Vintage Motocross Project: 1972 Husky CR400, Epic Failure

This is another late post, this picks up the day after my last one...

  
A glimpse and total internal combustion fail. 

Thursday night I start back into the motor after the big bang and now stuck motor.  I wasn't felling too bad about the work, I figured it was going to be something easy or something that was going to have me miss the race on Saturday.  With my fingers crossed hoping for something simple I drained the tank, then pulled the tank and seat.  When I pulled the exhaust I heard metal in the pipe, game over for racing in the near future.  


Chunks of piston and sleeve that dumped out of the pipe.
  
For those who do not know, metal chunks in the exhaust means the motor grenadeed itself.  I dump a small pipe of metal out of the pipe and onto the workbench, I can see it has chunks of the sleeve not just the piston in the pile.  Pulling the head it did not look too bad, then the fun of removing the cylinder came.  


Chunks I picked out of the motor itself, some piston, sleeve and connecting rod...

I should have been able to just lift the cylinder off of the motor, but then again if I was able to do that the motor would not have been seized either.  A quick change in music (from Cake to Rammstein) fit the change from race prep to an autopsy.  The industrial music fit a lot better with the big dead blow hammer that was needed to force the cylinder and piston apart.  As the piston and the cylinder started to separate I was able to see the damage, and what most likely was the cause.  


Broken conrod...


The crank with lots of crap still stuck to it, it will wait until I split the cases for proper clean up.


After I was able to get the topend off, the piston was still stuck in the bore and needed to be hammered out...

All said and done the piston has the better part of it's skirt broken off, the connecting rod broke where the wrist pin goes through it, and the sleeve had large chunks of it shattered off of it.  I think the pictures tell the tail pretty well.

In my best judgment the cause of this terminal failure of the motor was largely due to the missing base gasket.  It turns out the last person to assemble this motor decided that it was not needed or something.  That is not to say the carburetor jamming open didn't contribute to the problem, but I think most engines would have been able to run at WFO for 5 seconds or so without failing.  The missing gasket would have cause the bike to run very lean, which would explain the failure during warm-up at the last race as well.  The big kick in the pants on this one is I almost pulled the cylinder off when I was doing the timing to replace the base gasket, but decided to save it and use it for when I planned on rebuilding the motor over the winter. 

The parts hunt is now on, and turning out to be a bit of a pain.  I found the parts and it looks like it will cost me a little under a grand to get all of this fixed.  This will have to wait for other things in my life to get sorted before I can blow the cash.  I am not going to enjoy this, but I am reminding myself that even after I dump the correct amount of money into it I will still have less into it than I would have spent to get a race ready bike.

Vintage Motocross Project: 1972 Husky CR400

Note: I wrote this on Thursday, but am just now posting it...

Back to working on the motor, I picked up where my break down during warm-up (a DNF would sound almost better somehow) problem started. After waiting over a week for the replacement woodruff keys to come in I finally start the work on it. First step was to lap the flywheel to the crankshaft, hopefully this will help prevent it from coming off in the future. Timing the motor was a bit of a process, but not too tricky over all. After getting all of the tools I needed, which in and of its self was the biggest pain of the process. It seems no one stocks a 25mm socket locally, I ended up using a 1", I will find the proper tool later. Anyways back to the job at hand, the threaded spark plug hole insert for the dial indicator that I borrowed from my friend didn't work. The combustion chamber on this motor was just too tall. Pulling the head off the motor I was able to get the dial indicator on the piston and timing it was not a problem. All said and done the timing had been set to far advanced before, which could have cause the problem with the flywheel coming loose.

Dial indicator measuring the distance before TDC

Everything in the right spot, the flywheel with the timing pin inserted.

The marker lines are where the timing was set, a noticeable difference from the correct setting.

After getting all of the covers back on and the oil filled back it I went to start it. After a dozen kicks or so it started... But the throttle was jammed WFO and the motor revved all the way out of a few seconds before I was able to reach the kill button. *BANG* The drive gear coming off the crank shaft fell off, but the flywheel was still on. I remounted the gear, making sure the tapered shaft and the inside of the gear mating surfaces were clean. The motor is jammed, I am really crossing my fingers that it is not seized, but it is not looking too good. I can stand on the kicker and it does not move at all.

I'm going to pull the head and probably the jug too. Hopefully this can be worked around and I can still make the starting grid.

Mixed bag of bikes

I have been lazy updating this, then lazy posting this too. I wrote this on Tuesday and now it is Saturday that I am posting this. So this will be the first part of a big string of updates. I took a week off after the last race to just relax and get parts on order and got side tracked with some other projects.

My first project was getting my 2007 Triumph Tiger 1050i to run breath better. Anyone who has ridden with me has heard the big backfires and smelt overall rich smelling exhaust. Both are byproducts from the "race style" exhaust modifications I made last year. I have tried a handful of different tunes over the past year without much luck; at the end of the day I think the bike was just not sucking enough air to balance out the open exhaust. After hearing that I can stuff a Speed Triple tune into it if I swap the air box over to a Speed Triple specification unit I figured I would just try to modify the current airbox. The Tiger ended up get getting her spring cleaning too, it’s a bit weird seeing it all clean and shinny.

After opening the airbox and looking at the openings for the throttle bodies compared to the opening in the airbox (which is a lot smaller on the Tiger than the other 1050i motors) there is no doubt why the motor is having a tough time breathing.

The snorkel pulled out laying next the the intakes, note the size difference.

The two holes the bike now breaths though, the snorkel only used one of the holes to suck air though.

I pulled the snorkel out, opening the second air box breather hole up as well. Even with the same tune (I think I currently have the Arrow Race tune) it is running a lot better, almost no popping on deceleration, and it is popping now not huge "BANG" backfires as unburnt fuel just cooks off in the exhaust system. I am pretty happy at this point with it, next time I am at the Triumph shop I will probably try a Speed Triple race tune or something.

The second project was changing the seals and fork oil on both the Husqvarnas. The inside of the CR400 forks were not too bad, but I had also changed the oil before the last race. On both the bikes getting the oil forks seals out was a little bit of a pain, I ended up taking a Dremel tool to the seals to make it easier.

Cutting the old seals out, and you can also see the awesome double seal set-up.

While I was in the forks I did find the CR400 fork springs are undersized and in need of replacement. I also noted that the fork travel on it is a meager 6". The CR250 forks were pretty gross inside, as you can see in the picture there was a lot of muddy burnt up old oil at the bottom of the tubes.

Yummy muddy crap I found in the fork tube.

The oil that was in the forks didn't really smell too bad when I dumped it, so I think it might have been changed at some point and the guts were just not cleaned out. I used 30wt fork oil in both sets of forks, hopefully that will do fine, the factory manual calls for 10wt-30wt motor oil. I also pulled out the CR250 and washed it off a bit to take the "before" picture.

Don't mind the gaping hole where there is no motor.

The only other things really was a night put into trying to get the GS750 running so I can sell it, and spending a good part of the past weekend helping my buddy Zach get his GS500 back on the road again after a year slumber. Between that and helping Kellen with motorcycle and motorcycle gear shopping I have been dubbed a "Motorcycle Superhero." So that is pretty rad too.