I finally pulled the old ('69) Honda Trail 90 out from the back of the barn in order to get it running again. Cleaned the carb (was not in bad shape, but did it anyways), adjusted valves (they were close), new points, new plug, set the timing. It has a good spark, is getting fuel and compression (tough not measured) feels good when I crank it by hand. Nothing, not even a sputter. What's left? What am I missing? I forget the controls on this thing, the key switch is weird and there doesn't appear to be a kill switch, but since I was getting spark I figured I was OK....Do a real compression test?
Double check the valve lash, from my experience with the older honda single stuff (CTs and ATCs) if everything is right on the fuel and spark end its the valve lash causing the issue.
You have two out of the three bases covered and half-assed the third. Put some ass into kickin' the thing. The rings are prolly a bit gummy creating a leakdown situation. Either the current showering of unspent fuel will loosen 'em up or you may have to manually put some kinda gunk cleaner in. Take the plug out, add some lightweight oil or other petro-chemical, put the old plug in and give it a few kicks to dissipate the fluid while, hopefully, soaking the rings...no need for ignition. While turning it over, listen for escaping air from the intake and exhaust on the compression stroke. Give the soak a few minutes, kick it again, then reinstall the new plug and kick ass. A low compression test reading won't tell you where your problem is...
OK, Thanks. Checking lash (.05mm) is really touchy on this thing. Will try the oil next as that's simple, heard that auto transmission fluid was the ticket to free up rings.
I'm assuming locknut adjustment. They can tighten up when locking down, creating a leak at the valve seat.
Try some starting fluid in a spray can. Remove the air filter, shoot a small amount in with the throttle wide open. Then kick and see what happens. That will eliminate any fueling problems and is much easier to ignite in sub-prime conditions of low compression, tight valves, etc. Having said that, I'm betting if it isn't a fueling issue you have bad compression.
With the bike cold, at TDC on the compression stroke you should be able to grab either tappet and jiggle it and feel clearance. If it doesn't click, it's too tight. Also, did you remember the pin between the points rotor and cam shaft stub? Without that it'll have spark, but the timing will be all kinds of no good.
Just got done doing a compression test....75 psi, should be up around 120 psi (per my book at 8.2 ratio). Is this enough to prevent it from firing, even with ether?
Yes, I would think so. One way that we used to resuscitate bikes when I was a youth was to tow them in gear with another bike or a car to get revs up to build false compression. If they started, there was a good chance the rings would unstick (eventually) and the bike would run(ish) after that. Plus it's great entertainment to watch the looks on everyone's faces when it would start and the clutch wouldn't work, so you'd have to ride around in circles with the towee trying to untie the strap while the tower was trying not to get run over or run into an inanimate object (like a building, for example) or get the strap wrapped up into the axle, and etc.
