Mech

Yup, what Gw said, small drill right in the center, and be patient. Sometimes warming the aluminium up lets the oil or whatever you are soaking the thing in soak into the threads and loosens any corrosion in there.

Sounds good Sherlock. Do they have bushes ?

Oh ok. I was thinking it had started loose but run out of drive when it hit the peened/split end of the screw. And you've given the shaft a lube from inside ? Does the butterfly look nice and central on the shaft, and closing cleanly.. and fitted with the sloped edge to the plate the right way around. No suggestions about getting it out if it needs it.. You will have to get the screw right out to get the plate outt, so I'd drill a small not too deep hole and then tap something it to turn it.. Flat jewelers screwdriver perhaps. In fact, the right flat may grab in the cross head if tapped in. I think I'd try those before drilling it. If I got it to move, I might just seat the plate and tighten it back up again. Chokes closing/working properly ?

Might be that the butterfly isn't sitting in the shaft right. The plate has bigger holes in it than it needs so it can be positioned slightly different. It's normal to fit the plate into the shaft, put the screws in and then open and close the throttle a few times till the plate shuffles itself left or right and up and down so it's central with the carb body, then tighten the screws.

Yeah I've got books from 88 on and they are all basically the same. Here's a picture which explains better how the reverse switch works. I think I'd try jumping/bypassing the start relay to see whether the problems is in the relays trigger circuit, or after the relay and going to the start solenoid.. The relay works like this.. The power going through the key and kill switches goes into the relay at the O wire, and needs to short out to earth via the neutral switch to work/connect the start button to the start solenoid. The neutral light though puts power to the relay's L wire when the L wire isn't getting shorted to earth through the neutral switch. That means the relay has 12v on both sides of it's coil unless the neutral switch is shorting the L wire to earth, and so the coil doesn't energize. The reverse switch is a normally closed switch with the L/b and L wires connected in every gear position except reverse. When it's in reverse the L/r and L get connected so the reverse light comes on via the reverse and neutral switches because the bike can't select reverse unless it's in neutral and so the neutral switch is shorted to earth. When it's in reverse the relay has 12v on both sides of it's coil again via the neutral light same as when it's in gear and the neutral switch is open circuit. Notice though that the L/b wire going from the neutral light to the start relay branches off as a L wire to the relay.. the same colour as the neutral switches wire.. but it's not the same wire. That's perhaps what's catching you out. Hope that helps, ask if there's anything confusing.. haha.. It confuses me and I wrote it. output.pdf

Has it got good compression.. Have you checked the exhaust isn't blocked ?

On the slightly newer 250 models(88 one) it earths through the reverse switch then the neutral switch.. They are in series..

Good stuff..

Ha.. good bit of writing there Gw.. I like it .

Normally the first thing would be a standard tune.. Spark-plug, air-filter, valve adjustment, check for air-leaks at the manifold, check the tank breather, drain the carb looking for water and fuel flow, adjust the idle speed and mixture. If it's just conking out when you throttle off, a tune might be all it is. If it's faltering while you still have the throttle on, and you have a timing light, you could put that on and check the spark isn't failing once it's hot. If the spark is getting intermittent then that needs diagnosing. If the spark seems to be fine, and the plug is new, then it would be worth taking the carb off and cleaning it.

Oh ok.. Bit more use perhaps, or a squirt of wd40 into the butterfly shaft.

Not just the idle speed a bit too high ? I've seen things that idled high for two to five seconds after throttling off, then go to a reasonably slow idle, but once I wound the idle speed back to a slow idle, they fell straight back to the slower speed as soon as the throttle was let off. No good reason why they should do that, but some do seem to do it.

It's pretty chunky, and a funny shape, the T shape.. Should be identifiable.. Should...

Oh.. That is strange !! But a clue no doubt.. Wanders off musing...

Oh.. and that limited slip diff likely needs special oil, not regular gear oil like the manual diff has.

Yup.. There's a box with a lot of wires going into it and it's the charge regulator, the fan control and it has two circuit breakers in it. It's got a couple of different descriptions in the manuals.. Something like the power control module or an acronym for something like that..

Only two wires.. Maybe a circuit breaker, but they are mostly in steel cases as far as I know. I looked in two manuals, at the diagrams and the photos of around the battery.. nothing that looked right though.. But.. It does look well made and well mounted. You'd think it was genuine, or an accessory. Regulator for heated handlebars perhaps ?

Ok. If it doesn't read 2Wd, 4Wd, Diff-lock on the shift lever then it doesn't have a diff lock and is just a limited slip diff. The test for their functioning is as described earlier, jack up one front wheel and try to turn the other. It should take some specified amount of torque to turn the lifted wheel.. It's stated in the manual. And apart from being larger diameter wheels, if the new tyres have a flat tread/foot-print, then yup, they will really play havoc with the steering, and handling.

Oh ok.. The risks of buying not running.. At least it's a small part.. if you can get one.. An engineer could make you one and harden it for you.. Or you could buy high carbon (0.6%) steel rod and heat treat/harden it yourself.

Haha..

And, when you tried to get it out of diff-lock, did you try backing and turning and rocking the bike back and forwards to unload any load on the sliding dogs that engage diff lock(if it has one) ? Perhaps those big wheels are causing the problem, either preventing it coming out of diff-lock, or, if it has a limited slip front diff, just being too big for the torque the limited slip diff caters for. A lot of bikes have different sized front and rear wheels, and the diffs are set up with the right gear ratios to cater for wheels that size. If you change the size of wheels you can cause a lot of binding between the front and rear axles.. Perhaps that is happening and causing the bad steering. If you have the old wheels, or can borrow a set of original sized wheels, try them and see if it cures the problem.

In #1 you say it looked like it wouldn't allow the axles to be independent, then in #3 you say it looked like it should allow the axles to move independently.. What were you making that assessment on, and did you have the actual diff assembly, that being the crown wheel carrier and the side gears inside it, apart ?

Does it say on the shift lever above the fuel tank that it has a diff lock ? Because looking in the service manual, and the spares for that year, it doesn't show any diff lock.. It looks like it will be like hondas and others and have a limited slip diff. I was looking at LTF400F models.. If it has a limited slip diff you can jack one side only of the front up, and turn the raised wheel and it should turn, but there will be quite a bit of resistance..

Most of the older ones had a manual shift in and out of front diff lock.. You'd better tell us what year and size this is, and what sort of transmission it has.. belt with two speeds or five speed foot shift ?

Like a subaru.. Probably because you can leave it turned on all day long and it will only engage when it's needed.. I'm suspicious about them. In trucks with automatic free wheel hubs on the front end they are a dangerous trap for the unwary. If you start up a slippery slope they engage, but if it gets too slippery and you have to back down they disengage themselves allowing the brakes to lock up the front wheels and causing the vehicle to go out of control.. The only "safe" way of backing down is to move into reverse and then boot it in reverse and don't throttle off till you get to the bottom.