[John1028]

Took my first ride on the 'new to me' CM400T.

The bike actually runs pretty good! It was a 7 mile ride home, the bike shifted well, seemed to have adequate power, no major issues to report.

Notables:

• LOTS of smoke coming off the exhaust when I stopped the bike and got off. Not sure if there is a major leak or oil was spilled on it or what, I have not really started to investigate what might be happening.
• There is an occaisonal backfire/sharp pop on the right side when idling.
• The oil was overfilled by quite a bit, I drained at least a quart to get it down to the 'full' mark.
• The bike starts instantly and has no problem revving up.
• There was a slight shimmy when riding, seems like it coming from the front. Possibly related, the left fork showed a lot of rusty looking oil after the ride. I already ordered seals and oil to do a rebuild.
• Broken right side cover. There are 3 points of attachment, the rear attachment point is snapped off.

My next step is to work through the 'new to you' guide, I have no idea if the previous owner even put the right kind of oil in it, they evidentally did not know the right quantity. Everything is suspect. I'm not going to start troubleshooting things until I've worked through that guide.

 

[JamesPal]

Doers the oil small like gasoline? I wouldn't ride it anymore until the oil is changed. Don't forget to shut off the fuel petcock when parked. Serious damage could result. Smoke coming off the exhaust s opposed to coming out of the exhaust indicated oil on the pipe or muffler. If it doesn't bun off after a few minutes of riding then there is an oil leak. If the oil was over filled that can cause leakage past the engine gaskets or seals.
What is the back story? How many miles, has it been in storage and other historical items of interest. How about some pictures? We love pictures.

 

[John1028]

Thanks, Jim.

The oil does not smell like gasoline.

I won't be riding it at all until it's had all or most of the issues on the 'new to you' guide performed.

I suspect the overfill caused oil spillage, god knows where it could have ended up. I'm not seeing any wet areas externally now after spraying it down a bit with some engine degreaser.

I don't know much backstory, this was a barn find, the bike was roadworthy last year according to the owner (it still had a current registration). It fired right up after sitting all winter, I took that as a pretty good sign. The bike has 25k on it.

I posted a couple pics in the introduction forum, here is one that I posted there:

 

[Old Putz]

When you tear down the front end to change the fork seals, make sure to check that the fork tubes aren't bent- that could be a cause of the front end shimmy.
Another potential cause would be badly worn tires. Difficult to tell from the photo, but what sort of shape are they in? Any cupping or uneven wear? If they're more than 4 or 5 years old, the rubber petrifies, losing traction and sometimes creating handling issues.

 

[Ebuddy]

Don't forget to shut off the fuel petcock when parked. Serious damage could result. .

I'm curious to hear more about this. I have a CM400A also that I got last year (barn find also). I have it up and running, but have not heard about this (and haven't done so).

 

[1980CM400E]

The broken side covers are very common, lots of ways to reattach the post, acetone, glue, putty, jb weld, etc. With the burning oil, did you check on top of the h-box/power chamber? When I got my CM400E it had several small leaks(which of course add up to a decent leak) one of which caused oil to drip onto the h-box and burn. Mine also had a backfire, on the right side too! In my case it was the o-ring on the intake boot. It had blown at some point and was allowing some of the exhaust gases back and through the boot, also explained why that boot was cracked.

 

[1980CM400E]

Don't forget to shut off the fuel petcock when parked. Serious damage could result. .

I'm curious to hear more about this. I have a CM400A also that I got last year (barn find also). I have it up and running, but have not heard about this (and haven't done so).

Leaving the petcock on can cause a variety of issues, lines being compromised, carbs becoming fouled, gas going to waste, and worst of all, gas in your oil. Gas in your oil compromises it's lubricating properties and can lead to catastrophic engine failure amongst other things.