Second gear is broken i have replacement engine. Am i better to change the whole lot or is it easy to just change the gear itself?

What your talking about is commonly called the starter drive. If the starter itself is whirling over fast enough you can probably get away with replacing just that. Available thru Sears or any small engine facility which sells parts. If you attempt the job yourself do yourself a favor and order an extra lock ring which holds the drive on the starter shaft. You'll see why when you attempt to disassemble or assemble it. There's a lot of tricks to keep your eye on them when they go flying but it's better to have 1 just in case.

Totally disassemble the WHOLE ENGINE. Rebuild the WHOLE THING. Or go buy another motor and just write off the old motor. They aren't cheap or easy to fix. But they are pretty easy to just change the whole thing.

Changing gears is easy if you have the spare gears, tools and skills. But better is to find someone who have tools, and skills, because it is maybe easy but very dirty.

YOU CAN REPLACE THE TIMING CHAIN AND GEARS, OR CHANGE ENGINES! CHECK THE PRICE OF THE TIMING CHAIN AND GEARS, AND GASKETS! THEN COMPARE TO COST TO CHANGING THE ENGINE!

hi,2 possible causes,1-if the bike has remote linkages to the gear shift,check that the shaft that the gear lever itself is pivoted on,is well lubricated and moves freely,they sometimes have a habit of filling  with road grime over time and this will cause them to stick or become quite heavy in operation,2-and this requires removal of the crankcase cover to repair,the return spring on the shift drum has lost its strength and needs replacing,i hope that it is the first option as that is easy to fix,the second option not quite so easy and a lot more expensive if you have to have it done in a shop..hope this helps...cheeers

Ck your fluid level in the trans and shift through all the gears manually. You may want to replace the trans vacuum. modulator. It's inexpensive and easy to replace. Good Luck.

check the control linkage but!! first! remove the drive gear cover on th ewiper motor itself and ehck to make sure the plastic drive cog's/ gears haven't sheared off or the wedges inside broken? they do sell a repair kit for that!! withot haveing to buy the whole wiper motor and easy to installl

TO OVERHAUL ENGINE YOU HAVE TO REPLACE ALL WORN PARTS.LIKE VALVES + SEATS+ GUIDES.+ SEALS. ALSO YOU HAVE TO REPLACE CAMSHAFT AND GEAR+ LIFTERS NEW CAM BEARINGS.NEW OIL GALLORY PLUGS AND FREEZE PLUGS.THE CYLINDER BLOCK HAS TO REBORED BEFORE INSTALLING.NEW PISTONS + RINGS+ CRANKSHAFT AND BEARING HAS TO BE REPLACED.ALSO OIL PUMP TIMING CHAIN.AND CRANKSHAFT GEAR.IT WOULD BE A WHOLE LOT CHEAPER TO BUY REBUILT ENGINE THEN TO REBUILD.BECAUSE YOU HAVE TO HAVE A LOT OF EXPENSIVE TOOLS AND HIGHLY SKILLED TO REBUILD ENGINE.ITS NOT A EASY JOB.

Since you don't give any model specifics or state whether it is stick or hydrostatic drive I am going to assume that it is a stick shift when giving these directions

You are going to need to remove the complete trans-axle assembly and open it up. You axle splines into a gear within the differential inside the trans-axle. It is normally held in place with a snap ring versus a "c-key" (??) and it will need to be replaced whether it is broken or not. You should also inspect all the gears and the differential itself to determine why the axle came loose.
There is a lot of labor involved in doing this job and unless you are very comfortable with mechanics, it is really a job better left to professionals because there is a CERTAIN procedure for disassembling and reassembling one of these trans-axles. It is very easy to destroy the whole thing without the knowledge and experience of repairing them.

I would want to see that for myself, or get a second opinion. That really sounds suspicious since they claimed there was rust in a box that was mostly filled with oil. And I can't see any logic in paying a lot of money to fix a transmission that is working. Why don't you take it to another shop and ask them to change the transmission oil, and to save the old oil for you to look at. It would be even better to change the oil yourself. Don't tell the dealer what you are doing. The best thing would be to just pick up your car, as is. If it is a scam, they could put some stuff in the transmission if you give them time to do it. In fact, they may have already done that. I can't say it's a scam, but it sounds like it could be if you haven't done anything that would have broken off teeth in the transmission. And if teeth are broken off you should be able to hear it while accelerating at low speed in each gear.