mike in idaho· Registered
koolio said:Right, does anyone have any idea how you shift a frozen valve adjuster screw?
I've managed to get the lock nut off, but the screw is completely rusted locked, I've applied ACF-50/penetrating oil and tapped with a hammer. May pull out the blow torch tomorrow.
Also one of the valves adjuster screws has rusted together with the lock nut, so adjustment is with the lock nut only, I'm afraid of trying to rotate the lock nut more to open as it drags the valve adjuster with it.
You need to make sure you are at TDC on the compression stroke. See my thread:Sir Sherwood said:Howdy,
I have a '74 CB450 and I have been trouble shooting poor compression and poor performance. (Bike wont go over 50mph). I previously set the points timing -- I set the valves at TDC with a .0015 gauge as previously discussed, buttoned everything up and went to kick it over tonight. The bike was banging and jumping on the center stand trying to hold idle. Freaked me out... A lot.
When I first adjusted the valves, they could be wiggled, letting me know I was TDC. Knowing that small clearance adjustments can really affect performance, I am confused.
Can someone recommend a set of double check instructions because this is very wrong and I need my bike back
Thanks all and stoked to have found this forum!
There are these ways I've learned to find if you're on the compression stroke at TDC:
1) Start moving the crank counter-clockwise. Put your finger over the spark plug hole. When you start to feel a "push", then you are nearing where you need to be (which is going to be "LT" if you're doing the left cylinder or "T" if you're doing the right cylinder. The "LT" indication of the crank will "fall" when it's in the compression stroke, and I've been backing it up clockwise and holding it there. For the "T" indication, it stays put.
2) You should see the lobes face out on the cam if you're in the right spot.
3) You should be able to wiggle the rocker mechanism with your finger when you're in the right spot.
4) You should see the intake valve start to close if you choose to not put your finger over the spark plug hole and see that the piston moving to the top. This is an indication that you're close.
5) Having mechanic friends watch over you also helps, but they confirmed that I am at TDC in the compression stroke, so my methods mentioned must be accurate.
This is nearly identical to how I did my procedure, with the exception to the perpendicular marks on the cam follower shaft, thankfully all four of mine were pointing away from the spark plugs. I noticed 3 out of 4 valves had larger than .003" of gap, fairly large, and probably the culprit of a noisy head. I went with the recommendations of others on this forum and set to .002–.0025".Leigh said:Figured it out. It was unrelated as far as I can tell. The screws holding the points base-plate had become loose so my timing was way off. The plate was fairly loose and when I moved it with a screwdriver the idle came right back to normal. Re-timed it and set the points. It's running very nicely with the valve clearance at .002" Pretty quiet too. Thanks for the info on valve clearances, it was very helpful because the recommended clearance from honda at .0012" was freaking me out. Sooooo thin!
Some observations from a first-timer on this 1971 cb450 valve adjustment:
The valves on my bike were set so that the leg of the "T" on the adjustment for 2 of the cam followers was pointed toward the spark plug instead of away from it when I started the valve adjustment. The cam lobes nearest the backwards "T"s had more wear than the others. Coincidental? Probably not. I simply loosened the lock-nut on the outside of the cam follower and was able to turn it around in the proper direction. I went very slowly and felt resistance when I went the wrong direction then turned it the other way and it all went fine. The adjustment could still be made when the "T" was turned around and facing the proper direction. No biggie. Setting the gap took some time to get the knack for tightening the lock-nut while maintaining the proper gap. Trial and error. It helped a lot to have the lock-nut already a little bit snug instead of loose when doing the adjustment because the adjustment kept changing when I tightened the lock-nut. Took the vacuum cylinder and vacuum piston off of the carbs to get better access to the intake-side valve cover but left the carbs on the bike.
I have a strong belief that there is a leak in the carb boot. will replace and see what current tappet clearance is like then.mike in idaho said:An extra half a thousandths tappet clearance is not going to affect the way the engine revs up. If it affects anything it will maybe smooth out the idle a (tiny) bit. If it won't rev up, there's another problem you need to address. Make the usual checks for air leaks, plugged jets, weak spark etc.