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Why did Suzuki go to the one piece automotive style cranks on the 750s? I haven't read a good explanation on the pro's and con's. Seems like the one piece would be stronger, but they weren't used on the big motors. The expense of rebuilding cant be an issue, because even though the roller cranks are expensive to rebuild, it seems like the one piece cranks weren't meant to be rebuilt that many times judging by the availability of bearings. So what gives? I know one of you super gearheads is all over this subject. Got any links to some good reading?
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Main reasons would be manufacturing based, i.e. that plain bearing cranks are cheaper to make and are probably quieter and therefore more easily fit into recent noise regs. They also produce less friction and are therefore beneficial to maximum power output. Roller bearing cranks can survive on very low levels of lubrication (as in 2 stroke engines) and this is symptomatic of Suzuki's belt-and-braces approach to design, as well as their expertise in 2 stroke engines at the time of the design of the GS range. Nowadays, virtually no modern 4 stroke bike engine uses roller bearing cranks.
Ease of rebuilding would not be an issue for the factory, as they would expect the engine to last "long enough" for the first owner. They don't care after that.
The reason the 1100 didn't change at the same time is probably that Suzuki weren't ready to make a plain bearing crank and attendant lubrication system for a bike of that power output. They just therefore continued with the established GS1000 based design. Witness the fact that many of the first era of plain bearing cranks weren't exactly a roaring success; here in the UK most of the early plain bearing Suzuki engines died a long time ago (along with many similar Kawasaki's for instance). OK there are still some around, but not in the same quantities as earlier roller bearing types.
It wasn't until the GSXRs that they got it sussed. Most bikes thereafter are similarly robust, such as Honda CBRs which can rack up high mileages with minimal maintenance in the way that needed a roller bearing crank in the late 70s, early 80s.
The overiding reason for all decisions in manufacturing is usually the same: cost and therefore profits. Exceptions are to do with reputation, such as the first Hondda VFR, built to very high quality and sold at cost price to restore Honda's tattered rep after the VF. -
Yep, agree with Brit. Two strokes had the built up cranks, so makes sense early 4 strokes did as well as it was known technology. Manufacturing technology, costs etc lead to plain cranks..I mean all the cars have them!Comment
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I`ll add a thought on this though.....as for a aftermarket performance engine there is no crank as good as a roller bearing crank. All pro stock and for that matter drag racing engines use roller bearing bottom ends. The roller bearing crank is stronger and will absorb much higher loads than plain bearing cranks. I would have loved to see a newly designed roller bearing hayabusa engine...the plain bearing crank is probably thier weak point as was most of the gsxr series. Plain bearing cranks are one of the reasons you seldom see a honda or yamaha on the drag strip...I`ve tried them both...they just can`t take the abuse. One disadvantage I see from a roller bearing crank is that it is not nearly as smooth...its harder to balance. I`m sure bean counters have more to do with production than most anything these days.Comment
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cranks
interesting.......Comment
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Not sure thats true per se.Originally posted by cbxchris
There are some pretty lairy car engines out there using plain bearings, and bear in mind that cars with their superior traction load up their drive trains much harder than a bike.
Don't formula one engines use plain bearings? And what about the Rolls Royce Griffon. 37 litre V12, 2000 HP, 2 gear supercharged, water methanol injection etc etc.
Then there's all the new Moto GP bikes. I'm not sure, but I'd bet that none of them use roller bearing cranks.
And what about Kent Stotz's 500 bhp Blackbird Streetbike?Comment
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Originally posted by brit7.11
One word...plain bearings are cheaper to produce than a roller. If plain bearings were so great they would have turbine engines running them. can you get a plain bearing to rev to 14k or so? Sure, probably so, but compared to the same engine using a roller crank, the roller will last much longer.. :twisted:Comment
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Sorry Tim, but that doesn't make sense.
Is price really an issue in a Formula One car, or a Moto GP bike? I hardly think so. And I already said that yes, one piece cranks are cheaper to produce, but that doesn't mean they are worse, does it? After all, who recently had a crank wear out in their plain bearing car?
And turbine engines are a completely different kettle of fish to reciprocating engines. The requirements for the bearings for a gas turbine are totally different. For instance, radial loadings are quite low, but axial loadings can be quite high. You can't compare a bearing in a turbine to a bearing in a piston engine. Faster isn't necessarily better!
There have been tests done on plain bearing crank bikes in this country. A Honda CBR600 with 160,000 miles on the clock was stripped and found to have negligible wear. Would a roller bearing crank have lasted longer? Very possibly, but who cares? The point is that given proper care, a plain bearing crank will last as long as the rest of the bike.
Don't get me wrong, I like roller bearing cranks, but I think that to say that plain bearing cranks won't take the load isn't true. There are plenty of highly tuned GSXR's (and all sorts of cars etc.) out there to prove different.Comment
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Pre 1980 & post 1982, GS roller bearing crankshaft, or bearing problems, were virtually un-heard-of. The first 2 and 1/2 years of the GS1100 4 valve engines, some of them would twist the crank where it was pressed together. In mid 1982 this problem was taken care of by welding the crank pins. Not to say all plain bearing motorcycle crankshafts give trouble, but crankshaft & bearing problems are now just a normal problem, like my dodge pick-up that spun a rod bearing a couple of years ago, all of them don't but it's certainly not un-heard-of. Lets talk motorcycles, not v-8 chevrolets, formula one race cars, nor airplanes. I think the ultra high horsepower, top fuel drag bikes still use the old Kawasaki roller bearing crankshafts. If the newer plain bearing cranks were stronger or better, they would surely be used in these engines.Comment
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Cobblers! That is just not true. I can't recall hearing of anyone I know of with a modern bike or car which has had a crank problem, or of reading of anything in any motoring publication.Originally posted by rphillipsComment
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Yeah, lets. Except of course when it suits your argument to mention your Dodge van. Yes, thats good, lets just disregard any part of my argument which you can't answer!Originally posted by rphillips
The original question wasn't specific to top fuel drag bikes.Comment
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Brit7.11, crankshaft problems are very common with a large number of Kawasaki models: the old KZ440s would often lose main bearings and rod bearings, ZL900, ZL1000 and ZX1100 motors would almost always lose #3 rod bearings, and 250/500 ninja motors regularly lose main bearings (and they sound like they are knocking already when they are new). My shop has had 5 Kaw motors in for this problem in the last year with no other makes having similar problems.Comment
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My arguement here is mostly...thats mostly in a aftermarket performance application. For comparison sake lets take a old Z-1 kawasaki....originally 903 cc....with a stock crankshaft they routinely are ran as 1500cc drag strip engines with stock rods and only welding the pins. I cannot even think of a honda 900 doing anything at all like this. Plus you will have to go to a carillo rod or equivalent. The gsxr series which is plain bearing routinely cracks the crankshaft journals...even in stockers. Rod replacement is necessary for even the mildest mod. On FJ yamahas the bearing material is so soft anything with a load such as nitrous is disastrous...I can show you videos of that. Pro stock motorcycle at this very moment uses haybusa body work and GS based engines...roller bearing. One thing anyone forgot to mention is that the tranny is in the case...not like F-1 or cars. On launch no one has found a way for the crank shaft to not lose oil pressure...even that milli second is disastrous to a plain bearing crank....not so with the roller. I have to agree that its amazing how well a hayabusa engine now holds up...but can only imagine how good it could have been with a roller crank. I think by going to a plain bearing engine its only one more thing to worry about..the crank honestly is and was the last thing I worried about in my roller bearing race engines. Again I must say that we`ve probably seen the last of the roller bearing engines...they are complicated,expensive and heavy. Does that make them not as good..No Way! Given a choice I would gladly want and love to have roller bearing engines from now on.Comment
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Good points Chris, don't have a problem with any of that, but as I said, the original post was NOT just about drag racing, with its attendant problems.
Don, fair point again, but for every bike you quote with rod/crank issues, there are many more that never have problems. This is because the design is fundamentally sound, but a plain bearing crank is less forgiving of poor execution and maintenance. Sounds like Kawasaki have some issues they need to resolve, not that plain bearing cranks are crap.
In most other forms of racing, there is no problem with plain bearing engines. Drag racing has some very specific issues that can only be addressed by the use of components that can survive with zero, or close to zero, lubrication. That is the strength of a roller bearing crank, as stated by Chris.
I think you'll find that Formula one cars, and many other types of vehicle using plain bearing cranks, launch pretty damn hard at the start of a race, and then continue to do hundreds of miles flat out. Formula one cars go to what, 16000 rpm?
The problem with most bikes which use plain cranks when tuned for drag racing, is a problem common to most modern bikes..... they are CAD designed to produce xxxbhp and then be consequently as light as possible. They don't have the extra meat in the components to with stand really radical tuning. In the 70's things were designed manually using the equation " add p for plenty". Would a modern roller bearing crank be capable of handling twice its design power rating? Of course not! Because it would be half the weight of the old ones!
So, as I said right at the beginning, there's not a lot wrong with plain bearing cranks per se, and the reason GS cranks are so strong is not just because they use rollers (although this does help in margianl lube situations) but because they are so BIG!
Theory states that a plain bearing is stronger than a ball or roller, given adequate lubrication. If plain bearing cranks were so prone to failure as Don implies, every major car and truck manufacturer in the world wouldn't be using them. It wouldn't make commercial sense.
Please don't reply to this post by saying that you have a pro-stock GS thats done 6 seasons racing, and you've seen hundreds of plain bearing bikes bite the dust in the same time...Comment
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Hey brit7.11, it looks like you like plain bearing cranks as much as I like rollers. I don't have any problem with that, I'm proud for you. I'm not trying to say that all plain bearing cranks are bad, nor am I saying that all plain bearing motorcycle cranks are bad, cause they aren't. But mile for mile, on motorcycle engines, stock or hopped up engines, in my opinion the plain bearings will give quite a bit more problems per mi. And for automobiles, seeing as we can't stay away from them, I wish one of the auto manufacturers would spend the big bucks to try rollers in cars & trucks, just so we could compare one to the other. It would be hard for me to argue that a V-8 Dodge would hold up better with a roler bearing crank, if I have nothing to base it on. This has never & will never because of the $$$$. But we can compare the motorcycles, try asking some older motorcycle mechanics that have been around both kinds. The younger ones won't work, cause they've probably never seen an old roller bearing 4 stroke crank. Hope you will be as lucky with your plains as I've been with my rollersComment
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