Here it goes again!?! (sudden power loss)

markjs

Well-Known Member
Local time
4:30 AM
Joined
Jul 31, 2023
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299
Location
Port Townsend, WA, USA
So my PK80 already blew it's top end gaskets once and I suspect a similar failure this time?

I was riding in the rain, worse rain than I have run it in before, but I've seen videos of LA Hover putting a garden hose to his exposed magneto and nary a misfire...

Anyway, was riding towards the biggest hill in town, and it lost power. Didn't die, last time it died completely and would not start. This time it kept running but lost over 50% of it's usual power. I ended up having to walk it up one of the steepest hills in town. The usual route up the hill is a longer windier but less steep grade, but even with pedal assist I could tell it wouldn't make it. It also tends to die at idle since the power loss. So I walked it up the steeper but shorter hill. It did manage to limp home up some very mild hills, but it barely was able to build RPMs...

Anyway it's still wet and s**tty, but it stopped raining, so my first thing will be a compression check. I did check the head bolts and they seemed tight (yes I need a torque wrench but don't have one yet). Anyway it's very frustrating

I had more errands to run and had to resort to my 49cc bike. I found that with a 44 tooth sprocket, they only way it gets up the big long windy hill is with constant pedal assist. I got too tired to keep it up 3/4ths of the way up. What a crappy day! Still the 49cc made a much easier trip than it would have been without it.

Not expecting a super sleuth to guess my problem, but any ideas worth investigating will be appreciated. If it's not too wet I will go out and do that compression test and report back. Originally when it ran good it was at 120.
 
I was NOT expecting this?!?

IMG_20240528_193034.jpg

IMG_20240528_193237.jpg


So those look perfect, and it should be running great right? Well that's what I got when I just now checked it anyway.

It's AMAZING how fast it can dry up here. Was a s**tty rainy day all morning until late afternoon, way too nasty to go out and bother working on the bike beyond checking the head nuts. But in just the span of a few hours, even at 50f it's still windy enough to almost completely dry even the grass!

So anyway, seeing is believing, so next is a short ride to see if the running condition cleared up with the passing of the wet weather. I really can't believe that's the problem, but at this point it pretty much has to be fuel or spark or a horrendous intake leak. I just don't see any other real possibilities? Can rain kill the spark?

Anyway, off for a test ride to see if symptoms persist. I don't plan on getting deep into this tonight though. Either it runs right or it doesn't and I will be back to kick around possibilities if not, and sort it tomorrow if further sorting is needed...

I do recall that the magneto was not centered and I never fixed that. It was working so I figured why bother? It wasn't rubbing or anything. The only other possibility I can think of is that maybe my woodruff key slipped out?
 
OK, well I really hate these kind of mysteries!

Anyway it ran kinda poorly out the gate and I was about to think it was going to still lack power, but lo and behold, after warmup, it started running fine I'm like 95% sure. I won't be 100% until I tackle "the big hill" and get up without any pedal assist. Still I'm almost sure it will do it... Will see soon enough, just didn't want to go that far tonight as I have no reason to.

So yeah, water? Really? I have no idea but it definitely was less than half power for a little while today, in the rain when I most needed it...

To be fair though it was wet enough water was pooling on the crevices of the engine.

And still no clue why it failed temporarily?
 
Water probably shorted out the electrical system but not bad enough for permeant damage
How can LA Hover spray a garden hose on a running, exposed magneto and it didn't skip a beat? Could it be that mine is poorly centered (it is) and that with the cover on, if water gets in, it can pool up, rather than like in the LA Hover video where being totally exposed the water all ran right back off the mag?
 
How can LA Hover spray a garden hose on a running, exposed magneto and it didn't skip a beat? Could it be that mine is poorly centered (it is) and that with the cover on, if water gets in, it can pool up, rather than like in the LA Hover video where being totally exposed the water all ran right back off the mag?
Yup, precisely. A lot of those videos are just wrong. If he had a garden hose running on it on a 20 plus minute ride it wouldn't have stayed running long.
 
Yup, precisely. A lot of those videos are just wrong. If he had a garden hose running on it on a 20 plus minute ride it wouldn't have stayed running long.
Well LA Hover Bikes is a pretty honest reliable guy. To be fair though we're probably also talking the difference between his 80+ degree Louisiana weather vs my 45F Washington moderately heavy rainy day, as well as his having cover off and mine buttoned up but probably not water tight....
 
I carry a rain sock for my Harley because the air filter is exposed/open to the atmosphere
I put the rain sock on if I have to ride in the rain or should I say "get caught in the rain" :LOL:

I don't ride my Motorbike in the rain or ride my Motorbike if I think it's gonna rain
 
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