Author Topic: Engine Swap Required  (Read 786 times)

Beaker99

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Engine Swap Required
« on: November 12, 2024, 02:41:32 AM »
On my commute home last week I had a mechanical failure that I can only blame myself for. The nut that holds the outer variator plate in place worked loose and allowed that plate to slide half off the crankshaft and thrash itself to death. I’m guessing I simply didn’t tighten the nut enough the last time I was in there, which was about a month ago. I don’t have a torque wrench and just go by feel, big mistake! Unfortunately, it looks like the variator plate also damaged the crankshaft which is not an easy, or cheap part to replace.

Luckily, I bought a “parts bike” about 20 months ago. It was an insurance write off after some flooding here in Auckland and I picked it up for NZ$800 at auction. The bike was in great shape with 35,000km on the clock and after cleaning and replacing all fluids etc, it actually ran really well. Given my daily driver was now pushing 82,000km I didn’t even consider trying to replace the crankshaft and set about a straight engine swap with the parts bike.

The entire process was pretty straight forward with most of the time spent stripping fairings, shocks etc. Once I had the replacement engine installed and everything hooked back up the bike fired up perfectly and I’ve been riding in the past 2 days with no issues. I’m guessing it took me between 6-8 hours over the course of the weekend to complete the swap.

I now have a torque wrench on order and will check some of the nuts are correctly torqued once it arrives!

The parts bike is on the left and my daily driver on the right in the photos.

Ruffus

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Re: Engine Swap Required
« Reply #1 on: November 12, 2024, 12:08:41 PM »
Congrats and welcome here!
Good to see some mechnical work done here in the forum. Keep us posted.

Either use (if available) new nuts or put a drop of lockstop on it for peace of mind.

For the crankshaft thread, mostly not demaged by a loose variator plate or nut for those are way softer material.
This a security feature too, to safe the crankshaft as much as possible in case.
« Last Edit: November 12, 2024, 12:19:16 PM by Ruffus »
Happy and safe scootering, Ruffus

mousejunks

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Re: Engine Swap Required
« Reply #2 on: November 27, 2024, 11:34:16 AM »
I had the same issue as well years ago, the 19mm nut holding the drive pulley came off and the loose drive pulley grinded the splines on the crankshaft. Fortunately the bike lasted until 80,000km or so, then I got the 2nd gen Downtown which I still ride today.

Note: put threadlock on the drive pulley nut and torque to spec. No issues since.
'09 Kymco Espresso 150i
'11 Kymco Downtown 300i ABS - 79,500km
'17 Kymco Downtown 350i ABS

CROSSBOLT

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Re: Engine Swap Required
« Reply #3 on: November 27, 2024, 02:40:30 PM »
The biggest hassle with that nut on the crank is not providing enough slack in the belt so that outer plate gets fully seated when the nut is fully tightened. Has destroyed several CVT's on rubber band tranny's over the years...
Karl

Three motorcycles 1960-1977 (restored a 1955 BSA)
Agility 50
Yager 200i
Downtown 300i
Navy tech, Ships Engineer, pilot and aircraft mechanic

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