Vintage Dirt Bike Q & A

So I have a 1976 MT125. The other day, the engine seized. I pulled the top end off, and it looks good. Cylinder and piston both look good. So I currently have the engine off the bike, and I'm ready to start tearing it apart, but i have no literature. Should i get this clymers? http://www.ebay.com/itm/73-76-HONDA-MT1 ... 10488#shId I noticed its pretty broad. and as an inexperienced though mechanically inclined 17 year old, is replacing bearings seals and the crank (with rod already installed) beyond my skill level? This is the particular crank i had in mind. http://www.ebay.com/itm/Honda-MT-MT125- ... 25&vxp=mtr I also heard that i would need to have the crank balanced, although that did come from someone whose area of expertise is cars.-

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1976 Honda Elsinore MT125
1990 Toyota Celica

Do the gears or crank turn freely in neutral?

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I can turn the engine forwards with a wrench in neutral, but by hand i can only turn it backwards. What about this manual? http://www.repairmanual.com/online/used ... -u6136101/

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1976 Honda Elsinore MT125
1990 Toyota Celica

Both the manuals you linked to should work well - I like the Honda shop manuals myself, but others can have additional helpful info, especially British ones. I rebuilt an MR175 motor top to bottom over the winter using an MT125 gearset, and ended up using sections of four manuals.

If your budget allows - I spent nearly $200 just on tools - you should be able to do it, yes. If you're looking to do a complete bearing / seal replacement, many of the parts needed are discontinued and may be hard to find, as I'm sure you're aware.

That eBay crank looks like it may have damage to the threads, taper, and possibly keyway as well. I had my crank balanced at Crank Works, but mainly because I was using a CR125 ignition rather than the stock flywheel ignition. I don't know about the availability of MT125 or CR125 rods / bearings / crankpins etc., but it's got to be better than MR175 parts.

If you haven't already, I'd pull off the entire clutch and then recheck the crank and gearbox rotations.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I removed the clutch and flywheel, and the engine is spinning freely. I am going to replace the seals and hope it stays free.

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1976 Honda Elsinore MT125
1990 Toyota Celica

If the engine seized, you have a bearing problem. Replacing seals will only fix the old seal problem. You will have to split the cases to get to one of the seals. Plus you will be able to see the bearings.

Take lots of pictures during every step. I have the honda shop manual and it does not go into great detail. I also have the honda parts manual that has helped alot. It helped make sure i had all the parts in the right order when reassembling.

The case splitting tool will help if you don't already have one. Getting the phillips head screws loose will probably require an impact driver.