Topic: CB750K1 Strange Situation

[pjandrew99]

Been working on another project but now ready to get back to my CB750 and get it going.
Last time I took it out it ran like a bat outta hell for about an hour. Came off a highway ramp and the engine seemed to smooth out with some reduced power.
Rode it home and the engine seemed less sewing machine like and more V12 jag like. Again it had less power. Pulled in my driveway. It stalled and couldn't start it back up. Did the 3000 mile tune up. Still wouldn't start so put it away for the winter.
Before that ride I had added baffles to exhaust and wrapped the pipes. I also reduced one tooth on the front sprocket. WOW!, huge torque but wondering if I overheated or put too much stress on my engine possibly causing an issue.
So, my thoughts are to go through the entire electrical system again for starters. Did it once sometime before the ride and all checked out. Has newer coils, plugs and wires. Also, has Ricks combo regulator, rectifier. Battery is new.
The change in the engine smoothness may be a hint for one of the more experienced members to start me off in the right direction.  Thanks!

[Old Scrambler]

Assume you checked the plugs and points-gap.............but did you check the petcock and carbs for dirt?

[TwoTired]

I does sound like the plugs were  getting increasingly fouled.  Suspect the added baffles made the cylinders run a lot richer.  Pull the plugs and have a look.

[MauiK3]

Also check condensers

[pjandrew99]

Assume you checked the plugs and points-gap.............but did you check the petcock and carbs for dirt?

Plugs and points were good. Thought I checked the petcock but I'll check it again to confirm. Carbs were on the list based on the responses I got. Thanks!

I does sound like the plugs were  getting increasingly fouled.  Suspect the added baffles made the cylinders run a lot richer.  Pull the plugs and have a look.

Was wondering about the need to change the jets. Right now I have 115/38 and the needles one notch leaner. That was done before the baffles when the bike previously ran rich. Would you change the jets or needle position based on adding the baffles? Thanks!

Also check condensers

Condensors are newer. Is there a way to check them? Thanks!

[Kevin D]

There have been many of the the 3 bladed logo condensers fail.
A fat blue spark at the points can be a sign of a bad condenser.

It’s harder to pay for the more expensive ($28?)condensers when you can get them for $8?, but worth it when your CB is running like crap.

[pjandrew99]

There have been many of the the 3 bladed logo condensers fail.
A fat blue spark at the points can be a sign of a bad condenser.

It’s harder to pay for the more expensive ($28?)condensers when you can get them for $8?, but worth it when your CB is running like crap.

Thanks! I've been meaning to crank it in the dark to see any errant sparks. I'll be sure to look down at the points.

[Don R]

Maybe a plugged gas cap vent?

[pjandrew99]

Maybe a plugged gas cap vent?

Thanks! Will check it out.

[dave500]

jag v12 like?i would imagine that to be smoother than a rolls royce?

[TwoTired]

I does sound like the plugs were  getting increasingly fouled.  Suspect the added baffles made the cylinders run a lot richer.  Pull the plugs and have a look.

Was wondering about the need to change the jets. Right now I have 115/38 and the needles one notch leaner. That was done before the baffles when the bike previously ran rich. Would you change the jets or needle position based on adding the baffles? Thanks!

I would look at the spark plug tips for indications of mixture conditions when running.  Do you understand what metering circuit does what based on slide position?

[Stev-o]

jag v12 like?

A Jag V12 is as smooth as silk!

[scottly]

Deja vu?? Did you ever try removing the baffles and fiberglass packing?
http://forums.sohc4.net/index.php/topic,190366.msg2214129.html#msg2214129

[scottly]

Did you get rid of the #$%*ty ignition parts yet?
http://forums.sohc4.net/index.php/topic,190432.msg2215179.html#msg2215179

[pjandrew99]

Deja vu?? Did you ever try removing the baffles and fiberglass packing?
http://forums.sohc4.net/index.php/topic,190366.msg2214129.html#msg2214129

I did. Removed the slip on's and tried to start it. It didn't start and that's where I left it till now.

Did you get rid of the #$%*ty ignition parts yet?
http://forums.sohc4.net/index.php/topic,190432.msg2215179.html#msg2215179

Yes, points were upgraded. Honestly don't remember what condensors I put in. Believe they are TEC.

[pjandrew99]

Its' early. Had to think about it. Replaced the entire assembly plate with Honda assembly plate.