[sbaugz]

I am getting pretty frustrated with this CB350.

It ran well. I took it all apart and made some cosmetic changes, cleaned the carbs, powder coated frame, etc, etc.
Didn't do anything to engine except clean carbs and send them to CrazyPJ for rebuild. They have uni filters and stock exhaust.

wiring harness is a simplified harness that I made without signals, horn, etc. Just the basics.

Brand new Ricks Regulator and rectifier. Brand new battery.

Got the bike back together and it ran good except once warmed up the bike would randomly lose power. I trouble shooted the damn thing and couldn't get it fixed.

Got really mad and just pulled the trigger and upgraded the entire ignition system to include Pamco ignition, NGK wires, new coils, new plugs.

Got the ignition all dialed in and timed. Started it up. Seems to run really well. Has strong acceleration until I reach about 7000 RPM and I lose power. Its similar to before the upgrades except now it only seems to happen at around 7000 RPM. I cleaned out petcock, fuel filters and put new fuel lines on. No change. Plugs are new. No change. Carbs are synced pretty decently.

Any thoughts on what is going on?

 

[Yendor]

Are your new coils OEM or replacements, are they wired with the correct polarity?

You say you powder coated the frame are you sure you cleaned up ALL - ALL of the Grounds?
Not scraping the Powder Coat from ground contacts is a Prime cause of electrical issues.

Ditch the Fuel Filters. - If your gas tank is free of rust, your petcock is clean and has the proper screen in place there is no need for In-Line filters.
In-Line filters will only create resistance to the fuel flow.
These are gravity FEED Fuel Systems even with a FULL Tank at the highest level the pressure is nearly non-existent.

Uni-Filters - PODS?
Some Pod type filtesr will Block the Vacuum Ports on the Carb Intake side.
These bikes really like the Balanced flow of the Inter-connected Air Filters.
The connection chamber under the Battery Box helps even out the air flow.

 

[sbaugz]

Are your new coils OEM or replacements, are they wired with the correct polarity?

You say you powder coated the frame are you sure you cleaned up ALL - ALL of the Grounds?
Not scraping the Powder Coat from ground contacts is a Prime cause of electrical issues.

Ditch the Fuel Filters. - If your gas tank is free of rust, your petcock is clean and has the proper screen in place there is no need for In-Line filters.
In-Line filters will only create resistance to the fuel flow.
These are gravity FEED Fuel Systems even with a FULL Tank at the highest level the pressure is nearly non-existent.

Uni-Filters - PODS?
Some Pod type filtesr will Block the Vacuum Ports on the Carb Intake side.
These bikes really like the Balanced flow of the Inter-connected Air Filters.
The connection chamber under the Battery Box helps even out the air flow.

appreciate the input but I don't think its going to be any of those things you mention.

-I have a solid ground to the bare frame.

-fuel filters are required because tank has rust in it- but they are high flow filters.

- UNI filters don't block the vacuum ports, which is why i use this brand. I have also tried running bike without the UNI's and it still loses power around 7000 RPM anyway

- The coils are brand new, aftermarket. To my knowledge, you can't get OEM ones for the 350. The ones I purchased came in a complete electronic ignition conversion kit for the CB350 from 4-into-1 - these include two coils, two NGK wires and caps, and the pamco ignition.

 

[pamcopete]

If you have a charging system issue or if there is a high voltage drop across the ignition switch or the kill switch, those issues will be more pronounced at higher RPM's. If you have not cleaned the contacts on the kill switch, then chances are they have never been cleaned. Measure the voltage at the battery at 3,000 RPM + to see 14.5 Volts. Measure the voltage at the coils to see not more than .5 Volt less than the battery WITH THE ENGINE RUNNING. If the engine is not running, then there will be no current draw and the reading will show battery voltage. The engine has to be running to cause a draw.

From your description, it could still be a carb issue. Installing a new and better ignition system can serve to mask carb problems.

 

[sbaugz]

If you have a charging system issue or if there is a high voltage drop across the ignition switch or the kill switch, those issues will be more pronounced at higher RPM's. If you have not cleaned the contacts on the kill switch, then chances are they have never been cleaned. Measure the voltage at the battery at 3,000 RPM + to see 14.5 Volts. Measure the voltage at the coils to see not more than .5 Volt less than the battery WITH THE ENGINE RUNNING. If the engine is not running, then there will be no current draw and the reading will show battery voltage. The engine has to be running to cause a draw.

From your description, it could still be a carb issue. Installing a new and better ignition system can serve to mask carb problems.

There is no kill switch (I know, I know-- but the owner that I helped build this for didn't want one).
I suppose it could be an ignition switch issue (but I doubt it), its a brand new Emgo ignition switch.
Same thing with the charging system ( its a brand new Ricks reg/rectifier).

I am starting to think that its more of a carb issue, but I will measure voltage across coil wire and at battery as you suggest.

 

[brokencamchain]

The tank has rust... is it causing a restriction of fuel flow through the pick up tubes on the petcock?

 

[sbaugz]

The tank has rust... is it causing a restriction of fuel flow through the pick up tubes on the petcock?

short answer- no. . Last night I removed petcock and checked it over. There was some sediment on very bottom, but otherwise the pickup tubes and internals were spotless.

 

[doode]

What do your plugs look like?
What's your compression?
What gear are you in @7k rpm?
Can you jam past 7k rpm in 1st or 2nd?

 

[NE_Don]

Have you done anymore work on this problem, my problem is basically identical to yours, engine starts fine, runs great to about 7k and then wants to bog out, cant even red line it in 1st gear. I have nice power up that rpm range, try to go higher bogs, even seems to want to spit! About the only thing I haven't done that you have done is the Pamko ignition. Like you this really really is getting frustrating!!

 

[doode]

How's your battery and stator output?
Anything out of standard with your carbs?

Have you done anymore work on this problem, my problem is basically identical to yours, engine starts fine, runs great to about 7k and then wants to bog out, cant even red line it in 1st gear. I have nice power up that rpm range, try to go higher bogs, even seems to want to spit! About the only thing I haven't done that you have done is the Pamko ignition. Like you this really really is getting frustrating!!

 

[NE_Don]

I will put my volt meter on tomorrow and see, ... the battery is new...have no problem with plenty of juice to run starter motor, lights, no manual recharge ever needed.....if my battery was needing a recharge I could see this...I even put a couple of hundred miles on my old 82 "Vision" after it fried it's first stator, just had to make sure I kept the battery charged and didn't have too many restarts....can you explain this thought more? Carbs hooked up to factory air cleaner system...took em apart, dipped them, blew them out.....I guess if they have had jets changed by a previous owner I did not look for numbers on the jets, so I guess it is possible, bike came with Uni's but I would be greatly surprised that any re-jetting was done ....frankly I think the R&R was a waste of time, they had no sediments in them, all the needles looked fine, bike has 13,000 on odometer. Plugs light tan, look just fine if not a little lean. My problem was worse before new coils and cleaned the carbs, at least now I have no engine miss or bog until I try to go past about 6500 rpm...again, the bike runs very well from idle to about 7 grand...you can give it full throttle is 5 gear at 4k it will pull real nice till about 6.5 to7K (to about an indicated 65 mph) and then that's it, bogs out, seems to miss...it spits so to say if you hold it open long enough. Myself, I am inclined to think fuel starvation but why and how to fix? Saw the video on plugging one fuel line and using a T to connect the two carbs..I say this as I have noticed when draining the tank fuel will tend to drain out of one line...maybe some truth to it? Geez, I had 1970 350 from 1972 till 1984 and NEVER had such problems.

 

[Yendor]

Have you tried running with the Gas Cap Cracked OPEN to check if the Cap VENT might be clogged and preventing proper flow when the demand is maximized at high RPM?

 

[jeff6924]

I have the exact same problem with my CB200. Bogging at about 7kRPM. It runs really good through all gears until I get to 5th gear, and no power. It barely makes it to 50miles. Even standing when revving the engine boggling and backfire happens. I did pull the bottom of carb and it was full of gas. Played with ignition timing and no change.
I hope to find some answer here.

 

[A motorcycle nut]

Here is a possible solution to your problem.

 

[Yendor]

You do realize you are responding to a post from 5 years ago and that user hasn't been seen in 4 years+