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I think my tranny is bad

wa-chiss

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I bought a 76 750F and it's got a 92 K engine (from what the owner tells me). It doesn't like 2nd gear at all. I've noticed some hesitation in all gears, more prevelant when accelerating slightly and cruising at a constant speed. Feels like it's ignition related. I haven't gotten around to doing a basic tune up yet with plugs and an oil change. What concerns me most though, is when I shift into 2nd. It goes in easily with no grinding, but when I give it throttle again it bucks pretty good and then it kicks out of 2nd and back into 1st. It'll make a metal-on-metal banging noise a couple times and then pop, 1st gear. I've started to hold 1st and shift directly into 3rd with no problems besides the hesitation.

At first, I thought the hesitation was the cause, but I think it would then happen in all gears. I can't seem to find an answer whether or not there are detents for each gear, like in a car transmission, that keep the tranny in that gear until moved by the mechanism.

Anybody have an idea on what I'm going through?
 
92 K motor? Maybe 72K? There is not a 92 K. Yes there are detents for each gear. I would get it running good first though. The gears in most motorcycles use a slidding cog and slot type of engagement. One gear has pegs sticking out that engage into another gear that have slots and thats what holds them together. If they slide out a lot under acceleration chances are the cogs or pegs have the edges rounded off and they cant stay locked into the slot of the other gear. If you have ever heard of back cut or undercut transmission gears this is what they are trying to fix. The cogs have an angle machined on them and the other part has an opposite angle machined onto it. When they engage the angles result in the gears being locked together and wont slide apart under load anymore. Cycle X, and Ape can do this. I does make the gears harder to go into gear though. Or you can just replace the back gears in the transmission. I have also had the shift mechanism not turn the shift drum fully and the gear doesnt go all the way in and it pops out under accel or decel. You can also have bent or worn shift forks, there are three. You can inspect the shift mechanism from the left side cover but any transmission work the cases need to be split.
 
lol yeah, it's a 72. I don't know why I said 92. Happens to me all the time.

Well, thats what I was afraid of. I don't mind the work, as I'm Master ASE for automotive and I know I can do the work, but I'm always aprehensive at new things. I think I'm going to go with a Pamco Ignition w/ coils and wires, rebuild the carbs, and tune/time accordingly to see if I can get the shakes out first, then try my hand at the transmission. I feel that even if it's detent related, the unknown time it's been doing this (I've only had the bike for 2 weeks) has more than likely caused more damage.

Thanks for the advice.
 
I figure it was 72. I was ASE master certified also, but I got out of the automotive industry full time so I couldn't justify the expense of recerting. If it has been popping out of gear for some time it probably has the dogs rounded of and they cant be fixed only replaced. So I would get it running good like you said and see if it is related to the tranny problem or not. If you do end up going into the tranny it really isn't that hard its pretty straight forward. You can do it without pulling the head and cylinders off just flip the motor over. But Im getting a head of the game here so if you get to that point I have done several times before if you have questions. At least you being a mechanic too makes it easier to explain things :laugh:
 
I just took a peek at both sites, I like the Ape gears more. From what they were explaining on the site, it sounds like my "dogs" are worn. I'm curious if I can have a machinest fix the dogs on my gears. Just true them up or even undercut them a little to fix the issue until I can afford the Ape set. Befor you say anything, I'm a cruiser not a racer. I don't beat on my bike, so I think this will be ok.
 
That seems easy enough. Remove engine, flip over, remove lower case half with transmission. If this winter is any better than last winter, I can probably get the gears and replace them before spring.
 
From what I have been told..., both places send there transmissions out to the same company to have them undercut, Ape was going to start doing it themselves so I dont know for sure. They are the same product I have used both. Once the dogs are too rounded off they cant be undercut. If you send the gears in to be undercut and they are rounded off they wont cut them. I would maybe suggest finding a good used gear set or tearing it apart and replacing just the gear(s) that are bad. There are some gear changes in different years so get a tranny close to the same year if you go this route. Ebay has tons of 750 parts. The only problem with the undercut trans is it does shift harder and has a bit of a clunk when put into gear and when shifting. It takes more pressure on the shifter to get it to shift because that is the purpose of the undercutting to make it want to stay in gear. If you ride easy and dont plan on any engine performance upgrades I would maybe shy away from undercutting and stay with a stock tranny. Some people dont like the harshness of the undercut gears. Best thing would be to take it apart and inspect the parts and see what the culprit is.
 
Well, I think I found the source of my hesitation. I was riding home from work on my lunch break to pick up my chapstick. I got about 1/8th mile from my street and the bike started acting wierd. It would bog way down if I gave it more than half throttle. I made it to my street and when I pulled in the clutch to downshift, the engine stalled. I Could get it started but I had to hold the throttle open a little and it sounded bad. Definately a misfire issue. Pushed the bike the 50ft to my house and then it wouldn't even start at all. After work, I decided now would be a good time to look at my plugs. I pulled off the wires and pulled out the plugs. All but one looked good. #3 was ok but had signs of misfiring. I had new plugs so I figured while I had them out, might as well change them. Put the new ones in and went to put the wires back on. As I was trying to put #3 wire back on, the boot came off the wire.......... I went to try #2 and the same thing happened. I figured now that I'm screwed, I'd mess with #1 wire. It came out too! I was curious if I could put the wires back in the boots and maybe get the bike back to my shop. I pushed 'em in and she ran.......... Did a quick test drive around the block and it didn't hesitate at all.

Next on my list of things to buy are coils and wires. I guess there was enough connection there for cumbustion, but any bump would open the gap in the wires enough to soak up all the energy.
 
The ends are supposed to be able to be removed from the coil wire on the 750s. There is a sharp "needle" inside the boot that you push and twist into the end of the wire. I cut about a 1/4" off the wire and reinsert the boot and it holds on longer. Assuming you have the original style coil/wires that are built together.
 
Yeah, I looked in the boots and saw what looks like a screw. The wires ends are kinda messed up and the ends wont stay in the boot. I can barely touch the wires and they come out. I noticed today the screw in one of the boots is broken. I figured I might as well start making things "new" again. I'm getting a Pamco Ignition with coils and while I'm at it I'll be changing 2nd gear as well. A quick carb rebuild and I think I'm set.
 
Be sure to take a look at the shift forks while you are in there as well as the tranny bearings. For the case halves I really like the Hondabond sealant. I have had really good luck with it and it wont get soft and fall off on the inside like RTV will. RTV will plug oil passages in the 750 motor. It is always the passages going to the camshaft because there is an oiling orfice in the head. I always stress this fact when people do work on the 750s because it happens all the time when RTV is used. Any questions you can message me on this site also. The oem coils are kind of weak anyway so it is a good thing you are upgrading.
 
I'm assuming the case halves are a machined fit being they're the other half of the main journals. So I think I'll use Hondabond like you said, but I'll apply a small amount and spread it thin with my finger. Sealing Toyota transmissions and timing covers has made me a pro at FIPG's. I'll likely be making a "Winter fix-me-up" thread. Should be a fun project..........
 
Yup case halves are machined fit. One set of tranny gears stays in the top half and the other shaft stays in the top half. You will need gaskets for the side covers and its up to you if you want to change the crank seal and the output shaft seal while its apart.
 
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