Hello! New bike, rough idle, now oil leak.

[JohnMedic]

Hello! I'm new to Hodakas, bikes, small engines & carburators. But I've rebuilt a couple engines, I'm generally handy. I just bought a 99 Road Toad to get my hands dirty, have some fun, & the community sounds great! Anyways, after cleaning the carb while troubleshooting an idling issue, I noticed that there is oil leaking from the exhaust pipe. About a drop per kickstart attempt. It's definitely motor-oil. The spark plug also gets a good coat of oil on it. The bike has 936 miles on it, has been sitting for a year, hasn't been ridden in who-knows-how-long. How bad is this, should I just do a full teardown/gaskets/rebuild since I don't know the history?

[thrownchain]

If it is motor oil, then the right side crank seal needs replacing, which is a complete teardown. You can get an overhaul kit from Paul and makes the whole process easier.

[Bullfrog]

Thrownchain almost certainly nailed it. If you are set up to do a crankcase pressure test . . . a pressure test is in order - though we think we know the result. It certainly sounds like the clutch side crankshaft seal has failed. Time for a full tear down and new bearings and seals.
Ed

[Hydraulic Jack]

While it is likely that the folks are right about the seal, I am curious how it was determined that the oil present in the exhaust is, in fact, motor oil (oil that belongs in the transmission as opposed to the injector oil that is pumped into the engine to lubricate the crank and piston). Once oil passes through the cylinder, it is going to be "dirty" in appearance, so just wondering.

Also assuming that by "leaking from the exhaust pipe" you mean dripping from the exhaust spigot at the cylinder, and not dripping out the tailpipe or somewhere else. Two stroke motors do drool oil from here and there because there is always unburned oil in the exhaust. No premix or injector oil burns completely during combustion. So black exhaust oil drips are common in two stroke bikes of all makes and vintage.

That said, you bought an old bike, and its maintenance history is probably questionable at best. Even if the bike were not dripping some oil, a leak test would be at a minimum a good thing to do. Or if you don't want to spend days doing diagnostics, simply assume that being forty some years old and low mileage, this bike has done more sitting around than working for a living, and a complete tear down would be in order. Seals that are this old are not going to last long even if they are still pliable. Being a fairly simple engine to work on, get a manual, buy some parts, and rebuild it. If the piston and ring clearances are not within spec, have the top end rebuilt at the same time and you will have essentially a new engine.

While you are at it, verify the function of the oil injection system if you are using the oil system and not using premix. A failed pump or clogged oil line could cause engine failure.

The Road Toad is an under appreciated bike IMHO. It is an example of a well executed small bore road bike. I think they are a hoot to ride, and they are far more rideable on the street than was the Ace 100. Bring yours up to stuff mechanically, and then ride it with a smile.

[JohnMedic]

Right on, thanks for the quick responses. I'm using premix & have the oil pump closed off, also the fact that it coated the spark plug concerned me & made me believe it's motor-oil. The leak was right where the engine meets the exhaust. I wouldn't know how to do a leak test, I could take it to a small engine shop but as you said - it's likely going to need the seals replaced sooner rather than later. I'll start gathering parts!

When it comes time to do the work, I'll try to document it for y'all.

[Hydraulic Jack]

Photo documentation is always appreciated here.

Here's a way to verify the oil thing that costs nothing: remove the carb or remove all fuel from the carb so that kicking the engine over won't draw liquids from that source; use a dry plug but don't connect the plug wire; kick, check, clean, and repeat. If the plug constantly comes up oiled, then you either have a great deal of residual oil in the crank case, or there is an oil leak from transmission into the crank case. Residual oil is pretty normal if the engine has idled before shutting down, but kicking the engine over will quickly clear residual oil. Half a dozen test cycles should confirm that the oil is a constant, or it is declining. Has to be one or the other.

Google two stroke leak testing. You can buy the gauge and parts as a kit, which isn't exactly cheap, or you can make up a test kit easily enough by yourself. Folks here have posted photos of home brew systems from time to time. Perhaps someone has a photo handy showing what the parts look like, or you can probably find a YouTube video showing a how to. As for taking the engine to a shop, you can try this, but my experience is that bike shops and small engine shops these days don't do diagnostics on two strokes, they sell parts and overhauls. If you can find someone who has the equipment to do a leak test, great. Take the whole bike. It is easier than pulling out the engine.