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I believe my issue is electrical, had a gas leak those few months ago so decided to do a full service.
Started w/ the throttle and cable as the cable was cracked and no longer responsive. fuel line, then Oil change, cleaned carb, peacock, clean tank, new gaskets, etc. Noticed my battery was weak when I’d press the horn, so replaced that, the battery.
Other issue I noticed The bike would reach top speed/full throttle then bog down. Didn’t know how to approach it so I ignored it by not going full throttle.
I’m assuming now that these issues are correlated and was inevitable. A timing / points issue possibly.
So I adjusted points today after reading some of y’all’s posts. Unfortunately still nothing. I also replaced the spark plug, and I’m out of ideas. I really don’t want to pay for someone else to fix my bike.
Started w/ the throttle and cable as the cable was cracked and no longer responsive. fuel line, then Oil change, cleaned carb, peacock, clean tank, new gaskets, etc. Noticed my battery was weak when I’d press the horn, so replaced that, the battery.
Other issue I noticed The bike would reach top speed/full throttle then bog down. Didn’t know how to approach it so I ignored it by not going full throttle.
I’m assuming now that these issues are correlated and was inevitable. A timing / points issue possibly.
So I adjusted points today after reading some of y’all’s posts. Unfortunately still nothing. I also replaced the spark plug, and I’m out of ideas. I really don’t want to pay for someone else to fix my bike.
If you haven't done it yet, you should go through the entire tune-up procedure to be sure of everything. PM sent.
ballbearian
Veteran Member
I approve of those heat shields for sure.
Yes, I meant to comment on the creativity.
kbongos
Veteran Member
My experience is limited, but here would be my suggestions.
You could check for spark with plug pulled and sitting or strapped to engine to ground. Can you see spark?
You could try and verify points at open time(fire time) matches when they should fire compared to valves/piston/crank position.
What year and make is this? OK, other posts indicate 1971 Honda CL100.
Pull the plugs after a few attempts and smell and look for gas. Is it getting gas? Or flooding. If plugs are wet with gas try and air it out before retry.
Gas good? I hear gas can get stale.
I'm not sure if this is useful on these bikes, but a can of starter fluid can be a useful trick. Seems most helpful on my fussy old lawn mower.
You could check for spark with plug pulled and sitting or strapped to engine to ground. Can you see spark?
You could try and verify points at open time(fire time) matches when they should fire compared to valves/piston/crank position.
What year and make is this? OK, other posts indicate 1971 Honda CL100.
Pull the plugs after a few attempts and smell and look for gas. Is it getting gas? Or flooding. If plugs are wet with gas try and air it out before retry.
Gas good? I hear gas can get stale.
I'm not sure if this is useful on these bikes, but a can of starter fluid can be a useful trick. Seems most helpful on my fussy old lawn mower.
stl360+450
Veteran Member
+1 on going through the tune-up.
Afterwards, it would be a good idea to verify that the charging system is working properly. Poor or no charging could explain both the high rpm issue and the weak battery.
My first vintage bike (74 CB450) was sold to me with a non-functional charging system — it was running purely on the battery when I test drove it.
Afterwards, it would be a good idea to verify that the charging system is working properly. Poor or no charging could explain both the high rpm issue and the weak battery.
My first vintage bike (74 CB450) was sold to me with a non-functional charging system — it was running purely on the battery when I test drove it.
ballbearian
Veteran Member
Do you mean that it still runs but won't take full throttle long?
Yeah, do it all and do it right. I like to adjust valves then cam chain, to get that out of the way before points and timing.
I'm guessing it's a fuel thing. Starving at high speed. Unplug fuel line from carb and turn on petcock. Is it a healthy steam? A plugged gas cap vent will flow strong then get less as the vacuum builds.
kbongos
Veteran Member
I see, I assumed it just would not start after doing the work on it. So you do all this work on it and it just runs poorly? Tell us about the carb and cleaning. I like BB's suggestion to focus on gas/carb.
No it will not start now, hasn’t started since November.
Maybe that’s my situation as well, I haven’t gotten it to start up, I see fuel is in the line and when I adjust the Petcock fuel flows out. The fuel I have in it may be stale as another mentioned. I know my carb is fine I cleaned and replaced most of it.
Did you check for spark? Even if you have spark, if the points are worn and the gap is closed down from spec, the timing would be retarded and it would be hard to start.
Is there something you're trying to show us in those pics? We've seen two of them, and the newest one doesn't show the points or timing.
Your engine runs off the battery, not a magneto or the alternator (the alternator recharges the battery, but it needs a strong battery to run). And I see in this pic above that you still have the rectifier in use, which could easily be very ineffective at this age.
Your engine runs off the battery, not a magneto or the alternator (the alternator recharges the battery, but it needs a strong battery to run). And I see in this pic above that you still have the rectifier in use, which could easily be very ineffective at this age.
View attachment 30950
Yes it has spark, I’m looking for a Manuel on how to cam chain adjust and valves
I’ve heard it go back and forth w/ starter fluid. How would you suggest I go about it?
I suspect you may not have seen this from an earlier post.
Your engine runs off the battery, not a magneto or the alternator (the alternator recharges the battery, but it needs a strong battery to run). And I see in this pic above that you still have the rectifier in use, which could easily be very ineffective at this age.
So, having spark may not mean it has strong or properly timed spark in order to run. You're not giving us many details to work with, so we have to assume you've not yet checked the timing. Setting the points alone isn't enough. Adjusting the valves and cam chain is a good idea, but the cam chain on the 100 engine is adjusted while the engine is running so the first place to go is the points and alternator covers so you can set the points gap correctly, then adjust the timing properly. Then find T (top dead center) on the compression stroke to adjust the valves.
Check your PMs, I resent the FSM link.
Your engine runs off the battery, not a magneto or the alternator (the alternator recharges the battery, but it needs a strong battery to run). And I see in this pic above that you still have the rectifier in use, which could easily be very ineffective at this age.
So, having spark may not mean it has strong or properly timed spark in order to run. You're not giving us many details to work with, so we have to assume you've not yet checked the timing. Setting the points alone isn't enough. Adjusting the valves and cam chain is a good idea, but the cam chain on the 100 engine is adjusted while the engine is running so the first place to go is the points and alternator covers so you can set the points gap correctly, then adjust the timing properly. Then find T (top dead center) on the compression stroke to adjust the valves.
Check your PMs, I resent the FSM link.
kbongos
Veteran Member
Typical use is to give a spray toward carb intake and then try to start. Sometimes it's enough to get it running, or just a brief moment of running if normal gas is not being delivered. You can use it to detect intake leaks spraying around intake looking for a rise in RPM.
Not sure what you mean by back and forth. How about plug, did you pull that out and inspect after start attempt? Can you see or smell gas on plug or in cylinder? You said you cleaned carb, what is your feeling on how that went? Did that go well? Carb cleaning can be a challenge. How about the points timing? Did you use a trouble light or multimeter with that? Do the points open at the desired starting timing mark?
I got it to run, the needle pushing on the float was stuck inside the carb.
Now, Its like it won’t grab a gear and accelerate past 10mph regardless of gear I’m in. I’ve tuned the carb mixture of fuel and air so that the idle is smooth but as soon as I pull on the throttle it bogs down. I feel the bike wanting to go but it just feels lethargic. Also noticed a clicking sound as the motor idles.
Now, Its like it won’t grab a gear and accelerate past 10mph regardless of gear I’m in. I’ve tuned the carb mixture of fuel and air so that the idle is smooth but as soon as I pull on the throttle it bogs down. I feel the bike wanting to go but it just feels lethargic. Also noticed a clicking sound as the motor idles.
As some of you may now I’ve been struggling for the last 4 months to get my 1971 CB100 to start. Well I have, took it for a spin and Its like it won’t grab a gear and accelerate past 10mph. regardless of gear I’m in. I’ve tuned the carb mixture of fuel and air so that the idle is smooth but as soon as I pull on the throttle it bogs down. I feel the bike wanting to go but it just feels lethargic. Also noticed a clicking sound as the motor idles.
I’m stumped
I’m stumped
Use a timing light to check that the ignition advances.
Dmoh
Well-known Member
It may be that your advancer mechanism (item 6 in the diagram), located behind the contact points plate, is defective.
If your ignition timing does not advance correctly as engine revs increase, then the engine will not make power.
At a minimum, see if the 'weights' move smoothly and the springs have tension enough to keep the weights in position.
I have owned a CB100 for 25 years.....they're great little bikes when everything is working!
Good luck.
If your ignition timing does not advance correctly as engine revs increase, then the engine will not make power.
At a minimum, see if the 'weights' move smoothly and the springs have tension enough to keep the weights in position.
I have owned a CB100 for 25 years.....they're great little bikes when everything is working!
Good luck.
stl360+450
Veteran Member
I'm not familiar with the choke on this carb, but this sounds a lot like what it would do if the choke was closed. I know the carburetor was cleaned and rebuilt, but assuming it's not related could be a mistake.
I've run into a stuck advancer after getting a dormant bike running for the first time in ages and in my case that sounded pretty different, not bogging down so much as uneven and breaking up, but I agree it's a good thing to check.
It's a long lever that would be pretty obvious if it was up at all from its completely off position. This is an aftermarket replacement pic but basically the same.
ballbearian
Veteran Member
Yeah, or maybe the needle isn't riding with the slide right. Re-check that re-assembly.