72 Wombat rear end locked up while riding

[Jerrycole1318]

My bike had been running great last few times but this past weekend I took it for ride and at 40 miles per hour the rear end locked up and the bike died. (That'll scare the crap out of you) Once stopped, the bike started right back up and it did this 2 more times before I had had enough and went and got a trailer. On the third time it wouldn't start right away but eventually did. I don't think it is brake related, but transmission related. I drained the trans oil and it looked like frothy chocolate milk coming out. Any suggestions on what might be going on?

Thanks Jerry

[thrownchain]

Choco milk usually means water in the oil. If it came to a stop, new bearings are in the works.

[ossa95d]

While there are a few transmission related issues that might cause a rear wheel to lock up and then release, it is more likely that the piston is seizing. You may have several issues going on including bad crank seals. Diagnostics and a rebuild may be in order.

[TheBevman]

I have a M94 '72 Wombat as well and mine did some what the same thing... But mine was a different problem. What I've found is that if my Wombat sits for a bit or has old fuel in it that the float valve in the carb tends to stick closed, in its seat, if the gas isn't fresh and/or the fuels been sitting stagnant in the float bowl for a week or 2.

In effect what happens is that the float valve sticks closed (I've also had it stick open too , but that's a different story) and starves the engine, since the fuel supply in the bowl can't be resupplied at the rate the engine is consuming it... the engine dies. Had it happen to me once at 50 mph and things got interesting really quick, luckily I always ride with a finger in the clutch. Sometimes, after the bike sits for a bit the valve allows enough fuel by to fill the bowl again, so the bike will start again... and so the cycle goes (pun intended) until the bowl empties.

It took me a week to figure out what was happening and 3 carb strip and cleans. I even bought a new float valve and seat, which cured the problem... for a while. In the end youtube came to the rescue, I found this video:

https://www.youtube.com/watch?v=zlez_hdoWYk

I used the same Mother's brand polish and used the q-tip in the drill trick too. I polished the needle and seat until they were nice and shiny, then cleaned them with aerosol carb cleaner and reassembled... and it worked.

Now I drain the carb and leave the main jet holder/drain bolt out to let the bowl drain and dry and I haven't had a problem since. (I'd did a post on it a year or so ago, if you feel like reading my anguish.)

As for the milkshake, I agree with the above gents. to get the H2O out you could flush the trans with ATF, I fill it up pull the plug, drop it into gear and spin the rear tire to get everything moving. Then drain and pull the cover to let the remainder drip out. Then reassemble and refill.

Hope it helps


Bev

[hodakamax]

Hmm, I'm with Ivan. Sounds like a piston seizure. I'd check that first. It may well be running out of fuel and causing the seizure. Running out of fuel alone shouldn't cause a rear wheel lock-up. Time for a look at all of the above for a reason. A bad crank seal could be causing both seizure and transmission foaming. Unless you've had a submersion lately, I doubt that water is in the transmission as it usually evaporates quickly. Overfill is also a common cause of vent foaming.

Maxie

[Bullfrog]

I'd agree that a peek up the exhaust port (remove the exhaust pipe) is in order -- sounds like repeated light seizures to me. Could be from an air leak . . . and it could be from something as simple as a plugged pilot jet. At low throttle settings while cruising, the pilot jet delivers a significant percentage of the fuel . . . and if the pilot jet is plugged an overly lean condition can result and cause seizures.

Ed

[waynesworld66]

Sounds like a piston deal. Has happened to me often, with the same reaction. Pull your exhaust off and check out the rings. After it cools down you should be able to try kick start it. Normally it’ll run for about 3 seconds and then die or you can kick it forever and nothing will happen. Sorry to hear that. Heads up and soldier on , it can only get better

[Al Harpster]

I did the rear wheel lock up a few weeks ago with my B+.

Done it a few times before that too. For me it was piston seizure every time.

I'd suggest pressure test for air leaks. Could be leak from crankcase into transmission cavity. Could be a lot of places. Seems like I find a leak 50% of the times I test. You'll know right away if it's leaking. The guage will drop off the 6 pounds test pressure pretty darn quick.

If you don't find any leaks, I'd go thru the carb to clean and check all the jets are open and verify they are all the ones specified in the manual. Buy or make new carb manifold gaskets.

You may be able to reuse the piston and rings if they aren't too bad. Polish up the piston marks with, say, 400 wet/dry sand paper.

My last lock up, the piston was too far gone.

It's a real drag when this happens in traffic. Best not to have anybody too close behind you.

[MTrat]

If you can quickly pull the clutch when the seizure starts and the engine keeps running but the wheel skids, it says it isn't piston problems but tranny, rear brake or bearings.