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crankshaft strength question

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Ross.
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Post  jmw76 Mon 05 Nov 2012, 10:46 am

Hi Guys,

I am relatively new on here. Some might be familiar with my post on ASF and OSS.

I am keen to know if anyone has had experience with crankshafts breaking on tuned Bandit engines.

I would also like to know where they break and what damage is expereinced as a result.

I have heard that the 59mm crank is not as strong as the 58mm one.

Just trying to determine build direction on my next race motor.



Cheers



Peter.
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Post  Ross. Mon 05 Nov 2012, 10:52 am

Would this not depend on how much tuning has been done? How many kilometers on the crank before the tuning was done? What oils and how often they had been changed?

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Post  2wheelsagain Mon 05 Nov 2012, 11:09 am

Given that the oil cooled Suzuki engines have been used for years in many states of hyper tune I would think they were pretty must as robust an engine as you can get.

You can break any crank if you try hard enough. I know thats not an answer Wink

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Post  Hammy Mon 05 Nov 2012, 11:18 am

If you can break one. Then you've had a lotta fun doin' it.
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Post  mtbeerwah Mon 05 Nov 2012, 1:38 pm

What sort of hp are looking at tring to.achive?
I've been on a few sites where natural verse turbo,and no prob with turbo 210 hp.
The killer will be from detination, as some have blown up bandit engines from this.
Dont get that,and you should be right.
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Post  jmw76 Tue 06 Nov 2012, 12:04 am

MY previous engine build (1196cc) was knocking out circa 170bhp at the crank in normally aspirated tune.

I run 13+ to 1 CR on race fuel. There are no signs of detonation.

My engine spends most of it's life working at close to max rpms.

At Philip Island, earlier this year, it broke a con rod at 11,000+ rpm. Made a good deal of a mess.

The rod broke at the little end. The eye let go and split down the beam.

I have certainly seen my fair share of component failures in my oil cooled engines. THey might be pretty strong, but they are not unbustable. The engine is very heavily loaded and I am looking for every possible idea that I can employ to ensure that the next engine build is as strong as possible.

The plan is to base the next build on a Bandit engine with Busa rods, Wiseco 1216 pistons (low dome height -CK101 type), heavily modified 750 j/k head, improved gsxr j/k cams and earlier, beefed up spring clutch set up.

Peter.
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Post  rolls Tue 06 Nov 2012, 8:52 am

The 'busa rods are 2.5mm longer than the bandit rods. If you go for aftermarket Bandit/GSXR1100 pistons you can't use the busa rods, or the pistons will be way over deck height, let alone worrying about valve clearance. Post -07 busa rods are 18mm dia pins, not 20mm, so you need rods from pre 07.

Standard busa pistons are 81mm, giving 1216cc on a bandit, but they are dished and will sit lower in the bore and will lower the compression to around 9:1. The budget* upgrade to 1216 is to get busa rods and pistons, rebore and also shave the block to get the pistons to sit flush on the deck and shave the head to .5mm to give you ~10.8:1. Should make a great highway machine with heaps more torque from the heavier busa rods, but you might get a better track bike with a smaller piston and higher compression, like 80.5mm giving 1201cc.




* I bought a new std head gasket on ebay for $32 delivered. I thought "Hey, I'll shave the head and get heaps more compression and it'll go sick and it'll only cost $32. Sweeet!".

After machining costs, other gaskets, "mmm new cheap cam", and "better put a new one of them in while I'm there", and "fuck, that broke, need a new one", etc, - $780 later it does go really well, but it's still $780.
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Post  jmw76 Tue 06 Nov 2012, 9:25 am

Yep.

To run the Busa rods you have to run a spacer plate under the block. Carefull choice of the spacer plate thickness and base gaskets gets you a sqwish height of about 1mm. Which is where you want to be for efficient combustion.

Yes, you have to machine the piston crowns to cut deeper eybrows to clear the valves on the Wiseco pistons.

You can not get enough CR with the Busa pistons, even with the 750 head. This is a race motor and it needs high CR to get the power/torque.

Anyway, I gather no one has broken a crank? Just keen to know where they most likely break to assess the risk of running one vs the early (1052) GSXR crank.
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Post  jmw76 Tue 06 Nov 2012, 10:59 am

This like from OSS has a bit more info on broken cranks.

http://forum.oldskoolsuzuki.info/cgi-bin/Yabb/YaBB.pl?num=1297896836/0



It would appear that they then to break through the web. The one highlighted in the article would appear to have been cracked for quite some time.
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Post  mtbeerwah Tue 06 Nov 2012, 11:20 am

Hi Pete,

Sometime ago I had been following your progress from ASF forum.

Obviously you haven`t rebuilt yet to what you want.

I know you were looking at a few different rods in your build,have you got that sorted yet? as I thought that was your main prob from memory,not the crank blowing up from the main cause of distruction,was that right?

Or are you just on the hunt for total possible info to avoid terminal in the new build?
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Post  jmw76 Tue 06 Nov 2012, 1:42 pm

Yes.

My original point of failure was a broken rod. It destroyed a great deal of bits and pieces in the engine (clutch, crank cases, gearox input shaft, valves, piston, etc, etc). The only retrievable bits of sustance were the crank, cylinder head (fortunately as there is a lot of time invested in this) and a few gearbox bits.

I spent quite a bit of time just collecting parts for the rebuild. I did contemplete a complete swap to a later engine, but ditched this as I just love the old oil cooled technology and there are no changes required to the rest of the car.

I acquired a Bandit engine with only 27,000 kms on it, so the path was then set for the rebuild.

I know the Bandit clutch is weak so I managed to find all the bits to convert to the stronger spring set up (very hard to get now). I have heard tales of broken cranks on the 1127/1157 engines so I thought I would put out a general fealer to gauge just how common this problem actually is and weather it is worth my while using the earlier (reportedly stronger) crank. I have not heard any tales of broken 1052 cranks. This could just be because there are not as many out there and they do not tend to get as heavily modified as the 1127/1157 units.



Anyway, unless someone gives me advice to the contrary, I will probably rebuild with the 1157 crank (after a very carefull inspection).

I have a set of stronger, Busa rods to use. I did think about crome moly rods but they do get to be expensive and I have had very good reports from people using the Busa rods in some pretty high power drag engines without issue. The Busa rod has a much more robust, bronze bushed small end. The only hassle is they are slightly longer. Nothing that a block spacer can not fix.



Peter.
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Post  mtbeerwah Tue 06 Nov 2012, 3:23 pm

Yeah righto,

I`ve too got busa rods for a build,but im only chasing 140ish HP, I want more torque than HP,as has to be every day rider. was talked into it by the lad building it. They cost bugger all from the states,so i got them.

What induction are you using?

You say alot of time invested in the head..your own port and play,or someone of high reguards?
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Post  jmw76 Tue 06 Nov 2012, 4:23 pm

Always do my own head work. That is part of the fun. Making the changes and seeing the results. I have modified a number of heads for various vehicles that I have owned over the years.

We are running RS40 carbs and custom intake manifolds and air firter assy.

With the right mods, you don't loose much, if any, usable bottom end.

I regularly run on the track with a fellow in a similar vehicle but with an almost standard 1100W motor.

The difference we see when pulling away from him out of slow turns (and everywhere else) is as clear as day vs night. The guys that usually give us a hidding on the track are those with modified Busa and Zx12 powerplants, as well as some of the older, well sorted race cars such as F2 Elfins, Ralts and Dallara F3s. But we are then comparing cars in a very different league. A gun driver in a front running Formula Ford (Fiesta engine) will also put us to shame. Those guys just have no fear.

If you want really big power from the oil cooled heads you have to go up in valve size (primarily why the water cooled head works better in stock trim) but that tends to go hand in hand with lots of other changes and has an impact on reliability and general engine life expectancy. Not an area I have been willing to delve into with my current Suzuki engine builds. The 750 head is a good start as it is designed for revs of 13,000 or so. More than you will need on an 1100. So you can do a bit of tweaking without fear of any great dramas. The smaller combustion chamber does give a few clearance challenges on an 1100 though.



I have successfully run some big valve combinations on other engines I have worked on in the past. I built a low budget Triumph Herald engine a number of years back complete with custom designed electronic fuel injection that went very well in a little Clubman special that I ran for while. The valves in that head were quite large (relatively speaking). The car would never really challenge the lightweight 20 valve 4AGE based cars. But it put up one hell of a good fight. Particularly at tracks like Winton.

If you are seriously interested in doing your own modification work, I would recommend you get hold of some of David Vizzards books or watch his videos on the net. He is one guy that knows his stuff and has a lot of respect in the industry. There is a lot of crap advice out there.



I seem to have gone off topic a bit.

Sorry.





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Post  jmw76 Tue 06 Nov 2012, 4:24 pm

I hope someone can get some usefull information out of my ramblings.



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Post  jmw76 Tue 06 Nov 2012, 4:27 pm

For those that think I am just a car nut. My son has 3 bikes. 2 x road bikes and 1 x GSXR 750 based old school race bike that we are building.

Peter.
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Post  mtbeerwah Tue 06 Nov 2012, 6:23 pm

all good stuff mate,

as for doing my own porting..nah,not on this next engine,only for the fact the lad that is doing my head, has a flow machine,and has many many years of experience on suzi oil cooled.

i have another 3 bandit heads,so will play with one of them one day
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Post  jmw76 Tue 06 Nov 2012, 6:49 pm

Yep.

Made my own flow bench too.

Let me tell you though, there are other issues that effect cumbustion efficiency that will not show up on a flow bench.

Getting the biggest flow numbers possible isn't always a good thing. Unless you are after absolute horsepower at high rpms and any cost.



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Post  mtbeerwah Tue 06 Nov 2012, 7:21 pm

science,trial and error is basically the key to get the desired result(knowledge),which also applies to induction and correct header-exhaust set up to suit head and cylinder flow
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Post  jmw76 Wed 28 May 2014, 8:34 pm

crankshaft strength question Sam_1710
Hi Guys,

Been a while since I was on here.
I thought I should post a bit of an update after the rebuild.

Essentially rebuilt as planned using the Bandit engine as a basis.

Engine is now running just fine.

Seat of the pants result indicates that it is now quicker than previous builds.

I ran the car at Geelong speed trials in December last year.
The format of the event is a drag race down the Eastern Beach Rd adjacent to the beach.
It is only about 370m but we have a bend in the road and dust and sand to contend with. There is also a rule about no burn outs prior to your run, so cold tyres.

I managed a best time of 10.906 which was considerably better than my last time (10 years earlier) of 12.3. A friend in a similar car, but with a warmed Busa engine (claimed to be knocking out about 210bhp) managed a best of 10.880. Near as damn it the same time. Obviously my little machine is knocking out a few ponies now.

Here is a link to the event/times for those interested.
http://www.geelongrevival.com.au/
I ran on the Saturday.
My son also ran his 88 GSXR750 for the very first time on both days.
Times were not quite as good as the car but he had heaps of fun over the 2 days.

I have added a pic of the car and bike together in the pit area at Geelong.

Cheers

Peter.
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Post  mtbeerwah Wed 28 May 2014, 9:17 pm

Hi Peter, Good to see it all worked out for you, with no more destruction problems,

That's a good time, considering, its in a vehicle!

What`s it weigh, and what sort of power do you think its putting out?  it must be putting out quiet a bit to push a vehicle to achieve that time?

What was your terminal speed, about 128mph?
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Post  jmw76 Wed 28 May 2014, 10:55 pm

Yep, time was quite reasonable considering the fact that it is not a real dragstrip and I am in a circuit race car.

I am not sure of the actual power output, but it would have to be circa 180bhp.

The car with me in it weighs in at about 420kg.

I can not recall what the terminal speed was. 10 years ago, I was doing about 180kph. I would expect that I would have been up around 190 - 200kph this time. The fastest we have ever seen on a circuit (phillip island) has only ever been about 225. It's a bit like a brick as the speed increases. Not as aerodynamically efficient as you might expect.

I did flatten the wings right out this time in an effort to get a bit less drag.

It's all about getting it off the line effectively.

Peter.
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