Topic: Sheared Transmission Gear Teeth, Cracks in Engine Case

[Gitano]

Greetings,

I have been lurking on this forum for a few months and enjoying many of the threads. Lots of good information from a great crowd, and I’ve been learning a lot. Many thanks for your contributions. Now it is time to for me to reach out for some input. I recently acquired a 1975 400F SuperSport that is in quite good condition. The problem with it was something wrong with the transmission. The previous owner thought one of the shifter forks got out of whack, but after acquiring the bike I took the engine out, tore it down, and found what looks like some serious damage. I’m a newbie this this type of mechanical work and this is my first engine rebuild, but i am always up for a challenge. Here are some interesting pics showing the main damage to the transmission gears, followed by some questions with regard to the engine case that I need input on from the experts here.

So I’m down to the last stages of engine tear down and the engine case is split. Virtually everything is now apart. The first thing noted is confirmation that several transmission gears are indeed absolutely shot. Here are some pics of several gears showing teeth that were sheared off (and found when I removed the oil pan). There are at least three gears that are totally f-ed up):

Several teeth are sheared off.
 
Included in the debris found in the oil pan was what looked like a gear dog, and sure enough here is a pic of a gear with a sheared off dog:
 
All this is all OK as I can get a set of gears to replacement these. The key question I now have is whether, as a result of what ever happened to these gears, there was enough stress on the engine casing to cause significant damage. Following are some photos of what look like stress cracks on different points in the lower engine case:

What is the opinion of the experts here? Is some of this just normal for an aluminum cast casing? Or, s this engine case toast? Can it be welded, or should I start looking for replacement engine cases?

Many thanks in advance for any advice you may have!

Cheers,
G

[754]

 I might have a transmission,  have to dig it out and inspect.

[Gitano]

Many thanks for the responses so far. I'll try to get my post numbers up soon so other pics can be posted for further comment. Prior to splitting the case I had already seen the huge collection of sheered gear teeth in the oil pan (I counted 29 at that time!), and could see a couple of the sheared gears, so I already sourced another set of transmission gears. Nonetheless, thank you 754 for noting you may have a replacement gear set (which, depending on how the used set I got looks, I may want to talk to you about). At this point, what I'm most concerned about are what appear like cracks in the lower casing. I hope to sort that out soon (i.e., get my post number up for posting of additional pictures).

Cheers,
G

[Gitano]

Looking at other case problems and noting the discussion on repairs of some rather bad cracked cases (e.g., in thread below), I'd like to eventually get some input from you guys on the possibility of repairing the case I have rather than having to find a replacement.

http://forums.sohc4.net/index.php/topic,169025.msg1964563.html#msg1964563

The photos in that thread lead me to think I have little to worry about in my case, although some welding may be in order. If so, I can find someone local to do it.

Thanks again for your input thus far.

[jgger]

^^^^yea, just post thank you, then do it again.
I am interested to see the carnage, if nothing else like a train wreck. Just kidding.

[Gitano]

OK, so just to get that post count up, I'll play posting wh*re.....

[Gitano]

And, just once more to get to my first 5 posts to I can get some pics up....

[Gitano]

Ok, so now there's 5 posts. Let's give the pics a try.

Just to set the stage and perhaps provide some sense of what happened and the stresses the case may have been under, here are some of the pictures of the sheared gears. As mentioned in the original post, the debris originally found in the oil pan included what looked like a gear dog, and sure enough there was a gear with a chunk missing that likely included the dog.

Attached are also some pics of what I believe looks like stress fractures. They don't look like casting lines to me (but I'm a newbie to this type of work, so I may be wrong). This is clearly no where near the damage shown in those threads on the chain busting out pieces of the casing, so I hope that this is all rather easy to fix. What are your opinions? Fixable, or look for a replacement case?

[Gitano]

Apologies for the delayed follow up - been busy with other things.

Many thanks for your input and suggestions. After cleaning up the cases, it turns out that those were indeed not cracks but dirty casting marks. So, the casing is in good shape. I'm now getting back to further tear down, cleaning up, and rebuilding. I'll be posting more questions as I go along, so thank you all in advance for your advice and suggestions!

[setdog]

hey ive seen those teeth before, oh yea my ex

you should look for a whole trans, it appears like you got a lot of busted gears.  trying to buy specific gears seperately will more than likey cost more than just buying
a whole new trans.

those case cracks dont look good.  i would probably start looking for a whole engine.  instead of investing in transmission gears and all the costs to repair the bottom
end, only to have those cracks worsen and make your experience even worse.  i would instead try to buy an engine.  but you say they might not be cracks after all,


which ever direction you chose, a spare engine or 2 in your garage is never a bad decision. 

theres a fully loaded main and countershaft set on ebay as of this post for $100

[754]

I stil, have the cases with tranny and crank in it.
 Have not opened it yet.
 That tranny of yours is the worst I ever saw on a Honda 4..

[dave500]

man ive aint seen gears smashed up like that ever!if I hadn't seen those id say those case marks were just casting flash/flaws that are common on all these old Hondas,theres been a few posts about cracked cases but in fact they are only casting marks,in your case though id do a double take and look extra close,as already posted id look for a complete engine/bottom end and salvage what you can out of yours for spares?jeez what a mesh!umm I mean mess!