losing power in heavy rain

[seanfoot]

i have a p reg cg125 that is used quite alot. my question when it rains quite heavy i lose all power when in high gear it splutters then just dies please help

[Kickstart]

Hi

Heavy rain suggests water getting in somewhere. If so then possibly the HT lead or cap is shorting out when it gets wet.

Other thing I would check, especially if it has an aftermarket cone filter, is water on the air filter (lands up blocking the filter to an extent and making the mixture very rich).

All the best

Keith
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[chris-red]

Coat the plug cap, lead and coil in WD40, if it make it better but gets worse again, I would replace the lead and cap then the coil if I was still having problems.
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[Fizzer Thou]

Many many moons ago I had a CB125S that still had its OEM metal plug cap fitted to it.In heavy rain it would cut out whenever I used the indicators and at cruising speed on the A2 on the way to Navy College.I replaced the coil,the plug,the points,the condenser,all to no avail.Then,one day,I was reading MCM (Motor Cycle Mechanics) about a new ceramic/plastic plug cap that was being introduced onto the market by NGK.It was the only item that I had not thought about,so I bought one and it cured all of my starting and running problems that I had previously encountered.

I have recently read about someone who did not realise that he had a faulty plug cap.There was a hairline crack along the join on his admittedly 'original' plug cap that came with the bike and appeared to be okay with a cursory glance.But when the bike was running and viewed in the dark,a spark could be seen jumping to the engine case from this cylinder.He replaced the plug cap and the misfire disappeared.
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[MickC]

As 'Chris and Fizzer' said, Check HT lead and cap, also the wires connected to the coil (small ones as well as HT - if the connectors are lose they can let water in and short out)
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[tahrey]

You get this sorted Sean?

It's a problem I've seen a few times on cars before. Usually a new HT lead set sorts them out. Luckily as there's only one short one to be dealt with on the CG it should be a whole lot cheaper and easier to try out than with four or five long ones

They don't last forever, the rubber coating perishes on a microscopic scale over time and allows moisture in, which greatly reduces the coating's insulation ability. When it breaks down far enough, the current that should fire off the spark just arcs along the outside of the lead (or through the wet insulation itself!) and shorts out on the engine block or frame instead of going down the plug.

Weirdly, other than being correlated to how wet the environment is, the power loss mostly manifests at wide throttle and low rpm, I have no idea why. Presumably something to do with ignition advance and mixture richness. Low rpm and part throttle, or high rpm with part or full throttle are no problem. So you can crawl on down to Halfrauds (othermotorfactorsareavailable) by running the engine fast in low gear and slipping the clutch like billy-o, after very gradually revving it up at a standstill.