Mech

There are sites/lists like... https://atvmanual.com/kawasaki/frame-vin-and-engine-serial-numbers

You could take the pull start off and try turning the crank by hand(or screwdriver through the cup's slots.).

Welcome along Lewis. (Hope I pronounced that right.). This is a friendly site. Well run too. How old are these grandchildren ? I've got grown sons, and young grandchildren, all living here on our few acres. So far we just take the grands for rides.. but it won't be long.

Braided ropes and cords come in fractions of a mill differences in diameter. It's the hardness and the no-stretch you want to get in a new cord, and heat resistance too I'd think, they make fire resistant cords and ropes(for fire rescue work). The diameter will be close to either six or eight mill I'd think, but the replacement is very likely to be some fraction of a mill different. Look in an arborist or rock climbing site and they will have good cord, or, to find heat resistant cord get a catalogue and it will have it. Page 35.. see the melting temp differences.. https://www.maximropes.com/fileadmin/Download/22-03-20_MAXIM_Climbing_Catalog_USA_2022_EN_web.pdf

Oh man, that's a bummer. Probably just got the bearing cocked over a little by banging too much on one side(yeah I read about the socket etc). You could put a big bolt, or length of threaded rod, through the socket and a plate on the far side of the hub, and pull the bearing in. Grease the housing and bearing.

Not all the bikes had brake lights Gw..

We don't know what make or model of bike it is, so it's a bit hard to advise you about what might have gone wrong. Did the workshop tell you what they had found when they fixed it ?

No trouble. There are service manuals with wiring diagrams in the manuals section.. For free download..

It's for the brake lights if the bike has them.

If an engine has 80 degrees of ignition advance... it doesn't run.

Nothing runs at 80 degrees advance. Check/test your light.

The piston's aluminium, and it would get chewed up before the plug. Put it at the T mark on the crank and use a torch down the plug hole.. I don't think a piston could chew metal away like that. They bend the electrode, seen plenty of that, but I don't recall ever seeing bits of metal worn off like that.

!25 is a bit low, but it should start. That rough looking buildup could be burnt oil or be because the compression's too low. As you say, if it warms up and has a nice ride with a bit of load on the engine it might come better.

I don't know what this bike is but I'd doubt that nick in the side of the plug was caused by the piston. If a piston hits a plug it's nearly always right on the end of the plug, and it closes up the plug gap. That might have been hit by a valve at some time, and it might have been like that for years or since new. I wouldn't worry about that, but the blackness of that plug looks like burnt oil to me. It would pay to check the compression.

My sons have spent countless hours at the dinner table discussing and debating what they were going to do next to get some bike running by a combination of slotting the mounting bolts so the trigger coil could be advanced and retarded, and then how much air gap it should need to get the right curve. It's a process I've been through probably a dozen times, and they have been through scores of times(not all as successfully as me though.. haha. I know when to quit).

Good idea, and what I'd do with any slightly newer bike. The older ones though can often be got to run pretty well with some other bike's cdi. They all(even the later ones), run very similar timing and curve. If the capacitor gets enough charge, and the trigger coil produces adequate voltage, we can tweak things and get them to run close to specs.

Too much advance breaks compression rings and destroys big end bearings.. It doesn't have much effect on temperature. Coils don't affect the timing. You have about twice the advance your bike is meant to have at idle speed, and more than it's meant to have all through the range. Manufacturers have worked out how much advance engines can stand, and what's best for them, and trying to better all the years and years of testing and accumulated knowledge isn't a good idea. You should try to tune it close as you can to specs. The consequences will be dire if you don't.

And.. Check the cam timing for signs it's jumped the cam chain, or broken the crank key putting the firing timing out..

Low enough compression, or the ignition timing being far enough out can let them ignite the fuel without a sound or kick, and burn the plug almost dry, but not start. Try starting it and then pull the plug and check if it's wet, or perhaps, only wet on the metal part, or really completely dry..

I've got an Alterra 500\550\700 manual that has the 500 engine section and a 550\700 engine section separately, and most of the rest of it looks at a quick read mostly all the same for most of the rest of the stuff.. It may be better to use than the one you have. I'll post it up. Ooops, no I wont. The Alterra 500\550\700 one is already there. Try that one, it only does three models.

It looks like most of their manuals cover several engine sizes at a time. I know what you mean about the manuals not being very helpful laid out that way. It's always a good idea with any service manual to read right through it familiarising yourself with what's in there and what's covered in which section. If you do that and make yourself familiar with the manual, and perhaps make a few pencil notes of which pages are going to be the ones for your bike, it will no doubt get better the longer you use the manual. When I'm reading manuals for people in here I always have a pen and paper at my side noting things down. Like their bikes, the jap manuals are always excellent..

What model is it Alex ? Does it have a name ?

What do the bearings sound like, and is it smoking yet ?

And this is not even firing right ? No backfiring or anything.. Well a plug can fire just fine out of the engine, but then not fire once there is compression, so I'd try a second new plug. Sometimes, just very rarely, we get a dud plug, but also, if a plug gets stale fuel on it, it can get fouled in just a few cranks and near starts.

The Admin and Mod are both really helpful... And obliging..