CBR125 cutting out - things to check?

[J.M.]

A friend of mine's CBR125 has been suffering issues as of late.

Fluctuating idle speeds and bogging down whilst riding. It started happening when the cold weather set in. He presumed it to be down to carb icing, I told him that it shouldn't be that.

I enquired as to whether this still happens with a hot engine, it does.

Quote from him on FB...

[ricklincs45]

Hi,

Would I be right in reading that this only started after he'd had the bike serviced? If so, I'd be handing back to the dealer and tell them to sort it.

Otherwise: many years ago, a friend had running probs - took bike to dealer, dealer finds owners' cleaning cloth obstructing the intake to the airbox

Might be worth checking that first.

If no good, first thought would be a fuel starvation problem, though that would suggest float height, something that isn't part of routine service. Could be obstructed jets, but odd if the problem has suddenly appeared.

Is the air filter element in place/unobstructed?

Could also be an air leak on induction side. Also check for partially blocked fuel tap, or tank not venting properly (causing air lock).

Rick
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Author '80 Bikes, and counting...' Currently getting frustrated with an MZ 125 TS.

[J.M.]

Yes, recently serviced. Although I'm doubting that it's a service item that has gone wrong.

There has been slight gunk blocking one of the airbox holes which we've now cleaned out. Carbs stripped & cleaned.

All assembled again and we tried to check for a spark. Me holding the HT lead and forgetting to ground the plug against the frame... got a nice shock Spark present on the plug.

Put the plug back in, noticed a spark against the HT Lead and the engine block when trying to start it. Have wrapped the problem area in some electrical tape now to see whether that improves things a bit.

We flattened the battery trying to start it so that's on charge now. CBR125s are a pain to start when the carbs are empty of fuel
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2004 R1 & 2018 XSR900

[CarlosCBR]

HT lead and cap are a known issue on early CBR125s. Has it been changed since new? For the sake of £15 it would be worth it just to rule it out.
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https://www.youtube.com/watch?v=1OPv5mDPQ14

https://www.facebook.com/carl.simmonds.7

[J.M.]

06 model CBR. My mate says he doesn't think that the leads have ever been changed since new.

Battery is still on charge at the moment.

Is there anyway to prime the bik so that it starts easily for the first run?
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2004 R1 & 2018 XSR900

[J.M.]

Got it running, HT Lead definitely to blame.
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2004 R1 & 2018 XSR900

[P.]

[Clutchy]

[J.M.]