bike runs on 1 cylinder then stops and runs on the other

[jrod1540]

so my problem is as follows. full engine rebuild. piston sleeves etc. i have confirmed cam chain/ valves have all been set up correctly. triple checked.

set the timing and points as follows. right TDC T mark set gap to .14. static adjusted timing with on right points. rotated 180 degrees adjust left points. all should be good in the world.

Electrical. new battery, new points and new condenser ( points are oem new, condenser is aftermarket from 4 into1). new spark plug caps NGK from 4 into 1. using original coils and wires. Cut cables back to make sure i have fresh cable wire connected to at coils and plugs.

Carbs: rebuilt carbs, used original brass components and needles. only new piece is brass and little needle piece to allow fuel in to carbs. original had wear marks.
floats were set at 24mm i believe. aire fuel set to 1.25 turns out. I live in houston if that helps. but running all stock setup as i mentioned.


Preoblem. with full charged battery. i can pull the spark plugs and cycle the engine and see spark at each plug. screw plugs back in and it will run on both cylinders for a second. then only run on the right cylinder. then if i adjust the left points gap while it is running the left side will start to fire( odd because they were showing spark as if correctly adjusted before trying to start.) once left side starts to fire then the ride side will stop firing.

ill pull the plugs and a course the right side is now fouled because it has been running with out ignited the full. so then i will clean plugs and restart the whole process over again. but same situation. ill recheck the battery and it will still have 75 to 85 percent charge. makes since cause I'm barely above idle while I'm tweeking it.

i will feel the coils and they don't seem hot like they hare heating up and losing load.

i don't see a any significant spark at the condensers that may indicate a bad one.

one thought is that the carb floats may be adjusted poorly and it will work for a while then the carbs let in to much gas and foul the plug out.

I'm at a loss. i ordered new coils but at this point I'm just throwing parts at it. What does everyone think.

side note when i do get it to fire on all cylinders it wont idle even with idle screws all the way in. i have the carb slides with the more open end facing the air intake.(which i think is the right direction).

I'm not sure if I'm chasing an electrical issue or carb at this point. i also have rebuilt the entire wire harness to spec to rule out and shorts from battery to key to coil. and confirmed i have power at both coils while engine is running.

i almost feel like i have a short at the points plate between the points or something. which is stealing power between the points.




Sorry for the long thread.

[Nick]

It's firing the plug with the least resistance (the cleanest plug).

Charge the battery properly and have the battery load tested. (call some bike shops or auto parts stores to find a place that does it) If it's an old battery, ditch it, buy a new one and put in on the charger for a couple of hours before installing it.

Back in the day (my days) Honda said that something like 75% or more of all electrical problems and warranty claims were the result of weak batteries.

Of course, make sure that all ground straps are touching bare metal, not painted metal.

Don't forget that the line closest to the TDC line on the stator is the static timing mark. The strobe mark is marked F. When static timing these engines I just use a piece of cellophane between the points to determine when they open.

Check that the slides are opening simultaneously. Also, hold the throttle wide open and check that both slides are in the same position.
After you get it running, set the idle as per the manual, then confirm that both slides lift simultaneously.

[jrod1540]

thanks for the reply.

so i bought the battery new about 2 months ago and poured in the acid. charged it on 3 amp as to not fry it.

as far as the grounds go. Honestly i wonder if I'm missing one. Other than the battery ground to the engine bolt/frame ( which i scrapped off fresh powder coating to get bare metal) and the headlight ground, i don't have any other frame grounds. only the wires going back to the ignition switch. Am i missing a ground i wonder?

load test is a good idea. ive bought batteries before that seem fine but are not once load tested.

timing: So you are saying that i should static time to the T and not the F mark? when using a simple alligator clip to the points with a light grounded to the bike?

Points gap recommends .012 to .015 if i remember correctly. i tried that and could not get a good break in the points ( they seems to not close flush. I also noticed that the points can move on both the lower and upper screw if loosened. Should i just be loosing the top screw and adjusting the gap or both screws. seems there is play in the bottom screw of the points that will move it closer or further away to the camshaft which makes me need to readjust the timing. i have tried it both ways. not to sure

[DJM]

Points should break on the F and LF (Fire) marks not the T mark but in honesty if everything else is in order it should start and run anyway, these bikes aren't that critical on timing.

Tightening either screw will / can alter the timing a bit, you just have to keep at it by trial and error to get it exactly right with all the screws tightened up, might take a while!

Points gap is, as you say .012" to .015" in English measurements.

I'd also suspect the battery, Not many earth connections on these things, the CB models have a separate earth (ground) from the coil bracket onto the top engine bolt but I don't think the CL has one there. Extra grounds are a good idea for lighting circuit problems but I don't think are causing your issues. Make sure the plugs aren't fouled, fit new ones if there is any doubt, they will often spark across the gap when out of the engine but short out inside when installed. Plug gap around .024" but you could try closing it up a bit (temporarily) to see if that helps, also check coil polarity.

Let us know what you find, that way we all learn a bit more.

[Nick]

Most Hondas, such as my 305 Dream, have 3 timing marks on the stator. T=top dead center, the line next to the T is the static timing mark (timing fully retarded), the F line is the fully advanced timing mark used when timing the engine with a strobe light and with the engine revved to 3 or 4000 rpm.

Perhaps the CL has different stator markings.

In any case, with the engine not running (static timing, fully retarded) the points should open just before TDC

[DJM]

To avoid any confusion, the CB and CL72/77 rotors are NOT marked like that, I didn't realise that the Dreams were marked that way either.

Turning the engine, CB or CL at least, in the normal clockwise direction the first marks that come along are two lines about 3mm apart but unmarked on either cylinder.

THESE are the FULLY ADVANCED timing marks. When checking ignition timing using a strobe light the bike should be firing somewhere between the two lines; although not marked as such these lines are 45 and 48 degrees before top dead centre respectively.

Why two lines, I think that there is so much play in the cam chain, points shaft and spark advancer even on a new engine that it would be unrealistic to achieve fully advanced timing with better than a two degree level degree of accuracy, hence fully advanced ignition is fine anywhere between the two lines.

Next along is the F, or LF line. This is the STATIC Firing point when the points should just be cracking open at hand cranking speeds..

Next along, five degrees later are the T or LT lines for Top dead centre and Left Top dead centre respectively.

If you have the facilities you should set the static timing first on both cylinders and then, using a strobe light, check the fully advanced timing at say 4000 rpm to make sure ignition on both cylinders falls between the two fully advanced lines.

If the fully advanced timing doesn't fall between the lines adjust the timing to get the fully advanced timing correct even if the static timing is 'wrong'.

Unless there is a major problem the bike should still start up and run OK with the static timing a few degrees out although of course correct at both static and full advanced is best.

[jrod1540]

awesome. thanks everyone for the feed back. i was also reading on a separate thread that the gap on the points should be set at when they are at their widest not necessarily on the F or LF mark which i think has definitely been causing problems. using a basic light i didn't i set the points to just barely break and turn the light on for each points... throwing gap out the window... and waaalaaa... it is running strong. i think i miss understood where to set the gap. also i didn't know about the 2 marks for the timing advance before the TDC and F marks. i will try the strobe light on that later when i get to the fine tuning stage. I'm going to assume for now that my timing is off and that's why it will not idle with the idle screws turned in. Currently i have both the slide adjusters unscrewed a little to force them open so it will idle.

Thanks for all the feed back.