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Old April 8th, 2019, 07:42 PM   #1
Milpool
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Cold Engine Stalling

I've been having some trouble for a while with my '07 Ninja 250 (technically a GPX250 as I live in Australia but it's the same bike).

When the engine is cold and I come to a stop with the clutch in the revs just drop and the bike stalls. It starts up again without a problem and I'm on my way. Absolutely nothing wrong with it when it's warm. Also the colder the weather the worse the issue.

Around the same time this started happening I did have another issue where when I was starting the bike from cold the choke would send the revs to 2 - 3k rpm as it should then a few seconds later it would just drop to about 1k without stalling and honestly seemed quite comfortable there. A few twists of the throttle would send it back to where it was supposed to be then it would drop again a few seconds later.

I recently did an oil change (they are always regular) but I switched to 10w - 40 full synthetic. Before I had 15w - 50 "standard" oil as that is what the guy at the shop recommended, I now realise that's not great for cold starts. Since the recent oil change the above problem has got heaps better but the stalling when coming to a stop issue remains.

Also I've noticed that while it's sitting at a nice comfortable 2k rpm with the choke to warm up, the instant I put it into first with the clutch in it drops to 1k and sits there. This is new.

Other things I have tried include carb cleaner fuel additive. Spray carb cleaner into the carbs intake and a carb sync.

Is anyone able to give any advice on what it could be? Also beyond the inconvenience, how worried should I be?
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Old April 8th, 2019, 08:16 PM   #2
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Hi and welcome to Ninjette!

Your carbs needs thorough cleaning. Complete disassembly down to last nut & bolt. Every fuel passage massaged and flossed with wire. Soaked in real cleaning fluids (caustic and radioactive) in hypersonic cleaner for years on end. Soda blasted at 100000psi...

An interim test solution is to adjust pilot screws to 2,5-2,75 turns out.

Last futzed with by DannoXYZ; April 8th, 2019 at 10:33 PM.
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Old April 8th, 2019, 09:32 PM   #3
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Are your valves adjusted to spec? They can do goofy things to cold starting and idling, stalling, etc.. When I adjusted mine it was a different engine.
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Old April 8th, 2019, 10:24 PM   #4
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Quote:
Originally Posted by DannoXYZ View Post
Hi and welcome to Ninjette!

Your carbs needs thorough cleaning. Complete disassembly down to last nut & bolt. Every fuel passage massaged and flossed with wire. Soaked in real cleaning fluids (caustic abd radioactive) in hypersonic cleaner for years on end. Soda blasted at 100000psi...

An interim test solution is to adjust pilot screws to 2,5-2,75 turns out.
Damn I knew it! I can only soda blast things at 50000 psi

But seriously, I just looked into the procedure for adjusting screws and I'll give it a go. Just have to find myself a short enough screwdriver.

Also the valves haven't been done the whole time I've owned the bike. I'll look into doing it myself, I keep putting that one off.
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Old April 9th, 2019, 05:53 AM   #5
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Your problem may well be with the carbs, but if the valves are out of adjustment, you can chase carb problems forever.
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Old April 9th, 2019, 05:21 PM   #6
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I'll see if I can get time to look at the valves this weekend then.

Also I had a quick look at the idle mix adjustment screws and on at least one of them the coolant hoses look like it could get in the way. Is it possible to twist the connections in order to get more access or could that break something?
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Old April 9th, 2019, 09:52 PM   #7
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Sure, loosen hose-clamps, grab hose-end with pliers and twist back & forth lightly to break it loose. Then rotate out of way. Tighten hose-clamp temporarily.

Or drain and re-fill later.

Or remove carbs, I can do it without cutting air-box. Trick is to leave carbs connected to airbox while pushing back all the way. This opens up a 1cm gap between carb and rubber-tubes. Pull left tube out left side and then remove carbs form air-box. Pull carbs out left-side.
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Old April 10th, 2019, 06:34 AM   #8
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On my 2005, there is no hose in the way of the carb idle screws. I would think you can move the offending hose a little and leave it that way. I do need to use a very short screwdriver. Yesterday I used a slotted-head hex bit with a couple layers of tubing pushed over the hex end to make a little handle.

Of course this assumes the factory screw covers have been drilled out.
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Old April 10th, 2019, 04:44 PM   #9
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There weren't any screw covers. I don't think Australian delivered ones had them but I could be wrong.

I ended up getting a drill bit designed to take a 1/4" hex bit. It was slightly too long but I managed to get about a quarter turn out on each screw. It seems to be running much better now, even when warm. It did still stall 50m down the road at the first intersection with the choke on and I found the idle way too high once warmed so I knocked that back down to 1400rpm again.

I'll have another play with the hose trick and let you know results.
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Old April 10th, 2019, 05:28 PM   #10
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Keep in mind that having to back the idle mixture screws out to fix a problem is often an indication of internal clogs. There's nothing wrong with backing them out 1/4 turn, but if it happens repeatedly over the coming months, you'll know the carbs need to be cleaned.
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Old April 10th, 2019, 06:05 PM   #11
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Additionally, if you can swing it @Milpool adjust each bank pilot screw for highest RPM with the bike hot. Wear gloves, use shop rags for insulation....I know its tight and the engine burning hot, but worth the effort to find each "sweet spot".

I think I'd do this on center stand too, so you are not affected by, nor compensating for, any wacky fuel bowl levels which side stand may create.

And a note for anyone reading this...if turning pilot screw in/out has no effect on a cylinder, very likely that circuit is clogged to some degree, requiring "attention".

All this, provided no vac leaks, rubber manifolds configured correct, petcock operational, other tuning parameters in order ....blah blah blah.
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Last futzed with by ducatiman; April 10th, 2019 at 06:14 PM. Reason: clarify
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Old April 10th, 2019, 06:27 PM   #12
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Quote:
Originally Posted by ducatiman View Post
Additionally, if you can swing it @Milpool adjust each bank pilot screw for highest RPM with the bike hot. Wear gloves, use shop rags for insulation....I know its tight and the engine burning hot, but worth the effort to find each "sweet spot".

I think I'd do this on center stand too, so you are not affected by, nor compensating for, any wacky fuel bowl levels which side stand may create.

And a note for anyone reading this...if turning pilot screw in/out has no effect on a cylinder, very likely that circuit is clogged to some degree, requiring "attention".

All this, provided no vac leaks, rubber manifolds configured correct, petcock operational, other tuning parameters in order ....blah blah blah.
Okay I'll give that a go this weekend. I will be using many rags hahah.

I've sprayed carb cleaner at every hose and am pretty damn sure there isn't a vacuum leak.

Just as a matter of curiosity, am I able to spray carb cleaner directly into the carb where the hose from the petcock goes into the carb? Or am I better off using fuel additive for that sort of thing?

Also I just want to say a huge thanks to everyone for the help and advice.
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Old April 10th, 2019, 07:15 PM   #13
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The only fuel additive that I have found to work is one with Techron (PEA). It certainly can't clean a well-clogged carb, but if there's a fresh minor blockage I've had it correct the problem.
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Old April 11th, 2019, 06:11 PM   #14
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There's variety of fuel-system cleaners with high enough PEA level to clear clogged fuel-circuits and jets in carbs. Mostly works if you've got gelled petrol, but if it's completely dried to brown varnish, no way. This becomes poly-vinyl crossed-linked compound similar to old-school clear-coats such as tung or linseed oils. Only way to remove is mechanical scrubbing and chipping away at it. Try one of these first, can't hurt.

- Red Line SI-1
- Techron Concentrate Plus
- Gumout All-in-One
- 3M Max Strength Fuel System Cleaner #08814
- Royal Purple Max Atomizer 18000

Last futzed with by DannoXYZ; April 12th, 2019 at 02:22 AM.
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Old April 11th, 2019, 08:02 PM   #15
Milpool
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Thanks! I ended up getting a Nulon "Extreme Clean" as it's the only PEA one I could find here. Or at least the only one that even advertised it was PEA.

I'll throw it in next fill-up.

EDIT: Oh and I have zero stalling now and don't have to use as much choke anymore so you guys were right on the money. I'll do the proper warm tune this weekend but already really happy with the results. Thanks again so much guys.
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Old April 15th, 2019, 06:45 PM   #16
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Unfortunately the fix wasn't as permanent as I thought. I'll be doing valve clearances this weekend.

However I took a quick video of the warm engine idling and was just curious is it returning to idle normally or is it a bit slow and needing more idle mix adjustments?

https://youtu.be/rfUCwALwhWI
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Old April 16th, 2019, 06:20 AM   #17
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The return to idle speed seems normal. The loud ticking does not. Do you have an exhaust leak? It's hard to tell what's making that noise.
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Old April 16th, 2019, 06:28 AM   #18
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Deceleration looks good to me.
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Old April 16th, 2019, 04:20 PM   #19
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Thanks for letting me know. As for the ticking noise isn't that just normal valvetrain noise? Its VERY loud in the video for some reason, I barely notice it in person.
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Old April 16th, 2019, 04:27 PM   #20
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The valve clearances are very small. I don't hear my valves, but there are other noises like the clutch I hear at idle.
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Old April 16th, 2019, 05:34 PM   #21
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Measure cam-chain for wear.
Also check cam-chain tension. Tensioner may not be working properly or improperly set.
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Old April 16th, 2019, 06:04 PM   #22
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Measure cam-chain for wear.
Also check cam-chain tension. Tensioner may not be working properly or improperly set.
The bike has 38000kms (24000miles) which I didn't think was huge. Would the cam-chain be worn after that? I had a look at how to check the tensioner and that seems easy enough so I can give it a go.
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Old April 16th, 2019, 06:33 PM   #23
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Do you know complete service-history of bike?
It's possible someone ran it low on oil, or used low-grade oil, which can cause premature wear.

There's a measurement-spec in manual, measure between 10 or 12 links or something and that number will tell you condition of cam-chain. Worn chain may be beyond adjustment range of tensioner.
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Old April 16th, 2019, 06:48 PM   #24
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Do you know complete service-history of bike?
It's possible someone ran it low on oil, or used low-grade oil, which can cause premature wear.

There's a measurement-spec in manual, measure between 10 or 12 links or something and that number will tell you condition of cam-chain. Worn chain may be beyond adjustment range of tensioner.
I've owned it since 22,000 km (13,500 miles). I know I'm the third owner and I do the regular services, although I've never done valve clearances, will be doing that on Friday. The previous owner had regular services done by a mechanic (I have receipts). No idea on the first owner though.

Can it be measured without removing it?
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Old April 16th, 2019, 07:14 PM   #25
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yes, measure length between cam-gears. Might need to crank-engine by hand so chain is fully tensioned. Not sure of #-links, you'll have to refer to service-manual.
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Old April 16th, 2019, 07:19 PM   #26
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yes, measure length between cam-gears. Might need to crank-engine by hand so chain is fully tensioned. Not sure of #-links, you'll have to refer to service-manual.
Alrighty. Well it can't hurt to do it while I'm doing clearances anyway.
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Old April 20th, 2019, 05:05 PM   #27
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Well I've done the clearances with help from my Dad. I'm getting the proper tool next time, locknuts are the worst.

That was 100% the problem though. Bike runs so well from a cold start with needing very little choke and no stalling problems! Also way more power in the midrange. They were way too tight before. There's absolutely no signs of needing a carb sync but I'll do it anyway when I get a chance and maybe tighten those idle mix screws a bit now that I realise that was never the problem.
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Old April 20th, 2019, 05:35 PM   #28
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I'm glad you found the problem and fixed it Nathan. Happy riding!
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