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Discussion Starter · #1 ·
Hi everyone.

I have been lurking a bit on the forum but never made a post.

I bought a 93' EX500 last summer to practice on to get my license in Sweden. My sister was also taking a license but a A2(a restricted licens) so I found this beaten up bike with a A2 restriction. It didn't run great but we managed and got the licens. I realised the bike was in a too ruff state to be able to sell, and i been looking for a project to make a scrambler, cafe racer or something. So i decided to keep it and would start with the grinder during the winter. So i wanted to start by removing the A2 restrictor, because it's licensed with a restriction and the enginen won't rev past 5000-6000 rpm.

So when i tried to start it before starting to strip the bike nothing happened. Turns out that the gastank was all rusty and the gasoline was brown after i flushed it all out. That had clogged the gas-pipes. So all of the gas-pipes was sorted out, and a new tank will be bought. After the gas problem sorted out, I took down the carburettor and cleaned it all out, the right throttle wouldn't open more than 2/3 before but works like a charm now. I guess the carburator haven't been taken apart and cleaned in maybe 15 years. I thought i would find some restrictor rings somewhere around the carburettor, but couldn't find anything either at the air-box or in the tubes after the carburettor in to the cylinders.

Okey, maybe the restriction sits in the gas pipes after the combutionchambers? Took all of that down also and found nothing. The enginen runs a'lot better now UP to 5000-6000 rpm but won't move pass that. I don't have a clue of what the problem could be or where I should look. I can hear some kind of metalic ratteling at some rpms and after a rev when the enginen returns to idle. Maby it's some restriction somewhere still, or some other problem.

Here is the video so you engine whispers out there can figure it out.
Thanks alot, Gustaf

 

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Hi welcome to the forum. (y) I'm well aware of the restriction for the A2 licence, it's to reduce the revs and power of the GPZ/EX500 to 47bhp or 35kw. well known here in the UK (perhaps not so much in the US) it does this in 3 perhaps 4 ways dependant on how your locality (region) fixes the certified reduced power output, it will have, either or all.
1. reducer rings in the inlet rubbers between the carbs and the head. (looks like a big flat washer stuck in the middle of the rubber boot).
2. same thing only a brass inset into the exhaust ports between the head and the exhaust headers. usually fitted inside the exhaust gasket.
3. reduced throttle openings by having a mechanical throttle stop fitted to the accelerator linkage to stop it opening more than 1/2 throttle.
4. may even have smaller main jets fitted perhaps #115 or #120 instead of the stock (full power version) #130 mains.

the reason it will not rev passed 6k is because that is exactly where the GPZ/EX500 max power curve starts. the restriction prevent the engine from revving past 6k so it never touches anywhere near the stock 60ish bhp.
if you look hard enough you will find all the restrictors.
can be difficult if you do not know how the full power version should look it's easy to mistake a restrictor for a normal part (the very reason restrictors have to be certified) they look stock but are not.
if I can find the photos of a typical restriction device I will post it so you can see.
 

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here is a photo of a pair of restricted inlet rubbers.

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I cannot find one of the mechanical device to restrict the throttle. but if you look at the linkage while opening the twist grip you should see a bracket that stops the throttle opening fully. it is usually held on the carbs with tamperproof screws.
 

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Discussion Starter · #5 ·
Yes! I check the registration papers for it and the bike is only licensed for 20 kw (ruffly 28 Hp) and that should correlate with the "limit" of 5000 rpm as seen in the power band graph.
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I didn't find any washings in the inlet or outlet. I wasn't certain on the exhaust outlets, so I will dismantle it again and take a picture. Stupid of me not to do it when i already done the job. I will check the carbs again and see if the jet's are smaller. I will also check the throttle if it opens all the way. Should i do this while having the engine running and open carbs?

Does the bike have an CDI that could be restricted?
Also, can the exhaust be restricted further back? Because the pipes look like **** and have some bad welding, and i might the ratteling sound may come from there.
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right quite a bit to cover here, no it's not required to start the engine. your looking for a bracket that stops the butterflies opening fully (take a photo of yours) nothing else. the exhausts ports can be hard to see as the restrictor plates are only just smaller (5mm) than the gasket in the ports. the inlet rubbers should be more obvious as they are metal and there is no metal in the full power inlet rubbers.
main jets should be #130 the number is written on the jets. pilots should be #35 and needles should be N36N but these may well be stock sizes (but worth checking).
No the exhausts should not be welded like that as the cans are slip on with clamps you have some that has been altered from stock by some weld happy previous owner.
as far as I'm aware the CDI is the same restricted or not it is not likely that it differs from a full power one.

in general the power reduction is to drop the power of a bike so it conforms to the output of a A2 licence. the restrictors are after market and fitted to a stock bike to reduce the power output. but have to be certified the work has been done and a dyno certificate provided for proof.
they are not meant to permanently reduce the power level of any bike these can be reversed once removed. so altering the general specification of a stock bike is not written into the remit of the law, this means you have a stock full power bike with restrictors. once find and remove them all you will have full power.

please note, a couple of years ago we had a Dutch member who had the same issue (wanted to return a restricted bike back to full power) his bike was completely stock (no washers or changed jets) just a device to stop the throttle opening more than half way. once removed he had full power. I suspect yours could well be the same, but it depends on your region as to how the power reduction was done.
 

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Discussion Starter · #8 · (Edited)
Hi!

It's been winter here in Sweden and I'm working outside so I haven't gotten to it. I will check during Christmas probably.

But I started to check the cooling system, and when I open it up it only comes out a brownish foam, like peanut butter och brown whiped cream. I did a quick googling and it says it's either the enginen seal, or rust thats casing this effect. Is that a major problem or an easy fix?

Should i start to consider to abandon this bike as the starter for the project? We payed 1300€ for it just to learn and get the licensen, and we did. I'm starting to feel that this won't be a budget fix to get this one running great, and I might be better off bying a another better cared for bike?

For example, I think I can get a GPZ750R for 1000€ with a yosimora pipe, few miles and well taken care off. No restriction to find either. Maby that would be a better base for a build?

Or do you guys think the current one can be fixed easy to run great on a budget?
 

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hi thanks for getting back to us, as with all these things and has been said on the forum many times "it's your bike to do with as you wish" I won't lie to you these GPZ500's can be a dream to own or a pain in the ass it all depends on the level of servicing and general condition.
when you take one on be prepared for it to be either, also a project bike is just that a project, unknown faults that have to be assessed and repaired one at a time no matter how long or how many there are.
you have to put your heart and sole into doing one up properly, or there is little point.

quick easy fix, to be honest I doubt it in your case. the cooling issue is consistent with a low maintenance well used bike that has been run for along time short of coolant and without being changed, it should be ALL liquid (no bubbles or foam) and clear to a opaque brown colour, it could be as easy as completely flushing out and filling with new coolant or have major issues.
the restrictor bracket should be easy to find, but are these the only things required (I doubt it) if it has been run without regular maintenance. it will also probably require, the oil and filter changing the air filter changing. the valve clearances being set. the brakes servicing and the rear suspension (rocker bearings) cleaning and greasing and anything else you find while your in there like carbs, plugs HT leads to name but a few.

as I said a project is just that a project with the aim of repairing all the faults you find done over a unlimited time scale without a fixed budget in mind. definitely not a quick easy cheap fix up. depending what else you find along the way.
it's up to you to decide I can only inform you as it is. the level of dedication you put in will determine the outcome.

but as you mentioned another bigger better bike, with less work I suspect you have already partly made up you mind.
good luck with whatever you decide to do. lets us know either way if you decide to tackle the 500 we are here if you need help.
 

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Discussion Starter · #10 ·
I got inspired today and took my carburettor down to a local shop for some guidance. The mechanic told me that it was no restrictor in the carburettor, it just needs a cleaning. I told him that I took it down and went throw with wd-40/multispray. That didn't cut it, and I had also forgotten to detach all the screws. Especially "the front ones". So i redid it and removed all screws and got everything soaked in brake-cleaner and sprayed it all out with compressed air. I think i got allot of junk out, big diffrence with the break cleaner. The liquid was all dirty and black afterwards. Some of the dirt in the bucket are frim the carbs, some where the before i started. So it was THAT bad.

I checked the main jet screw and it was a 130 mm. So the bike was probably unrestricted, but left with the restricted license, and just so badly maintained that it performance exactly matched the restriction. What are the odds.

When i reassambled the tops, one corner broke off and the plastic cover got a crack so the vaccum didn't seal. Brittle plastic probably. I had to make a improvised fix, so I got some plastic padding for the plastics, and some chemical metal for carb. After two tries i finally got it together and feeling confident that the throttle behaved as it should. It felt okey and hope it will remain okey. It's not pretty, but hopefully works with some longevity.

I haven't tried it on the bike yet, but will do tomorrow. Hopefully she purs like a cat and revs higher than 5k.
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Have you adjusted the valves? Since it is a 1993, there is a fair chance that the cam chain has jumped time. The cam chain tensioners (1987-1993) are horrible and allow the chain to skip over the cam sprockets under certain circumstances. If that happens, the revs will definitely be affected. It is of course always good to adjust the valves, but also make sure the timing marks on the cam sprockets line up properly with the cylinder head surface.

Oh, while you have the carbs apart(?), give those rubber diaphragms (and intake boots) a good coating of Armorall. An hour or so in a 120-130F (48-54C) oven will help the Armorall to penetrate the rubber.
 
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Discussion Starter · #12 ·
I just tested the carbs, and she runs alot better, until 5-6k. I recorded a video, so you can see that the problem still remain. I'm queless right now. It might be the camchain like suggested?

Anyhow, here is the video, she still dosn't want to run higher than 5-6k.
 

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As posted earlier by @po18guy .... have you checked valve clearances/cam timing and changed to Gen 2 chain tensioner as yet? Wow....you are denying these essential maintenance checks/actions on your '93?
 

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had a look at your vid, I think I have your issue. the throttle cable is routed OVER the overflow tube instead of UNDER it.
so as the cable pulls up it binds at the wrong angle to get full throttle. try rerouting it and see if it changes things.
it's hard to spot at first, but it's there.
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Discussion Starter · #15 ·
As posted earlier by @po18guy .... have you checked valve clearances/cam timing and changed to Gen 2 chain tensioner as yet? Wow....you are denying these essential maintenance checks/actions on your '93?
I will check that. But we just had it one summer, and it was running enough for us to do the drivers test and get the licence. We didn't have the licence when we bought it so we bought it undriven, and it's my first dip in to the bikepool. And it was licensed as restricted, so we thought it was running fine, until we couldn't find any restrictions. I previously had a Porsche 944 and did all the work myself, chaning gearbox, starter enginen, renovating all the brakes and so on. So I do know how to wrench, and that's maby why this bike is getting some carbs cleaned for the first time in forever, and I even consider brushing her up, step by step :p

Thanks! I will check the throttlecable as soon as possible. That might be it! Great spotting, what a eagle eye!🦅
 

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It's not going to run right until you get the air box back on either.
 
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had a look at your vid, I think I have your issue. the throttle cable is routed OVER the overflow tube instead of UNDER it.
so as the cable pulls up it binds at the wrong angle to get full throttle. try rerouting it and see if it changes things.
it's hard to spot at first, but it's there.
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Oh-oh. you have just identified the über secret Euro 6 emissions restrictor! You'd best enter the witness secrecy programme for your own safety.
 

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Oh-oh. you have just identified the über secret Euro 6 emissions restrictor! You'd best enter the witness secrecy programme for your own safety.
Ha-ha. if you lived in Europe you would understand how ironic that statement really is.:oops:
however it's just pure deduction from the statements supplied. OP said he had bought a restricted (A2) licence bike, I asked for a photo of the carbs to look for the official euro restriction kit. but he never supplied one.
when he uploaded a vid of the bike running I just freeze framed a shot enlarged it to look for the restrictor bracket and tamperproof screw. and noticed the pull cable was over the vent pipe instead of under it. giving the same result as the bracket. this may or may not be the main issue for non revving.
who knows on a 30 yo bike with no history. if it is the problem good then the OP will have to tackle all the other issues you would expect on a well used gen 1. now whether that is possible in a Sweden winter out in the open who knows.
 

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Having an ex-pat Brit friend in northern Sweden, it is said that the oil freezes before the Swede does.
 
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