Author Topic: Failing transmission? (Read 2226 times)

Cb^_^750 · « **on:** May 30, 2015, 04:24:18 PM »

Here's a video of how my tranny sounds after I had switched out the forks because my bike was stuck in first gear. I am also running a new clutch and springs. Bike was running fine the first day I rode it and now it's slipping out of first and fourth gear and riding home yesterday the rear wheel locked up on me. My kick start is also extreme hard to push down. Assuming I just totally messed up putting my gears back together does anyone have any other insigh as to what the problem could be? Also in the video you can see I am able to pop into first gear without using the clutch lever

neurotoxin312 · « **Reply #1 on:** May 30, 2015, 04:51:47 PM »

How's your clutch? When was the last time you adjusted/changed it? How old is the transmission?

Cb^_^750 · « **Reply #2 on:** May 30, 2015, 05:04:36 PM »

My friction plates are brand new as well as the springs. When I split the cases a week ago everything looked good nothing chipped or worn. My bike is a 76 750f

neurotoxin312 · « **Reply #3 on:** May 30, 2015, 05:31:52 PM »

Hmm. What about the condition of the gears on the transmission? I am having a very similar problem after I installed a new clutch on my cb550. My kick starter pedal cannot be pressed down. Question, how much did you tighten the 4 bolts on the clutch plate down by?

Cb^_^750 · « **Reply #4 on:** May 30, 2015, 06:45:15 PM »

I tighten them down snug. At a certain point the screws can not be tighten any further. My clutch plate sits maybe 1/8 in.

neurotoxin312 · « **Reply #5 on:** May 30, 2015, 07:03:04 PM »

Hmm. Same here with me. How about the electric start? Does it engage when you try to start? So far, mine does not engage. Sounds like something is sluck. Perhaps starter engager clutch is stuck on both our engines? haha

Cb^_^750 · « **Reply #6 on:** May 30, 2015, 08:47:32 PM »

no i was having problems with my electric start as well i was having to kick start it or shorten the stater solenoid lol.

Don R · « **Reply #7 on:** May 30, 2015, 09:09:29 PM »

The kickers and electric starters are totally separate.

enwri · « **Reply #8 on:** May 31, 2015, 02:15:56 AM »

gearbox locking up is extremely dangerous, can happen by getting 2 gears at the same time, something is floating sideways in there.
Is the neutral light switch seated properly? if not the drum can move sideways .
if it hasn't got the retaining rings on the gearbox bearings the whole mainshaft can drift sideways, very bad things will happen.
going into gear clutchless is normal, just not recommended.
The clacking could be dogs rubbing or just backlashing, it's only running on 2 or 3 cylinders.

neurotoxin312 · « **Reply #9 on:** May 31, 2015, 02:53:18 PM »

How could you tell that it was only running on 2 or 3 cylinders? Kylemichael can you confirm this?

Cb^_^750 · « **Reply #10 on:** May 31, 2015, 03:58:59 PM »

as you can see i have found the cause to the noise. as far as way this happened i am still unsure. it couldve been my gears were not properly lined up or just worn gears that i didn't notice before. and yes i noticed that my shift drum did have movement due to and improper install of my neutral switch. either way i will now spend my day digging out metal chucks from my motor and sourcing out new tranny gears. and yeah my spark plugs are foul so its not firing on all cylinders. if you listen my bike sounds like a lawnmower lol

Sdsbassist · « **Reply #11 on:** May 31, 2015, 09:49:36 PM »

Pics didn't show....hope it went ok

Cb^_^750 · « **Reply #12 on:** May 31, 2015, 10:09:43 PM »

Pic is me holding chips of the gears in my hand

heyitsrama · « **Reply #13 on:** May 31, 2015, 11:11:05 PM »

Quote from: Sdsbassist on May 31, 2015, 09:49:36 PM

Pics didn't show....hope it went ok

Quote from: Kylemichael on May 31, 2015, 10:09:43 PM

Pic is me holding chips of the gears in my hand

so sad

SOHC4 Cafe Racer Fan · « **Reply #14 on:** May 31, 2015, 11:19:25 PM »

Damn, that sucks.

PeWe · « **Reply #15 on:** June 01, 2015, 03:52:42 AM »

Was it a half ring that should keep the bearings in place that was not in place and fell into the transmission when the cases were assembled? There are 3 half rings on same axis (primary axis too) that should sit in a groove in the ball bearing and fit into the upper case groove.
I have always worried about that should happen when I have assembled the cases.

enwri · « **Reply #16 on:** June 01, 2015, 04:40:03 AM »

Ouch, that would be the crunch crunch crunch noise then. how does it's opposite look? do it's dogs or teeth look impacted? could have been a foreign body getting jammed or two gears at once scenario.
Even with a smashed gearbox it seems to make less engine noise than mine.

Quote from: neurotoxin312 on May 31, 2015, 02:53:18 PM

How could you tell that it was only running on 2 or 3 cylinders? Kylemichael can you confirm this?

neuro, right at the end he gave it a rev and I could hear not all cylinders picked up, the clackety idle doesn't necessarily mean they wont all fire properly, carbs not quite synchronized will sound like that, once you open all the carbs past idle they can run fine, wider open the less it matters.

Cb^_^750 · « **Reply #17 on:** June 01, 2015, 09:57:38 AM »

All the gears look pretty much chipped and or damaged. Some are okay but for the most part I'll be switching them all out. Tbh I'm not sure what caused the gear lock up but I'll definitely be taking my sweet time next time when lining everything up. I suppose it could've been my Nuteral switch not fully inserted causing the shift drum to move around. Either way it's a hard lesson learned.

flybox1 · « **Reply #18 on:** June 01, 2015, 10:12:08 AM »

Hey Kyle,
PM me if you're interested. I have a good, working main & countershafts, and gear set from a CB750F3 for sale.
Full disclosure/transparency: Just to let you know, there is a lengthy thread of me dealing with this transmission.
I spent months and tore down this engine twice to figure out why I did not have 5th gear engagement.
All other gears worked properly.
I eventually bought ANOTHER full trans off ebay, and that one, STILL, had no 5th gear.
Finally, i found a thrust washer under my clutch basket installed backwards....and now, I have 5th
I cant say for certain if this trans on the shelf would have had 5th now that this clutch-side thrust washer is installed correctly, but I could find nothing wrong with any of its gears. Bushings, circlips, thrust washers.....all are within spec.
It has very little wear on the dogs, and I never had a slip in the few hundred miles i put on it...

Rob

the thread....http://forums.sohc4.net/index.php/topic,138663.msg1566863.html#msg1566863
I have close-ups if needed

Cb^_^750 · « **Reply #19 on:** June 03, 2015, 03:04:19 PM »

thanks for the offer flybox. But can I run those gears on my 750f? I'm not sure what which gears I can run in my tranny if they have to be the same year and model as mine or if I can use parts from a different year and model with out running into any more problems

flybox1 · « **Reply #20 on:** June 03, 2015, 03:26:43 PM »

Quote from: Kylemichael on June 03, 2015, 03:04:19 PM

thanks for the offer flybox. But can I run those gears on my 750f?

Yes, you can.

75-78F, 77-78K all shared trans parts.
Feel free to cross reference part numbers if you wish.
cmsnl is great for this. http://www.cmsnl.com/honda-cb750four_model14344/

There are also a bunch of complete trans sets on ebay for sale. $60-$150

News:

Author Topic: Failing transmission? (Read 2226 times)