at risk of upsetting: Bringing ER-5 up to GPZ Engine spec?

[Smooth]

The GPZ is the obvious parts donor for releasing the stallions from the softly-tuned ER5.

I've seen Stinkwheel's and others posts on Kwak 500s and wonder if anybody on here has bothered to swap the entire GPZ500 engine or just the cams, CDI and carbs onto an ER-5? Valve timing being the most obvious difference between them.

From a different approach, has anybody achieved any tangible improvements from an ER-5 with exhaust mods and re-jetting?

ps. Yes, I know that more power isn't everything and that going out and buying a better bike would be cheaper.

As per previous thread, I believe that improvements to handling (and riding skill) would be more beneficial.
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TDM850

[MarJay]

I think its pretty much just cams, exhaust design and airbox size/shape.

The cams will be a pain in the butt, and the GPZ exhaust is a two into two if I recall correctly.

But it is perfectly doable as far as I know. The other alternative of course is to look for a second hand GPZ engine...
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Smooth]

It would be easier to swap the whole engine out and fabricate an exhaust to suit, but the engines cost a few quid.

Fitting a set of cams and a new chain&tensioner would be fairly involved, but satisfying (and I could set the valve gaps properly at the same time!)
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TDM850

[MarJay]

[stinkwheel]

Valve timing, carb jetting and ignition advance curve are the biggest physical differences.

You would need to check the ER5 ignition system is compatable with the GPZ CDI. Some have one pickup, some have two (there is a GPZ CDI of each type, you'd just need the right one).

In real life, the main issue is the shape and size of the airboxes.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Smooth]

Yes, the ER5 has a single pickup coil.

Have you attempted anything similar with your KLE, Stinkwheel?
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TDM850

[stinkwheel]

My KLE has a GPZ500 engine in it. Complete with carbs and CDI.

Won't run on standard GPZ jetting, runs ok on KLE jetting but doesn't have the GPZs top-end silliness.

Exhaust diameter identical, inlet stubs identical.

Conclusion: Airbox configuration is very important. The GPZ relys on pressure waves to stuff air (and therefore fuel) into the engine. This is achieved by clever airbox design (which is also what made the 900R the first 150mph bike, the 500s is essentially half a 900R). The KLE airbox is around half the size of the GPZ one.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Smooth]

Interesting.

It must be similar to 2-stroke expansion chamber pulse tuning.

I wonder what would be the best way to optimise the 'effective length' of the air passage-way for the KLE/ER-5?

I wonder if modifying the KLE/ER-5 air box would have any benefit on a standard engine? -obviously not wanting to run lean.
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TDM850

[mudplug]

Not seen a KLE air box (and none on ebay to compare lol) but the ER5 air box is pretty big.

For the benefit of all readers, I was thinking about modifying the air inlet on my ER5 air box to supply extra air, if I re-jet to GPZ spec, along with the camshaft swap.
However I'm now concerned that even though my planned mod (a hole in the centre of the inlet cover) isn't engine-side of the air filter, it might still mess up the pulses.
It would effectively be by-passing much of the the inlet trunk-tube thing; which I notice is also a feature of the GPZ air box.

Maybe some sort of hole nearer the tip of the trunk would be of more benefit; I suppose the ideal would be a larger-diameter trunk, not easy to fabricate.

ER5 airbox photo:

https://i10.ebayimg.com/05/i/001/01/b5/fb73_1.JPG

[Kickstart]

Hi

Suspect the important part is the length of the trumpet from the carbs into the airbox.

Playing with the tubes feeding air into the airbox might upset things. Shape wise the intake is probably quite good (the shape of the edges of the intake is pretty important to the flow), and drilling extra holes might screw that up.

I do have a GPZ500 airbox floating around.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

[virus]

Jesus christ who designed that airbox? it looks like someone has been playing too much tetris.

No wonder joe had so much trouble refitting his at R+S with no tools.


Cheers
John
____________________
own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

[stinkwheel]

[virus]

GPZ750r/900r airboxes are quite random, there a complete pain in the arse to get in the frame let alone connected to the carbs.

I keep telling myself to keep it and not convert to K+n's, its got to have some use other than a battery box.


Cheers
John
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own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

[Smooth]

[mudplug]

I think the 'pods' house the inlets.


So is the route anyone takes in trying to tune these engines just a matter of choice, or more of common sense?

What I mean is, I'm sure it would appear to be the cheaper option to go down the route of cone filters and bigger jets, but there are so many stories of people never getting the fuelling right; even if they get more top-end power, it's at a big pay-off regarding how usable the engine is.

Whereas the manufacturers had all the time, money, expertise etc to put into development, so used the pressure-wave approach to tune it. It's obviously going to produce both more top-end power and more usable power across the rev range.

I don't have the facilities that they do. But I can buy an airbox which they've developed. (Don't know if it fits in the frame yet.)

Does it make sense to utilise the development Kawasaki put in, rather than using more basic methods (which won't really achieve the same results)?

Or does it make sense to be content with a smooth, average bike, and accept it's substantial merits rather than looking at it's relative flaws...

I suppose a lot is down to what I'm going to use my bike for. (i.e. not racing.)

[Purplepill]

Edit: beaten to it
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''He had the confidence of a baby-goat dared to tickle a t-rex's nutsack''

[mudplug]

Interesting reading for anyone (like myself) that only has a basic understanding of how this works:

Wikipedia pages on Manifolds and Helmholtz Resonance.

I'm sure there are more accurate and detailed sources, but Wiki's free

[Smooth]

Resonant frequency indeed.

Those links takes me back to uni days... although I've only an appreciation, rather than an in-depth knowledge of waves and vibrations, having not looked at it for about a decade.

what I recall:

Mass, spring constant and damping constants are the major considerations (as they are in many aspects of engineering)

For acoustics, column length is important.


Interestingly, the EX500 (The USA GPZ500)has this air box
EDIT: These are the SIDE covers, I can't tell if they are different to Mudplug's photo

https://www.stevemorley.com/ex500/airbox/sidebyside.jpg

https://www.stevemorley.com/ex500/airbox/open.jpg

The accepted mod from the resident guru on the EX-500.com forum for this airbox is to
drill a second 1" intake hole as shown here in this link

https://www.stevemorley.com/ex500/airbox/aftersm.jpg[/b]
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TDM850

[Kickstart]

[stevo as b4]

I'd consider going for the K&N type clamp on filter's, but only if when they are fitted that they are fairly well covered by the tank/seat/side panels etc. I think running any bike on exposed filters is a pain, and wet weather could really bugger up the carburation and running. I would also try and fit the K&N's as far back as possible and use some long ram tubes of a similar length and design as those that go from the carb bellmouths, to the airbox. That way it's likely to be a bit less hassle getting the jetting close to what is needed.

It goes without saying that you should also use the biggest sized filters that you can fit in, as they will take longer to clog up and will be less sensitive to airflow restriction.

I'd be dissapointed TBH if the route of a set of open filters+ 2-1 exhaust and race can+ stage 3 dyno jet kit or alternative jetting kit, could not find you another 3-4bhp at peak. The midrange would possibly improve more than this however. I don't know how the ER5 lump would respond to a 3-4deg ignition advancer, but fitting one and using super unleaded, could possibly sharpen up the throttle response noticably.

To get the full 60bhp, you either would need GPZ or aftermarket GPZ cams, and or a gas flowed head at least. This is much more expense and finding the last 10bhp might not be worth the cash for the results? If going to those lengths i would consider a Big bore kit, as tuned 600-650cc big bored lumps, have seen over 76bhp at the crank.

[tsmith]

if you are considering engine work on the EX500, check out

https://www.enginedynamics.com/kits/kawasaki.shtml

[Smooth]

[stevo as b4]

True that unless you had a specific reason to tune the ER5 lump significantly or were trying to make the bike competative in a race class etc, then the cost is not justifiable in most cases.

However the cost of say re-building a worn engine, or buying a GPZ engine to transplant, would go some way towards tuning the original motor possibly with a big bore kit, cams and head work etc.

I agree that you probably wouldn't need 10bhp to make the bike feel nicer to ride and more responsive, so some good VFM breathing mods and some time spent on the carburation/dyno setting up, could land you a more responsive bike that is slightly faster, for a reasonable amount of spend.

I used to see a guy riding around near where i live with an ER5 that had motocross wide bars on it, and a short race can fitted. It seemed to go well, and you could hear the popping from the exhaust which sounded .

[Purplepill]