Hot starting problem - ZXR250

[Kwakka Kilt]

Hi All,

OK as a follow up to a previous thread - viewtopic.php?f=21&t=17274&start=0&st=0&sk=t&sd=a" target="_blank , where my bike was running rough under load, and cutting out in the wet (Both problems were dodgy plugs and leads, and carby synch required), as seen in the other post, the carbs have been serviced, valves adjusted, and was running great, except it was overheating after this work was done.... Never did this before on the same run to work, the fan was never required ....

I have now fixed the overheating (Refilled coolant, removed / bled out as much air as possible, found a broken fan switch on the radiator (Temporarily wired the fan on permanently - Thx for the tip Rossi !! )

Still have the following problem though, even the garage that did the other work could not work it out, can anyone use their technical savvy to suggest a fix please ??

Here goes, symptoms :

Starts cold on minimal choke for 30 secs when cold, then idles fine, runs a treat, pulls great now under acceleration.

When warm / hot (Temp Gauge can only be reading 1/4 or less when the problem shows itself), if you kill the ignition and try to restart, the bike will try to catch, but using any variation of choke or throttle or both, or just using the starter button, the bike will not start.

Then, during the same time period of trying to fire the bike up, if you leave it and try starting again, you get a high pitched wine from somewhere in the circuit, and no starter motor action, turn it off and leave it 2 - 5 mins or so, the starter motor will turn over no problem, sometimes not ....

Today, when I was trying again to start the bike after trying all of the above, the rev counter went up to 4000 rpm every time I pressed the starter button, again with no starter motor turnover, dash lights would dim quite a lot, this is the first time it has ever done the rev counter trick .....

Halfway through the above hassles, I tried restarting again,(Bike was still warm), the bike fired into life with a smooth idle, right off the starter button, with no choke or throttle

Bump starting does not work, when the starter is not able to turn over, the rear wheel just slides with my full body weight jumping onto the bike when I dump the clutch in 1st gear after running down the road, I have successfully bump started the bike like this when I first bought it ....

Even when I use jump leads from the car battery, if the bike battery is getting tired, does not improve the situation ....

I reckon I will be genuinely shocked if there is a logical fix for this .... Come on guys, I can't afford any more garage bills, got to suss this one on my own ....

Cheerrz.

[Kwakka Kilt]

Actually, just had a thought about vapour lock when the carbs are hot ?? If I use unleaded on a 1989 ZXR 250 (A Model), should I use Premium instead, is this type of fuel better for older bikes ??

Thx....

[dave#3]

It's almost certainly electrical and pretty bloody bizarre. Considering that the plugs and leads have been replaced recently (and I assume this problem has only appeared since the leads were replaced) it would be logical to start by looking there I suppose, but my gut feel is a bad earth somewhere, probably on the starting circuit but not necessarily.

Actually, I wonder if your starter-motor is failing to disengage - that might explain locking the rear wheel when you try to dump start it and the odd hissing sound (solenoid under load). I don't know the layout of a zx2 engine, but if you can, try tapping the starter motor with a gentle persuader (hammer and a length of pipe).

Whereabouts in Sydney are you? If you made it up the OPH on a Sunday morning you'd be sure to get plenty of unhelpful advice ... but it's often easier to diagnose problems when you can see/hear/feel/kick them.

[Kwakka Kilt]

Hey Dave #3,

The problem was there before the leads / plugs / coils were changed, the bike now runs sweet after these were changed when riding.

I am going to give the starter a bit of a tap to see if this frees it off, I can hear the starter relay clicking away when I try to start the bike, so as you reckon, the solenoid may be sticky ....

After I do this, I shall go for a long run and see if when I open the tank cap, if I get a rush of air into the tank, maybe the tank breather is blocked, causing vacuum lock, this could be the cause of the problematic starting after a run.

I also read that vapour lock could be an issue, but I can't see how these bikes don't have heat shields on the carbs out of the factory if this was the case.

I read on a Google search that these bikes are sensitive to batteries not being the best, so I will have another go after I know it is as good as it is going to get.

Thanks for your help mate.

[Neka79]

also- try jump starting in 2nd gear (hard if it has pos nuetral finder i kno) as 2nd gear seems to work better...

[Nathanb4]

Hay guys, I think it is common for the zxr250, that when you try to start it pulls. I have a few questions for.
Is your bike heating up while on a long ride?
Do you need to top the radiator up every so often?
I have had most of these problems and found that most of this was caused by air getting sucked into the radiator generally when you give it a boot full. These radiators are coated on the inside (i think some rust proof shit) well radiator fluid actually slowly eates away that shit and the cap is not able to keep it air tight.
One solution is to seal the cap to the radiator and use the reserve bucket under the seat. Or you might need to purchase a new radiator .

[Slow and wobbly]

Hay guys, I think it is common for the zxr250, that when you try to start it pulls. I have a few questions for.
Is your bike heating up while on a long ride?
Do you need to top the radiator up every so often?
I have had most of these problems and found that most of this was caused by air getting sucked into the radiator generally when you give it a boot full. These radiators are coated on the inside (i think some rust proof shit) well radiator fluid actually slowly eates away that shit and the cap is not able to keep it air tight.
One solution is to seal the cap to the radiator and use the reserve bucket under the seat. Or you might need to purchase a new radiator .

Nathan not too sure exactly what you are trying to describe but, why not a new radiator cap? - silicone is great stuff but I dont think it should be used on a radiator cap? As far as I know the radiator would pretty much be stock standard aluminium alloy, almost all coolants now contain a corrosion inhibitor that prevents the glycol ( the active ingrediant in coolant ) from destroying alloy.

From my understanding of what you have written you have actualy described a faulty radiator cap. If it does not seal and hold pressure then the cooling system will fail to operate as it should and the end result is a hotter operating temp. I think the problems you have had are somewhat different to what has previously been described.

[Gosling1]

KwakkaKilt - the problem with your starter solenoid is that the contacts inside it have carboned-up. Over time, and many hundreds of start-cycles, the copper contacts will build up a coating of carbon, and stop the full current flow through to the starter motor. The symptom of this happening is the 'clicking' noise you can hear when you hit the starter button. Sometimes it will work, and other times it won't.......typical of the joys of electrical problems......

If you can remove the starter solenoid altogether, you shoud be able to split it, and give the contacts are thorough cleaning with wizards piss and a brass toothbrush. I have even used a piece of wet'n'dry paper to get the contacts *shining* !!

This will address one part of your problem, hopefully.

One other tip - Find the end of the earth lead from the battery that bolts onto the motor. Undo it, give it a really good tub in wizards piss, and clean up the area where the bolt and lead are positioned when tight. Dodgy earth terminals are often overlooked when fixing electrical problems, they were the cause of many electrical issues with a lot of GpZ900's ........

[Kwakka Kilt]

Heyo guys,

Thx for all the tips, I have cheated a little for the moment with the overheating - I have bypassed the fan switch (It was stuffed), so the fan runs constantly.

Now the temp will never go above 1/3, even after fanging the crap out of the bike and sitting at the lights after...

Gos mate, the starter solenoid fix sounds the biz, but what the hell is Wizards Piss ??!! (WD40????)

Oh, I have cleaned the main earth to the motor 3 times now.

I found that if I hooked up the car battery via Jumpers, and started when hot, it would start every time, without that, the bike would crank, but not quickly enough to get the motor to fire ...

I thought the starter motor might have been sticky, so I removed it and gave it a dose of the car battery directly - Spun up a treat with no noisy bearing type rumbles etc ....

Just this weekend I charged the crap out of the battery (Ended up with 13.8 volts just off the charger), started great, ran fine, tried restarting again when hot - It started !!

That was Saturday, but today just took it for a 5 minute " Rev the tits off it " type thing, back home tried restarting again, no go - 5 mins later it started straight off - Tried a third time, dash lights dimmed, cranked but did not want to start - Whaddya think, Battery needs replacing ??

Thx again boys.

[Gosling1]

......Gos mate, the starter solenoid fix sounds the biz, but what the hell is Wizards Piss ??!! (WD40????)....... Whaddya think, Battery needs replacing ??......Thx again boys.

indeed, WD40 it is laddie !

and yes, that battery sounds like it has seen better days.......whats the electrolyte level like ?? You can get some 'battery reconditioner' from most battery places, if you have any sulphation in the cells (any cells gone white ?), this stuff will reverse the chemical reaction and get your battery charging properly again......INOX Battery conditioner. Works great !

[Kwakka Kilt]

Oh Aye !! WD40 is indeed Wizards Piss Old mate !!

Yeah, I thought about getting some electrolyte, but I am thinking about trying to get a battery with a bit more OOMPH !! (Higher cranking rating)

Just gotta find one that I can squeeze into the battery box.

Hey Gos, whaddya reckon to those Gel type, new fangled batteries, worth the extra coin ??

So you reckon putting in some fresh INOX would make the battery good as ?? Not sure about white cells, the electrolyte is still near the top, but who knows, the old box of volts may have been in the bike since 1989 !!

[Gosling1]

It may be difficult to fit a bigger battery into the battery box - more cold cranking amps = bigger physical size. You could be lucky and find a battery with the same physical size and more cranking amps, only your local battery shop will know if this is possible.

Gel batteries ? I haven't used these (yet), a mate has one in his XS650, and it seems to hold a charge and keep the bike running OK. I intend to fit one into the Z750 trail bike at some point, but it uses a kick-start only, so I will probably drop the amp rating and get as small a battery as possible (that will still cope with the stock charging system), just for the weight factor.....talk to the battery shop - It depends on the cranking amps your starter motor requires, if a gel-cell battery that fits in the stock battery box can supply these, then I don't see why you couldn't use one in your bike....

INOX can help a good battery stay good for longer, and it can also help turn a bad battery good again - but it does have its limits. If your battery is total white (sulphated to the max), then its beyond help. If only 1 or 2 cells have started to develop the 'white dust of death', then a good dose of INOX will remove this, and the battery will take a charge and hold it. If your battery has been in there since 1989 , I think a new battery is the go !! But try INOX first, its pretty inexpensive, and small batteries only need 5-10ml per cell. Can't hurt to try it.