GPX250RR Problem

[gamgee]

not sure if this is the right place to post this but anyway...
The problem seems to happen more on cold mornings and nights, but what happens is the bike starts up fine, idles fine, but as soon as i let the clutch out to go and take off, the revs drop and it either stalls, or i jam the clutch in and stop it from stalling, give it a bit longer to warm up and it eventually takes off and rides as if nothing is wrong
choke doesn't make a difference, it doesn't seem to be the kickstand sensor as it 'fixes' itself without me touching the kickstand, so has anyone got any ideas?

[Ixion]

You're in Dunedin. it's winter. Let the poor bugger get warm first. sorted

[Buster]

Yep, warm it up before you take off and dont ask too much from it for the first few kays.

[gamgee]

yeah but should i just be putting it down to the cold when it does it even when i try and take off at 5krpm and it still just drops off the revs and does the same thing
it's also done it a couple of times when i've turned it off to unlock the garage, so it shouldn't have cooled down much in the 30 seconds it takes me to unlock that

[gamgee]

and yeah i usually give it a good 2 minutes of warming up before riding and real easy on it even when it has reached optimal temp, i don't want to kill another 250

[Ixion]

It's winter! In Dunedin! Remember that bike carbs are not as sophisticated as car ones. (Even bike FI likewise, except may be BMW).

Carbs have a special fuel passage for idling.Which is normally pretty rich. So they'll idle even if it's cold. But as soon as you open the throttle you are off the idle circuit. That cold petrol in a cold carb won't vaporise easily.

Warm it up. Even in Auckland I need to warm Ratty up for a bit these mornings.

One other possibility is that you have the idle mix REAL rich for starting on cold mornings and it's fouling a plug, cos the plug is cold. I assume you are using the choke judiciously?

[gamgee]

i stopped using the choke at all as it wasn't making any difference

[skidMark]

maybe the choke is jammed?

if all else fails take it to a mechanic

[Ixion]

So maybe your idle IS too rich? They fit the choke for a reason.

[gamgee]

nah choke works lifts the idle a bit higher, it just doesn't make a difference to this problem, i'll get dad (mechanic) to have a look at it, but he's a car mechanic and doesn't really seem to know a lot about bike specific problems

[gamgee]

and i'll check the plugs but last time i checked them a few months ago (yeah i know they probably are dirty now) they were clean as

[Ixion]

It's not really bike specific. Cars used to have the same issues back in the days when they had simple carbs. Things like the old SUs and Solexs. If you Dad was wrenching back in the 50s or 60s he'll remember .

EDIT: the plug will clean itself once the engine heats up. You'd have to whip the plug out immediately after it stalled to tell. Just gets a bit of fluffy carbon on it, that burns off once the plug reaches full heat.

[gamgee]

so there is absolutely nothing else i should check?
haha and he was only born in the 60's

[Ixion]

Well, yeah, there's a bazillion things you COULD check.

Zorst could be blocked. Or air filter. Oil may be too thick for winter (that's actually not a bad one). Ignition timing could be out. Valve timing might have slipped. CDI unit could be on the fritz. Coil could be bad. Carb could be worn or dirty. Carb could be icing up. Water in the fuel or fuel lines . Blocked tank vent (ice?) Heaps of oddball stuff.

But odds are 100 to 1 it's the carb . May just be normal. Is this the first winter you've had the bike?

EDIT: We used to put hot water bottles on the carb overnight when cars did this back in the day. You could try that. Some folk used blankets. (Yes, I am serious)

[gamgee]

yeah first winter, and it does mainly seem to be when it's cold, except those odd times, after i've just got home, so the bike is warmed up, i turn it off while unlocking the garage, start it up again... stall, start it up, fine off we go.
oil is 5/40 sinthetic is due for a change in about a month, but it was as clean as when it went in last time i changed and did filter, so yeah maybe i will just put it down to friggen cold dunedin winters, brrr, i'm going to bed where it's warm, will report back if dad finds anything wrong

[The Pastor]

yeah man, give it a good 5-10 mins to warm up, be gentel on your bike.



EDIT: We used to put hot water bottles on the carb overnight when cars did this back in the day. You could try that. Some folk used blankets. (Yes, I am serious)

yeah my mum had a 70's mitzi lancer once, we used to put a sheepskin on the engine over night to help it start in the morning.

[T.W.R]

So what your saying is everything is per normal until you put it into gear then release the clutch to take off then it dies ? then try it again and alls OK ?
It starts OK, idles Properly (around the 1000rpm +/- 50rpm), the choke works properly, it runs & performs normally ?.

Could be a weak spark possibly & if it runs fairly normally, then it may be deteriorated plug leads (H/T leads) breaking down under initial load occasionally, if their hard & stiff to bend then ditch them for new ones.

Otherwise it sounds like the clutch plates are partially binding & being a smaller capacity engine its enough to stall the bike. Change the oil to the specified viscosity, 5w-40 is too light of oil for a older GPX250 and from that the clutch isn't being lubricated properly

[gamgee]

so what weight should i be using? i've got some 15/40 non synthetic would that be good?

[inlinefour]

take it to a mechanic

Finally some good advice from the GPx killer himself. Sounds like the lad has learnt? gamgee I do not believe you have a problem, apart from the fact that the bikes not being allowed to warm up properly. I have a old z50 that does exactly the same thing that you have described with your GPx. It allways comes right once the little engine is warm enough. Give the GPx a tune and then allow however long your bike needs to heat up to where its running good. The z50 takes at least 3 times longer to get heated up to a point that its happy to run. Used to also happen to one of my little xl100s bikes and the problem was resolved by sorting out the timing.

[SwanTiger]

I had a similar problem with one of my dirtbikes and occasionally (on really cold nights) encounter the same problem with my Hyosung.

I've found a quick amount of throttle action clears it up, usually getting 4,000 revolutions then dropping off then bringing back up again (for 2 seconds at a time) gets things running smoothly. However, I'll only do this if the engine is warm.

Otherwise its choked to life.

When was the last time you cleaned your carbeurators?



if all else fails take it to a mechanic

That's rich comming from someone who has "Motorcycle Mechanic" as their Occupation in their profile and can't fix their own bike.

[SwanTiger]

This is a website I sourced when I did a little research on Marks bike to familiarize myself with some of the common pitfalls and 'functions'. A very informative website and certainly worth browsing through.

http://faq.ninja250.org/index.php/Main_Page

[gamgee]

When was the last time you cleaned your carbeurators?

:mellow: never
i've had it for what? must be about 6 or 8 months now so yeah i'll do a big tune up clean everything out change the oil and filter, check the timing, (i've got the owners manual) and whatever else i can think of...
damn speedo stopped working last night too, i'll have a look at that eventually as well, tacho etc still working fine
stupid thing is it's got all these wee niggles but once it gets going it runs like a dream, so yeah thanks guys

[skidMark]

That's rich comming from someone who has "Motorcycle Mechanic" as their Occupation in their profile and can't fix their own bike.

i ended up fixing it in the end stop your jaw flapping shit

[JimO]

winter in Dunedin...HA bloody Aucklanders how cold do you think it gets here 30 below jeez havnt had a proper winter here for years

[gamgee]

the year before last we had a proper winter, it snowed just about every week between mid july and mid september
got the speedo cable fixed... well plugged back in if you can call that fixing it :doobey:

[Gixxer 4 ever]

We have an 02 Zuki DR 250 for farm work. It has the same problem. You need to give it more time to warm up. The DR is doing as you have described.
Even at work the oil cooler is taking the temp down soon after you stop it at work and with in a few minutes you have to warm it up again. I will remove it and plum a line from the inlet to the out let for the winter. Not something you should do but you don't have a problem as far as I see. Be patient