cegan09 Posted September 8, 2010 Share Posted September 8, 2010 OK, still working on the bike, turns out i don't have as much free time as i thought. I have a few things i'm trying to diagnose so i can fix them. 1. Timing. I went and checked it the other day, spot on, tightened the screws on the plate, still spot on. I take a spin around the block to see how it's riding, then check again, way advanced (this is all at idle when i'm checking, so the advance cam shouldn't be on). I adjust, and have the plate rotated as far as it can go, and it's still not quite where it needs to be. It's running much better now, but i'm concerned that it's as far turned as it can get, and is still not right. picture below shows where the mark is with it in this position. 2. Carb sync. I built a simple sync tool, and i'm getting conflicting results. At dead idle (throttle as closed as it will go, the left cylinder pulls significantly more. As soon as you ease into just a little throttle the right side pulls significantly more. How do I remedy this? I'm not even sure what would cause it. I do think one cylinder is running richer than the other, so i'm thinking that is playing a part in it, but i'm not sure what i should set for, closed throttle, or open. Link to comment Share on other sites More sharing options...
Speedshop Posted September 9, 2010 Share Posted September 9, 2010 Points: sounds like the points gap has altered after running the engine: recheck and set it to the mid point of the limits. carbs: sounds like a conflict with the cable tension/idle adjustment/carb sync adjustment - maybe with some finger trouble on the owner's part thrown in. Don't try and rush these jobs - if you haven't got enough time - leave them - it will be the same when you return to it! Link to comment Share on other sites More sharing options...
KirriePete Posted September 9, 2010 Share Posted September 9, 2010 Points - it's years since I last looked at a set of points, so anything I say is likely to be bolleaux, but is the advance mechanism (springs 'n' weights iirc) maybe a bit sticky? Carbs - did you set the valve clearances before balancing the carbs? If not, the carb synch exercise is futile. Balance them at tickover, then check the take-up on the throttle cable(s) so that both butterflies open at the same time. Another thought - how are the carb diaphragms? The tiniest pinhole will make a mockery of your balancing and cause some dodgy running on the road. HTH Link to comment Share on other sites More sharing options...
cegan09 Posted September 9, 2010 Author Share Posted September 9, 2010 I'll try and address these points today. These carbs have only one throttle cable, so both butterfly valves are opening at the same time. The idle adjustment screw is actually backed out as far as it will go, so the throttle stop arm isn't even touching it at full closed. I believe the engine is running rather lean at idle, something i'm trying to address as well. I just wanted to get them close to synced before i went changing things in the carbs again. My diaphrams are brand new, so there shouldn't be any holes, but i can check them again. Valve clearances were set less than 1000 miles ago, but i suppose it can't hurt to check them again. I'll look at the points gaps and see about adjusting them as well. I'm still learning this stuff, so i appreciate the assistance with the learning curve. One other question. On the piece in the picture above, the shaft that protrudes from the center has a collar on it that is what the points actually slide along. That collar has a section that is thinner than the rest, making it basically a cam shaft. The collar can be removed, and can actually be installed 2 ways. Now i don't think I've messed with the one on the bike, but i've messed with one from the spare engine, and turned it around before noticing it was cam shaped. Am i correct in saying that it is important to have that on the correct way, and how do i know which way is correct? There is no indication on the parts themselves, and i didn't see anything in the shop manual. Link to comment Share on other sites More sharing options...
Speedshop Posted September 9, 2010 Share Posted September 9, 2010 If the idle adjusters are backed right out you most certainly have issues as per my original post. There will be an adjuster that allows the carbs to be sync'd up with each other (this is how its done with twin carbs/single throttle cable). Its normally between the two carbs. In your case it sounds like its this that has been mis-adjusted and is holding one carb open to the point where the engine idles on on cylinder only. Link to comment Share on other sites More sharing options...
cegan09 Posted September 9, 2010 Author Share Posted September 9, 2010 If the idle adjusters are backed right out you most certainly have issues as per my original post. There will be an adjuster that allows the carbs to be sync'd up with each other (this is how its done with twin carbs/single throttle cable). Its normally between the two carbs. In your case it sounds like its this that has been mis-adjusted and is holding one carb open to the point where the engine idles on on cylinder only. Ah, i missread what you were saying. Yes, that adjusted in the middle is what i was trying to set. Guess i'll pull the carbs first and see if they look really out of whack. Link to comment Share on other sites More sharing options...
cegan09 Posted September 9, 2010 Author Share Posted September 9, 2010 Sigh. i should really check things before giving them up for broken. I had adjusted the carb balance screw too far in one direction, and yes, it was running on one cylinder at idle. Had to take the carbs off to see it. Figured out timing too. The advance mechanism had gotten stuck open. Pulled the assembly out, and re-seated it, it moves freely now. Just waiting for the battery to charge back up and i'll re-set the timing and get the balance back where it needs to be. Link to comment Share on other sites More sharing options...
berniebee Posted December 8, 2011 Share Posted December 8, 2011 In a previous post, you were given the the wrong info about which timing marks to use for ignition timing at idle. You need to use the mark just to the left of the F for timing. The timing marks to the right of the F are used to check that the advance is working. But because your advance unit was stuck open anyway, using the right hand marks for timing would put it in the ballpark. By now, you probably realize which timing mark is correct, but i replied just in case someone else needs to know... Regarding the collar on the breaker point shaft, it definitely makes a difference if the collar is turned around 180 degrees. That corresponds to 360 degrees on the crankshaft and the the spark will happen on the intake stroke , ie: the engine won't run. Link to comment Share on other sites More sharing options...
Recommended Posts