Author Topic: Early CB750 KO - Start Again (Read 34055 times)

edhaeuser · « **Reply #225 on:** August 15, 2014, 03:09:35 PM »

Wow! I just got caught up on your build. I don't know how I let this one slide by. It's going to be beautiful with all that fresh chrome! I might have to hop on my K1 and take a run to the East side of the state one of these days :-) There sure seems to be a lot of SOHC guys over your way. I feel lonely over on the West Coast.

Johnie · « **Reply #226 on:** August 15, 2014, 06:20:49 PM »

Thanks Ed. Come on over anytime. We east side guys are always looking for a ride.

Johnie · « **Reply #227 on:** August 20, 2014, 04:50:55 PM »

Update August 20th - made some progress today. Did a bench sync and found the slides far off the mark. Will do a vac sync last once the other issues are done. Found the timing was so bad that was the reason for the intermittent firing of #3. Got the timing as close as I could with these old points and it runs OK, but not like the others. I have come to the conclusion the points are shot. Ordered points and condensers from my dealer. Will get those in a few days and get this baby running smooooooth...no tank yet. I always end up with new points. I can not figure out why I put myself through the hassle every time to try and use the old points. Smack me in the side of the head next time fellas

Stev-o · « **Reply #228 on:** August 20, 2014, 05:09:14 PM »

Gotta replace the points, Johnie. Been there....

Johnie · « **Reply #229 on:** August 20, 2014, 06:08:48 PM »

Right on there Stev-o...you would think I would have learned my lesson by now

I think I just wanted to hear it run...and run she did. I will fine tune it and call this one done...if I ever get the tank and side covers back. She shifts unbelievably smooth too.

bjatwood · « **Reply #230 on:** August 22, 2014, 08:00:45 AM »

Johnie, these 750's shift like butter compared to our Goldwings clunk into gear everytime shifting...

Johnie · « **Reply #231 on:** September 05, 2014, 10:15:53 AM »

Update Sept. 5th - got the tank back from the painter today. What an awesome job he did. Gold stripe is NOT a decal. Now to finish this one up. Installed the new points and condensers a couple weeks ago, but that did not make a difference in #3. I have good color on #3 plug, just not much back pressure compared to the others at idle. Seems weak, but compression was OK. Adjusted the valves last week and will give it a try today to see if that makes a difference. If not, I am thinking maybe intake rubber. However, sprayed some carb cleaner on the intake and did not notice a difference. Might do a leak down test depending on what I get today after the ride. When I ran it to 3,000 on the stand the back pressure on #3 out the exhaust was stronger than the other 3 if that tell you something. Again, will no more after todays trial.

edhaeuser · « **Reply #232 on:** September 05, 2014, 11:38:55 AM »

That paint is beautiful!

Greggo · « **Reply #233 on:** September 05, 2014, 12:03:00 PM »

I'm not an expert in engine dynamics, but is it possible it is a carburetor issue with #3?

Johnie · « **Reply #234 on:** September 05, 2014, 12:14:50 PM »

I hope that is all it is Greggo is a carb issue. Weird how the back pressure on 3 is lower than the rest at idle but higher at 3,000 on the stand. You know I did dump a half gallon of acorns out of the mufflers last winter. I am very sure I got them all out. Carb issue...maybe. All cleaned out and running all stock in there. Was real picky on the float heights so was really ruling that out. Going to get the bike out now and will report back.

Greggo · « **Reply #235 on:** September 05, 2014, 12:16:33 PM »

Have you done a vacuum sync? Take a quick visual inspection of the brass adjuster atop the carburetor to see if it's different from the others. Then again, maybe the pipe is just plugged still...

Johnie · « **Reply #236 on:** September 05, 2014, 12:18:53 PM »

I did do a bench sync and then a vac sync. All are pretty close. Guess I will just keep going through the process of elimination.

SOHC4 Cafe Racer Fan · « **Reply #237 on:** September 05, 2014, 12:29:51 PM »

Holy crap! What an amazing paint job. The painted (no-decal) graphics are amazing! Your painter has some skills!

Old Scrambler · « **Reply #238 on:** September 05, 2014, 03:04:22 PM »

Johnie..............I'm holding a dyno-case-cover for you................its from an F motor but no scratches. You can check it out when your ready for a ride.

Johnie · « **Reply #239 on:** September 05, 2014, 03:41:54 PM »

Thanks Dennis...a trip over will be nice. Thanks for keeping me in mind. Here is the latest after my test ride today. I rechecked the new points and timing which are right on. Got out the Morgan and did a low idle and high RPM sync. Got it all spot on the button. I sure got some nice readings for only 3 cylinders

Took the test ride and no change. #3 still sluggish and just a little warm. I swapped plug wires 2 & 3 with no change in pipe temp. Good spark on #3. I now plan to replace the intake. I saw just a very small bead of a wet spot on the side of #3 intake rubber. Hoping that is the issue. So off come the carbs and I will double check all that again too.

Tews19 · « **Reply #240 on:** September 05, 2014, 07:53:52 PM »

Hey Johnnie could it be a float level? Maybe not enough fuel that could be causing this, hence the pipe not as warm as the other 3? Just a shot in the dark.

Johnie · « **Reply #241 on:** September 06, 2014, 07:34:18 AM »

Thanks Tews...I will certainly check the carbs over again once I change out the intake. I just hope it is not a broke ring or something of that nature.

Tews19 · « **Reply #242 on:** September 06, 2014, 07:36:10 AM »

Johnie can you do me a huge favor? Possibly take a picture of your wire harness and how you mount it through the coil area and the spine of the frame?

Stev-o · « **Reply #243 on:** September 06, 2014, 10:57:50 AM »

+1 amazing paint work. Did you take the bike out for a test run? If yes, how is it running?

Johnie · « **Reply #244 on:** September 06, 2014, 02:08:10 PM »

Stev-o...test ride info is 5 posts up. I have ordered a new intake for #3. Just as a side note I did replace the 4 brass floats with the plastic Honda ones. I did not want to go through the leaking float issue.

Johnie · « **Reply #245 on:** September 07, 2014, 07:20:22 AM »

Nick...here are the harness pics for you...

Tews19 · « **Reply #246 on:** September 07, 2014, 08:04:11 AM »

Thanks a lot!

jerry h · « **Reply #247 on:** September 07, 2014, 05:48:34 PM »

That Blue is amazing - when you get the bugs worked out, it's going to be a sharp looking bike.

Any chance the #3 muffler is still stuffed full of nuts, or enough to be causing problems???

bjatwood · « **Reply #248 on:** September 08, 2014, 11:33:04 AM »

Beautiful paint job there John. You'll get #3 worked out I'm sure of it.

I use an infared hand held heat gun for a quick check on how my carbs are running. Right after I get back from a ride I will have 140ish~ on #1&4 and upper 150ish~ on #2&3 pipes right where they down turn out of the heads in front of the frame uprights...

Johnie · « **Reply #249 on:** September 08, 2014, 12:44:50 PM »

Thanks guys...today I got the gas cap and HONDA emblems on the tank. Waiting for the intake and tach seal from the dealer. Then I hope to get the #3 issue behind me. I really doubt there is anymore acorns in #3 exhaust. I shook those out pretty good. I am really thinking low gas issue from a leak in the intake. Got the air cleaner off again and I can see gas residue in the carb base of all except #3. When the carbs are off I will go over it all again.

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Author Topic: Early CB750 KO - Start Again (Read 34055 times)