My 15 year olds 2000 Honda 125 R had the back tire lock uo and it died and now will roll but has no compression. This is all going from what the boys have told me. Taking that info it sounds like it needs a complete rebuild.

Im no mechanic but seem to remember hearing 2 strokes are easy to rebuild. I was told to have it done would be between 1500 and 2 k.. im not thinking a 26 year old bike would be worth putting that much into. So im thinking it may be a god project to tackle and something to do with the boys. Looking up rebuild kits it looks like about 7 or 800 will buy all the parts IF im looking at the right stuff. I may need a few tools I dont have to check and se if the cylinder are round not oval from basic readi I have done.

I have been cutting back hours at work some(called in and took my last vacation day last night along with not working my day off Monday but 16 tonight. Baby steps) So with more time a project with the boys seems nice.

Does anyone know if ther is a book or video on this model with step by step guide to do a rebuild with tools and parts list for beginners? Any idea how many hours it should take to complete if starting out prepaired so I can allocate # of days off to the project if it looks like something I think we can tackle.

Any insight and info would be appreciated.

Should be a repair manual out there also consider machine shop work as a possibility cost wise.

Pretty fast to rebuild maybe two days drinking beer without any machining, I’d say a valve stuck open, pretty easy to tell take the head off and see if both are up.

If the engine turns over but no compression I would suspect something relatively simple in the head; valve broken, timing chain broken etc.. Try tackling it yourself, but I'd tear into it first.
If it actually froze up first, then turned over with no compression I would suspect bad piston and a scored cylinder.

YouTube is your friend.

2 strokes are easy to rebuild , for example , it doesn't have valves like a 4 stroke , it uses reed valves , which rarely fail.

I've changed out piston rings , new jug and head gasket on a 1 cylinder in under a half hour on a bike I had.

The lockup was probably from the piston seazing in the cylinder. Maybe not enough oil,mixed into the gas. I would expect piston and cylinder damage.

An air cooled, single cylinder, 2 stroke should be a snap to rebuild. I work on lquid cooled 2 stroke twins in snowmobiles and they can get pricier and a bit more involved. If it has cylinder damage, it can be replated and a new piston, should not break the bank. If it does though, and has high hours, may be worth getting the crank done and new crank seals, no idea how bad that is on a bike but surely doable.

Probably should invest that money into a vehicle...
Looks like he will be 16 soon....and a vehicle would be my choice at

16. Then he can pick up chicks...and park by the lake and watch the submarine

Races. And fill the trunk up with dead yotes.

He will be covered on a vehicle. Im keeping my eye out for another vehicle. My daughter is also talking about a van or suv to have more room for her dog and said he can have her truck I bought her when she gets something else. Should be up town chick attracting machine 98 s10 4x4

Your on the line of thought I had when he bought that dirt bike. Now that its there May as well fix it and all 3 of us learn something. Worst case we tear it down mess it up and scrap it but learn some things. Everything cost money and education can be expensive. Mistakes are some great things as long as you can learn from them.

Before I decide I need to find out everything involved, terms and what to look for and check.

Yup...my favorite saying ...when things don't go as planned..." The High Cost of an Education"

Here is the manual for your bike. It was a race bike and when new required a lot of maintenance. You don't know how well the first owner did maintenance, and it sounds like you have not done any, so the whole bike could be worn out, right down to the chain and sprockets. It requires fresh 32:1 premix and needs a clean, oiled up airfilter so it's not sucking dust and sand into the engine and eating the piston and bore up. Just be careful and don't think it might be something miner. There are a lot of people that restore the old dirt bikes.
https://ru.enduro.team/images/0/0f/2000-2003_cr125.pdf

I rebuilt my 2001 Honda CR250 R one winter. Complete frame up rebuild/restore. Very enjoyable project. Rode it one time after completing the project and sold it for big bucks.

2 stroke ..cheap and easy

This

Get a manual, or online like someone else said. They r not hard to do. Should be plated cylinder so no machine work. Just buy a new cylinder normally cheaper than getting replaced. If it needs a crank need a tool to split cases, probably can make one. Flywheel puller. Bearing-seal driver, harbor freight will work. Press to push crank out of other case half unless u get creative.. Transmission inside case too, easy. Warm up crank brgs by heating the bearing driver with a small propane Torch and sitting it on bearing. Put crank in freezer. Freeze brgs before u put in case. Some aftermarket companies used to make rebuild kits. I haven't messed with a 2 stroke in years but did a ton back when u had to rebuild the crank.
Hard to put a time frame on it being the 1st u will do and with helpers learning.

I would print the PDF manual and study it and if it seems like to much for you to split the cases to rebuild the crank and everything. Clean it all up and sell it as is to a collector that wants to restore it. Instead of tearing it apart for fun and scraping it.

It just needs a top end.you can get a top end rebuild kit with new piston and rings and everything for under 200$.eaven if you have never done one you could probably have it done in a couple of hours if your mechanicaly inclined.back wheel probably locked up when it chewed the piston ring up and went out the pipe.if you decide not to mess with it and would be interested in selling it,pm me

I was just wondering if it still has the original 26 year old foam air filter that got rotten and isn't stopping anything from being sucked in. I wouldn't buy a new cylinder and piston and rings if the crank bearings are worn out. At 26 the crank seals could be sucking air and that could be one of the reasons it seized up. It could need crank seals for sure at that age. It could be restored for sure but to fix it right it might need more than a piston and rings. I would like to see a picture of the airbox, and the spark plug, and the transmission oil. It's all guessing at this point.

If it was me, I'd take 5 minutes to get a sense of what's wrong with it before making any decisions.

Remove a spark plug, squirt a teaspoon or so of oil in it. Crank it over a few times (do not start it), then retest compression. If the compression goes up noticeably, that suggests you're looking at rings/cylinder