250rr-bogging, cutting out, fouling plug (loose CDI plug)

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250rr-bogging, cutting out, fouling plug (loose CDI plug)

Postby beta250rrowner » Sat Sep 25, 2021 3:55 am

I'm having this problem with my 250rr today.

It feels hesitant, it bogs out when I open the throttle and stalls.

It wouldn't then start and ride, so I had to get the recovery mechanic out.

I suspected the spark plug, as I had this issue with an old KTM 250exc and it turns out the spark plug was fouled.

We cleaned.it.with a wire.brush and some wd40, put it back in and the bike ran like a.charm...for all of about 5 miles.

It then started.bogging and cutting out again, much to my dread.

It would start but it wouldn't run right and it would rev all the way out when I opened the throttle, or it would bog down and cut out.

When I had an old KTM 250 exc, this turned out to be some obscure fault with one of the crank case seals where it was leaking gearbox oil into the combustion chamber.

To replace the seal, the cases would have to be split and have a new one pressured in. I sold it as I just wanted to ride.

Could my beta 250rr have fallen victim to the same issue? If so, I will not be happy and may even quit 2 strokes.

I run 100 mil 2 t oil to 5 litres of fuel, btw. That makes a ratio of 50:1 if my maths is correct.
Last edited by beta250rrowner on Tue Sep 28, 2021 3:28 am, edited 2 times in total.
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Re: 250rr-bogging, cutting out, fouling plug

Postby JoeMaico » Sat Sep 25, 2021 6:50 am

When the Primary Seal on my 300 was failing, the bike smoked like a freight train. But. It still ran – even down low. Also, you do not need to split the case to replace the primary (Crank) seal. You only need to remove the clutch basket and primary gear. You do not mention if your bike ran great before, then all of sudden it started to foul out and die. Or, has there been a noticeable degradation in performance over the last few rides – where now it is unrideable? If it was sudden, my thoughts would turn to either fuel delivery or electrical. Because you indicate it fouls out down low - but runs at higher revs, that would lead me to a weak spark, or intermittent spark. Regardless, I would start my diagnosis by going through the carb and the reeds for any issues. Are the gaskets shot, any jets plugged, how to the reed petals look, etc. If all checks out there, I would move on to the coil, and then on to the stator, pick up and regulator.
joe
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Re: 250rr-bogging, cutting out, fouling plug

Postby beta250rrowner » Sat Sep 25, 2021 9:15 am

Hi

Thanks for a speedy reply. I wrote this OP on my phone sat at a local pub near the track where I could hear bikes in the background-what torture!

ImageIMG_20210925_114257_788 by a a, on Flickr

I am now back at my garage where I type this in the attached property.

The information you provide on your experience with crank seals is most helpful, I wonder in fact whether I misdiagnosed the problem with my old KTM that kept fouling plugs in the first place. I can't remember if I ever actually looked at the ignition system on that, but I feel like I must have done. If I didn't, big oversight.

Anyway, back to the Beta.

Once he arrived, I spoke to the recovery mechanic, who was also a biker and he suggested what you say. I've decided to go for the ignition system first-we suspected an ignition fault due to no spark up on testing, I've got the bike back to my garage and I've began removing the ignition components.

It looks as though the terminals on the coil back were quite corroded, the bike was sat in my unheated garage for a couple of years until recently. But I've had it on some outings and it's been reliable until today! Apart from a slight hesitation, that is.

ImageIMG_20210925_135730_556 by a a, on Flickr

I've cleaned them up with some sand paper, they looked worse than they were. It was only surface corrosion.

Okay, I've tested for spark, there isn't one.

The mechanic suggested I order a new coil pack, ht lead and spark plug.

Edit before I've even finished typing the original draft of the reply!

Okay, I believe I've found the fault. There is no continuity on the ignition coil

ImageIMG_20210925_170400_625 by a a, on Flickr

I think the added resistance must have burnt out the coil.

Edit: No, I'm an idiot, volt meter on wrong setting

Ref this video on testing

https://www.youtube.com/watch?v=ahKB3c4Zhis

I DO actually get a reading when it is on the right setting

ImageIMG_20210925_172518_770 by a a, on Flickr

So now I'm back to being clueless as to why I have no spark.

Edit: I guess I'm looking at the stator, now!
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Re: 250rr-bogging, cutting out, fouling plug

Postby JoeMaico » Sat Sep 25, 2021 10:12 am

Coils have been known to fail intermittently. Usually when they get hot. If your bike runs great when it is cold, but only starts to fail, or foul out, when it is hot – I would still consider the coil a suspect. Regardless, sounds like you are digging into the electrical aspects of your issue – and I think that is where your problem lies.

Good luck.
joe
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Re: 250rr-bogging, cutting out, fouling plug

Postby beta250rrowner » Sun Sep 26, 2021 8:36 am

I found the problem!

I did resistance tests on the stator, pickup magnet and coil and they all gave a resistance value, so I knew they weren't open circuit. I don't have specs because Beta as a manufacturer are half assed and don't provide them in the owner's manual. However, at least I knew I was getting readings.

Then I had a look at the CDI box inside the air filter housing, it looked fine. I'd cleaned the air filter a week previous in preparation for the motocross track day, which must have disturbed the CDI box plug.

ImageCDI box location by a a, on Flickr

I unplugged it, took it off, photographed it

ImageCDI box 2 by a a, on Flickr

and then plugged it back in thinking "wouldn't it be crazy if it was just a loose plug" then I cranked it over and spark!

Celebratory sparking video

ImageSpark by a a, on Flickr

So that's all it was then, a loose CDI connection. It is weird, it was running but running poorly on Saturday, making a lot of smoke, I guess the combustion process was weak due to a faulty connection to the CDI? I almost forgot to write, there was corrosion on the coil contacts to the frame which I cleaned up before remounting the coil. Perhaps it was two separate problems that I've solved at once?

I immediately noticed a difference in how it was running when I started it after reseating the CDI plug. It sounded crisper and was barely making any smoke, just a light haze. As soon as I touched the throttle the revs shot up beautifully.

It still feels slightly hesitant off the pipe and feels like it wants to "get up on the pipe" so to speak, but that might be due to me adjusting the power valve down significantly and having the map switch in "wet" mode.

But anyway it's running great now!
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Re: 250rr-bogging, cutting out, fouling plug (olose CDI plug

Postby JoeMaico » Mon Sep 27, 2021 9:02 am

Glad you resolved your issue. You had a lot of corrosion on your coil connections. My guess is that will not be the only corrosion you will find if you start digging into it. A good project this winter would be to go through every electrical connection, including your grounds, and clean them all up and apply dielectric grease where required. Also, perhaps it is only an optical illusion, but your coil looks like it has a crack running through it. If so, replace it.

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