I ran a cyl without oil

[rd400canuck]

I swapped out the pilot jets yesterday and went for a quick boot around the block. /I was looking the bike over afterwards and noticed that there was no oil in the oil line feeding the left cylinder. It was a few inches back. I'm guessing it dripped out while I had the carb out. Now I'm thinking ive scarred the sides of the piston or rings. I'm going to removed the head and have a peak at the cylinder walls to look for transfer but I wanted to ask....

Whats compression supposed to be on a stock RD400c?

[Barrie]

There probably will not be anything wrong as normally  there is quite a residue of oil held within the crankcase, I which case you got away with it.

[Czakky]

If it didn't seize why mess with it?

I went through this same issue last year. My conclusion was that I either didn't properly prime the pump or that when I removed the nozzles I didn't get a good seal due to working them out and not pulling them straight out.

Good luck

[rd400canuck]

It's running fine, thankfully. Just paranoia that the piston wall is smudged now.

[pdxjim]

These little motors are actually pretty tough.

While sometimes it may seem they are prone to failure they can actually handle quite a bit of abuse without serious damage.

[Striker1423]

These little motors are actually pretty tough.

While sometimes it may seem they are prone to failure they can actually handle quite a bit of abuse without serious damage.

Reminds me of my bike when I first got it running (right after buying it). Grinding away, sounded angry. It was idling with no cages in 2 of the main bearings, a giant crack down the cylinder wall, and a piston so scorched it had chunks missing from it. Oh and no base gasket on the burnt piston side.

[m in sc]

when in doubt, pull the exhuast pipe and look at the cyl/piston thru the exhaust port with a bright flashlight.   

but i bet its ok.

[rd400canuck]

Good idea. I'm gong to do a leakdown anyways so I'll have a peek.

Edit.... yup... had a peek up the ports before doing a leakdown and the pistons look perfect. No blowby passed the first ring either :)  Very happy to see that.

[quocle603]

If it didn't seize why mess with it?

I went through this same issue last year. My conclusion was that I either didn't properly prime the pump or that when I removed the nozzles I didn't get a good seal due to working them out and not pulling them straight out.

Good luck

I recall this. Glad you figured it out!

[forexer]

Whats compression supposed to be on a stock RD400c?

to answer your initial question  - compression should equal about 125 +/- 10