Topic: Gearbox fixing with engine upside down

[Canucklehead]

I have the engine on my cb750 K5 out of the frame and most of the peripheral stuff stripped off. My intent is to turn it upside down and attack the gearbox that way as the top end is good but the 2nd gear is hooped-probably worn dogs although I noticed that the bike had thrown a chain at some point and the area in front of the front sprocket is epoxied all over. There may have been some damaged casing parts thrown into the gear box but I won't know until I'm in there. I want to know, do I have to remove the counter shaft bearing holder and more importantly is this feasible to attack the gearbox from below? I'm a bit nervous about doing it and I'd appreciate any insights or advice anyone has to offer.
Thanks.
Canucklehead

[HondaMan]

I have the engine on my cb750 K5 out of the frame and most of the peripheral stuff stripped off. My intent is to turn it upside down and attack the gearbox that way as the top end is good but the 2nd gear is hooped-probably worn dogs although I noticed that the bike had thrown a chain at some point and the area in front of the front sprocket is epoxied all over. There may have been some damaged casing parts thrown into the gear box but I won't know until I'm in there. I want to know, do I have to remove the counter shaft bearing holder and more importantly is this feasible to attack the gearbox from below? I'm a bit nervous about doing it and I'd appreciate any insights or advice anyone has to offer.
Thanks.
Canucklehead

That's actually the best way to do it! (Do you have my book?) It shows in many of the pix I've posted over the years. Remove the points plate, the side covers (tranny, alternator, clutch, sprocket cover) and all the bolts on top and bottom, then split from the back toward the front, like a clamshell. I usually use a [very] long screwdriver across the final drive shaft to help open the goo that seals the cases together, although that epoxy situation might be more demanding. Be SURE to remove all the case screws, especially the one lurking near the starter, or the cases will not open.

[Don R]

Yep, it seems there is always one more screw. My brother did his F'nK trans repair that way.

[lucky]

I have the engine on my cb750 K5 out of the frame and most of the peripheral stuff stripped off. My intent is to turn it upside down and attack the gearbox that way as the top end is good but the 2nd gear is hooped-probably worn dogs although I noticed that the bike had thrown a chain at some point and the area in front of the front sprocket is epoxied all over. There may have been some damaged casing parts thrown into the gear box but I won't know until I'm in there. I want to know, do I have to remove the counter shaft bearing holder and more importantly is this feasible to attack the gearbox from below? I'm a bit nervous about doing it and I'd appreciate any insights or advice anyone has to offer.
Thanks.
Canucklehead

I would remove the oil pan first before turning the engine upside down. Sometimes there is debris in there.

Its not worn dogs. But a dog can get broken off.
the most damage is caused by people pounding down with a big boot on the shift lever bending the shifting forks.

Every time I see some one KICK a shift lever I cringe at the damage being caused.

[754]

 Be very carefull  moving an engine around, if the pan is off, puts a lot of weight on a hanging out part of the pump.. You can lift motor on side, remove pan and clean out and reinstall if it will be sitting upright. When you roll the mottor over, use padding undedr valve cover, get the right size block under the rear part, and you are set to go. You may have trouble seperating the chain repair..probably cut thru it and redo.. may be have to weld cases or replace.. I may have a set.

[Canucklehead]

Thanks 754, depending on the mess in there I might have to take you up on that. By the way, I have a buddy who's having carb issues with his CB750, I suggested he track you down in Kelowna and see if you can help him out.
Cheers.
Canucklehead

[HondaMan]

One thing to watch out for: many times after splitting the cases upside-down, the oil pump loses prime. So, pull out the sparkplugs and spin the engine with the starter for 5 seconds at a time, for a few times, to make sure the pressure comes up before restarting. Otherwise, you'll have to manually prime it again.