or form. Does this guy THINK a piston can 'collapse', flop over sideways, then return to PRISTINE condition??? (The piston out of that 450 engine in my  pic is not worn at all & neither was the bore.) Slipper pistons like these have been used for decades. They don't do shapeshifting! NO WAY is his B/S story a remote possibility. Ever.

^^ You can say this all you would like... but have a picture or 2

[Shawn_Mc]

Believe it or not, I've seen worse!!

[Jason Metropolitan]

Can i put a crf450x crankshaft into a crf450r of the same year model