[9hondas]

Like I mentioned in a different thread I'm finally getting around to fixing my RC51 after the previous owner broke the drive chain and subsequently the case around the countershaft sprocket.

Historical perspective: When I bought the bike it was presented and sold to me in "mint" condition before I became a member of speedzilla. Who would think to strip off the bodywork for inspection before purchase? The damage would've been hard to notice anyway. I discovered I was ripped off when I went to replace the drive chain which had a dirt-bike master link on it. After I joined speedzilla and started asking for help, Roningsr put 2 and 2 together and realized the dude that ripped me off was a member here and had posted about his problems prior. I tried to prosecute the crook but was ultimately unsuccessful. Lets just say I discovered the difficulty of going after crooks in their home states, and to also never underestimate the willingness of local police to hassle outsiders to protect "family." After that the bike sat for a quite awhile until I learned how to weld aluminum, and I then got the idea to fix it as shown below.

Here is the first thread from before I was a member of this forum or even interested in buying an RC51.....where member rsxjosh broke his chain doing 75 mph.
Chain broke while riding. Clutch problems...

Then he posted this thread where he tried to dump the bike:
FS: 05 Rc51 (needs left crank case)

But then he disappeared. I now know that he cobbled it back together with some all thread barely engaging the remaining threads. It was totally unsafe.

Last night I finished the repair on the motor and thought you might like to see some pictures of how it came out. It's not super pretty, but I think it is a solid repair that is probably stronger than the original section damaged.

Unless you guys tell me it's a complete waste of time, while I have the motor out I'll probably check the valve clearances. Also I'm waiting for the pair blockoff plates I made to come back from the anodizer, but otherwise I can't wait to get my motor back in and RIDE the damn thing!

A special thanks goes to SubSailor. His suggestion to use TimeSerts instead of heli-coils was excellent, they work great! I measured out the holes/threads on an ebay case I have here and then decided to use the longest available 19mm (6mm x1.0) inserts to obtain the same thread engagement as Honda initially had. Something not possible with heli-coil!

Here's the before pics:

 

[bmfgsxr]

now post up the after pics.

way back when on my 84 interceptor 1000 i snapped the chain and busted open my case. it cost me 1200 bucks to have it repaired and the guy did a crap job in hindsight. but i was a fairly young kid and the bike worked when i got it so i didnt say much about it.

then i had the same thing happen to my 99 gsxr 750 although it wasnt as severe so i just had a couple new studs welded on and ground them down and tapped them.

 

[9hondas]

Give me enough welding rod - and I'll build you a motorcycle

Here's some pics of the build up. I ended up using 24 feet of rod!

I was careful not let the heat build up too much, so I cooled the cases near the weld with a wet rag. The aluminum transfers heat so well it wasn't a problem at all. I didn't even melt the masking tape used to cover the clutch rod hole.

I used a washer to keep the groove preserved around the clutch rod seal. It took about 9 hours of work on and off through the day, and I was careful to make sure there was no porosity in the material I was laying down. I didn't worry about filling in the bolt holes all the way since I knew I would be drilling them out again anyway.

I'm impressed at Honda again. Their cast aluminum is super dense and welds nicely, like welding billet. Its got just about zero encapulated air, unlike the corvette bell housings I've welded before which are full of air bubbles which explode like little pressurized volcanos when you melt the metal around them. It was noticeably better than the Suzuki RM85 case I repaired last year too.

 

[RVTMAVERICK]

I HATE heli-coil!
But I have to say, I've Never heard of "TimeSerts" What we get here which in IMHO is Way WAY Better then heli-crap, is called "Kingserts" :clapper Great stuff for fixs like this!

DAMN Brother,... You've been down with this for along time now!:banghead

Glad to hear you're NOT giving up and moving forward to getting her done.:clapper

Peace Jeff

 

[9hondas]

Machining the parting surface

After building up the case, I put the whole thing into my Bridgeport milling machine. It barely fit, and even with the knee at its lowest.

The first task was to make sure the machine was going to cut the parting surface on the correct plane. I did this by centering the quill over the countershaft sprocket and then installing a dial indicator on the quill. I then bolted a scrap of material under the counter shaft bolt for the dial indicator to ride on as I rotated them around together.

At first it was way off, 7-8 thousandths. I then carefully adjusted the height of the nuts supporting each engine mount until the milling machine quil and the countershaft were in perfect alignment. When I was done the dial indicator barely moved as it rotated a complete circle.
YouTube - Honda RC51 Crankcase Repair

Once I got the machine set up it was pretty quick to take it down to the previous level since I still had some undamaged case to start with.

BTW If you're wondering why I have all this machinery at my house, I acquired it along the way for my other hobby, an aerobatic biplane project - 2wings.com is my website for it.

 

[sburns2421]

I have an 851 engine sitting in my garage at the moment with the same fatal injury. In my case a total chunk about the size of your palm was broken out of the alternator cover and main case. Busted her up real good...

 

[9hondas]

Timesert.com to the rescue

I ordered a M6x1.0 Timesert kit along with some longer inserts, 19, 17 and 12mm since I wasn't sure what I would end up using. I'm on the west coast and it came from Reno the next day. Awesome!

Turns out I was able to use the 19mm inserts which matched exactly the length of thread in the original holes machined by Honda.

The kit comes with four tools besides the inserts; drill, counterbore, tap and inserter.

The basic procedure for a M6x1.0 timesert is to drill the hole to the depth of the insert + 6mm. The extra 6mm is to allow room for the tapered end of the tap, since its not a bottoming tap, the bottom 6mm of the hole will not have fully formed threads.

Once the hole is drilled, the counterbore is used to machine a lip into the hole so the shoulder of the insert sinks down flush with the parting surface.

I didn't use the counterbore on the hole that has the 8mm diameter locating pin, I just ran an "O" drill (.316" = 8.03mm) down 10mm into the hole, which after the insert was driven down there allowed the pin to set on the insert's shoulder and stick up above the hole at the right height.

Once the counterbore was done, the holes were tapped and the inserts screwed onto the inserter and screwed in. As the insert bottoms, the inerter tool expands the bottom 2-3 threads outward which creates a positive lock into the base material.

I like the timeserts compared to helicoils because they are available in long lengths, and being one piece are more tolerant to imperfections in the tapped hole. Thanks for the suggestion SubSailor - I owe you a beer!

 

[9hondas]

Finished - Ugly but structurally beautiful

Once I got the holes done and the cover bolted on, I considered doing some creative work with the die grinder, but have decided against it.

I like the extra material thickness on there since it makes up for the lower quality of aluminum used to build it up. Also, once I hit it with a die grinder it will always have that lighter shinier "machined" look which will be more eye-catching than the current welded surface.

Anyway, I am sooooo relieved to have the motor fixed. This bike has been quite an ordeal, but the worst is well behind me. I really appreciate this forum and ALL the help I've received here. Hopefully I can return the favor sometime in some way.

SO......should I bother with checking the valve clearances on it before it put it back in? It's a 2005 with 3350 miles since new.

 

[RAZR51]

Good job on the repair. :clapper
You could easily check the valves but I'll bet they're all within specs. :rockon

 

[RVTMAVERICK]

It IS So Easy to check the valve clearance anyhow but with the Engine out.... even though you don't have 3,400 miles on her> "I'd check them" just because it would be even easier to get at everything!:clapper

 

[BRod]

Very nice job. Maybe I missed this but what weld procedure did you use? TIG I assume?

 

[bmfgsxr]

great work man, and youll never see it behind the cover anyway so who cares. as for the valves, i wouldnt bother since you only have 3000 miles, its a honda, and even better; its an RC.

 

[sburns2421]

Any chance the heat from welding and building up all that material warped anything with the cases?

 

[9hondas]

Very nice job. Maybe I missed this but what weld procedure did you use? TIG I assume?

Oh sorry, yes it was TIG. I have a Lincoln Precision TIG 275, with a water cooled torch. My previous aircooled 175 amp unit worked great, I used it to weld up my airplane fuselage, but its nice not having to wait for the torch to cool off. Also the extra amperage was certainly needed on this project, at the bottom of the flanges that aluminum case soaks up a lot of amps before it starts to melt.

Any chance the heat from welding and building up all that material warped anything with the cases?

No I didn't put that much heat into it. I kept a soaking wet washcloth on the case near the weld. It certainly got warm, but never steamed. Also I only welded a minute or so before stopping to cool the case down with other wet towels before proceeding again. Although warm, the case was always cool enough to rest my hand on it, I'm sure it gets a lot hotter when riding it.

You can see in one of the pictures I used a washer to preserve a groove near the clutch rod seal while I added material there. After doing that section, I put a piece of tape over the clutch rod hole and cleaned up that area with a die grinder. I then left the tape there while I completed the rest of the welding. It never got warm enough to even melt the adhesive. That big aluminum case is giant heat sink.

 

[b.miller123]

It's hard to believe that someone was a big enough douche nozzle to sell you a bike without telling you about this.


Glad that it worked out though! :clapper

I am totally jealous of anyone who has a Bridgeport in their garage.

 

[wingnutt]

Respect

A lesser man would have snibbled and bitched...way to take the bull by the horns :rockon

B.T.W. RESPECT !!!

 

[wingnutt]

Now do the "NICKY" mod or I will diss your ass

 

[PSk]

Impressive! :notworthy

Pete

 

[3stripes]

impressive indeed:rockon

 

[9hondas]

Now do the "NICKY" mod or I will diss your ass

Just got done researching the nicky mod threads and understand the how, but not the why. Is it to inspect the security of the countershaft sprocket bolt? Doesn't look like much weight loss.

I've had offroad bikes for a long time and its common to take the countershaft cover off to keep rocks and mud etc from getting jammed in there and breaking the case.

Hopefully I'll be keeping the RC out of the dirt!

Impressive! :notworthy

impressive indeed:rockon

Thanks guys, except for starting it up every few months, that RC has been sitting for almost 2 years because I was not happy with the options I saw.

Swapping the guts to a new set of cases was a big BIG job, and I also considered an ebay motor, but wasn't happy with the idea of putting an unknown condition mid or high mile motor in such a low mile bike, so I let it sit.

Today I told my son it was a good thing he over-torqued the drain bolt on his RM85, otherwise I never would have thought myself capable of fixing the RC like I did.