Pushed to the limit

[Mikkel]

I think I've now managed to push my ZXR250A to the limit... And needless to say - I want to go faster still!

Today I started getting a funky fluctuation in the power delivery while pushing hard at the track. Exhaust note changed and in the mid-range it started feeling as if it was running out of petrol (switched to reserve, made no difference and there was heaps of petrol in the tank).

I cruised off the track and after having had it sit for a while I took it back out again. Was absolutely sweet for ~3 laps and then the fluctuation came back.

Went of the track packed my stuff together and decided to go home... and the bike was riding like a dream, no issues whatsoever.

Anyone got an idea about what might be causing this? I've had one person say "maybe the air filter needs cleaning" another went "perhaps sparkplugs are getting too hot" and another suggested that there might be some sort of leakage at one of the manifolds. Any clever suggestions would be appreciated.
Dunno if it's just because it's a very hot day and I was going hard on it...

Anyway, I might consider looking for a bigger trackbike (I was thinking 400-600 ccm) - perhaps even a road legal thing that I could use on the track until I get my full in ~4 months. Any suggestions for a suitable bike for such a purpose?

Oh - and there's a nice song to go with the post btw:
http://www.youtube.com/watch?v=cN0auZtm2tg

[FROSTY]

I'd like to make a suggestion--Flick the tap to PRIME --not on or reserve.
Im thinking your fuel flow for one reason or another aint enough to keep up with constant full or nearly full throttle riding.
That kinda lines up with the simptoms too.
That then leads me to think--Fuel pump is a bit old or maybee part blocked fuel filter -either the intank one or inline somewheres.
the other possibility worth looking at is the vac line having a kinkor split in it-Not allowing the fuel tap to flow enough fuel
Id like to bet too that if ya keep the tank topped up its not such a problem
sparkplug suggestion clearly nonsense
Airfilter suggestion--yep but would be a constant rather than a come and go issue

[Mikkel]

I'd like to make a suggestion--Flick the tap to PRIME --not on or reserve.
Im thinking your fuel flow for one reason or another aint enough to keep up with constant full or nearly full throttle riding.
That kinda lines up with the simptoms too.
That then leads me to think--Fuel pump is a bit old or maybee part blocked fuel filter -either the intank one or inline somewheres.
the other possibility worth looking at is the vac line having a kinkor split in it-Not allowing the fuel tap to flow enough fuel
Id like to bet too that if ya keep the tank topped up its not such a problem
sparkplug suggestion clearly nonsense
Airfilter suggestion--yep but would be a constant rather than a come and go issue

That sounds very plausible - and if there is a bit of crap sitting on the filter in the tank it won't move away when it first has been sucked in. When I turn the engine of it'll flow away with the fuel around in the tank. Perhaps time to give the tank a thorough look over, then fuel filters and perhaps the fuel pump.

[FROSTY]

SORTA. What I'm saying is that as long as ya give it short bursts of fullish throttle the bowls still have enough juice to keep the plot rolling. When ya back off the carbs refill and all is good
You could be right with the floating thing but more likely its a coating just not letting enough gas through. -or fuel pump too old n worn to keep up.
Given its 3 laps that suggests only a partial blockage.
HMNMM--Hang on it could be the filters IN the carbs too--or even just one for that matter.
In fact the more I think about it the more likely it is just that

[Mikkel]

Hmmm, so how do I check (and fix) this problem? I am fairly new at the art of motorcycle maintainence and that stuff.

[FROSTY]

Just went to send ya a fairly indepth description--frigging broadband dumped me

[dipshit]

First cheek there isn't any twists or kinks in the fuel lines.

[FROSTY]

Just to 100% qualify--you aint bouncing off the speed limiter at 190k are ya?

[FROSTY]

First cheek there isn't any twists or kinks in the fuel lines.
Yep--good point--kink = reduced fuel flow

[Mikkel]

Aww, sucks when the connection slips. Occassionally I've had the odd big post or email disappear because I've managed to get the browser to go backwards on page... :(

Hmmm, it's a 250 4-stroke I'm quite stoked to hit 175-180 km/h at the end of the straight ;) So yeah, definately not a 190 km/h limiter...

I'll have a look at the fuel lines at an appropriate time.

Anyone got good advice on how to clean out the tank if there should be some crap in there?

[Morcs]

Im sure skidmark would have something to say about pushing a zxr250 to the limits. He would be able to lean it so far It goes through the road, do wheelies on the front wheel and 300kph.

[Mikkel]

Oh, btw. it might be worthwhile mentioning that this is my fourth time out at the track. All the other times I have also been pushing quite hard and the bike has taken that in stride.

Today there was nothing of note until the 4th 30 min session - and then it occurred about 15-20 mins into the session.

[headlesschicken]

I had a similar problem before my bike totally cut out. It was running too rich. The bike shop tuned it and it ran sweet since. Just another idea to consider.. :confused:

[R6_kid]

Just so you know, your bike dont have a fuel pump, it's gravity fed.

[Mikkel]

Just so you know, your bike dont have a fuel pump, it's gravity fed.

I guess that both simplifies matters and makes it cheaper... ;)

[Mikkel]

Hmmm, tried to take the fuel tank off to get to the air filter.

No luck - the fuel tap was free flowing and there was crap/rust in the petrol.
Guess I got a good place to start out from now!

[L.L. Cool M]

Sorry, I can't help you with this, but I just wanted to say I have the exact same problem. It's a bit un-nerving when it happens mid corner at speed!

Please to inform if you find the problem/solution. Cheers and good luck.

[The Pastor]

Sorry, I can't help you with this, but I just wanted to say I have the exact same problem. It's a bit un-nerving when it happens mid corner at speed!

Please to inform if you find the problem/solution. Cheers and good luck.
he has, it was rust in the tank causing a reduced flow rate.

now how to fix it, im sure somone on here said if you put a bit of gravel in ur tank with 1L of gas and swish it around it will get rid of the rust. but im not sure if it was a p/t?

[Kickaha]

I think I've now managed to push my ZXR250A to the limit... And needless to say - I want to go faster still!

Any idea of your lap times?

[Mikkel]

Any idea of your lap times?

Not really no. I don't think anyone has timed one.

I'm not saying that I can't go faster on the 250 ccm - sure I can. But the amount of strain I put on the bike to go as fast as I do now will make it wear out pretty quickly I think.

There's heaps more I can learn - also on a 250 ccm, but I'd like to maintain the value of the bike I have now by not blowing it up.

[imdying]

It's not so much of a lap time issue, more of a bike is getting raped constantly issue. Even if he weren't lapping faster, something like an old GSXR600 wouldn't need to be beaten into the red line quite as much. Typically I wouldn't be recommending a GSXR600 for someone who has been riding for less than 6 months, but I'm quietly confident that in this case it will be the correct step.

Yes, a ZXR250 will most likely take a beat all day every day, but there doesn't seem to be much point in buggering it 'just cause you can'.

If racing interests you, then perhaps an SV650 would be a nice choice? Of course, racing has other associated costs, not just a bike, so depends on if you've other obligations and a reasonable income to utilise in such adventures.

Cheap, local, give it the learn mate (http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Motorbikes/Sports/auction-141720792.htm).

[skidMark]

I guess that both simplifies matters and makes it cheaper... ;)

Wire in a cheapy fuel pump, see if that fixes it.

Strange that you havnt had the problem ever before.


Get the carbs cleaned
Clean your fuel filter in the gas tank
If you have an inline fuel filter replace it.
Plugs are buggered.SM

[skidMark]

Not really no. I don't think anyone has timed one.

I'm not saying that I can't go faster on the 250 ccm - sure I can. But the amount of strain I put on the bike to go as fast as I do now will make it wear out pretty quickly I think.

There's heaps more I can learn - also on a 250 ccm, but I'd like to maintain the value of the bike I have now by not blowing it up.

Yeah don't go full balls to the wall.

I was pushing way too hard thrashing the hell out of the poor thing, too much adrenalin just trying to see how hard i had to push before the bike would crash.

I didn't crash but my poor wee motor went bang.

[Nagash]

Yeah don't go full balls to the wall.

I was pushing way too hard thrashing the hell out of the poor thing, too much adrenalin just trying to see how hard i had to push before the bike would crash.

I didn't crash but my poor wee motor went bang.

Soo... you're agreeing with him?

It would of been a hell of alot easier to just say, "Yes, I agree. 10 Char"


Unless there was a hidden message in there?

[skidMark]

Soo... you're agreeing with him?

It would of been a hell of alot easier to just say, "Yes, I agree. 10 Char"


Unless there was a hidden message in there?

I prefer to put effort into my posts rather than say the minimum needed just to raise my post count.

SM

[Mikkel]

Anyway, I'm pretty confident that it's a crap/rust in the tank issue. I drained the tank into a jerry can today.
Took the tank off and cleaned the air filter.
Removed the fuel tap (which was free flowing as opposed to working properly)
Shook the tank around a bit and could hear something moving around in there.
Got a small LED light and got some light into the tank to take a peek.
There was all sorts of crappy rust AND a weird little piece of plastic tubing.
Turns out the plastic tubing was supposed to sit in the tap assembly.
Went fishing with a slightly modified wire coathanger and got it out of there.
Then I chucked some small aquarium rocks into the tank and gave it a good shake.
Then I flushed the thing with water (dunno if that was dumb, but now it's done)
The tank is now sitting on the deck to dry - then I'll apply Jim2's vacuum method to get the last rocks out.

I also took the tap assembly to pieces and it didn't look too bad.
Flushed the crap out of it and reassembled it.
Chucked the piping that had come loose back in.
Now I'll just have to wait and see if that was indeed part of the problem.

Anyway, replaced the inline fuel filter and it was FUCKED. I'll try and chuck a picture up of a new and the old...

All in all I hope this will help to get it sorted.


It's not so much of a lap time issue, more of a bike is getting raped constantly issue. Even if he weren't lapping faster, something like an old GSXR600 wouldn't need to be beaten into the red line quite as much. Typically I wouldn't be recommending a GSXR600 for someone who has been riding for less than 6 months, but I'm quietly confident that in this case it will be the correct step.

It's almost been 6 months now ;) Looking forward to getting at my 6R!

[Sully60]

Number one had a ZXR back a few years ago that vacuum locked in the fuel tank. That would just misfire until it stopped, open the cap to check it hadn't run out of fuel and the problem disappeared.
Might be worth an investigate of the tank breather route. I have seen this on other Kawkas also.

[imdying]

Mike, if you experience some rough running post putting water in the tank, you'll need to add some meths to it to remove it. If you search these forums, you'll find posts the detail the procedure.

[Mikkel]

Mike, if you experience some rough running post putting water in the tank, you'll need to add some meths to it to remove it. If you search these forums, you'll find posts the detail the procedure.

Ok, I was mostly concerned with corrosion.

I was planning to let it sit and dry overnight - and then put it all back together tomorrow. (Or perhaps even take the tank to a panel beater to see if they can fix the rust issue in the tank properly.

I thought you'd be on your way to Duvauchelles at this hour... ;)

[Renegade]

make sure you blow out all your lines with compressed air to get any gunk out before re-assembly, i dont think a panel beater will be able to fix the rust in the bottom of your tank some how, you can only clean it out as best as you can and make sure all the plumbing is free flowing as it should be, be interesting to see how it goes after ward.