Ahh I'm going crazy '89 GSXR-250R

[juddnz]

Took my bike into a well known mechanic about 4 weeks ago to see if he could get it going. Rode it home today, got my gear on and got 500m down the road and it stopped. would idle at full throttle and the rpm would come back up as i decreased the throttle, would rev for a bit then do the same thing when i tried to move.

Got it home and let it sit for a while. started sweet and rev's up but when you start moving it does it's weird rev thing.

I'll call the mechanic when i can but has anyone got any ideas?

I feel that it's like the bowls in the carbs fill up and are sweet but the fuel tank doesnt keep up when you go to move.

The fuel hose is pretty long, do you think if i shortened it up so it wasn't in a big 'U' shape it might help?

Cheers,

[juddnz]

blocked tank vent?

Im gonna give it a go when i get hme

[MSTRS]

blocked tank vent?


Not in isolation. Would take quite a while for the vacuum to build up to the level that would give your symptoms. That long hose is a possiblility...kinked?

[juddnz]

and now it wont even start. just turns over and over then occasionally backfires MASSIVELY and a whole lot of vapor stuff comes out the tail pipe. I'm ever so pissed.

[tri boy]

Starting to sound like a ign pulser coil or CDI.

[White trash]

Carb diaphragms are fucked.

Price em up, you'll blow your fucken brains out.

You're welcome.

[juddnz]

the carbs just got pulled apart so it's unlikely, plus it's quad carb

[White trash]

the carbs just got pulled apart so it's unlikely, plus it's quad carb
Are they CV or flat slides?

[Katman]

Possibly recessed inlet valves.

[juddnz]

Are they CV or flat slides?

Slides, started sweet as yesterday.

[juddnz]

dunno, the guy said he sused out all the valve clearances because thay were too tight apparently

[Katman]

dunno, the guy said he sused out all the valve clearances because thay were too tight apparently

That's what happens when the inlet valves lose their metallurgical (is that even a word?) integrity. In other words - they go soft. They start to recess into their seats and close the valve clearance up. Adjust the valve clearances and they just recess further. It's not uncommon with those engines.

[juddnz]

Anyone in new plymouth wanna fix it for me?

[xwhatsit]

Possibly recessed inlet valves.
How does that cause this effect? Do they heat up or something and change once hot?

[mister.koz]

I had a really similar problem with my GN250, i know it doesn't have allot in common with this bike but it might help.

Replaced the carb, no change.
Replaced the coil + spark - no change.
Re-set the tappets and it seemed a little quieter but not better.
I replaced the CDI, and the rectifier and recharged the battery and the problem went away.

Turns out the rectifiers on some bikes can start to leak high voltages as they die over time (1983 gn250) and those high voltages can cause the CDI to malfunction creating misfires and the such. I imagine if the same thing was happening in a 4 cyl bike you would have much worse trouble.

The key thing was that the problems started when i went over certain rev's, my mate explained to me that the rectifier wouldn't have faulted at low rev's because the windings wouldn't have the momentum to charge the battery so it would be inactive.

HTH

[juddnz]

Rang the mechanic and he said i probably just flooded it trying to start it? -- i figure he knows more than i do so i pulled the plugs to see if i'd covered them in petrol, they were dry as but black, not like gunky black but more like a powdery carbon black.

Gave them a good clean up and tested for spark. Sparks pretty sweet but it's a yellow spark. Not the blinding bright blue i was expecting, so im thinking coils are on their last legs (20 year old bike).

Anyone agree?

I had a search on here and someone mentioned that there are some readily available Honda coils that will work sweet, but he doesn't metion the model. Anyone know?


Cheers

I think if people agree i might replace the coils and the cdi if i can find a cheap one, and if that doesnt work then take it back to the mechanic since im not made of money here.

[mister.koz]

Rang the mechanic and he said i probably just flooded it trying to start it? -- i figure he knows more than i do so i pulled the plugs to see if i'd covered them in petrol, they were dry as but black, not like gunky black but more like a powdery carbon black.

Gave them a good clean up and tested for spark. Sparks pretty sweet but it's a yellow spark. Not the blinding bright blue i was expecting, so im thinking coils are on their last legs (20 year old bike).

Anyone agree?

I had a search on here and someone mentioned that there are some readily available Honda coils that will work sweet, but he doesn't metion the model. Anyone know?


Cheers

I think if people agree i might replace the coils and the cdi if i can find a cheap one, and if that doesnt work then take it back to the mechanic since im not made of money here.

Dusty black is incomplete combustion or misfiring surprised the sparks didn't have petrol on them 2 b honest... i mean if it was throwing petrol in there and it wasn't ignited then it should still be there.

It sounds really similar to the problems i was having with my GN - i know totally different bike but the fundamentals are the same. See if you can pick up a 2nd hand ignitor (or CDI) from a wrecker, chuck it in and disconnect the rectifier and try again.

I say remove the rectifier because thats the only place the ignitor could get a blow-out voltage from. Your bike will run for a reasonable amount of time on one charge so its only for testing, if you can charge your battery right up before doing it.

Also check for burns on the coil -> spark leads they hold in some 1000's of volts to they have to be pristine.

[mister.koz]

http://nz.vicdir.com/sn44514-0-taranaki-motorcycle-wreckers.htm

These guys might help :)

[skidMark]

The vapour out exhaust is obviously unburnt fuel... Weak spark...

Take it to a mechanic and get them to check how much grunt you are getting from your alternator.

Generally coils wont get old and weak as such, they just die. rather than produce a lesser spark...

I would be suspicious of alternator.

Also battery can be a factor.

Take it to a mechanic who isn't a bunny like the last one.

Hope that is of some help.

Skid. :Punk:

[mister.koz]

Cut the alternator and rectifier out completely, your battery will have plenty of punch without them if its fully charged, if that fixes the problem then its one or both of them.

Diagnosis by exclusion, of course makes it hard to test the sparks, coils, leads and CDI lol

[juddnz]

Hey

how would the alternator and or rectifier stop the coils from functioning?

I figured you've got 12V at the battery and once the charging system spins up you get say 13ish volts available. So if the charging system fails wouldnt you just be relying on the battery to provide your voltage source, or is the alternator/rectifier somehow lessening the ability of the coils/cdi to draw current?

I figure if the aternator burns out and shorts to earth the current would take the path of least resistance and all go through the short circuit (apart from a little bit). And if so, the battery would flatten itself pretty quickly even while sitting idle in my garage

i'm an electrial and instrumentation tech so maybe i'm over-thinking this

[skidMark]

Hey

how would the alternator and or rectifier stop the coils from functioning?

I figured you've got 12V at the battery and once the charging system spins up you get say 13ish volts available. So if the charging system fails wouldnt you just be relying on the battery to provide your voltage source, or is the alternator/rectifier somehow lessening the ability of the coils/cdi to draw current?

I figure if the aternator burns out and shorts to earth the current would take the path of least resistance and all go through the short circuit (apart from a little bit). And if so, the battery would flatten itself pretty quickly even while sitting idle in my garage

i'm an electrial and instrumentation tech so maybe i'm over-thinking this


alternator doesnt burn out as such, will just provide less grunt....

well they can burn fully out but if that was the case you would only get approx an hour max runtime before it died.

depends how the bike is wired, it varys from bike to bike, find a wiring diagram and scratch head, might help ya understand how it works a little better.

Alternatively (lol alternators...pun much) take it to a decent mechanic.

[motorbyclist]

Took my bike into a well known mechanic about 4 weeks ago to see if he could get it going.

what was wrong with is beforehand?


and did shortening that line help at all?

[juddnz]

It was the exact same problem it has now. And nah changing that fuel hose didnt do anything

[motorbyclist]

so what did the mechanic do to "fix" it?

[juddnz]

Stripped down the carbs and cleaned them out. And reset the valve clearances, new plus, and fixed my choke cable because it was all jammed up

[motorbyclist]

would idle at full throttle and the rpm would come back up as i decreased the throttle,

assuming all cylinders are firing, and the carbies are ok since the mechanic fiddled with them, and this isn't a case of a blocked air filter or fuel filter, I have no idea what could cause that described symptom of flooding

(which means check the filters and spark, then take the carbies back to the mechanic cause 4 carbs are a nightmare even on a good day)

bump

[mister.koz]

Hey

how would the alternator and or rectifier stop the coils from functioning?

I figured you've got 12V at the battery and once the charging system spins up you get say 13ish volts available. So if the charging system fails wouldnt you just be relying on the battery to provide your voltage source, or is the alternator/rectifier somehow lessening the ability of the coils/cdi to draw current?

I figure if the aternator burns out and shorts to earth the current would take the path of least resistance and all go through the short circuit (apart from a little bit). And if so, the battery would flatten itself pretty quickly even while sitting idle in my garage

i'm an electrial and instrumentation tech so maybe i'm over-thinking this

The alternator is pretty simple on a bike and its likely that a problem with it will only stop the battery charging, the rectifier smooths and drops the voltage to the charging voltage (13.8v?) which the whole bike is designed to run on.

If the rectifier is damaged it will either stop working or it will deliver an incorrect voltage.

The CDI is basically a timing circuit that delivers a controlled burst and then a gap to the coils. The coils charge on the burst and kick out a serious punch (blue spark on the plugs) when the burst voltage is cut.

If the burst voltage is too high the timing is out (RC timing circuit (http://en.wikipedia.org/wiki/RC_circuit)) and it can let go before the coil is fully charged, without load this can seem fine but under load the spark will be insufficient to ignite the fuel correctly because there is more fuel and more pressure in the cylinder.

From memory most 250cc inline 4's have 2 coils and run a 1 & 4 and a 2 & 3 firing sequence, coil A is charging while coil B is firing 2 cylinders at once and vice versa.


Stripped down the carbs and cleaned them out. And reset the valve clearances, new plus, and fixed my choke cable because it was all jammed up

Can't hurt :) did it help much? I bet the choke cable gummed up could have caused this problem or at least made it worse.


I am only pushing the CDI thing because its happened to me and the CDI & rectifier was the last thing to replace after HOURS of playing around with the carbs, sparks and coils.

[motorbyclist]

cdi can cause random problems like this too....

[juddnz]

Just checked the resistance of the coils, read somewhere it should be 3-4 ohms. I've got 10 ohms on one coil and an open circuit across the primary of the other one so i might be onto something. I pulled out the CDI and found it's been previously repaired / tinkered with. (held together with silicone gasket goo) but yeah, i brought some new coils today so i'll see how that goes.


Oh and does anyone know where the rectifier is on my bike. I think it's the thing just aft of the cdi thats looks like a magnesium type box with a massive heatsink on it.

[mister.koz]

Just checked the resistance of the coils, read somewhere it should be 3-4 ohms. I've got 10 ohms on one coil and an open circuit across the primary of the other one so i might be onto something. I pulled out the CDI and found it's been previously repaired / tinkered with. (held together with silicone gasket goo) but yeah, i brought some new coils today so i'll see how that goes.


Oh and does anyone know where the rectifier is on my bike. I think it's the thing just aft of the cdi thats looks like a magnesium type box with a massive heatsink on it.

Sweet, that sounds like the rectifier man.

Odd that the coils died?? But weirder things have happened.

[howdamnhard]

Oh and does anyone know where the rectifier is on my bike. I think it's the thing just aft of the cdi thats looks like a magnesium type box with a massive heatsink on it.

Yip that will be it.:yes:

[juddnz]

ok so a box of gsxr bits arrived today (thanks Pumba) so i changed out the coils, (after re-checking my original ones they actually seem ok) nothing changed, still wont start. I went to change the rectifier but my new one has an extra wire on it. My old one has 3 yellows from the alternator, and another plug with a red and a black. the new one has another wire in the red & black plug.

Also the CDI is the wrong one unfortunately so i can't check that.

I tried disconnecting the output of the rectifier and starting it that way but still nothing,

If i biff my multimeter into the output of the CDI i can see the voltage bouncing up and down so that seems ok.

Does anyone have a wiring diagram for this piece of sh!t because im going a bit mental.

Cheers

[mister.koz]

ok so a box of gsxr bits arrived today (thanks Pumba) so i changed out the coils, (after re-checking my original ones they actually seem ok) nothing changed, still wont start. I went to change the rectifier but my new one has an extra wire on it. My old one has 3 yellows from the alternator, and another plug with a red and a black. the new one has another wire in the red & black plug.

Also the CDI is the wrong one unfortunately so i can't check that.

I tried disconnecting the output of the rectifier and starting it that way but still nothing,

If i biff my multimeter into the output of the CDI i can see the voltage bouncing up and down so that seems ok.

Does anyone have a wiring diagram for this piece of sh!t because im going a bit mental.

Cheers

I got 30gb of bike manuals stored at work, will check it out tomorrow dude. Drop you a PM if i find it.

[Pumba]

Ahhh stink man, if none of that stuff works package it up and send it back and ill flick your money back through. Possibly the difference between the 88-89 models.